Changing arctic snow cover: rain-on-snow and ice layer detection using passive microwave radiometry
Alexandre Langlois, Caroline Dolant, Ludovic Brucker, Alain Royer, Benoit Montpetit, Alexandre Roy
Corresponding author: Alexandre Langlois
Corresponding author e-mail: firstname.lastname@example.org
The first and strongest signs of global climate variability and change have been observed in the Arctic over the past three decades. Patterns in the spatial extent and mass balance of snow show a statistically significant trend towards negative anomalies. More specifically, the currently observed warming in the Arctic leads to winter rain-on-snow (ROS) events, which are now more frequent. Those events often leads to the creation of ice layers, which prevents ungulates from accessing their food. We present here results from ROS detection algorithms, validated with 625 ROS observations across the Canadian Arctic Archipelago. Three periods were studied separately and results show that, despite no significant trends in the cumulated yearly occurrence, an increase is seen in the occurrence of fall and winter ROS events. Furthermore, an anomaly analysis suggests positive anomalies in event occurrence starting in the late 1980s. In addition to monitoring ROS, presence of ice layers is detected from satellite observations using variability in the polarization ratio at 11, 19 and 37 GHz. Observed trends in ice-layer presence and ROS occurrences are similar. It is shown, however, that ice layers are less frequent, given that not all ice layers are of sufficient thickness to be detected by our algorithm. Finally, a spatio-temporal analysis identified specific areas such as Cornwallis Island, Sommerset Island and Northern Baffin Island to be more prone to ROS and ice occurrence.
Understanding temporal variation of δ17O and 17O excess in an alpine ice-core drilled in central Alaska
Akane Tsushima, Vasileios Gkinis, Kumiko Goto-Azuma, Sumito Matoba, Hideaki Motoyama
Corresponding author: Akane Tsushima
Corresponding author e-mail: email@example.com
Ice-cores obtained from glaciers are important archives for paleo-climate and environmental changes. The most important climate changes, such as the variation in temperature, precipitation, and the hydrological cycle, are reconstructed from water stable isotope ratios (δ18O, δD, and d excess) measured in ice cores. With the improvement of water-stable isotope analyzers, the ability to measure δ17O in water with high precision provided another parameter, 17O excess. Previous studies reported that 17O excess in polar snow is mainly controlled by the relative humidity of the source region of water vapor; it was therefore expected to be a new proxy of past climate and environmental change. However, at present, there are few studies of 17O excess in ice cores, and therefore an understanding of its variation factors is incomplete. In this study, we analyzed δ17O and δ18O with high precision, and we also calculated 17O excess in an ice core drilled in central Alaska in 2008. 17O excess shows a trend towards having a low (high) value during periods of high (low) d-excess. When the water vapor flowed from the western side of Alaska, the d-excess value was high. Therefore, we consider that 17O excess values may tend to be low (high) when water vapor flows from a high- (low-) latitude area.
In situ imaging of the sea-ice matrix: can hyperspectral imaging and digital photogrammetry be used to quantify the distribution and abundance of sea-ice algae?
Emiliano Cimoli, Lars Chresten Lund-Hansen, Arko Lucieer, Klaus Meiners, Fraser Kennedy, Andrew Martin, Andrew McMinn, Vanessa Lucieer
Corresponding author: Emiliano Cimoli
Corresponding author e-mail: firstname.lastname@example.org
Sea-ice algae form the base of the polar marine food webs and play a critical role in large-scale biogeochemical cycles. Traditional point-sampling techniques are labour-intensive, spatially limited, and invasive – this limits our understanding of algal spatial variability and has implications for quantifying both primary production in polar regions and the microbial response to environmental stress. To address the sampling limitations, this study explores the potential of hyperspectral imaging (HI) technology to capture the distribution and abundance of ice-associated algal communities. In addition, the extensive amount of spatially and spectrally resolved information acquired through HI allows for our understanding to reach further beyond the pure discrete biomass distribution estimates. Using a state-of-the-art inverted ice tank with inoculated algal distributions, this work unveils the potential of HI to; a) quantify per-pixel biomass abundance over millimetre scale resolution imagery, b) detect differences between algal physiological conditions, and c) couple biomass distributions with sea-ice physical parameters derived from digital photogrammetry to better understand algal distribution drivers. While the application of HI in situ would allow for unprecedented datasets of the under-ice biome, there are logistical, technical and scientific challenges associated with HI being deployed in such a demanding environment. These aspects will be discussed in the context of our upcoming deployments at the Ross Sea region of Antarctica using an under-ice tether system specifically designed to scan the ice–water interface over meter-scale transects. The presentation concludes with an outlook on how the technology can be aligned with autonomous or remotely operated vehicles to greatly increase the spatial extent of the surveys.
Modelling development and decay of cryoconite holes on Qaanaaq Ice Cap, northwestern Greenland
Koji Fujita, Nozomu Takeuchi, Masashi Niwano, Teruo Aoki
Corresponding author: Koji Fujita
Corresponding author e-mail: email@example.com
Cryoconite holes on ablation zone of glacier and ice sheet have been simulated mainly with respect to their deepening development, for which the models employed simplified schemes for penetration of solar radiation through the ice. In this study we developed a cryoconite hole model to elucidate the meteorological factors controlling collapse of cryoconite holes, which we have observed on Qaanaaq Ice Cap, northwest Greenland. The model employs energy balance, in which each heat component differs between the ice surface and the bottom of the cryoconite hole and its difference varies with its depth. The model is validated with observed changes in the depth of cryoconite holes druing two melting seasons in 2014 and 2015. Analyzing the meteorological variables, we find that windy conditions are preferable for shallowing of cryoconite depth.
Genomics diversity and adaption to cryosphere of 21 psychrophilic/psychrotolerant Cryobacterium strains
Yongqin Liu, Tandong Yao, Liang Shen
Corresponding author: Yongqin Liu
Corresponding author e-mail: firstname.lastname@example.org
Bacteria are the most essential life form in glaciers and ice sheets. Little is known about the mechanism of bacterial adaptation to the cryosphere. We hypothesis that bacteria gain a gene resistant to the harsh habitat. Aiming to find how the genomic content and dynamics of bacteria are driven by glacier and cold environmental stressors, we compared the genomic sequence of 21 psychrophilic/psychrotolerant (P/P) Cryobacterium strains, 19 isolated from glaciers and the other two from Antarctic rock and high Himalayan soil respectively, to 11 mesophilic counterparts . Although cold shock genes are absolutely necessary for the psychrophilics, cold-adapted species in the family Microbacteriaceae did not contain significantly high numbers of copies. P/P Cryobacterium genomes significantly have a higher composition of genes involved in stress response, motility and chemotaxis than their mesophilic counterparts (P < 0.05). They have also undergone a more dynamic phase in genome content than their mesophilic counterparts. The phylogenetic birth-and-death model imposed on the phylogenomic tree indicates a vast surge in a recent common ancestor of P/P Cryobacterium (gained the most number of genes by 1168) after the splitting off of the mesophilic strain C. mesophilum CGMCC1.10440. Expansion in genome content brings key genes dominated by the categories cofactors/vitamins/prosthetic groups/pigments, carbohydrates and membrane transport. P/P Cryobacterium has a relatively low amino-acid substitution rate, two orders of magnitude lower than that in mesophilic strains. Extensive gene acquisition and a low amino-acid substitution rate may be strategies of P/P Cryobacterium to resist low temperatures, oligotrophic conditions and high levels of UV radiation.
Perchlorate in surface snow along a traverse route in East Antarctica
Su Jiang, Jihong Cole-Dai, Yuansheng Li, Chunlei An, Guitao Shi
Corresponding author: Su Jiang
Corresponding author e-mail: email@example.com
Perchlorate in the environment is of significant interest because of the potential threat it poses to human health. Recent research suggests that perchlorate is naturally formed in the atmosphere and atmospheric formation constitutes a significantly large portion of the perchlorate in the current environment. By virtue of its geographical position and meteorological conditions, the Antarctic ice sheet provides chronological records for atmospheric deposition of different substances. Surface snow samples collected along a traverse route from Zhongshan Station to Dome A in East Antarctica were used to assess the spatial variability of perchlorate along the traverse route, to explore possible sources of perchlorate in Antarctic snow and to determine what atmospheric and glaciological factors influence the spatial variability of perchlorate in snow. Results show that the perchlorate concentrations vary between 32 and 200 ng kg–1, with an average of 104.3 ng kg–1. The perchlorate concentration profile presents an apparent decreasing relationship with increasing distance inland in the coastal region and a generally increasing trend approaching the dome in the inland region. Perchlorate in Antarctic snow is probably formed in the atmosphere and deposited in snow. Different rates of atmospheric production, dilution by snow accumulation and re-deposition of snow-emitted perchlorate (post-depositional change) are the three possible factors influencing the spatial variability of perchlorate over Antarctica.
Quantitative method for evaluation of seasonal variation in snow depth
Konosuke Sugiura, Takuto Ukai
Corresponding author: Konosuke Sugiura
Corresponding author e-mail: firstname.lastname@example.org
Seasonal variation in snow depth is one of the important types of data for understanding snowfall and snowmelt processes and cryosphere ecosystems. Although seasonal variation in snow depth from beginning to end has been classified and the characteristics clarified, seasonal variation in snow depth may easily depend on specific winter extreme snowfall events. It is necessary to evaluate a seasonal variation pattern of snow depth quantitatively for better understanding from the point of view of climatology. Therefore, the purpose of this study is to establish a method for evaluating the seasonal variation pattern of snow depth characterizing the area quantitatively in the long term. The daily maximum snow depth data set of AMeDAS (Automated Meteorological Data Acquisition System) by the Japanese Meteorological Agency were used. The target area is Sapporo, Japan. The target period is from 1961 to 2010. We used the beta distribution that could express the probability density of a variety of shapes quantitatively to evaluate the seasonal variation pattern of snow depth. As for the seasonal variation pattern of snow depth in Sapporo, the middle of February of the latter half of the snow period is the maximum in any year, and the snow depth decreases rapidly afterwards. It was revealed that the seasonal variation pattern of snow depth has a roundish shape in comparison with a normal distribution if the curve fitting with respect to the snow depth using the beta distribution is performed. In addition, it was able to grasp the actual situation of the seasonal variation pattern of snow depth, which reflected a climate state, without being influenced by the sudden change of snow depth caused by a snowfall event in a specific year.
Soil biological activity along a latitudinal transect in Arctic West Siberia
Anna Bobrik, Georgy Matyshak, Dmitry Petrov, Olga Goncharova
Corresponding author: Anna Bobrik
Corresponding author e-mail: email@example.com
Understanding the heterogenity in carbon exchange in cryosphere ecosystems in different permafrost zones is a significant step towards understanding the global carbon cycle. The aim of our study was to assess variability in the parameters of soil biological activity (CO2 efflux, contents of the microbial carbon) from the cryosphere ecosystems in taiga, forest tundra and tundra zones of Arctic west Siberia (Russia) under conditions of climate change. The taiga research site (Nadym) is located in a discontinuous permafrost zone (65°18′ N, 72°52′ E). The average active layer thickness was 163 ± 8 (August 2015). The CO2 efflux from the peatlands was low (202 ± 37 mgCO2 m–2 h–1). The upper horizons of the peatland soils statistically differed from those of the bog in the contents of the total (31.88 ± 3.02 and 37.96 ± 2.00% respectively), labile (1400 ± 300 and 31100 ± 2200 mgС kg soil–1) and microbial carbon (4260 ± 330 and 240 ± 50 mgС kg soil–1). The forest–tundra research site (Urengoy Gas Field) is located in continuous permafrost zone (66°18′ N, 76°54′ E). The average active layer thickness was 85 ± 10 (August 2015). CO2 efflux from peatland soil was low and characterized by high variability (202 ± 25 mgCO2 m–2 h–1). The average content of total organic carbon was high (29.58 ± 5.02%). The average content of labile organic carbon in the peatland soils was less than in the bog soils (1350 ± 150 and 25 400 ± 4000 mgС kg soil–1 respectively). The tundra research site (Urengoy) is located in the continuous permafrost zone (67°48; N, 76°69′ E). The soils of this research site are characterized by a low active layer thickness as well as bu the CO2 efflux and microbial carbon content (August 2016). The spatial distribution of CO2 efflux and content of water-extractable organic carbon are strongly correlated with hypsometric levels (r = –0,33, and r = –0,42 respectively, p <0,05) in tundra ecosystems. Despite the wide array of changes in both physical (soil temperature, soil moisture) and biological conditions (vegetation composition, content of labile and microbial soil carbon), our results showed that soil CO2 flux did not vary significantly across the transect (taiga–forest tundra–south tundra). However, the depth of the permafrost table differed significantly. This explains the necessity for adequate assessment of spatial variability of the active layer thickness as a significant factor influencing regional CO2 emission and soil biological activity.
Sr and Nd isotope ratios of cryoconite in western Greenland: identification of sources and the process of transportation of minerals on the dark-colored ice
Naoko Nagatsuka, Nozomu Takeuchi, Jun Uetake, Rigen Shimada, Yukihiko Onuma, Sota Tanaka, Takanori Nakano
Corresponding author: Naoko Nagatsuka
Corresponding author e-mail: firstname.lastname@example.org
Recently, the area of dark-colored ice covered by cryoconite has expanded on the Greenland Ice Sheet. Cryoconite is a biogenic surface dust consisting of organic matter mainly derived from living microbes on the glaciers and mineral particles originated from basal till and/or wind-blown dust. Since cryoconite is dark in color, it can reduce the surface albedo of glaciers and is likely have contributed to the recent high ice loss rates observed in Greenland. In this study, we analyzed the Sr and Nd isotopic ratios of minerals in cryoconite collected from glaciers in northwest and southwest Greenland. Based on the isotopic ratios, we identified the source of the minerals and the transportation process on the dark-colored ice. Previous studies had identified three possible sources of minerals in cryoconites on the Greenland Ice Sheet: (1) dust transported by wind from the local area, probably the nearby tundra; (2) englacial dust deposited in the past in the accumulation area that had traveled through the ice sheet and outcropped again in the ablation zone; or (3) long-range transportation of dust from distant deserts. The mineral components of the cryoconite showed variable Sr and Nd isotopic ratios that corresponded to those of the englacial dust and moraine but were significantly different from those of the distant deserts that had been considered as primary sources of mineral dust on the Greenland Ice Sheet. This suggests that the minerals within the cryoconites were mainly derived from local sediments rather than from distant areas. The Sr ratios in the northwestern region were significantly higher than those in the southwest. This is probably due to geological differences in the source areas, such as the surrounding glaciers in each region. The isotopic ratios further varied spatially within a glacier (Qaanaaq and Kangerlussuaq areas), indicating that the minerals on the glaciers were derived not from a single source but from multiple sources, such as englacial dust and wind-blown minerals from the moraine surrounding the glaciers. In the Qaanaaq area, a major contributor to the dark ice surface is likely to be outcroppings of mineral-rich layers of glacier ice.
Current research and plan for blue ice drilling in China
Zhengyi Hu, Jingxue Guo
Corresponding author: Zhengyi Hu
Corresponding author e-mail: email@example.com
An ice core provides the only sample of ancient Earth’s atmosphere that we have access to, so it created a stir when Michael Bender’s team announced that a core drilled in Antarctica had yielded 2.7-million-year-old ice. This discovery comes from a largely ignored ‘blue ice’ area, where peculiar dynamics can preserve old layers. Actually, we had ourselves begun to conduct research into blue ice drilling in 2015. The special national key research and development plan for China was then approved, in 2016, one of the aims of which is to find and acquire an ice core from a blue ice area. We want to develop a set of blue ice drilling tools with an outer diameter of almost 300 mm and a drilling capacity of 300 m. This blue ice drilling system will be designed to incorporate a portable operating cabinto improve efficiency and make operation easier. What’s more, this system can be operated by fewer than three people and will be able in theory to drill to 100 m within 2 days. The blue ice core obtained by this drill system will be used for research in physics, chemistry (e.g. Na+, NH4+, K+, Mg2+, Ca2+, Cl–, NO3–, MSA and SO42–), isotopes (δ18O–H2O,D and 15N–NO3–), gas(CO2 and CH4) and other elements, especially verifying the isotopic dating method for krypton.
Independent shifts of abundant and rare bacterial populations across a glacial foreland in East Antarctica
Hongmei Ma, Yu Zhang, Wenkai Yan
Corresponding author:Hongmei Ma
Corresponding author e-mail: firstname.lastname@example.org
Glacial forelands are extremely sensitive to temperature change and are therefore appropriate places to explore the development of microbial communities in response to climate-driven deglaciation. In this study, we investigated the bacterial communities that developed at the initial stage of deglaciation using space-for-time substitution in the foreland of an ice sheet in the Larsemann Hills. A series of soil samples across the glacial foreland were deeply sequenced with 16S rRNA gene amplicon sequencing to determine the bacterial community, including both abundant bacteria, which contribute more to geobiochemistry, and rare bacteria, which serve as a seed bank for diversity. Our results show that abundant bacterial communities were more sensitive to changing conditions in the early stages of deglaciation than members of rare communities. Moreover, among the environmental parameters tested, which included total organic carbon, pH and moisture of the soil, ice thickness was the most influential factor affecting the community structure of abundant bacteria. These results show the different effects of abundant and rare bacteria on community shifts and highlight ice thickness as the primary factor affecting the bacterial community in the early stages of deglaciation. The response of the microbial community to climate change can be predicted with more certainty in this polar region.
The Snow Eagle 601 airborne platform and its application in East Antarctica
Corresponding author: Xiangbin Cui
Corresponding author e-mail: email@example.com
Ice geometry and basal conditions are still now well constrained in East Antarctica, especially in Princess Elizabeth Land (PEL) and coastal regions. According to the newly compiled Bedmap 2 , a large data gap exists in PEL due to lack of direct geophysical measurements. These prevent our understanding of the ice-sheet dynamics, subglacial morphology and geology of the region. In 2015, China deployed its first fixed-wing airplane, named ‘Snow Eagle 601’. It is an old DC-3 aircraft with special modifications to the airframe and electronics for polar operation and installation of scientific instruments. The deep ice-penetrating radar system updated from the HiCARS (High Capability Radar Sounder), GT-2A gravimeter, CS-3 magnetometer and other auxiliary instruments, such as laser altimeter, GPS and camera, are configured in the airplane to measure the ice sheet and subglacial conditions, as well as bedrock geology and tectonic. Snow Eagle 601 was used to implement airborne geophysical investigation in the PEL sector during the 32nd and 33rd Chinese National Antarctic Research Expeditions (CHINARE 32 and 33, 2015/6 and 2016/7). During this season (CHINARE 34, 2017/8), the field campaign will focus on a survey of the Amery Ice Shelf. Here, we first introduce the Snow Eagle airborne geophysical platform. Then we present some preliminary results from CHINARE 32, 33 and 34.
Determination of the three-dimensional ice-sheet structure of the internal layers of Dome A, East Antarctica, by radio-echosounding
Xueyuan Tang, Bo Sun
Corresponding author: Xueyuan Tang
Corresponding author e-mail: firstname.lastname@example.org
Twice grounded radio-echosounding surveys, covering a 30 km × 30 km section, were carried out over Dome A on the central East Antarctic ice sheet by the Chinese National Research Expedition during two austral summers(2004/5 and 2007/8), aimed at mapping the internal isochronous layers and subglacial reliefs, so that this can be used effectively to find the pre-sites for older ice around Dome A. Thw typical geometrical structure of the internal layers along the ice divide were revealed by tracing continuously ten dated isochrones between Dome A and the location of the Vostok ice core. The pattern of the isochrones with smooth distribution shows that there some relatively steady-flow areas have existed around the dome for the last 152 000 years. However, some sharper disruption was also identified in a few local areas, which was most likely caused by larger basal shear stresses and enhanced flow. Overall, the topographic structure of the layers shows larger local variations in depth between isochrones and the bedrock and provides interpretation of the ice sheet structure around the drilling site of Kunlun station.
Storage-period dependence in cryopreservation of CHO-TRET1 cells with trehalose
Tsutomu Uchida, Maho Furukawa, Takahiro Kikawada, Kenji Yamazaki, Kazutoshi Gohara
Corresponding author: Tsutomu Uchida
Corresponding author e-mail: email@example.com
We recently reported that the viability of mammalian cells (CHO cells) after a slow freeze/thaw operation is greatly increased by transporting trehalose into the cells through the trehalose transporter 1 (TRET1). In this study, we carried out experiments to reveal how long this cryopreservation is effective for long storage in a deep freeze at 193K. The stored CHO-TRET1 cells were the same as those used in the previous study (Uchida et al., Cryobiology, 77(50), 2017). The cultured cells (about 105 cells mL–1) were dispersed in the 1 mL cryopreservation solution (culture medium including trehalose) for several hours prior to freezing to allow the uptake of trehalose into the cells. These samples were then deep-frozen in a freezer (at 193K) in a cryo-tube. In these conditions, the freezing rate is about –15K min–1. After storing for a period, the frozen sample was thawed quickly in a water bath at 310K. The viability of the cells was measured by staining with a cell analyzer (Merck, Muse). It was found that high viability was maintained for several months. However, viability gradually decreased after long storage for more than a year. This indicates that the trehalose transported into the cell through TRET1 is effective for cryopreservation below 193K (a slow cryopreservation technique using trehalose). However, the storage temperature is not sufficiently low at 193K for long-term cell preservation of the cryopreserved cells.
Long-range transported bacterial communities relating to ice-nucleic particles accumulated in snow cover on Mount Tateyama, central Japan
Teruya Maki, Shogo Furumoto, Yuya Asahi, Koichi Watanabe, Kevin Lee, Kazuma Aoki, Masataka Murakami, Takuya Tajiri, Hiroshi Hasegawa
Corresponding author: Teruya Maki
Corresponding author e-mail: firstname.lastname@example.org
The westerly wind blowing at high altitudes over east Asia transports aerosols from Asian desert areas and anthropogenic areas to downwind areas such as Japan. The long-range transported aerosols include not only mineral particles but also microbial particles, ‘bioaerosols’, which impact ice-cloud formation processes. However, the sequential changes in ice-nucleation bacterial communities in high-elevated aerosols have not been investigated in detail. Here, we used the aerosol particles recorded in the snow cover at 2450 m a.s.l. on Mt Tateyama to estimate sequential changes in ice-nucleation activity and bacterial communities in aerosols and to clarify their relationship to one another. After stratigraphy of the snow layer formed on the walls of a snow pit on Mt Tateyama, snow samples, including aerosol particles, were collected from 70 layers including both upper layers (spring accumulation) and lower layers (winter accumulation). The snow samples with Asian-dust particles indicated higher nucleic activity at lower temperatures than snow samples without Asian-dust particles, and the activity positively related to the organic particles originated from microorganisms. MiSeq sequencing analysis using 16S rRNA genes revealed that the bacterial composition of the snow samples predominately included members of the plant-associated and marine bacteria (the phylum Proteobacteria) during winter and changed to the main group of terrestrial bacteria (the phyla Actinobacteria and Firmicutes) during spring, when dust events occurred frequently. Those without particles mainly included Proteobacteria sequences. The relative abundance of Firmicutes positively increased in correspondence with high activity of ice nucleation of the snow samples. Moreover, the isolates of Firmicutes (Bacillus species) showed greater ice nucleation activity than Proteobacteria isolates. Presumably, Asian-dust events change the airborne bacterial communities over Mt Tateyama and carry terrestrial bacterial populations, which induce ice-nucleation activity in the atmosphere and indirectly affect climate change.
Environmental changes over the past 128 000 years deduced from terrestrial biogenic ions in a deep ice core drilled during NEEM in Greenland
Kumiko Goto-Azuma, Motohiro Hirabayashi, Takayuki Kuramoto, Anna Wegner, Birthe Twarloh, Margareta Hansson
Corresponding author: Kumiko Goto-Azuma
Corresponding author e-mail: email@example.com
A 2540 m long ice core was drilled during 2008–10 by the NEEM (North Greenland Eemian Ice Drilling) international ice coring project. Discrete samples were collected from the continuous flow analysis melt fractions during the field campaigns carried out within NEEM in 2009–11. The discrete samples were distributed to different laboratories. Ionic species were analyzed at the Japanese National Institute of Polar Research. Here we discuss the variability of terrestrial biogenic species, data about which have been very sparse. Oxalate and acetate show variations associated with Dansgaard–Oeschger events, as do ions originating from sea salt and dust aerosols. In contrast, neither ammonium nor nitrate shows such large variations, as was previously reported for other deep ice cores from Greenland. During the Holocene and Eemian, ammonium, acetate and formate show coherent variations. During the mid-Eemian, these ions all show decreased concentrations during a short period, while stable isotopes of water show little change. Since these terrestrial biogenic species likely originated from North America, this would indicate a mid-Eemian cold spell in North America, although there was little change in temperature in Greenland.
Influence of surface melt on dark-ice extent variation on the Greenland Ice Sheet
Rigen Shimada, Masahiro Hori, Nozomu Takeuchi, Teruo Aoki
Corresponding author: Rigen Shimada
Corresponding author e-mail: firstname.lastname@example.org
Darkening of the Greenland Ice Sheet is one of the factors affecting its mass loss in recent years. Expansion of the dark ice area has possibly contributed to a reduction in the surface albedo of the ice sheet. The dark ice appears on ablation areas in summer and accelerates melting of the ice sheet due to its intense light absorption. Darkening of the ice is caused by impurities in the surface ice such as mineral particles, glacial microbes, organic matter and their aggregates, called cryoconite granules. Cryoconite granules are formed by microbial activity and are darker than abiotic mineral particles. Since the microbes can be active only on a melting ice surface, the duration of surface melt on the ice sheet possibly affects microbial activity and the formation of cryoconite granules. Therefore, spatio-temporal variation in surface melt is important in understanding the darkening process. We investigated the influence of surface melt on dark-ice extent variation using optical and microwave remote-sensing data, meteorological observation and meteorological reanalysis datasets. Meteorological observation and optical remote sensing match-up data analysis from April to September during 2009–16 in the southwestern region showed that the early onset of melt caused early appearance of bare ice and continuous appearance of a dark ice surface. Comparison between surface melt extent and dark ice extent of the ice sheet below 2000 m from 2000–16 using microwave and optical remote-sensing data revealed a significant positive correlation between surface melt extent in spring (April–June) and annual maximum dark-ice extent. There is a similar positive correlation in the southwestern and northeastern regions of the ice sheet where the bare ice extends widely. Meteorological reanalysis data showed that there is a significant positive correlation between spring air temperature and surface melt extent. These results suggest that early melt onset caused by air temperature rise in spring induces a continuous wet surface environment during the ablation season, which is beneficial for the growth of glacial microbes.
The elevation-dependent behavior of hoar-prominent snowpack on forest slopes, based on the decade minute observations
Yusuke Harada, Ryuzo Wakabayashi, Yoshikage Inoue
Corresponding author: Yusuke Harada
Corresponding author e-mail: email@example.com
During the 10 winter seasons from 1995–2004, full-snowpit surveys were performed on a monthly basis at 15 study plots at 100 m intervals from 1300–2700 m a.s.l. in the mountain forest of Japan’s Central Alps (Chuo Alps). We observed snowpack depth of 558 m in over 500 pits, an average depth of 1.1 m, including density measurement of a combined total of 2610 layers with an average thickness of 15.6 cm. Observations are as follows. 1. At midwinter, the trends in snow metamorphism were similar through different elevations. Faceting processes were generally predominant but, during seasons of heavy snow, the process of rounding was observed more frequently. 2. The positive correlation between elevation and snow density was clearer at midwinter, when there were no or little wet snow or melt–freeze layers. 3. The differences in grain type and density between the upper and lower layers in each snowpit were greater at midwinter, when new snow crystals piled up on the upper layers while the lower layers were influenced by metamorphism and consolidation. 4. The positive correlation between the snow density of a layer and the snow load on the layer was stronger in rounding snow and weaker in faceting snow and melt–freeze snow. 5. The higher the plot elevation, the finer the decomposing and fragmented particles became. Grain size indicated that in higher plots the particles were more fragmented by low temperature and strong wind. Finer DF particles had greater density than coarser ones, especially in near-surface snow, which experienced less snow loading. We can speculate from these facts that snow drifts are more frequent in higher elevations and resulted in high-density windslabs by processes such as sintering, their creation also being accelerated by filling of ice powder dust into spaces created by fragmented snow particles on the snow surface. 6. Upon analysis of monthly trends, snow depth showed a strong linear correlation with elevation, and mean density of snow cover showed moderate linear correlation with elevation. As a consequence, the snow water equivalent can increase as a quadratic function of elevation. 7. Where the snow depth exceed 50 cm, the average snow temperatures of the lower layers near the ground surface are generally as high as 0 °C.
Interactions between snow cover and forest: ancient preserved trees record centuries of avalanche activity in their tree-rings
Adrien Favillier, Christophe Corona, Jérôme Lopez-Saez, Sébastien Guillet, Nicolas Eckert, Jean-Luc Peiry, Markus Stoffel
Corresponding author: Adrien Favillier
Corresponding author e-mail: firstname.lastname@example.org
Snow avalanches are a common process in mountain regions where they potentially damage infrastructure or even causes loss of life. On forested slopes, snow masses repeatedly interact with trees and therefore meet all the criteria to be considered as an agent of disturbance to forest dynamics, since they typically disrupt forest ecosystem structure, composition and processes and ultimately cause the destruction of tree biomass. At the forest stand level, snow avalanches may create patchiness or spatial heterogeneity, thereby contributing largely to the existence of a wide range of ecological niches and favoring uneven-aged forests, which are considered beneficial for plant diversity. Through the impact of falling snow masses, trees may be uprooted, suffer from stem breakage, or be decapitated if kinetic energy is transferred to the crown. These disturbances to trees will cause immediate changes in their growth, thus allowing the retroactive assessment and reconstruction of past and contemporary avalanche activity. During recent decades, tree-ring-based reconstructions of past avalanche activity have been developed worldwide. Yet, to date, these reconstructions do not account for interference between snow avalanches and climatic and exogenous ecological signals in tree-ring series that can potentially affect the quality of reconstructions. In this context, we are developing a specific procedure allowing evaluation of the quality of reconstructions in three snow avalanche corridors at Täsch (Swiss Alps). Analysis of past events was based on tree-ring series from 307 heavily affected multi-centennial European larch trees (Larix decidua Mill.) growing near or next to the avalanche paths. A total of 2570 growth disturbances, such as scars, tangential rows of traumatic resin ducts, and compression wood as well as abrupt growth suppressions or releases, were identified in the samples, indicating 71 destructive snow avalanches since AD 1740. At the same time, 24 potential events were rejected from the final reconstruction due to potentially strong interference between the different signals. This high rejection rate underlines the necessity to systematically – and carefully – discriminate ecological and climatic noise from avalanche-related disturbances. This discrimination is even more crucial as a significant proportion of dendrogeomorphic studies in the Alps are based on L. decidua trees, which are cyclically affected by larch budmoth outbreaks.
Feedback analyses of the seasonality of polar amplification driven by changes in the orbital parameters with MIROC-GCM
Kanon Kino, Ayako Abe-Ouchi, Ryouta O’ishi, Fuyuki Saito, Masakazu Yoshimori
Corresponding author: Kanon Kino
Corresponding author e-mail: email@example.com
Studies of past climates can provide a constraint on the uncertainty of climate sensitivity. In this study, we focus on the seasonality of polar amplification, whereby surface warming over the polar regions exceeds that elsewhere, and examine how the seasonality induced by orbital parameters compares to that induced by CO2. We use an ASVGCM (MIROC-LPJ) to investigate the effect of changes in the orbital parameters, spanning the past 500 000 years, and apply feedback analyses proposed by Lu and Cai to understand the seasonal climate response to changes in obliquity and precession. Surface temperature change across ocean induced by the insolation change is similar to that induced by CO2 change. Increased solar absorption leads to an increase in ocean heat storage in the summer and to an increase in heat release in the winter, or to changes in long-wave radiative forcing. Surface temperature change across land induced by obliquity change is much greater than that induced by precession change, because of the positive insolation anomaly in the early spring, putting forward the snow melting and promoting albedo feedbacks, especially with the northward shift of the forest–tundra boundary. The relationship between summer insolation and summer temperature across land in the NH high latitudes does not take a simple linear form but is dependent on both obliquity and precession.
Methanesulfonate over eight glacial cycles in the EPICA Dome C ice core
Corresponding author: Margareta Hansson
Corresponding author e-mail: firstname.lastname@example.org
The EPICA Dome C ice core from Antarctica spans more than eight glacial cycles. Unique high-resolution chemical records were obtained by analysis of discrete samples by ion chromatography*. The long-term trend in the methanesulfonate (MS–) record will be examined here. Both MS– and non-sea salt (nss) sulfate are considered to be derived mainly from oxidation of marine biogenic DMS (in the rough relation 1:10). The deposition flux of nss sulfate is almost constant through the eight glacial cycles while more MS– is deposited (or retained in the snow) during glacials than during interglacials. Since nss sulfate at Dome C is assumed to be mainly dry-deposited and not affected by post-depositional processes, the stable nss sulfate flux suggests that the local atmospheric concentration was constant. This leads us to the conclusion that marine biogenic DMS emissions did not vary between the different climates. The large variation in MS– flux must therefore reflect other changes. Methanesulfonate shows a decreasing long-term trend in concentration. Nss sulfate, and the marine components chloride and ss sodium, show an increasing trend in concentration while nitrate and nss calcium show no trend over the eight glacial cycles.
*EPICA chemistry consortium IC analyses performed by six laboratories: 1. Stockholm University, Sweden; 2. British Antarctic Survey, UK; 3. University of Florence, Italy; 4. University of Copenhagen, Denmark; 5. LGGE, CNRS, France; and 6. AWI Bremerhaven, Germany.
Artificial cryoconite holes created in a cryospheric environmental simulator
Nozomu Takeuchi, Satoru Yamaguchi, Kazuma Togashi, Ryutaro Sakaki, Chika Okamoto, Koki Ishiwatari
Corresponding author: Nozomu Takeuchi
Corresponding author e-mail: email@example.com
Cryoconite holes are cylindrical water-filled holes formed on the ablation ice surface of glaciers worldwide, and are features that play a significant role in supra-glacial ecosystems as well as in the ablation process of glacial ice. In order to assess the conditions for development and decay of cryoconite holes, artificial cryoconite holes were created in a cryospheric environmental simulator (CES). The CES is a large, state-of-the-art facility at the snow and ice research center of the National Japanese Institute for Earth Science and Disaster Prevention and can reproduce various cryospheric environments including snowfall, solar radiation, air temperature and wind speed. A commercial cube of ice (25 × 25 × 30 cm), which is almost transparent and contains some air bubbles, was placed in the CES and a cylindrical hole 10 cm in diameter and 2 cm in depth was created on the surface of the ice. Cryoconite that had been collected on a glacier of northwest Greenland was placed at the bottom of the hole. Solar radiation, wind speed and air temperature in the CES was controlled to be constant in value and the holes were monitored for change for approximately 20 hours. The hole developed over the first few hours; however, after a few hours, meltwater leaked out and the hole did not then retain its cylindrical shape. The cryoconite spread over the ice surface and the hole finally became an irregular depression. This is probably because solar radiation penetrated the ice and melted the boundary of ice crystals, and water then leaked through the gaps between the ice crystals. We alternatively used iceberg ice collected in Antarctica consisting of smaller ice crystals with abundant air bubbles for the experiment. Here, meltwater was retained in the hole and the cylindrical shape was maintained throughout the experiment. The results suggest that certain physical properties of ice, such as ice-crystal size and air-bubble content, are required to form cryoconite holes on glacial ice and that meltwater collecting in holes plays a role in maintaining their cylindrical shape. This has implications for spatial and temporal variations in cryoconite hole formation across glaciers, which may affect meltwater production and microbial activity.
Long-range avalanche–forest interactions leave strong environmental footprints in medium-high mountain ranges
Florie Giacona, Nicolas Eckert, Robin Mainieri, Brice Martin, Christophe Corona, Jean-Matthieu Monnet, Mohamed Naaim, Markus Stoffel
Corresponding author: Florie Giacona
Corresponding author e-mail: firstname.lastname@example.org
Unlike alpine-like high mountain ranges, medium-high mountain ranges are generally not considered to be avalanche-prone areas. However, when terrain and climate characteristics are favourable, significant avalanche activity can affect these environments, playing a major role in landscape structuring. Specifically, avalanche–forest interactions leave strong environmental footprints up to the immediate vicinity of te release areas. These interactions also control the landscape dynamics and are strongly linked with climate and anthropogenic drivers. The aim of this work is to refine our understanding of these complex processes representative of the deep changes undergone by sensitive systems submitted to rapid global changes. To this end, an avalanche-prone area representative of the Vosges Mountains – the avalanche complex of the Rothenbachkopf–Rainkopf 1316 m a.s.l. – was studied via a comprehensive multidisciplinary approach associating geo-history, forest ecology, remote sensing and climatology. Avalanche activity has been documented over more than 200 years using a combination of different sources: administrative archives, local press, scientific papers, iconographical documents, oral testimonies, etc. Land use and land cover evolution have been identified through the diachronic analysis of a large set of old maps and aerial photographs. In addition, the current state of the forest landscape has been characterized through field surveys and analysis of aerial laser scanning data. It first appears that forest stands show a clear longitudinal (upstream–downstream axis of the avalanche paths) and transverse (from the center to the margin of avalanche paths) structure. This pattern of tree species, sizes and morphologies form ‘avalanche landscapes’ in near-equilibrium with the frequency/intensity of avalanche activity. From a dynamic point of view, diachronic analyses reveal that avalanches of high intensity (multi-decadal return period) regularly destroy large parts of the forest stands, inducing quasi-cyclic changes in the landscape mosaic. However, changes in sylvo-pastoral practices and climate warming have led the study site to evolve towards almost total forest colonization over recent decades. Outlooks include a refined characterization of avalanche activity using tree-ring techniques and how it relates to the characteristics of the forest stands (species, ages, sizes, shapes, number and type of growth disturbances, etc.).
Mapping vegetation propagation along the preglacial zone of a rapidly retreating temperate glacier in southeastern Tibet using long-term Landsat NDVI
Qiao Liu, Ji Luo
Corresponding author: Qiao Liu
Corresponding author e-mail: email@example.com
The Hailuogou glacier, a typical monsoon temperate glacier located on east slope of Mt Gongga in the southeastern Tibetan Plateau, has retreated more than 2 km since the Little Ice Age (LIA). The LIA preglacial zone (2980–2800 m), characterized by very fast primary succession due to local warm–wet hydrothermal conditions, possesses an integrated succession community from cold-adapted herbaceous to Abies fabri forest. During past decades, although a number of studies related to the primary succession have been carried out based on plot investigation, soil diagnosis and succession modeling, a comprehensive investigation of the vegetation distribution and propagation is still lacking. In this study, we use long-term Landsat NDVI (1982–2017) combined with field investigation to map vegetation propagation. A spatial pattern of NDVI was demonstrated to explain the spatial heterogeneity of the vegetation distribution along the LIA preglacial zone of Hailuogou glacier. Several key geomorphological factors, such as slope, aspect, preglacial stream morphodynamics and debris-flow disturbance, are analyzed to investigate their influence on the propagation pattern and succession rate of the preglacial vegetation.
Pollen grains in shallow ice cores drilled from the western cwm of Khumbu glacier, Mt Everest, Himalaya
Yoichiro Hori, Nozomu Takeuchi, Minoru Yoshida, Yoshiyuki Fujii
Corresponding author: Yoichiro Hori
Corresponding author e-mail: firstname.lastname@example.org
Pollen grains are commonly contained in ice cores drilled from polar and alpine glaciers and can be used as a proxy of the paleo-environment. Because of the phenology of pollen release, they are also useful to identify annual layers in the ice cores. However, studies on pollen analysis in ice cores are still limited. In this study, we analyzed pollen grains in two shallow ice cores drilled from the accumulation area (the western cwm) of Khumbu glacier, which is a large valley glacier flowing from Mt Everest, Himalaya. The ice cores were drilled in winter 1980, were transported in their frozen state to Japan and have been preserved in a freezer at the National Institute of Polar Research without any analysis. The first core (Core1) was 8.83 m long and was drilled at 6100 m a.s.l.; the second (Core2) was 4.06 m long and was drilled at 6400 m a.s.l. In this study, we record the visual stratigraphy and analyze stable isotopse, major soluble ions and pollen grains. In order to quantify the pollen grain concentration, 5–10 mL of the melted core samples were filtered on membrane filters and pollen grains on the filter were directly counted using a microscope. Various species of pollen grains were found in the ice core. Pollens of Pinaceae, Cupressaceae, Ephedra, Artemisia and Betulaceae were identified. These pollens were generally abundant in Core 1 but hardly observed in Core 2. The pollen-grain concentrations ranged from 0.0 to 2.1 grains mL–1, which was generally lower than those reported in other mountain glaciers in Asia. The most dominant pollen in the core was Pinaceae (55%). Based on the peaks of the Pinaceae pollen, Core 1 can be divided into seven annual layers, although the isotope or soluble ions did not show a clear seasonal trend in the core. The annual accumulation rates obtained from the annual layers were approximately 820 mm in water equivalent. The composition of pollen grains in the cores differed from those in ice cores from other regions of Asia, such as Tian Shan, Altai and Pamir, and are likely to be indicative of the vegetation in southeastern Nepal.
Incubation experiment demonstrates the effects of carbon and nitrogen on microbial phosphate-solubilizing function from an alpine soil ecosystem
Hongyang Sun, Yanhong Wu, Haijian Bing
Corresponding author: Yanhong WU
Corresponding author e-mail: email@example.com
Phosphorus is a vital element for organisms but becomes the main limiting nutrient of some ecosystems. Changes in the availability of carbon (C) and nitrogen (N) may alter the availability of phosphorus due to ecological stoichiometric requirements. However, few studies used a controlled experiment to confirm the impact of available C and N on the availability of phosphorus from a microbial perspective. In this study, three phosphate-solubilizing microorganism (PSM) communities were separated from the alpine soils to conduct a microbial phosphate-solubilizing experiment under different C and N conditions. The phosphate-solubilizing efficiency (PSE) of PSM communities differs between the different alpine ecosystems in Gongga mountain. C and N affect the phosphate solubilizing function of PSM communities by means of their ratio and level. It suggested that a single indicator (ratio or level) may not be reliable for assessing nutrient stress in the ecosystems. A phospholipid fatty acid analysis showed that changes in the microbial community composition and metabolic activity contributed to the response of PSE to the treatments of C and N. These results also imply that global changes are altering the phosphate-solubilizing processes to affect the geochemical processes of phosphorus in alpine soil ecosystems due to changes in C and N.
Simulation of snow algal growth and its effect on snow albedo using a global land surface model, MATSIRO
Yukihiko Onuma, Kei Yoshimura, Nozomu Takeuchi, Tomoko Nitta
Corresponding author: Yukihiko Onuma
Corresponding author e-mail: firstname.lastname@example.org
The snow-covered area in the Northern Hemisphere has recently reduced due to acceleration of snow melting. The recent acceleration of snow melting is likely caused by air-temperature rise and snow albedo reduction. Recent studies have revealed that snow algae, which are photosynthetic microbes growing on snow and ice, can also affect the albedo of the snow surface. Therefore, it is important to estimate snow algal abundance and to quantify its effect on surface albedo in order to project present and future melting of snowpack in the Northern Hemisphere. However, snow algal abundance and its albedo effect have not been simulated by a global climate model and a global land surface model. In this study, we aim to reveal the temporal and spatial characteristics of snow algal abundance, and to estimate the effect of snow algal abundance on snow albedo worldwide using a global land surface model. We incorporated a microbial growth model known as the logistic model into a global land surface model, MATSIRO, and simulated snow algal growth globally. The logistic model, which requires an initial cell concentration, algal growth rate and carrying capacity, can calculate temporal variations in algal abundance in the snow surface. In this study, we used an initial cell concentration of 6.3 cells m–2, a growth rate of 0.2 h–1 and a carrying capacity of 3.5 × 107 cells m–2 reported by the previous study. The algal abundance was assumed to increase when snow temperature in the top layer of snowpack calculated by MATSIRO was above 0°C. We also calculated snow albedo including the algal effect, using the model. The snow albedo was calculated from visible albedo with a reduction rate of albedo per algal cell, which was assumed to be 7.9 × 10–9 m2 cells–1 based on observation. The global simulation by MATSIRO showed that snow algae reached the carrying capacity every year in the coastal area of North America and in southwest Greenland. The timing to reach the maximum abundance differed between the two areas. It was spring for North America but summer for Greenland. The effect of algal growth on the surface albedo was calculated up to 0.2 in the area, suggesting that algal growth substantially affects the melting of snowpack in the regions. Although more studies are necessary to validate and calibrate the model, our results demonstrate the geographical variations in snow algal growth and its effect on surface albedo.
Seasonal feedback analysis on polar amplification in a warming climate induced by orbit/CO2
Ryouta O’ishi, Kanon Kino, Ayako Abe-Ouchi, Masakazu Yoshimori, Marina Suzuki
Corresponding author: Ryouta O’ishi
Corresponding author e-mail: email@example.com
Past proxy records indicate that the mid-Holocene (6 ka) and the last interglacial (127 ka) were warmer than the present day because of the different orbital parameters of the Earth. In both periods, high-latitude warming was much greater than the global average. This is known as polar amplification, and it is also seen in projections of CO2-induced climate warming. In 2011 O’ishi and Abe-Ouchi used a vegetation-coupled GCM and quantified the contribution of vegetation feedback to warming in the mid-Holocene. For the present study, we applied a feedback analysis method proposed by Lu and Cai on 6 ka, 127 ka and doubled CO2 by vegetation-coupled GCM experiments similar to those of O’ishi and Abe-Ouchi to reveal more detailed feedback mechanisms with and without vegetation feedback.
Spatial variations in chemical soluble ions in the ablation area of Ürümqi Glacier No.1, Tien Shan, China
Ryo Sugiyama, Nozomu Takeuchi, Zhongqin Li
Corresponding author: Ryo Sugiyama
Corresponding author e-mail: firstname.lastname@example.org
The chemical soluble ions in snow and ice can affect abundance and diversity of microbes growing on glaciers. For example, autotrophic microbes growing on the glacier surface, such as algae and cyanobacteria, require nitrogen and phosphorus as nutrients and are also affected by the pH of the meltwater. Their abundance and species composition vary spatially on a glacier and may be affected by the chemical condition on the glacier ice. However, there are few studies on spatial variation in chemical soluble ions in the ablation surface of glaciers. This study aims to describe the spatial variations in chemical soluble ions in the ablation area of Ürümqi Glacier No.1, located in the Tien Shan Mountains, China. We collected surface ices from the various locations in the ablation area of the glacier in August 2017 and measured the oxygen and hydrogen stable isotopes and the concentrations of major ions (Cl, NO3, SO4, Na, NH4, K, Mg, Ca) of the samples. Based on the results, we created maps showing the spatial variations of each variable using GIS software. The results show that the concentrations of water-stable isotopes were relatively higher on the upstream and eastern side of the glacier than on the western side. This spatial variation is probably due to the different ages of the ice accumulated on the glacier. Since the accumulation area is distributed along the ridgeline from south to east of the glacier, the ice appears to be older on the western than on the eastern side. The spatial variations in the concentration of chemical soluble ions in the surface ice differed among the ions. The concentration of Cl, NO3, SO4, Na and NH4 were relatively higher on the upstream and eastern side of the glacier. This is also likely to be due to the age of the ice. In contrast, the concentrations of Mg, and Ca were relatively higher lower down the glacier. This is probably due to additional solutes originating from chemical weathering of dust deposited on the glacier surface. Results suggest that the spatial variations in chemical soluble ions in the ablation area are mainly determined by the age and flow of the glacial ice and by the additional solutes from surface dust on the glacier.
Difference in snow processes between three Japanese cedar stands and an opening during snowmelt season
Shigeki Murakami, Yukari Takeuchi
Corresponding author: Shigeki Murakami
Corresponding author e-mail: email@example.com
Snow water equivalent (SWE) and daily snowmelt were measured at three Japanese cedar stands and an opening. The degree of canopy closure in cedar stand A (tree height of 13.2 m, 23 years old) was 17.8%, in stand B (24.8 m, 72 years old) 5.2% and in stand C (36.6 m, ~130 years old) 2.4%. SWE measured at the opening and at stands A, B and C in the pre-snowmelt period, 9 March 2005, was 1048 mm, 1016 mm, 944 mm and 838 mm, respectively, which was the same order as the canopy openness of the sites. The values of SWE in the snowmelt period, 12 April 2005, in the order of smallest to largest were 585 mm (the opening), 639 mm (stand C), 785 mm (stand A) and 825 mm (stand B), which corresponded to the order of the date of snow melt-off, i.e. the snowpack disappeared on 28 April at the opening, 7 May at stand C, 8 May at stand A and 16 May at stand B. However, the order of snow melt-off at the cedar stands did not agree with that of the canopy closure. We calculated heat balance based on the micrometeorological data at each site so that measured snowmelt on a daily basis could be reproduced. The cumulative values of measured daily snowmelt for 20 days at the opening and at stands A, B and C were 571 mm, 357 mm, 311 mm and 345 mm, respectively, while the estimated snowmelt using a heat balance model agreed with those values with an accuracy of 1 mm. At the open site and stand A the major component of snowmelt was net radiation, while at stands B and C net radiation and sensible heat accounted for nearly the same percentage and the contribution of latent heat became large during the last stage of snowmelt. In May the ratio of net radiation to total snowmelt energy tended to decline with increasing canopy closure.
Ecology of collembola (springtails) living on seasonal snow in the deciduous forest in Yamagata Prefecture, Japan
Koki Ishiwatari, Nozomu Takeuchi, Ichiro Tayasu, Tamihisa Ohta
Corresponding author: Koki Ishiwatari
Corresponding author e-mail: firstname.lastname@example.org
Collembola (springtails or snow fleas) are typical insects commonly observed in snowy environments. They are usually black and small (body size < 0.5 mm), and are actively jumping on the snow surface. They occur on snowpacks worldwide, including polar and alpine regions, and may play a role as consumers in the snow ecosystem. However, their lifecycle and food are still not well understood. In this study, we investigated the lifecycle and food resources of the collembola living on the snow surface in deciduous forest in Yamagata Prefecture, Japan. The study site is located at 750 m a.s.l. close to Mt Gassan. In this area, the snow season is November–May; the maximum snow depth is about 6 m in March. We described the morphology of the collembolans observed on the snow surface and identified them. We also investigated temporal and seasonal changes in the population density of collembolans on the snow surface. In order to identify their food resources, we microscopically observed their gut contents. Furthermore, we analyzed the ratios of carbon- and nitrogen-stable isotopes in their bodies and compared the values with those of possible food sources. The collembola specimens collected in this study were mostly Desoria yukinomi, which has been reported as a common species living on the snow surface in Japan. They were found not only on the snow surface but also on a tree trunk. They were found on the tree trunk in the season without snow (October), suggesting that they migrate seasonally between the trunk and the snow surface. Individuals became abundant in the early morning (4:00–6:00) and evening (16:00–18:0). During the day and at night they were observed in the subsurface layer of the snow or under fallen leaves on the snow. This daily cycle suggests that the collembola are not found accidentally on the snow surface, but actively migrate to it. Microscopy revealed that fungi, pollen, algae and spores of lichen were contained in their gut. The nitrogen-stable isotopes of the collembola were –3.2 ± 0.2‰. Two species of lichen were generally low in nitrogen isotope values compared to collembolans, suggesting that they are their most likely food source.
Carbon dynamics in different primary succession stages on the Hailuogou glacier forehead on Gongga mountain, China
Ji Luo, Wei Li
Corresponding author: Wei Li
Corresponding author e-mail: email@example.com
Hailuogou glacier has been retreating since the Little Ice Age and a succession of primary vegetation has taken place in the deglaciated region on Gongga mountain. In the area of glacial retreat at Hailuogou, there developed an integrated and continuous primary succession chronosequence. In the 2 km long chronosequence, the ecological factors change little, human disturbance is small and there is a rich variation of vegetation types, which is helpful for measuring and simulating the cadmium dynamic in the vegetation succession area. Seven sampling sites in vegetation primary succession of the Hailuogou glacier forehead were set up to analysis the organic carbon content in vegetation, coarse woody debris and soil. Furthermore, continuous observations and tests were also carried out at these seven sites. Result shows that organic carbon storage in the seven sites of the primary forest succession was 889.3, 8930.3, 13902.5, 17021.5, 19699.9 ,26121.9 and 34587.4 g C m–2, and the ecosystem components ranged as vegetation > soil > coarse woody debris when comparing organic carbon storage. The carbon flux of soil respiration for the seven sites was 326.7, 265.7, 260.3, 382.5, 555.6, 774.9 and 1030.5 g C m-2 a-1.In case of future climate change, soil respiration in all different stages of succession will increase as the temperature increases; the seasonal pattern of soil respiration in the early stages of succession changes significantly and will be more sensitive to climate change, while the variation tends to be more moderate in the later succession. The total organic carbon storage of ecosystem showed an increasing trend over the succession, and the efficient carbon sinks in the later succession were greater.
Observations and numerical simulations of the braking effect of forest on large-scale avalanches
Yukari Takeuchi, Koichi Nishimura, Abani Patra
Corresponding author: Yukari Takeuchi
Corresponding author e-mail: firstname.lastname@example.org
The role of mountain forests in stopping avalanches is an important topic. The braking effect of forests on snow avalanches has not been investigated in detail; the disaster-reduction effects of forest braking are known empirically but not quantitatively. In this study, we used the avalanche dynamics program TITAN2D to model two large-scale avalanches. One occurred in the Makunosawa valley, Myoko, Japan, in 2008 and damaged the cedar (Cryptomeria japonica) forest, and the other occurred on the west-facing slope of Mt Iwate, Japan, in the winter of 2010/11 and damaged many trees in the subalpine forest, such as Maries’s fir (Abies mariesii) and Erman’s birch (Betula ermanii). Both avalanches damaged many trees and appeared to terminate in the forest. The purpose of this study was to confirm the braking effect of forest by reducing avalanche velocity and eventually terminating it. In our simulations, forested areas were distinguished from non-forested areas by assigning them a larger bed friction angle. Bed friction angles were estimated by trial and error to be 25° in the forested area and 13–14° in the non-forested area, to fit the observation results for the avalanche in the Makunosawa valley. The avalanche flow on Mt Iwate could be calculated accurately when the same bed friction angles were used for the forested and non-forested areas. The simulation revealed that, if the forest had not existed, the avalanche would have traveled 200–m further than the actual termination in the forest in the Makunosawa valley, and more than 500–m further on Mt Iwate. Therefore, the braking effects of forests on the avalanches were confirmed.
The chemical composition of snow cover at Mt Tateyama, Japan, and measurement of bioaerosols in the atmosphere using a real-time viable particle counter
Koichi Watanabe, Taiki Hirai, Hiroshi Sato, Kensuke Fukai, Keisuke Nakagawa, Kohei Takatsuji, Ryosuke Ejiri, Teruya Maki
Corresponding author: Koichi Watanabe
Corresponding author e-mail: email@example.com
Snow cover in high mountain sites preserves environmental signals during cold seasons. Mt Tateyama is located near the coast of the Sea of Japan, where air pollution and Asian dust particles are actively transported from the Asian continent. More than 6 m of snow cover is formed in April near the summit. We have made snow-pit observations and carried out snow sampling at Murododaira (2450 m a.s.l.), Mt Tateyama, every April since 2004. Measurement of the concentrations of ionic constituents and aldehydes of the snow samples has been performed. High concentrations of nssSO42–, which might have been due to trans-boundary air pollution, were measured both in winter and spring snow layers. The mean concentrations of nssSO42– and NO3– in the snow pits were higher than those in 1990s. The mean nssSO42– concentration was highest in the 2007 pit. Concentrations of nssCa2+ were usually high in the upper parts of 2––m of the snow pits deposited in the spring, when Asian dust particles are frequently transported. The high-nssCa2+ layers usually correspond to high nssSO42–. The results show that not only Asian dust particles but also anthropogenic aerosols are transported long-range from the Asian continent. The concentrations of HCHO were well correlated with nssSO42– in the spring layers. Acidic species with HCHO may be transported to high elevations in Japan from the Asian continent. There was no significant correlation between HCHO and CH3CHO. We also performed measurements of microorganism particles (bioaerosols) at a windward site on Mt Tateyama (about 50 km west of Mt Tateyama) using a real-time viable particle counter. Number concentrations of bioaerosol particles clearly increased during the periods of influence of Asian dust. Asian dust particles containing microorganisms may act effectively as ice nuclei.
Temporal trends in the bacterial communities of cryoconite holes
Francesca Pittino, Andrea Franzetti, Federico Navarra, Ilario Tagliaferri, Isabella Gandolfi, Giuseppina Bestetti, Umberto Minora, Roberto S. Azzoni, Guglielmina Diolaiuti
Corresponding author: Francesca Pittino
Corresponding author e-mail: firstname.lastname@example.org
Cryoconite holes are peculiar structure of glacier surfacees first described by the explorer A. E. Nordenskiöld in Greenland in 1870. They are small ponds with a depth and diameter that can range from millimetres to tens of centimetres. These structures, full of melting water, contain a sediment on the bottom (cryoconite) that represents a hot spot of biodiversity, especially for microorganisms (i.e. bacteria, fungi, rotifers, algae, viruses). They are located in many different cold regions (the Poles, the Alps, Patagonia, etc.). The ecological role of these structures in the glacial ecosystem is not yet completely clarified. It is known, for example, that the sediment decreases the albedo effect and that bacterial communities are metabolically active during the ablation season, but a lot still needs to be investigated. This study has been conducted on Ghiacciaio del Forni (Italian Alps, Ortles–Cevedale group), a temperate glacier where cryoconite holes are ephemeral structures that can be repeatedly destroyed and assembled during the ablation season. In this study, the bacterial community of cryoconite holes was investigated, in particular its temporal trends in relation to environmental conditions such as pH, temperature, forecast data, conductivity and oxygen concentration. This study addresses the temporal trend of the cryconite microbial community structure based on samples collected during the ablation seasons of the years 2012, 2013, 2015 and 2016. In 2012 and 2015, samples were collected only in July, while in 2013 and 2016 samples were collected also in August and September. Bacterial communities were characterized by high-throughput DNA sequencing of the 16S rRNA gene. The results of intra-year analyses showed that Cyanobacteria were more predominant in the first part of the ablation season, and this is consistent with the hypothesis that filamentous Cyanobacteria are the first colonizers in ecological succession and responsible for cryoconite grain formation. The other predominant orders were Sphingobacteriales and Burkholderiales. Inter-year analyses showed significant differences between the 4 years considered, especially in 2015, when Cyanobacteria were more abundant than in the other years. Intra- and inter-year analyses of this work represent preliminary results to assess whether bacterial communities change after changes in environmental conditions over years, and especially under a global warming scenario.
FrozenNature: the contribution of palynology to reconstruct large-scale paleo fire and vegetation dynamics from high-alpine ice cores
Sandra O. Brügger, Erika Gobet, Michael Sigl, Dimitri Osmont, Tatyana Papina, Natalia Rudaya, Margit Schwikowski, Willy Tinner
Corresponding author: Sandra O. Brügger
Corresponding author e-mail: email@example.com
Wild fires are a disturbance agent across ecosystems, driving vegetation dynamics and societal hazards. They also play an important role in the global carbon budget. Nevertheless, the drivers for long-term biomass burning trends on continental to global scale are still debated. This uncertainty, combined with rising fire severity in past decades, raises major concerns about future management strategies under climate change. Palynology from high-alpine glaciers provides a fairly novel tool to address long-term vegetation dynamics, land-use activities and the role of fire at regional to subcontinental scales. We analyze existing ice cores using pollen and spores as proxies for vegetation composition and structure, microcharcoal for fire activity, and spheroidal carbonaceous particles (SCPs) to infer fossil fuel combustion. Our project concentrates on the geographical regions of Western Europe, Siberia, tropical Amazonia and the Arctic. The regions either contribute greatly to global fire emissions or provide high-quality data for proxy calibration. Here we choose one site, Tsambagarav glacier (4130 m a.s.l.), located in the Mongolian Altai in the Central Asian steppes, to illustrate the potential of our approach. The region is increasingly vulnerable to environmental shifts such as drought and overgrazing, but data about past vegetation and fire dynamics that might contribute to a better understanding of future ecosystem dynamics are scarce. Our record provides unique paleoenvironmental information at the landscape scale with an exceptional temporal resolution and a sound chronology covering the past 5500 years. We present the first microcharcoal-inferred fire history from Mongolia, which we directly link to past vegetation dynamics. Reconstructed mid- to late-Holocene forests collapsed and fire increased, likely in response to climate change. Our results underscore the vulnerability of relic forest ecosystems in the Mongolian Altai and imply that, in these steppic areas, moisture was more important for tree growth than temperature. We conclude that Central Asian forests, including the Russian Altai are highly vulnerable and may rapidly collapse in the future, if global warming is associated with a decline in moisture as anticipated by regional climate models.
Seasonal ecology of snow during spring and summer melt in Svalbard
Archana Dayal, Andrew J. Hodson
Corresponding author: Archana Dayal
Corresponding author e-mail: firstname.lastname@example.org
Melting snow packs provide liquid melt water and act as a reservoir of nutrients (snow is an effective scavenger of aerosols) that enable photoautotrophic and heterotrophic microbial activity. In addition, a melting snowpack profile usually consists of snow and refrozen ice layers with different densities, hardness, structure and water content. We therefore hypothesized that snow stratigraphic differences and the percolation of meltwater through a ripe snow pack will result in greater heterogeneity in microbial cell numbers, species richness, nutrients and viability. To test our hypothesis, field work in Svalbard (High Arctic) was undertaken for a period of 4 months in 2016, from spring to summer at seven different sites on an ice cap, Foxfonna. During this time, changes in Foxfonna’s snow profile were documented via snow depth measurements and systematic sampling of the different surface, intermediate and basal layers as melt season progressed. Shallow snow and ice cores were collected, processed at the University Centre in Svalbard and then several analyses such as flow cytometry, microscopy, pigment studies and nutrient concentrations were conducted at the University of Sheffield. This work also examined the viability of microbes in the different layers in order to gain further insights into ecosystem dynamics and the meltwater export of live or dead cells to downstream ecosystems. Our pigment and flow cytometry results demonstrate low photosynthetic activity and a bacterial dominance in the snow pack. In addition, clear depletion of nitrogen species is observed, indicating possible microbial transformation of nutrients. These data will therefore be used to establish the links between the thermal evolution of a High Arctic snowpack and its seasonal ecology, which will then help us understand the effect of microbial communities on the physical and geochemical properties of snow.
Biogeochemical (biomarker) approaches to Arctic sea-ice reconstructions in Arctic North America: the present as a key to the past
Anna Pienkowski, Samuel Mugo, Craig Neilson, Mark Furze, Jose Santos, Jelena Fleet, Rachael Mackie, Roland Lee, Alix Cage
Corresponding author: Anna Pienkowski
Corresponding author e-mail: email@example.com
The recently observed decrease in Arctic sea ice has raised considerable concern because of its wide-ranging implications for lower latitudes through climate interlinkages and feedback mechanisms. However, in order to contextualize modern and recent sea-ice decline, long-term data are needed beyond the time scale of instrumental measurements (post ~1970s). Proxies preserved in marine sediments provide such indirect measurements of sea-ice variability, as inferred from sedimentology, micropalaeontology and biogeochemistry. A relatively new spring/summer sea-ice proxy is IP25, a C25 mono-unsaturated highly branched isoprenoid alkene biomarker produced by selected sea-ice diatom taxa inhabiting brine channels within first-year ice. Sea-ice melting releases IP25-producing diatoms to the water column, to accumulate in seabed sediments. Although diatoms are prone to dissolution and selective preservation, IP25 preserves well in the sedimentary record, is resistant to degradation and is detectable and stable on scales of thousands to millions of years. To provide a modern baseline on which to base accurate palaeo-sea-ice reconstructions in the Arctic–Atlantic ocean realm, we here present a comprehensive dataset of the IP25 biomarker in surface (modern) sediments across the Canadian Arctic Archipelago and adjacent regions (Baffin Bay, Beaufort Sea). These data are supplemented by open-water-algae biomarkers (brassicasterol), and other biogeochemical (biogenic silica, total organic carbon (TOC)) and sedimentological (grain size) parameters. Although open-water algae (brassicasterol) values are broadly equivalent to those previously reported from Fram Strait, many of the IP25 values within the Canadian Arctic Archipelago are higher than those previously reported around Greenland, and the Eurasian Arctic, possibly reflecting the different oceanographic settings (archipelago shelf sea vs open ocean). We discuss complicating factors in the biomarker approach, including absolute vs TOC-normalized biomarker values and regional scaling factors, as well as post-depositional and post-sampling degradation. We conclude by comparing the biomarker approach to sea-ice reconstructions with other methodologies based on micropalaeontology.
Island biogeography of cryoconite hole microbial communities in Antarctica’s Taylor Valley and around the world
John Darcy, Pacifica Sommers, Dorota Porazinska, Steve Schmidt
Corresponding author: John Darcy
Corresponding author e-mail: firstname.lastname@example.org
Antarctic glaciers are often thought of as large abiotic geological features, but microbes living on and within these glaciers are important components of mass balance, carbon exchange and hydrological budgets. These microbes arrive on glaciers in the McMurdo Dry Valleys via wind-born sediment, and the predominance of microbial life on a glacier occurs within melted-in pockets of sediment called cryoconite holes – ‘islands’ of liquid water formed as the sediment absorbs solar energy. Since the Dry Valleys experience frequent and strong winds, it is tempting to assume that microbes are transported easily between glaciers and between cryoconite holes, leading to cosmopolitan spatial distributions. However, preliminary work based on limited microscopic observations of algae, diatoms and mesofauna suggested that different glaciers within the Taylor Valley harbor distinct microbial communities, even though the vast majority (i.e. almost all) of Antarctic cryoconite microbes have yet to be described. Here, we present a thorough biogeographic investigation of the Canada, Commonwealth and Taylor glaciers at scales from several centimeters to several kilometers, using DNA sequence data spanning all three domains of life. We present our results in the context of the theory of island biogeography, by testing predictions it makes about the biodiversity, biogeochemical properties and spatial structuring of cryoconite-hole microbial communities. Specifically, the theory of island biogeography predicts that larger islands house more taxa, and this was true for cryoconite holes, since larger holes (more surface area) were found to contain more species richness. This observation correlated with the biogeochemical properties of cryoconite holes, where larger, more diverse holes contained higher concentrations of inorganic N and dissolved organic C than smaller, less diverse holes. To analyze the spatial structuring of cryoconite hole microbial communities, we expanded the scope of our study to a global scale by incorporating DNA sequencing data from multiple previous studies of cryoconite holes. This global meta-analysis revealed strong spatial structuring of cryoconite-hole bacterial communities at the continental scale.
The UK Polar Network: inspiring the next generation of polar scientists
Archana Dayal, Kyle Mayers, Chelsey Baker, Malu Avila, Samantha Buzzard, Tun Juan Young
Corresponding author: Archana Dayal
Corresponding author e-mail: email@example.com
The UK Polar Network is a national committee of the Association of Polar Early Career Scientists (APECS) with 600 members across the UK, ranging from undergraduates to postdocs. Our primary goals are (1) organizing and participating in career development programmes, (2) conducting education and outreach activities to inspire and enthuse young minds about the Polar Regions and (3) providing early career support and representation on national and international polar organizations such as the UK Arctic & Antarctic Partnership (UKAAP) committee, Antarctic Science Ltd, the UK National Committee on Antarctic Research (UKNCAR) and others. Our education and outreach activities include school visits, science festivals, workshops wherein we organize polar-related activities to generate interest and inspire budding scientists. One of our most successful outreach activities has been the Antarctica Day Flag event where school students design flags for Antarctica, which are then sent south, with research expedition members participating, from not only the UK but also New Zealand, Belgium and Australia. We also received worldwide participation in this activity and last year successfully sent 232 flags with 40 schools participating from 11 countries, of which 18 were from the UK. Our upcoming activities in 2018 include organizing UK–Russia Year in science workshops, science festivals, school visits and live feeds on science and life from Antarctic research stations. Through our network, early-career researchers experience personal and professional development, are presented with unique opportunities and develop excellent networking and outreach skills. During this poster presentation, we aim to introduce these networks and the work they conduct to the participants. We therefore hope to provide stimulus and ideas to the future generation of cryospheric scientists as well as discuss on the future directions for polar science outreach.
Characteristics and sources of dissolved organic matter in a glacier in the northern Tibetan Plateau: differing between glacial zones and seasons
Lin Feng, Jianzhong Xu, Yanqing An, Shangchang Kang
Corresponding author: Lin Feng
Corresponding author e-mail: firstname.lastname@example.org
Dissolved organic matter (DOM) in mountain glaciers is an important nutrient for downstream aquatic systems and increasingly impacts on remote ecosystems due to the increased melting rate of glaciers. We present a comprehensive study on Laohugou glacier No. 12 (LHG), at the northern edge of the Tibetan Plateau, to characterize the DOM content and source by analyzing surface snow/ice samples collected from the ablation zone and snow-pit samples dug from the accumulation zone in 2015. The snow samples in the snow pit covered a whole year record and were divided into warm and cold period samples (summer and winter snow) according to measurements of an oxygen isotope (δ18O), which is an index of air temperature. The mass concentrations of dissolved organic carbon (DOC) in fresh snow were higher than in granular ice (aged snow), yet with little difference between summer and winter snow samples in the snow pit. These mass concentration differences were also proved by ultraviolet–visible absorption spectrum analysis, in which more DOC content had a higher absorption strength. Excitation emission matrix fluorescence spectroscopy analysis on the DOM with parallel factor analysis (EEM-PARAFAC) identified four components, including a microbially humic-like component (C1), two protein-like components (C2 and C4), and a terrestrial humic-like component (C3). The use of Fourier transform ion cyclotron resonance mass spectrometry (FT-ICR-MS) showed the DOM from all these samples was dominated by lipids and proteins, which reflected the presence of significant amounts of microbially derived and/or deposited biogenic DOM. However, the molecular-level composition of DOM showed more lignin contribution in snow/ice from the ablation zone and more microbially derived DOM contribution in the snow pit in the accumulation zone, suggesting that the DOM in the ablation zone was more affected by terrestrial material and the DOM in the snow pit in the accumulation zone was more modified by microbes.
The wingless winter stonefly and its food on snowfields in Japan: analysis of the food web using stable isotopes of carbon and nitrogen
Chika Okamoto, Nozomu Takeuchi, Ichiro Tayasu, Tamihisa Ohta
Corresponding author: Chika Okamoto
Corresponding author e-mail: email@example.com
On snow and ice surfaces, there are diverse living organisms that are adapted to a cold environment. For example, snow algae, heterotrophic bacteria and insects can be found on Japanese snowfields. A wingless winter stonefly is one of the typical insects that appear on the snow surface in mountainous regions during winter or spring in Japan. Although they spend most of their time on the snow surface, their food resources are still not well-known. It is important to clarify the food web of the organisms living in snowfields to understand carbon and nitrogen cycles quantitatively in snow and ice environments. The stable-isotope ratios of C and N of the specimens provide a means of analyzing their food resources. In this study, we analyzed the food webs of the winter stoneflies and other organisms on Japanese snow fields using C and N stable-isotope analysis. The stonefly specimens were collected on the snow surface at six sites in Japan during spring in 2015 and 2016. The study sites included two sites in Yamagata (150 and 1300 m a.s.l.), one site in Niigata (210 m a.s.l.), one site in Nagano (1300 m a.s.l.), two sites in Toyama (490 and 2300 m a.s.l.). Furthermore, other specimens including springtails, spiders, leaves, snow algae and particulate organic matter found on the snow were collected. The δ13C and δ13N values of the stoneflies varied from –30.5 to –24.1‰ and from –1.2 to +1.7‰, respectively. As compared with those of other organic matter collected on the snow surfaces, the δ13N values of the stoneflies were significantly higher than those of dead leaves, springtails, aphids, small spiders and snow algae, while they were lower than those of big spiders and centipedes. Based on the enrichment of C and N stable isotopes in trophic levels, the results suggest that potential food sources of the stoneflies are mainly dead leaves, and also springtails, aphids and small spiders, but are unlikely to include snow algae. The difference of δ13N between the stoneflies and dead leaves varied among the study sites, suggesting that the stoneflies eat mainly dead leaves but also eat some additional foods that vary among the study sites.
Biogeography and demographic analysis of cryoconite-forming cyanobacteria on glaciers
Takahiro Segawa, Takahiro Yonezawa, Arwyn Edwards, Koji Fujita, Vladimir Eisen, Francisco Navarro, Zhongqin Li, Nozomu Takeuchi
Corresponding author: Takahiro Segawa
Corresponding author e-mail: firstname.lastname@example.org
Cryoconite, a microbe-mineral aggregate found on glaciers worldwide, is formed by the action of microbial phototrophs, principally Cyanobacteria. Despite the ecological importance in supraglacial environments, the phylogeographic distributions and genetic structures of supraglacial cyanobacteria are hardly known. Here we present detailed pictures of their geographical distribution over the Arctic, Antarctic, and High Mountain Asia based on combined sequences of 16S rRNA and 16S–23S internal transcribed spacer (ITS) regions determined by the long read strategy in 38 glacial samples. The cyanobacterial 16S rRNA sequences were grouped into only 20 OTUs and the major six OTUs were distributed widely from polar to Asian glaciers, suggesting that they are cosmopolitan in species level. However, analysis of the more variable ITS region revealed geographical differentiation at the strain level. A total of 19 OTUs, including the six major OTUs, showed considerable genetic differentiation among geographic regions; at the population level they are thus geographically restricted. This suggests that selection pressures among geographic regions are strong driving forces shaping genetic structure in cyanobacteria. Despite the crucial role of cyanobacteria in various ecosystems, little is known about cyanobacterial evolutionary histories, especially microevolutionary dynamics such as fluctuations in population size and genetic differentiation processes, because of the lack of knowledge regarding cyanobacterial mutation rates. Therefore, we directly estimated cyanobacterial mutation rates based on analysis of ancient DNA from ice core samples collected from Kyrgyzstan that dates back to approximately 12 500
Growth of ice crystals in the presence of type 3 antifreeze protein
Dmitry Vorontsov, Gen Sazaki, Evgeniya Titaeva, Yoshinori Furukawa
Corresponding author: Dmitry Vorontsov
Corresponding author e-mail: email@example.com
Antifreeze proteins (AFPs) exhibit a strong ability to control the nucleation and growth of ice. The inhibition effect of AFPs on the recrystallization and growth of ice is very common in nature, and it helps living organisms (sea fish, plants, insects) to survive in a subzero environment. A great interest in the properties of AFPs in biology, physics, chemistry and engineering is explained by high expectations for the applications of AFPs in the food industry, medicine and cryobiology. The purpose of our research is to explore how type 3 AFP (AFP-III) modifies the morphology and growth kinetics of ice crystals, and to reveal the action mechanisms of AFP-III. In a glass capillary tube seed crystals of ice of hexagonal modification were formed in supercooled water with AFP-III concentrations of 0–0.8 mg ml–1. Measurements of growth rates were performed by Mach–Zehnder interferometry at supercooled temperatures from 0–1.0K. We have found that AFP-III exhibits an extremely high activity. Even at a concentration of 0.001 mg ml–1 it changes the morphology of ice crystals, and prismatic faces appear instead of the circular disk-like shapes typical of growth in pure water. Our measurements of growth rates have shown that AFP-III molecules can act both as an inhibitor for the prismatic faces and as a promoter for the basal faces of ice crystals, and cause the formation of macrosteps on the basal faces. The value of growth thermal hysteresis rises non-linearly with the increase in AFP-III concentration. The influence of AFP-III on the crystallization of ice was explained by adsorption of the protein molecules on the crystal surface. Retardation of ice growth in the presence of AFP-III occurs due to blocking of the prismatic faces by adsorbed protein molecules. From thermodynamics, it can be expected that a prismatic face covered by the protein molecules will be able to grow when the intermolecule distance exceeds the critical value predicted by the Gibbs–Thomson law. Direct observations by confocal fluorescent microscopy of the protein molecules labeled with a fluorescent isocyanate allowed an estimate of the average distance between AFP-III adsorbed on the prismatic surface of ice crystals. The theoretical values of the freezing point depression in the presence of AFP-III corresponded with the experimental data when we assumed that AFP-III decreased the surface free energy of the faces of the ice crystal. The supports of JSPScience and Hokkaido University is gratefully acknowledged.
The characteristics of cryoconite granules in the glacial forefield of Ürümqi Glacier No.1, Tien Shan, China
Masato Shiomuki, Nozomu Takeuchi, Zhongqin Li
Corresponding author: Masato Shiomuki
Corresponding author e-mail: firstname.lastname@example.org
Cryoconite is dark-colored surface dust in the ablation area of glaciers. It usually consists of organic matters produced by microbes on glaciers and inorganic particles such as windblown mineral dust, and often forms spherical aggregations called cryoconite granules. The characteristics of cryoconite have been well studied on many glaciers in the world, since cryoconite can reduce surface albedo and accelerate the melting of glaciers. Cryoconite is finally washed out of glacier by running meltwater, accumulates in glacial forefields and may contribute to the formation of organic soils downstream of the glaciers. In particular, cryoconite acuumulation would be significant in Central Asia since the cryoconite is generally more abundant than in other polar glaciers. However, studies of cryoconite in the glacial forefields of Central Asia are still limited. In this study, we analyzed the distribution and decaying process of cryoconite granules collected along the meltwater river in the glacial forefield of Ürümqi Glacier No.1, Tien, Shan, China. Cryoconite granules were found in the river flowing from the glacial forefield for a distance of approximately 1600 m from the glacier terminus. The mean size of the granules generally decreased with the distance from the glacier terminus. Microscopy revealed that there were granules that had fewer cyanobacteria and cracks on the surface, and the abundance of such granules increased with the distance from the glacier terminus. The percentages of the granules were 14%, 22%, and 41% at the sites of 400 m, 800 m and 1200 m from the glacier terminus respectively. The water temperature of the river was 1.3°C near the terminus, but was 8.4C 1000 m downstream, suggesting that the increase of water temperature inhibits the activity of microbes in the cryoconite that had been originally active on the glacial ice. Results suggest that cryoconite granules washed out of the glacier keep their granular shape for a while but are gradually decomposed as they move downstream.
A comparative study of the formation of cryoconite granules and sludge-originated photogranules
Chul Park, Wenye C. Kuo-Dahab, Gitau J. Gikonyo, Nozomu Takeuchi
Corresponding author: Chul Park
Corresponding author e-mail: email@example.com
Cryoconite granules are sedimentary agglomerates found in the base of melt holes on glacier surfaces. These glacial aggregates have been shown to possess phototrophic microorganisms, including cyanobacteria, green algae, diatoms and other general microbes, such as protozoa and heterotrophic bacteria with a high content of inorganic matter. An earlier study showed that the structure of this granular biomass is basically maintained by a network of filamentous cyanobacteria that enclose the inner biomass and mineral particles. Cryoconite granules contribute to the reduction of albedo from glacier surfaces. These granules may also be washed off, along with melting and destruction of holes, and redistributed over the surface, which then can become the source of new granules and holes. Hence, their hydrological and ecological role in the glacial system cannot be overlooked. Despite this importance, our understanding of the formation of cryoconite granules remains rather limited. Recently, a similar granule type has been reported from a seemingly unrelated field. These granules, named oxygenic photogranules (OPGs), were originally found from the incubation of activated sludge under hydrostatic conditions. Activated sludge, used in contemporary wastewater treatment, usually has extremely low levels of phototrophic microbes. However, its incubation in a closed glass vial under hydrostatic conditions with illumination leads to an enrichment of filamentous cyanobacteria, changing flocculent sludge into spherical granular biomass. Despite the substantially different ‘cultivation’ environment, cryoconite granules and OPGs seem to share the hydraulic conditions under which they are generated, because cryoconite granules are also formed within semi-stagnant melt holes. Nevertheless, since OPGs can also be produced in water with the presence of high mixing, a quiescent hydraulic condition alone may not explain this ‘photogranulation’ phenomenon. This study discusses further conditions that may serve as selection pressures leading to the formation of cryoconite granules and OPGs. We will also discuss the structural, ecological, and physicochemical characteristics of both granules. This study is expected to be helpful in achieving a better understanding of the formation of photogranules, which seems to occur across extremely diverse environments.
Pigment composition of a cultivated strain of the cyanobacterium Phormidesmis priestleyi isolated from cryoconite on Qaanaaq Glacier, northwest Greenland
Ayumi Kizawa, Jun Uetake, Makiko Kosugi, Shigeki Ehira, Nozomu Takeuchi
Corresponding author: Nozomu Takeuchi
Corresponding author e-mail: firstname.lastname@example.org
Cyanobacteria are oxygen-generating photosynthetic microorganisms widely distributed in terrestrial and aquatic environments. Several cyanobacterial species are found in polar and high alpine habitats, and they contribute to the darkening and melt enhancement of glaciers. Cyanobacteria contain pigmented compounds, mainly light-absorbing pigments related to photosynthesis (chlorophyll a and phycocyanin) and photoprotection (carotenoids and scytonemin). Therefore, the intracellular pigment composition and concentration may directly affect photosynthetic activity and the resistance of high-intensity visible and ultraviolet (UV) light. Cyanobacteria are found on glacier surfaces during melting seasons, and they must accomplish photosynthesis under unstable light and nutrient conditions. However, the effects of external environmental conditions on the pigment composition of cyanobacteria living on glaciers are largely unknown. The aim of our study is to identify the pigment composition of a cultivated strain of filamentous cyanobacterium Phormidesmis priestleyi isolated from cryoconite on Qaanaaq Glacier, northwest Greenland, under different environmental conditions such as light intensity and nutrient concentration. P. priestlyi was grown in diluted BG-11 medium (optimized synthetic medium for most cyanobacteria) at 17°C under continuous light (9 μmol photons m–2 s–1). The pigment composition of P. priestleyi was estimated by absorption spectrum analysis and thin-layer chromatography. The location of pigmented compounds was observed by fluorescence microscopy. The color of colonies of P. priestlyi dramatically changed with the concentration of medium, growth period and growth light intensity. When P. priestleyi was grown in highly diluted medium and/or for a prolonged period, the color changed from blue-green to orange, the carotenoids/chlorophyll ratio became higher, and UV absorption compounds, such as scytonemin, appeared in the absorption spectrum. In contrast, when P. priestleyi was grown under high-light conditions (27 μmol photons m–2 s–1), the color became dark grey. These results suggest that the composition and concentration of light-absorbing pigments related to photosynthesis and photoprotection in P. priestleyi is regulated in response to changes in light intensity and nutrient conditions on glaciers.
Physiological characterization of a bacterial community, cryoconites, on the glacial surface in Spitsbergen, Svalbard
Makiko Kosugi, Mitsuhiro Yano, Jun Uetake, Yuichi Suwa, Hiroyuki Koike
Corresponding author: Makiko Kosugi
Corresponding author e-mail: email@example.com
Cryoconite particles, bacterial communities constructed on the surface of a glacier, have a critical role for ecosystems in glacial environments. Cryoconite particles maintain their internal material cycle in spite of severe conditions. We carried out some incubation experiments in their habitat, cryoconite holes, at Austre Brøggerbreen, Ny-Ålesund, Spitsbergen, Svalbard, to clarify the characteristic features of their physiology, e.g. photosynthesis, respiration and nitrogen fixation. Photosynthetic activity was measured using a stable isotope of water (oxygen-18), and measuring concentrations of both CO2 and 18O16O with gas chromatography and mass spectroscopy (GCMS). CO2 fixation under the habitat was especially suppressed because of the low temperature, near to zero; however, the rate of O2 generation caused by water splitting in photosystem II was much higher than CO2 fixation. This result suggests that there are some alternative electron transport reactions for protecting photosystems from excess reduction in power. The temperature dependency of photosynthetic activity was measured by using a PAM chlorophyll fluorometer. The most suitable temperature for photosynthesis was around 30°C. Some photosynthetic activity was preserved even at 0°C, although it was suppressed under 10°C. These results revealed that photosynthetic organisms in cryoconite particles experience suppressed activity of CO2 fixation under low temperature condition, however they show prominent activity of alternative electron transport mechanisms, to avoid photoinhibition.
Masking effect of vegetation on snow albedo feedback in a future climate change projection
Corresponding author: Manabu Abe
Corresponding author e-mail: firstname.lastname@example.org
Multiple climate models have projected that the snow-cover area in high latitudes will decrease with future global warming. The decrease in snow cover enhances surface warming with reduced surface albedo, and then the enhanced warming decreases the snow cover further. This positive feedback is called the snow albedo feedback (SAF). The effects of SAF in northern high-latitude regions in the Earth system model MIROC-ESM were examined under the future climate scenario RCP8.5. In MIROC-ESM, the leaf area index (LAI) is calculated interactively with an ecological land model. The simulated surface air temperature (SAT) in spring increases greatly across Siberia, whereas the snow cover decreases significantly only in western Eurasia. Our analysis shows that, in Siberia, both the reduced snow-cover fraction and the surface albedo of the snow-covered portion, reduced by the vegetation masking effect in the grid cells, caused the strong SAF that led to the large increase in SAT. A comparison of the future changes with and without interactive LAI changes shows that the masking effect of vegetation increases the spring SAF in Siberia by approximately 1.5 times. This implies that a future increase in vegetation biomass is a potential contributing factor to warming. The masking effect of vegetation may be needed to be researched further for reliable future projection.
Analysis of the community structure and metagenome of the bacterial consortium from the gut of the glacier stonefly
Takumi Murakami, Takahiro Segawa, Nozomu Takeuchi, Gonzalo Barcaza Sepulveda, Shiro Kohshima, Yuichi Hongoh
Corresponding author: Takumi Murakami
Corresponding author e-mail: email@example.com
In recent decades, investigations on glacier ecosystems have intensely been conducted; nevertheless, most of those have focused on microorganisms, and information on invertebrates, which are the major consumers in glacier environments, is still limited. To understand the ecological roles of these glacier invertebrates in detail, we have focused on their gut-associated bacterial communities, which would play important roles in the host’s nutrition and material cycles in glacier environments. In this study, we conducted the sequencing of bacterial 16S rRNA gene amplicons and metagenomic analyses on the gut bacterial community of the glacier stonefly Andiperla willinki in order to reveal their community structure and metabolic capabilities. DNA was extracted from the gut and feces of the glacier stoneflies. Bacterial 16S rRNA gene amplicons and fecal metagenome were sequenced on the Illumina MiSeq platform. We conducted the same analyses on the bacterial communities on their habitat glacier surfaces for comparison. Additionally, the localization of several dominant bacterial lineages in the stonefly’s gut was identified by using fluorescence in situ hybridization (FISH). The bacterial gut community of glacier stoneflies exhibited quite different community structure from those on their habitat glacier surfaces. Notably, several gut-symbiotic bacterial lineages such as Lachnospiraceae and Porphyromonadaceae were abundantly and exclusively detected from the glacier stonefly samples. FISH analysis revealed that they densely colonized the gut of the glacier stoneflies. Furthermore, draft genomes of these gut-associated bacterial lineages were reconstructed from the fecal metagenomes. Genes retained in these draft genomes suggested that they possess the metabolic capability to digest recalcitrant polysaccharides contained in the host’s food such as algae. These results imply that the gut bacteria of the glacier stonefly contribute to the host’s nutrition and material cycles in glacial environments.
Simulating topographic controls on the abundance of larch forest in eastern Siberia, and its consequences under changing climate
Hisashi Sato, Hideki Kobayashi
Corresponding author: Hisashi Sato
Corresponding author e-mail: firstname.lastname@example.org
In eastern Siberia, larches (Larix spp.) often exist in pure stands, comprising the world’s largest coniferous forest, changes to which can significantly affect the Earth’s albedo and the global carbon balance. Our previous studies tried to reconstruct this vegetation, aiming to forecast its structures and functions under a changing climate. In previous studies simulating vegetation at large geographical scales, the examining area is divided into coarse grid cells such as 0.5 × 0.5° resolution, and topographical heterogeneities within each grid cell are just ignored. However, in the Siberian larch area, located on the environmental edge of the existence of the forest ecosystem, the abundance of larch trees depends largely on topographic conditions at the scale of tens to hundreds of meters. In our preliminary analysis, we found a quantitative pattern that topographic properties control the abundance of larch forest in eastern Siberia via both drought and flooding stresses. We therefore refined the hydrological sub-model of our dynamic vegetation model SEIB-DGVM, confirmed that the modified model can reconstruct the pattern and examined its impact on the estimation of biomass and vegetation productivity under the current and forecast future climatic conditions.
The effect of canopy drip on snow algal bloom in the deciduous forest of Mt Gassan, Yamagata prefecture, Japan
Akane Watanabe, Nozomu Takeuchi
Corresponding author: Akane Watanabe
Corresponding author e-mail: email@example.com
Blooms of snow algae usually become visible on open snowfields in polar and alpine regions as red snow, but also on snow at the forest floor as mostly green snow. Such snow algae on the forest floor may have a different life history from those on open snowfields, since the snow should be associated with trees and other organisms living in the forest. However, the life history and conditions for blooms of snow algae on the forest floor are still not understood well. This study aims to describe the temporal changes in the snow algal community and the physical and chemical conditions of snow in the deciduous forest in Japan and discuss the conditions causing the algal bloom. The field investigations were conducted biweekly over the melting season (April–May) in 2016 and 2017 in Mt Gassan, Yamagata prefecture, Japan. The study site is located at 750 m a.s.l. in a Japanese beech forest. The maximum snow depth exceeds 3 m during winter and gradually melts after March. Green algal snow appears on the snow surface in the melting season. We collected snow samples from the surface and a vertical pit and samples of rain water in the forest. Chlorophyll a, EC, pH and major soluble ions in the samples were analyzed. Algae in the samples were observed with a microscope. Green algal snow was not observed in early April but appeared patchily in late April on the forest floor. From late April to May, the number of green algal patches increased. Microscopy revealed that the green snow mainly contained spherical and oval green algal cells. The algal patches were observed more often on the surface under the trees than on the open sunny surface. Chlorophyll a concentration gradually increased in the snow under the trees during the study period. Phosphate concentrations in the snow were low in early April and increased in snow under the trees, but retained their low values on the open snow surface. Phosphate was not detected in rain water in late April, but was detected in early May at the forest floor, while it was not contained in the rain in open sunny areas. These results suggest that phosphate was supplied to the snow surface by the rain water dripping from the trees and induced the algal bloom.
Permafrost environment at the bottom of a block slope enabling alpine flora to survive at 1300 m a.s.l., 36.6°N
Corresponding author: Kaoru Izumi
Corresponding author e-mail: firstname.lastname@example.org
It is known that a small area of natural ice on the ground exists even in summer in the deepest part of Kohri-dani (which means ‘ice valley’), Kusatsu town, Gunma prefecture, Japan. As the altitude and latitude of Kohri-dani are 1300 m a.s.l. and 36.6°N, it is a rare phenomenon in Japan for natural ice to exist at such low altitude and latitude even in summer. We found local permafrost under the ice where it is in front of a wind-hole at the bottom of a block slope. Temperature observations near the wind-hole indicate that the active layer under the snowpack continues to freeze until snowmelt season. In the spring, snowmelt water flows down to the frozen ground and refreezes as the basal ice. After the snow melts, a cold wind begins to blow out from the wind-hole until the fall. Due to the cooling effect of this cold wind (0–3°C, 0.5 m s–1), the basal ice is preserved until summer and alpine flora can survive near the wind-hole even in the hot season. Ground temperatures in the active layer increase from snowmelt season to late fall, but the permafrost below ~1 m under the ground surface continues to freeze throughout the year.
Influence of a deciduous broad-leaved forest on snow-surface energy balance in Chilean Patagonia
Takane Matsumoto, Katsuhisa Kawashima, Tsutomu Iyobe
Corresponding author: Takane Matsumoto
Corresponding author e-mail: email@example.com
Native forests dominated by tree species peculiar to the Southern Hemisphere widely cover snowy regions in southwestern South America. However, the influence of such forests on snow accumulation and ablation in South America has never been studied. This study aims to evaluate the influence of a native forest of lenga (Nothofagus pumilio), a deciduous broad-leaved tree, in central Chilean Patagonia on snow-surface energy balance, comparing meteorological elements and heat fluxes measured in the forest and those at an open site nearby. Field observations were carried out at Portezuelo Ibáñez (46°04′ S, 72°02′ W, 1110 m a.s.l.), a pass 55 km south of the city of Coyhaique in the Aysén Region, southern Chile, during the period from mid-September to mid-October 2012. Weather stations measured and recorded air temperature, relative humidity, up-/downward shortwave radiation, up-/downward longwave radiation, wind speed, wind direction, precipitation and snow depth at 10 min intervals at two sites: LNG, in the lenga forest (stand density: 1875 trees ha-1, mean DBH: 19 cm, dominant height: 11.6 m, PAI: 1.4), and OPN, in the open field 250 m from LNG. Evaporation/condensation from the snow surface was directly measured 5 times at each site using plastic dishes filled with snow. The turbulent heat fluxes were calculated using a bulk aerodynamic approach and it was decided that the bulk exchange coefficients were best fitted to the measured evaporation/condensation rates and other meteorological conditions. Because of the difficulty of obtaining accurate albedo on the snow surface below the canopy, we assumed in this study that the snow albedo at LNG was the same as that at OPN in any time. The snow depth at OPN in mid-September 2012 was around 70 cm, and snow cover completely melted out in mid-October. During this period, the global radiation and the wind speed at LNG were on average 34% and 32%, respectively, of those at OPN, whereas the air temperature and the relative humidity at LNG were always quite close to those at OPN. As a result of such differences in meteorological conditions, the net radiation, the sensible heat flux and the latent heat flux at LNG were on average 43%, 54% and 58%, respectively, of those at OPN. Consequently, the mean heat source for snowmelt at LNG was 27.2 W m–2, corresponding to 47% of that at OPN (57.8 W m–2). This ratio tended to be larger on clear days (52%) than on cloudy/rainy days (41%).
Estimation of Antarctic land-fast sea ice algal biomass and snow thickness from under-ice radiance spectra in two contrasting areas
Pat Wongpan, Klaus Meiners, Pat Langhorne, Petra Heil, Inga Smith, Greg Leonard, Rob Massom, Lesley Clementson, Tim Haskell
Corresponding author: Pat Wongpan
Corresponding author e-mail: firstname.lastname@example.org
Fast ice is an important component of Antarctic coastal ecosystems, providing a habitat for thriving ice algal communities. This work examines the relationships between the normalized difference indices (NDI) calculated from under-ice radiance measurements and both sea ice algal biomass and snow thickness for Antarctic fast ice. While this technique has been calibrated to assess biomass in Arctic fast ice and pack ice, as well as Antarctic pack ice, relationships are currently lacking for Antarctic fast ice. We analyze measurements along transect lines at two contrasting fast ice sites: near (affected by platelet ice) and distant from an ice shelf, i.e. in McMurdo Sound and off Davis Station, respectively. Snow and ice thickness, and ice salinity and temperature measurements underpin our paired in situ optical and biological measurements. NDI wavelength pairs near the first chlorophyll a (chl a) absorption peak (≈440 nm) explain up to 70% of the total variability in algal biomass. Snow thickness is estimated from an NDI with a wavelength pair of 648 nm and 567 nm explaining 88% of its total variability. Accounting for pigment packaging effects by including the ratio of chl a specific absorption coefficients improved the NDI-based algal biomass estimation only slightly. Our new observation-based algorithms can be applied to estimate Antarctic fast-ice algal biomass and snow thickness non-invasively, for example using moored sensors (time-series) or mapping their spatial distributions using underwater vehicles.
Life in the dark side of a glacier: supraglacial debris and bacterial communities of Ghiacciaio del Forni, central Italian Alps
Roberto S. Azzoni, Roberto Ambrosini, Francesca Pittino, Andrea Zerboni, Guglielmina A. Diolaiuti, Andrea Franzetti
Corresponding author: Roberto Sergio Azzoni
Corresponding author e-mail: email@example.com
It is generally believed that glaciers are white, inhospitable and cold deserts, substantially lacking of any forms of life. On the contrary: ice bodies present a dark side, teeming with life. In this work we focused on the supraglacial debris, on organisms that live within it and on the ecological processes acting in it, which are strictly linked to the evolution of glaciers’ surface. The glacier under magnifying glass is Ghiacciaio del Forni, one of the most important Italian glaciers located in the central Italian Alps. On this ice body, since 2011, many field campaigns have been performed in order to deepen our knowledge of the evolution of supraglacial debris and about sources and characteristics of bacterial communities living therein. From a glaciological point of view, we observed a wide increasing of the debris cover in a short time and quantified its impact on ice albedo. The rapid darkening process greatly influences the bacterial communities of the debris cover. Consequently, we investigated the potential contribution of ice-marginal environments, which may act as sources of both debris and bacteria for cryoconite holes. We observed that differences in environmental conditions limit the number of bacterial strains that may survive in cryoconites. Furthermore, we analyse the large variability of characteristics of supraglacial debris and of cryoconite communities during an ablation season, noting a rapid change in the ecological condition of the hole and consequent temporal variation in the communities. Finally, we considered human impact on the dark side of the glacier: in cryoconite holes we found a relevant quantity of black carbon and we also describe the crucial role in the biodegradation of a contaminant (chlorpyrifos, an organophosphorus insecticide) played by the bacterial communities of cryoconite holes.
The secret life of icy bacteria: physiological adaptations to the variability of cryoconite hole environments
Ewa Poniecka, Elizabeth Bagshaw, Henrik Sass, Christopher Williamson, Alexandre Anesio, Martyn Tranter
Corresponding author: Ewa Poniecka
Corresponding author e-mail: PonieckaEA@cardiff.ac.uk
Polar regions serve as a natural laboratory for the study of simplified microbial and biogeochemical processes in habitable niches. An example of such niches are cryoconite holes, regarded as hotspots of microbial processes on glacier surfaces. Microscale measurements of oxygen show that the cryoconite environment is spatially and temporally variable, with complex feedbacks between physical and biogeochemical conditions. Within the community, heterotrophic bacteria are believed to sustain the ecosystem by decomposing organic matter and releasing nutrients. Data on how microorganisms, especially anaerobic ones, function in cryoconite holes are, however, scarce. We applied a range of microbiological tests to understand the physiological capabilities of the most abundant cultivable microorganisms from cryoconite holes worldwide (Greenland, Svalbard, Antarctica). Oxic and anoxic conditions were applied to mimic the microniches within the habitat. The growth of bacteria was assessed under a range of treatments: freeze–thaw cycles, temperature gradients and varying organic carbon substrates. In anaerobic incubations, the largest proportion of the community was able to grow in the lowest tested temperature (0.2°C). Furthermore, most of the anaerobic strains were able to thrive in oxic conditions. Similarly, many oxic strains were able to survive without oxygen. Freeze–thaw incubations revealed the contrasting capacity of microorganisms to survive multiple cycles, depending on the presence of a cell wall. The heterotrophs were able to utilize a wide range of carbon substrates, with a preference for less complex organic compounds. Our study demonstrates that heterotrophs of cryoconite holes are adapted to fast-changing environmental conditions by their ability to survive multiple freeze–thaw cycles and changing oxygen conditions, and scavenging a wide range of organic substrates. The elevated growth of the anaerobic part of the community in the lowest temperatures indicates they might be key players in winter conditions or in early melt season, when the oxygen is likely depleted and accumulated dead cells provide a source of organic matter for scavenging. Consequently, anaerobic heterotrophs might contribute to springtime ‘ionic pulses’ and the reactivation of the community after the polar night.
InSAR observation of seasonal ground subsidence due to a tundra wild fire near Batagay, Siberia
Kazuki Yanagiya, Masato Furuya
Corresponding author: Kazuki Yanagiya
Corresponding author e-mail: firstname.lastname@example.org
Thawing of permafrost can lead to ground deformation. Ground deformation has been studied as a serious problem in the Arctic region for a long time, because the deformation causes damage to built structures in these areas. On the other hand, in relation to recent global warming, the importance of organic carbon stored in permafrost is pointed out. Although the release of methane gas has been confirmed in some thermokarst lakes, it is difficult to directly observe the permafrost in a wide area by field study. Instead, it is technically possible to monitor the subsidence and uplift of the ground over the permafrost area, which could potentially make a significant contribution to monitoring thawing processes of permafrost. In this study, we attempted to detect a ground deformation signal in permafrost area by remote sensing using two SAR (Synthetic Aperture Radar) satellites, ALOS2 and Sentinel-1. ALOS2 is the L-band SAR satellite launched by JAXA and Sentinel-1 is the C-band SAR radar launched by ESA. We detected ground deformation using recently acquired data from 2014–17. Focusing on the mega-slump terrain caused by thawing permafrost, we examined the area near Batagay, Siberia. We detected ground subsidence signal at 20 km northwest of Batagay. The diameter of the displacements area covers about 7.7 km and at most 10 cm subsidence signal is detected in that area. Notably, the subsidence signals could be detected only during summer. Examining the optical remote sensing images taken by Landsat and MODIS, we noticed that the subsiding area exactly coincided with the area that underwent wild fire in 2014. This is the second case to be detected of ground subsidence associated with an arctic tundra fire, following that detected at North Slope, Alaska, USA. Whereas the wildfire stopped in the middle of August 2014, we could still detect subsidence signals even during 2017. The total radar line-of-sight (LOS) changes reached 10 cm during the period from 30 July 2016 to 8 October 2016. The recent LOS changes in 2017 amount to 6 cm, suggesting a slow-down of thawing.
Thermal response of pyrimidine nucleotide genes expression in the psychrophilic bacterium Glaciibacter superstes
Antonio Mondini, Cristina Purcarea
Corresponding author: Antonio Mondini
Corresponding author e-mail: email@example.com
The response of ice-contained bacteria to environmental changes, in particular to temperature variations in the context of global climate change, is related to structural and functional characteristics of key enzymes and gene expression. To unravel the thermal adaptation mechanisms of DNA synthesis in psychrophilic bacteria, we investigated the structural and functional properties of aspartate transcarbamoylase (ATC) from Glaciibacter superstes, the key enzymes of pyrimidine biosynthesis, and the effect of heat shock treatment on this cold-adapted strain targeting the expression of the corresponding pyrB gene, in order to evaluate the efficiency of this enzyme as a putative biomarker for cellular response to temperature variation. Sequence analysis of G. superstes ATC revealed a series of cold-adaptation structural features, with a reduced Cys and Phe content, and increased Gly content and changes at subunit interface conferring the trimer stability. Functional characterization of the enzyme was carried out using the recombinant psychrophilic ATC obtained by cloning in pHAT2 vector and expression in Escherichia coli BL21 (DE3), indicating high stability and kinetics adaptation to low temperatures. The heat shock response of ATC gene expression was analysed after treatment of G. superstes with 24-hour heat–freeze cycles, and alternatively incubated at 4°C and –18°C constant temperature, during 1 week. After each cycle, total RNA was extracted, transformed in cDNA and the expression of ATC was quantified by qPCR using specific primers for the G. superstes pyrB gene. The comparative data revealed associated changes in the microbial DNA synthesis. Cell viability was assessed after each step based on dead/live cell counting in order to correlate the specific increase in ATC expression with the cellular division. The analysis of variations in the expression ratio between ATC and heat/cold-shock proteins lead to evaluation of the general disturbance response promoting a specific or stochastic gene expression as a short-term strategy for survival after disturbances. Corroboration of the structural/functional properties of this key enzyme of the de novo synthesis of pyrimidine nucleotides and genes expression pattern in a cold-adapted bacterium will contribute to the understanding of adaptation mechanisms to extreme environmental conditions and to temperature variations when habitats change due to glaciers melting. Project funded by H2020 Marie Skłodowska–Curie ITN 675546
A cave ice microbiome
Cristina Purcarea, Corina Itcus, Victoria I. Paun, Constantin Marin, Aurel Perşoiu, Alexandra Hillebrand-Voiculescu, Traian Brad, Carmen Badaluta, Paris Lavin
Corresponding author: Cristina Purcarea
Corresponding author e-mail: firstname.lastname@example.org
Microbial diversity across the perennial ice block of Scarisoara Ice Cave, Romania, was assessed by Illumina sequencing of both 16S rRNA and ITS2 genes and by shotgun metagenomics. Ice core chronosequences up to 13 000 years BP containing clear and organic-rich layers were collected and analyzed. Total and viable cell content determined by flow cytometry varied in the 103 106 cells mL–1 interval, showing a decrease with the age of ice deposits. Chemical composition of the ice substrate, showing large variations over the last 5000 years was analyzed in relation to the microbial density and diversity of corresponding ice layers. The cave microbiome is dominated by Proteobacteria with taxa variations based on the age and geochemistry of theice layers. Archaeal OTUs, mainly present in older ice and dominated by Euryarchaeota, also showed a distinct metabolism depending on organic content and independent of the age o the ice. The fungal community belonged to Ascomycota, Basidiomycota, Cryptomycota, Zygomycota and Cercozoa, with different content of genera from cold habitats. Shotgun sequencing of seven ice samples gDNA and the metagenome reconstitution of their microbiome revealed both structural and functional variability in the microbial communities across the cave ice block.
Effect of organic matter on the albedo of Glacier de la Plaine Morte, Switzerland
Margit Schwikowski, Anna dal Farra, Andrea Marinoni, Kathrin Naegeli
Corresponding author: Margit Schwikowski
Corresponding author e-mail: email@example.com
Light absorbing impurities (LAIs) can darken ice surfaces and accelerate melt. LAIs commonly found on glaciers include black carbon (BC), mineral dust and organic matter. Efforts to allocate the relative contribution of different LAIs to snow/ice albedo reductions have been limited by uncertainty about the optical properties of LAIs. We developed a new method to measure the spectral reflectance of the different LAI classes in an environmental sample at the submicron scale with a hyperspectral imaging microscope spectrometer (HIMS). The method was validated by comparison of reflectance spectra of various standard materials obtained with the HIMS at the submicron scale and for the bulk material with a field spectroradiometer. The agreement was good overall, with an average deviation between the spectra of 3.2% for the 400–1000 nm wavelength range. With the new method, the characteristic reflectance spectra of BC, mineral dust and the humic substances present in surface samples from snow-free Glacier de la Plaine Morte were obtained. They served as endmembers for the spectral unmixing of the reflectance spectra of the glacier surface, collected both with a field spectroradiometer and with the Airborne Prism Experiment (APEX) imaging spectrometer. The latter technique allows upscaling from single-point measurements to the entire glacier surface with a resolution of about 2 m and revealed a mean albedo of 0.29 ± 0.12. Overall the spatial variation of the LAI composition on Glacier de la Plaine Morte was low and dominated by mineral dust of local origin with about 85% abundance, followed by organic matter and BC with 12% and 3% abundance, respectively. Thus, the observed albedo variability on Glacier de la Plaine Morte is mainly driven by the total amount of LAI present and not by its varying composition.
Snow cover development in a High-Arctic coastal tundra environment: present state and predictions for the future
Daniel Kepski, Bartlomiej Luks, Marzena Osuch, Andreas Dobler, Krzysztof Migala, Sebastian Westermann, Tomasz Budzik, Tomasz Wawrzyniak
Corresponding author: Daniel Kepski
Corresponding author e-mail: firstname.lastname@example.org
Snow cover plays a critical role in the Arctic tundra environment, where small changes in its thickness and duration time could have serious implications for, for example, plant development, bird-nesting conditions or food availability for herbivorous animals. Rapid change in the Arctic climate leads to later snow onset, earlier snowmelt in spring and more frequent rain-on-snow events in the middle of the winter. All these factors drastically change the tundra ecosystem, providing an opportunity for colonization of the Arctic by more thermophilic species. On the other hand, the more frequent occurrence of melting events during winter leads to the creation of basal ice or thick ice layers in snowpack that could damage plants and impede the feeding of herbivores. We present snow cover development in a small unglaciated catchment of Fuglebekken, located in southwest Spitsbergen, Svalbard. The actual state of the environment is extrapolated from the example of years 2014–16, when snow transects (depth and snow water equivalent measurements) were made as a weekly routine and melt season snow-cover extent was monitored with time-lapse photography. In situ snow observations merged with meteorological forcing from automatic weather stations were used to feed and validate SNOWPACK and Alpine3D numerical models. Results were superimposed on to a map presenting tundra vegetation types. The longest persistence of snow cover turned out to be associated with places with no vegetation. The fastest snow melt-out was found on lichen–herb heath tundra occupying wind-exposed parts of raised marine terraces. The current state of snow cover was compared to one projected for the end of the century (years 2089–00) obtained from the Alpine3D model run with modified climatological forcing. To simulate future conditions high-resolution climate simulations over Svalbard (0.022°N, ~2.5 km) were applied (COSMO-CLM nested in the MPI-ESM-LR following the RCP 8.5 emission scenario).
Preferential elution from snow pack as a possible source of nutrients for supraglacial environments on the Greenland Ice Sheet
Alexandra Holland, Christopher Williamson, Martyn Tranter, Alexandre Anesio
Corresponding author: Alexandre Anesio
Corresponding author e-mail: email@example.com
Microbial communities have recently been shown to play key roles in the bio-albedo of the Greenland Ice Sheet (GrIS) and consequent melt rates. As such, there is significant interest in understanding how these microbial communities survive and thrive in such harsh and oligotrophic conditions. Current knowledge gaps include the effect of nutrient limitation on the primary production of surface-ice microbial communites and the potential sources of nutrients for supraglacial environments. This study sampled a small section of the GrIS surface, approximately 35 km inland from the margin, prior to and throughout the 2017 melt season. We investigated the potential source of nutrients to supraglacial environments via preferential elution from the snow pack. We hypothesize that, throughout the winter months, the snow pack undergoes metamorphism, creating a solute-rich exterior on the snow grains. When the melt begins, the initial melt water will be highly concentrated with insoluble ions, a situation that stabilizes as the melt continues. This concentrated melt water could supply the initial source of nutrients required by the microorganisms to stimulate growth. Snow pack melt water experiments were conducted in situ and in the laboratory. From these two experiments, we report nutrient ([phosphate, chloride, sulphate, ammonium, nitrite, nitrate, calcium, potassium, sodium, magnesium, total phosphorus, and total nitrogen) concentrations and elution factors. Initial results suggest the existence of preferential elution from the snow pack, while further analysis will determine if this can be considered a key source of nutrients for supraglacial environments.
Effects of a polycyclic aromatic hydrocarbon on cryoconite
William Smith, Joseph Cook, Emma Wharfe
Corresponding author: William Smith
Corresponding author e-mail: firstname.lastname@example.org
Cryoconite holes are hydrologically connected to a porous weathered layer of glacier ice, subjecting cryoconite to near-continuous interaction with meltwater during the summer, as well as occasional high-magnitude flushing events. These meltwaters may contain polycyclic aromatic hydrocarbons (PAHs) delivered during snowfall. Cryoconite has recently been found to accumulate and interact with these PAHs, with communities also possessing the required genomes for PAH resistance and degradation, implying a role in modifying and/or metabolizing PAHs before delivery into extra-glacial environments. Despite this, PAH effect on cryoconite biogeochemical cycling is currently unknown. Here we present the first investigation into the effect of a common PAH on Greenlandic cryoconite net ecosystem productivity (NEP). NEP was unaffected by PAH concentration, but both respiration (R) and primary productivity (PP) increased when exposed to concentrations previously recorded on the GrIS. In contrast, a PAH concentration two orders of magnitude higher caused a decrease in R and PP. A critical concentration is therefore suggested to exist above which PAHs inhibit cryoconite microbial activity. In addition, PAH concentration did not modify total cell abundance, or the ratio of filamentous :unicellular photoautotrophs. These results indicate that supraglacial biogeochemical cycling may be influenced by PAHs.
Characteristics of ice segregation in plant, Keiskea japonica Miq., Lamiaceae
Kazuo Takeda, Karen Tanino
Corresponding author: Kazuo Takeda
Corresponding author e-mail: email@example.com
The plant Keiskea japonica Miq. is an endemic species of Lamiaceae growing as a forest floor plant, distributed from the Tokyo area to Kyushu island in Japan. In the early winter, live stems segregate ice near the ground when the temperature decreases below –2°C. Many thin ice sheets grow radially several centimeters long. Although the ice segregation in the plant is the same phenomenon as in soils, the mechanism has never been suffieciently clarified. The purpose of this study is to identify the characteristics of ice segregation in Keiskea japonica through laboratory tests and through SEM images, and by microscopic video, comparing with that in soil. Since the existence of super-cooled water is necessary for ice segregation to occur, ice nucleation is commonly necessary to break the super-cooling of water as a trigger. It is generally known that nucleation in soil occurs spontaneously. Meanwhile, in order to evaluate nucleation activity in Keiskea japonica, the seasonal nucleation active temperature was measured through a series of laboratory tests. As a result, the nucleation temperature of bark in Mt Takao, in the suburbs of Tokyo, increased with time from –4.9°C in August to –2.8°C just before ice segregation on 27 December, while the xylem nucleation activity increased from –6.1°C to –3.7°C respectively. The specimens sampled in Mt Jinba near Mt Takao showed almost the same trend. In order for ice segregation to occur, the existence of a semi-porous structure is also necessary. There is a minimum pore size that blocks the intrusion of ice from the super-cooled water feeding the expanding ice sheet. According to the laboratory tests using microporous filters, the short axis should be less than 1 μm. The pore size of soil was estimated to be 0.83 μm in Tomakomai silt. When the tissues were observed by SEM, the simple, oval pit was 0.94 μm × 0.34 μm on the xylem surface. It may play a role in block ice intrusion, because ice sheets grow from the slit on the xylem surface as shown by the microscopic video, ice continues to grow after the xylem breaks and the vessel seems to be a water pathway, as shown by the laboratory test using fluorescence. As a whole, ice segregation in Keiskea japonica is characterized by controlled ice nucleation and a porous structure consisting of simple pits on the xylem vessel, while that in soil is brought about by spontaneous nucleation and is different in degree in various soils due to their differing porous structures.
Remote sensing reveals a curious pattern of cryoconite
Corresponding author: Daichi Yamaga
Corresponding author e-mail: firstname.lastname@example.org
At present, cryoconite, a dark substance made of algae and mineral particles that exists inside and on the surface of glacier ice, is widely known to accelerate glacier retreat. The range it covers differs greatly over seasons and years, offering an important role for remote sensing to map out the distribution of cryoconite. In previous studies, cryoconite was analyzed in satellite images only by the single blue band. However, this blue band also represented water and shadows distant from cryoconite, due to their identical reflectance. In this research, we mapped out cryoconite distribution by using a cryoconite-sensitive index. Cryoconite has low reflectance in the region of blue and high in the region of NIR, while glacier ice and water have the opposite tendency. Based on this, the NDCI (Normalized Difference Cryoconite Index) ((NIR-Blue)/(NIR+Blue)) was developed. NDCI was applied to Landsat7 (resolution 30 m) images of the Qaanaaq glacier made in 2012 and mapped out the region with a high density of cryoconite. The points reported to have a great density of cryoconite in a field survey carried out on 2012 were included in the area with a high density of cryoconite observed by NDCI. As a result, NDCI succeeded in highlighting the areas of cryoconite cover. Using NDCI to obtain detailed distribution of cryoconite this study adopted the optical satellite Sentinel2-A (resolution 10 m). When an image of Qaanaaq glacier in 2016 was analyzed by NDCI, an unusual pattern of cryoconite appeared. It is thought that the density of cryoconite is greater at lower elevations. However, in this image the pattern indicates that the cryoconite quantity is greater at high elevation. To investigate the cause of this contradiction, we intend to research the relationship between cryoconite density and elevation.
How biology shapes the ice: crystal growth and physical properties of ice under the influence of ice-binding proteins from a polar diatom
Maddalena Bayer-Giraldi, Gen Sazaki, Nobuhiko Azuma, Morimasa Takata, Sepp Kipfstuhl, Yoshinori Furukawa
Corresponding author: Maddalena Bayer-Giraldi
Corresponding author e-mail: email@example.com
Ice-binding proteins (IBPs), produced by polar and cold-tolerant organisms, have the ability to bind to ice, affecting its growth. They are key elements in biological adaptation to cold environments, and no other particles, either natural nor synthetic, show a comparable effect in controlling ice growth. Here we present the IBPs from the polar sea-ice diatom Fragilariopsis cylindrus (fcIBP). This protein can shape the ice and allows survival of the diatom within sea-ice. It belongs to a protein family defined by a domain (DUF 3494) that is extremely successful among marine polar microorganisms but is also identified in other habitats such as, for example, an Antarctic ice-core. In order to shed light on the details of the interaction between IBPs and ice, as a first step leading to a better understanding of the effect of the proteins in their natural icy environment, we studied the effects of fcIBPs on single crystal free growth. Different IBP families affect ice in different ways and the relevant common traits, as well as the differences of the ice binding mechanisms, are still under investigation. We analyzed crystal morphological changes and crystal growth rates dependent on supercooling and fcIBP concentration, applying optical bright field and interferometric microscopy. We saw differential effects of the protein on the growth of the different crystallographic planes, revealing a new pattern of IBP–ice interaction. Furthermore, switching to a more macroscopic level, we analyzed the effect of fcIBPs on the physical properties of polycrystalline ice. We observed the evolution of microstructure in fine-grained ice samples over longer time periods (several weeks), and were able to show a strong inhibition by fcIBPs of grain growth. Also, we showed that the effect of IBPs on the driving factors for ice deformation during creep, i.e. on internal dislocations due to incorporation within the lattice and on the mobility of grain boundaries due to pinning, make these proteins particularly interesting in studying the process of ice deformation. Our results of ice single crystal growth and of the microstructure evolution of polycrystalline ice in the presence of fcIBPs show that these proteins have remarkable properties that make them suited to basic understanding of the mechanisms of grain growth, recrystallization and deformation processes, but also to be adapted for industrial applications wherever ice grain control is of interest.
Field observations on tipping of deciduous shrubs in snowpack on a steep slope in Niigata, central Japan: the mechanical interactions between shrubs and snowpack preventing snow gliding throughout the 2016/17 winter
Takane Matsumoto, Katsuhisa Kawashima, Shun Watabe, Takafumi Katsushima, Ayana Miyashita, Fumichika Uno, Akihiko Sasaki, Motoshi Nishimura, Kyoko Kataoka
Corresponding author: Takane Matsumoto
Corresponding author e-mail: firstname.lastname@example.org
Mechanical interactions between snowpack and vegetation on steep slopes are quite complicated and have been poorly understood. Shrubs can prevent snow gliding in some phases of a snow-cover period, but in contrast, they can further gliding in other phases. This study aims to discuss the mechanical interactions between deciduous shrubs and snowpack on a steep slope which remarkably prevented snow gliding throughout the 2016/17 winter. Field observations were carried out on a steep slope (30–40°) at Oshirakawa (400 m a.s.l.) in Niigata Prefecture, central Japan. The wintertime mean air temperature (December–February) and average annual maximum snow depth at Oshirakawa are –0.8°C and 2.7 m, respectively. The slope is covered by deciduous broad-leaved trees (dominant species: Acer, Hamamelis, Alnus, Quercus and Clethra) with flexible stems. We chose six sample trees and put seven to eight marks at 50–80 cm spacing along their stems in December 2016. Then we removed the snowpack on one side of the each sample tree and measured the depth from the snow surface, the height from the ground and the inclination of the stem at the marks several times during the period January–March 2017. On each day, snow pit observations were also made. Two shoe-type glidemeters to monitor snow gliding and an interval camera were installed on the nearby slopes throughout the winter. We found that two of six sample trees (and many other trees on the slope) were completely covered by snowpack in mid-January and a part of these stems lay on the ground in February. However, the greater part of the stems were kept buried within a snow layer that mainly consisted of rounded grains, even in the final phase of the snow-cover period in late April. The glide rates on the nearby slopes where glide (full-depth) avalanches were released in most of the previous winters were kept at nearly zero throughout this winter. These results imply the following interactions between the shrubs and the snowpack: (1) Meteorological conditions during this winter maintained the compact snow layer with rounded grains until spring. (2) Many stems within this layer prevented snow gliding throughout the snow-cover season. (3) Complete tipping of the stems over the ground, which could form a slippery surface on the ground, was prevented due to the lack of snow gliding.
Local air circulations around Bowdoin Glacier, Greenland, simulated by a non-hydrostatic regional weather model
Akihiro Hashimoto, Daiki Sakakibara, Shin Sugiyama, Masashi Niwano, Teruo Aoki
Corresponding author: Akihiro Hashimoto
Corresponding author e-mail: email@example.com
Local air circulations around the Bowdoin Glacier, northwestern Greenland, have been investigated using the Japan Meteorological Agency Non-Hydrostatic Model (JMA-NHM), focusing on the period of glaciological observation at the terminus of Bowdoin Glacier in summer 2016. During most of the period, the weather stayed fine. A diurnal cycle appeared in the surface wind and air temperature, which were observed by an automatic weather station (AWS). We performed numerical simulations throughout the observation period, using the JMA-NHM with 5 km and 1 km horizontal resolutions (5km-NHM and 1km-NHM, respectively) to study a link between the diurnal cycle and the surrounding air circulation in this region. In the simulations, 1km-NHM shows better reproducibility of the diurnal cycle of local weather elements observed by the AWS than 5km-NHM, indicating that, in reality, local air circulations are composed of structures much finer than that are resolvable by 5km-NHM. Further examining the results of 1km-NHM, it is found that the diurnal cycle at the AWS site is affected by two major factors. One is the katabatic wind from the Greenland ice sheet (GrIS). Another is the upslope wind in the marginal region of the GrIS, which is induced by an increase in the ground surface temperature due to solar radiation. The katabatic airflow coming down from the GrIS encounters the upslope airflow from the counter side. Looking at the vertical cross-section across Bowdoin Fjord, the front between the two airflows lies several km east of the shoreline and moves upslope and downslope as the sun angle increases and decreases, respectively. On the opposite (west) side of the fjord, there is another katabatic airflow coming down from the Qaanaaq Ice Cap (QIC), which is affected by the upslope airflow, as is the case on the east side of the fjord. However, this airflow from the QIC advances more closely to the shoreline than that from the GrIS. Although we have not finished our conclusions, a complicated wind system around the isolated QIC seems to strengthen the katabatic westerly airflow from the QIC, and we expect that this will be a third factor impacting local air circulations in this region. This work was partly supported by JSPS KAKENHI Grant No. JP16H01772. The field observation campaign at Bowdoin Glacier was carried out under the research project ‘Arctic Challenge for Sustainability’.
Cryosphere changes on the western shore of Admiralty Bay,King George Island, West Antarctica
Corresponding author: Joanna Sziło
Corresponding author e-mail: firstname.lastname@example.org
Recession of the glaciers covering King George Island and evolution of the whole cryosphere at the western shore of Admiralty Bay has been observed since 1979. Negative mass balance for the entire ice cap and visible changes of the glacier front positions confirmed this changes. Recently, deceleration of mass loss due to regional cooling has been noticed. However, the frontal positions of the glaciers have shown new ice-free surfaces that have been already uncovered. Suszczewski Cove was created at the front of Ecology Glacier with its area expanding yearly, covering around 0.3 km2 in 2016. When the front position of the glacier was stable, the bathymetry of the cove showed a strong correspondence with accumulation of the glacier deposits. Since 1979 a major change of the frontal position has been observed for land-terminating Baranowski Glacier. The glacier has divided into two tongues. Its forefield, with total area 0.7 km2 is varied by the creeks, lakes and cove, which create living conditions for marine fauna. Due to the recession of the glaciers, determination of their front position changes in time can deliver much valuable information about regional climate conditions. Furthermore, during the last 40 years, melting of the glaciers has caused changes in the whole ecosystem inhabited by birds and marine mammals – elephant seals and penguins. This knowledge can also contribute to prediction of future changes in this area.
Abiotic controls of Greenland ice sheet ice algal blooms
Christopher Williamson, Alex Anesio, Marian Yallop, Ewa Poniecka, Alex Holland, Joesph Cook, Andrew Tedstone, Jenine McCutcheon, Martyn Tranter
Corresponding author: Christopher Williamson
Corresponding author e-mail: email@example.com
The significant potential for blooms of pigmented micro-algae to drive surface darkening and melt of the Greenland ice sheet (GrIS) necessitates an understanding of those factors that regulate bloom formation and development. To date, however, few studies have detailed the influence of key abiotic stressors on ice algal physiology and productivity within surface ice environments, fundamentally limiting our ability to project the occurrence, magnitude and thus impacts of future blooms. Here we report on a series of in situ incubation experiments and monitoring of surface ice environments conducted ~35 km inland from the south-western GrIS margin as part of the 2016/17 Black and Bloom field campaigns. Manipulations were designed to test the influence of irradiance, dissolved inorganic nutrients and inorganic particles on ice algal physiology and productivity, while monitoring of surface ice allowed the tracking of bloom development in relation to prevailing abiotic conditions. Photo-inhibition was highlighted as a strong regulator of ice algal productivity, with an inverse relationship identified between productivity and irradiance above ~50% ambient levels. While inorganic nutrient limitation was indicated by nutrient addition incubations, the presence of inorganic particles strongly influenced findings, demonstrating their potential importance for GrIS bloom development. During the snow–slush–ice transition, nutrient inputs from the melting snow-pack and the hydrological dispersion of algal cells during snow-pack retreat facilitated the rapid colonization of surface habitats by ice algae. Increases in algal biomass with time over the subsequent ablation period were punctuated by short-term variability driven by hydrological flushing events. Taken together, the findings advance our knowledge on the controls of GrIS ice algal blooms and improve our ability to project their occurrence and impacts into the future.
Surface snow density of Antarctica derived from in situ observations
Yixiang Tian, Shanshan Zhang, Jiajin Chen, Wenjia Du, Huan Xie, Rongxing Li
Corresponding author: Yixiang Tian
Corresponding author e-mail: firstname.lastname@example.org
Models based on physical principles or semi-empirical parameterizations have been proposed to describe the near-surface snow density that is essential for the study of surface processes in the Antarctic ice sheet. The density and the densification process in the firn layer play important role in interpreting satellite/airborne altimetry data, calculating mass balance and analyzing climate change. However, parameterization of surface snow density for the Antarctica may neglect local differences. In this study we tried to generate a surface density map for East Antarctica from all the filed observations that we could obtain. The observations spanned 59 years, from 1957–2015, and are non-uniformly distributed around Antarctica. Considering the spatial and temporal inhomogeneous, we averaged the observations every ~5 years per 30 × 30 km2 square to calculate the surface density of each center. If there is no data within the time period at the square, we set the value as 0. Then, a matrix completion algorithm was applied to the matrix, with a lot of zeroes. After the accuracy of matrix completion had been confirmed by cross-validation, we adopted empirical orthogonal function (EOF) to decompose the matrix (each column is one map, and each row is a time series of observations for a given location) and take first several lower-order modes to separate the information related to spatial and temporal, since these modes already contain most of the information. We were then able to obtain the surface density by multiplying the modes interpolated by kriging and the corresponding amplitude of the modes. On the basis of several sequential surface density maps, changes in surface snow density can be discussed. Comparative analysis has also been done between models and our results.
Glacier ecosystems and the glaciological importance of glacier microorganisms
Shiro Kohshima, Yoshitaka Yoshimura, Nozomu Takeuchi, Takahiro Segawa, Jun Uetake
Corresponding author: Shiro Kohshima
Corresponding author e-mail: email@example.com
Biological activity on glaciers has been believed to be extremely limited. However, we found various biotic communities specialized to the glacier environment in various part of the world, such as Himalaya, Patagonia and Alaska. Some of these glacier-hosted biotic communities including various cold-tolerant insects, annelids and copepods that were living in the glacier by feeding on algae and bacteria growing in the snow and ice. Thus, the glaciers are simple and relatively closed ecosystems sustained by the primary production in the snow and ice. In this presentation, we will briefly introduce characteristics of glacier ecosystems; ecology and behavior of glacier animals, altitudinal zonation of snow algal communities, and the structure of their habitats in the glacier. Since the microorganisms growing on the glacier surface are stored in the glacial strata every year, ice-core samples contain many layers with these microorganisms. We showed that the snow algae in the ice-core are useful for ice-core dating and could be new environmental signals for the studies on past environment using ice cores. These microorganisms in the ice core will be important especially in the study of ice cores from the glaciers of warmer regions, in which chemical and isotopic contents are often heavily disturbed by melt water percolation. Blooms of algae and bacteria on the glacier can reduce the surface albedo and significantly affect glacier melting. For example, the surface albedo of some Himalayan glaciers has been significantly reduced by a large amount of dark-colored biogenic material (cryoconite) derived from snow algae and bacteria. It has increased the melting rates of the surfaces by as much as three-fold. Thus, it was suggested that the microbial activity on the glacier could affect the mass balance and fluctuation of glaciers.
The pigment composition of snow algae on Mt Tateyama, Toyama prefecture, Japan
Tomomi Nakashima, Nozomu Takeuchi, Jun Uetake, Yukiko Tanabe, Chika Okamoto
Corresponding author: Tomomi Nakashima
Corresponding author e-mail: firstname.lastname@example.org
Snow algae are photosynthetic microbes inhabiting melting snow surface in alpine and polar regions. Their blooms cause visible red- or green-colored snow due to various pigments in their cells. Such algal blooms can reduce the surface albedo of the snow and result in acceleration of the melting rate. Variation in snow color may be associated with environmental conditions and/or taxa of the algae. However, factors affecting the snow color are still not well known. It is important to understand the relationship between taxa and pigments of algae in order to clarify the generation process of colored snow. In this study, we analyzed pigment composition and presence of 18S rRNA gene of algal snow collected in Mt Tateyama in Toyama prefecture, Japan, in the melting seasons of 2015 and 2016. This study aims to describe the spatial and temporal variations of algal pigments and community structure on the snow fields and discuss relationship among species, life cycles and the pigments. Red algal blooms were commonly observed on the snow surface in June and July in Mt Tateyama. Analyses of pigment composition showed the presence of two chlorophylls and six carotenoids. The pigment composition varied among the samples and can be classified into four types: type A (rich in astaxanthin), type B (poor in astaxanthin), types C and D (rich in other carotenoids). Types A and B were most commonly observed in this study area. Analysis of the 18S rRNA gene revealed that there are six major algal OTUs in the colored snow. There was no significant difference in the community structure of the algal OTUs in samples between types A and B, suggesting that the abundance of astaxanthin was determined not by algal species but by environmental conditions affecting the production of astaxanthin. The community structure of types C and D differed from those of type A and B, indicating that the pigment compositions of types C and D were derived from different algal species from those of types A and B. These results indicate that a red algal bloom occurred widely on the snowfield of Tateyama, but the pigment composition of the algal snow varied due to environmental conditions and to the community structure of the snow algae.
The methanesulphonic acid record in snow, firn and ice as a proxy for marine productivity; examples from Svalbard and coastal Antarctica
Carmen P. Vega, Elisabeth Isaksson, Anja Eichler, Margit Schwikowski
Corresponding author: Elisabeth Isaksson
Corresponding author e-mail: email@example.com
Methanesulphonic acid (MSA) is an atmospheric oxidation product of dimethyl sulphide, produced by marine biota and therefore often attempted to be used as a proxy for sea ice and marine productivity in ice-core studies. In this work we are presenting results from snow, firn and ice cores from Svalbard and coastal Antarctica, hoping to improve our understanding of using these records as proxy for past environments. Early studies with a Svalbard ice core suggested a negative correlation between MSA and sea ice conditions in Barents Sea MSA between 1920 and 1995. However, prior to about 1920 this relationship failed. Instead, the MSA concentrations were about 100% higher despite a more extensive sea-ice cover during the colder Little Ice Age. After exploring different possibilities it was suggested that increased vertical stability, due to greater melt-water production from the extensive sea-ice cover favouring the primary production, was responsible for the higher MSA concentrations. More recent work from the same ice-core site instead suggests a positive link with sea ice and a high correlation with NO3– favouring a fertilising mechanism, where higher atmospheric NO3– concentrations yield higher nitrogen input to the ocean, triggering the growth of DMS-producing phytoplankton. Elevated DMS concentrations then result in enhanced concentrations of MSA in the atmosphere. MSA records from snow pits and 20 m firn cores retrieved from three ice rises on the Fimbul Ice Shelf, Dronning Maud Land, Antarctica, present a marked sub-annual pattern with higher (lower) concentration values in the spring–summer (winter) months. The clear MSA seasonality captured in these cores suggests that MSA could potentiallybe used as a proxy of sea-ice extent and biological activity in the vicinity of the drilling sites. We will compare our high-resolution MSA records with new remote-sensing products and discuss the subannual MSA signal and implications for interpretation of biogenic records from both coastal Antarctica and Svalbard.
An analysis of short-term albedo variations at Ürümqi Glacier No.1, Tien Shan, China
Xiaoying Yue, Zhongqin Li, Nozomu Takeuchi, Mingjun Zhang, Feiteng Wang, Puyu Wang
Corresponding author: Nozomu Takeuchi
Corresponding author e-mail: firstname.lastname@example.org
Surface albedo is a key variable controlling the energy balance at a melting glacier surface and, in turn, influences glacier surface melt. The variations of short-term (half-hourly and daily) albedo were investigated using a data set of high-frequency albedo measurements from Ürümqi Glacier No.1, a reference glacier in an arid and semi-arid region of central Asia, over two melt seasons (26 June-2 August 2007 and 29 July-12 August 2016). The data suggested that short-term albedo variations were characterized by a large range and very high frequency. Most of these variations were caused by changes of cloud, while solar zenith angle variations below 65° were of minor important for the ice surface. Snow albedo was more sensitive to the influence of cloud than that of ice, particularly in the visible wavelength. Moreover, the profile of daily albedo variations was different at various ice sites on melting glacier surface, due to the concentrations of light-absorbing impurities. Organic matter was a dominant factor in reducing surface albedo over ice. At snow sites, air temperature and precipitation were indirect factors affecting the profile of daily albedo variations, which influenced the behavior of snow. The results implied that the data collected at a single site were not representative of the entire glacier. For the ice surface, satellite-derived albedo can represent the short-term albedo values under conditions of more intense ablation, if there is no snowfall. However, for snow surfaces, rapid albedo variation due to fresh snowfalls and snow metamorphism can quickly render satellite-derived albedo measurements out of date.
Fungal–algal interactions on the surface of the Greenland Ice Sheet
Laura Perini, Alexandre Anesio, Christopher, Williamson Miranda Nicholes, Jens Christian Frisvad, Cene Gostinčar, Nina Gunde-Cimerman
Corresponding author: Nina Gunde-Cimerman
Corresponding author e-mail: email@example.com
Research has recently highlighted the importance of ice-algal blooms in driving darkening and surface melt of the Greenland Ice Sheet (GrIS); however very little is known about the interactions between ice algae and other supraglacial microbial communities. This is of particular importance given that interactions between microorganisms are crucial for the colonization and survival of communities in extreme environments; endosymbiotic, antagonistic and competitive interactions are just some examples of the relationships that can occur in nature to allow microbes to thrive. In particular, there is limited knowledge about fungi proliferating on the surface of the GrIS and whether algal–fungal interactions have a positive or negative impact on ice algal survival and bloom development. To address this significant knowledge gap, fungi were isolated from surface ice collected from the southwest part of the GrIS and a combination of both in situ and ex situ incubation experiments were performed to characterize fungal–algal interactions taking place within the GrIS surface. In situ incubations were performed during the 2017 ablation season at the ice camp located ~35 km from the GrIS margin. Outcomes demonstrated potential influences of fungal addition on ice algal physiology monitored using PAM-fluorometry. Although no major impact of fungal addition on ice algal physiology was apparent, short incubations indicated that fungal–algal interactions within surface ice were likely to be beneficial, as opposed to detrimental for ice algae. Subsequently, a novel ex situ incubation experiment was designed to fully constrain the nature of the relationship between ice algal and fungal taxa. To this end, the ice algae Mesotaenium berggrenii and Ancylonema nordenskioeldii were incubated with 1% of Penicillium sp. spores and/or Articulospora sp. mycelium at 4°C under continuous lights (181.45 ± 24.5 μmol m–2 s–1 PAR) for 4 weeks. To assess the nature of the relationships, concentration of inorganic and organic nutrients, bacterial dynamics, algal and fungal abundances were monitored weekly (four time points in total). Scanning and electron microscopy were performed at each time point and secondary metabolites were extracted after 8 days of incubation. Here we present the first findings detailing these interactions, demonstrating their potential influence in ice-algal bloom development or ice-algal degradation.
Bacterial dynamics in supraglacial habitats of the Greenland Ice Sheet
Miranda Nicholes, Christopher Williamson, Alexandre Anesio, Marian Yallop, Ewa Nowicka
Corresponding author: Alexandre Anesio
Corresponding author e-mail: firstname.lastname@example.org
Bacteria are known to play a pivotal role in regulating the biogeochemistry of cryoconite holes within supraglacial environments, though these habitats account for only ~11% of the ice surface landscape. In contrast, little research has addressed the role of bacteria in other supraglacial environments, notably the extensive bare ice surface. This is of particular relevance given the potential role of bacteria in supporting widespread ice algal blooms that occur within surface ice. These blooms have been observed across vast areas of the ablation zone on the Greenland Ice Sheet (GrIS), and have been identified as a potential driver of surface melt, given the relationship apparent between algal pigmentation, albedo reduction and melt generation. This study aims to understand variability in bacterial abundance and production during summer ablation seasons on the GrIS, in relation to dynamics in ice algal blooms. Data was collected over two field campaigns during consecutive ablation seasons (2016 and 2017) timed to target different stages of algal bloom development. Experiments to constrain bacterial dynamics were conducted at a primary ice camp, located ~ 35 km from the southwestern margin of the GrIS, and supplemented with helicopter transects spanning the ablation–accumulation zones. Data demonstrated that bacterial production was negligible within the upper 30 cm of surface ice during the early ablation season. Bacterial production varied in conjunction with ice algal biomass, such that greatest production (0.72 ± 0.17 μg C L–1 h–1) was identified in surface ice which contained the highest abundances of ice algal cells (9537 ± 930 cells ml–1). During the latter stages of the ablation season, production in cryoconite holes remained high, whereas production in surface ice containing a range of algal biomass decreased vastly. These findings demonstrate a strong relationship between bacterial production and ice algal biomass within surface ice that likely reflects mutualism between these two ice-surface communities and indicates an important role for bacteria in supporting ice-algal blooms. Understanding the interactions between bacteria and ice algae will be crucial in understanding the development of algal blooms.
Online measurement of black carbon aerosol in the Altai Mountains
Corresponding author: Zhang Xiaoyu
Corresponding author e-mail: email@example.com
Abstract black carbon (BC) mass concentrations were measured by an aethalometer (AE-31) at the Tian Shan Glaciological Station (TGS), China, from August 2016 to July 2017. Different from previous filter-sampling studies, the first high-resolution online BC measurement conducted in the central Tian Shan is reported here, allowing discussion of the diurnal variations as well as monthly variabilities of BC. Average daily BC concentration was 512 ± 265 ng m–3, reflecting a regional background level. Meteorological conditions influenced BC concentrations largely at monthly scale, and they were higher in October. The highest BC concentrations (>777 ng m–3) were more associated with southwesterly winds lighter than 1 m s–1. The diurnal variations in BC showed plateaus from 08:00–12:00 and 18:00–20:00 with monthly variations associated with local anthropogenic activities, such as indigenous Tian Shan burning animal waste, industrial and mining enterprises, and tourism traffic. The planetary boundary layer height showed co-variance with BC concentrations, implicating close sources. This backward air-mass trajectory and AOD also suggest that nearby or short-distance sources could be important contributors to BC concentrations at the TGS.
Terrestrial substances in an ice core drilled at Mount Wrangell, Alaska, USA
Sumito Matoba, Hirotaka Sasaki
Corresponding author: Sumito Matoba
Corresponding author e-mail: firstname.lastname@example.org
To quantify the atmospheric mineral dust deposition on the northern North Pacific region, we measured concentrations of iron, non-sea-salt (nss) calcium ion and insoluble particle in ice cores drilled at Mount Wrangell, Alaska, USA, in 2003 and 2004. The annual iron fluxes calculated from the ice core records ranged from 3.2 to 27.0 mg m–2 a–1, and the temporal variation in the iron flux was significantly correlated with the frequency of dust storms on the east Asian continent and the total number of Kosa days observed in Japan, but not with the precipitation amount in Alaska. We concluded that the amount of iron deposition on to the northern North Pacific is controlled mainly by the emission of dust from the east Asian continent and not by scavenging processes in Alaska. The annual depositional flux of the mass of insoluble particles correlated with iron. On the other hand, the annual depositional flux of nss calcium ions did not correlate with iron, but with acid species such as nss sulfate and nitrate. Moreover, nss calcium showed high values during the 1990s. Calcium ion determined by ion chromatography is only dissolved calcium. Therefore, the high value of nss calcium in the 1990s was caused by acidification of mineral dust with acid species. Furthermore, the acidification can also enhance the solubility in the ocean of atmospheric iron, an essential micronutrient controlling phytoplankton growth in the ocean.
Parameterization of snow/ice albedo with cryoconite from Ürümqi Glacier No.1, Tian Shan, northwest China
Huilin Li, Zhongqin Li, Mingjun Zhang, Xiaoni You
Corresponding author: Huilin LI
Corresponding author e-mail: email@example.com
The albedo of snow depends on the grain size of snow, snow depth, cloud cover, cloud optical thickness, solar zenith angle and impurities. In most existing melting models, the albedo of ice is fixed as a constant, whereas it is significantly influenced by the impurities inside or overlying and can vary over a relatively wide range. The impurities include black carbon, mineral dust and organic matter. Mixtures and/or aggregates of these biotic and abiotic impurities on glacial ice are called ‘cryoconite’, which appears on glacier surfaces globally. Due to its diversity and complicated propagation and accumulation processes, how cryoconite affects the surface albedo and the corresponding mechanisms are still not clear. In the present study, the surface albedo at specific points along the main flow-line of Ürümqi Glacier No.1 was observed in August 2006. Samples of cryoconite were collected simultaneously and analyzed in the laboratory to quantify its composition, size and abundance (g m–2). The characteristics of the glacier surface (color, crystal size and water content), meteorological parameters (mainly air temperature and cloud cover) and time of observation were recorded at the same time to assist analysis of the influence of cryoconite on solar radiation reflection. The results showed a rough inverse correlation between cryoconite abundance and albedo. For snow, the cryoconite abundance was quite low and the corresponding albedo was as high as ~0.6. For ice, most cryoconite abundance was concentrated in the range of 200–~500g m–2 and albedo was decreased to <0.2. The emergence of singular points was noticed, i.e. quite low albedo was found at sites with small cryoconite abundance and cryoconite with extremely high abundance exerted a negligible effect on surface albedo. To investigate the reason for those singularities, a parameterization of albedo with snow crystal size, snow depth, cloud cover, solar zenith angle, and especially the abundance, size and color of cryoconite as variables, was developed. The simulated albedo was compared with results obtained by existing models without consideration of cryoconite. The effect of cryoconite and the combination effect of cryoconite with other mineral impurities on the surface albedo and melting of glaciers are discussed.
Temporal CO2 flux variations of Lake Nam Co in the central Tibetan Plateau
Corresponding author: Shiqiao Zhou
Corresponding author e-mail: firstname.lastname@example.org
Lakes are important CO2 sources or sinks in the global carbon cycle. However, how a lake acts as a source or a sink of CO2 in different environments still remains uncertain. This study provides the first in situ observation of CO2 fluxes on the great lake of Nam Co, central Tibetan Plateau, from 2012–14 using the eddy covariance method. Daily average CO2 flux over the lake ranged from –134.9 to 110.2 mmol m–2 d–1, with a mean value of –8.l mmol m–2 d–1 during the observation periods from June to November, indicating a weak CO2 sink. Both seasonal and diurnal fluctuations of CO2 flux are very clear. The flux was positive (CO2 emission) from June through August, and negative from September through November. Biological respiration and physical process of the lake water are determined to be two major controls of the seasonal change. Diurnal variations of the CO2 flux are largely related to the changing photosynthetically active radiation.
Unveiling the biotic and abiotic processes affecting ice reflectance in an Alpine glacier
Biagio di Mauro, Giovanni Baccolo, Andrea Franzetti, Francesca Pittino, Roberto Garzonio, Barbara Leoni, Alessandro Gargan, Giulia Tagliabue, Roberto Colombo
Corresponding author: Biagio di Mauro
Corresponding author e-mail: email@example.com
Glacier retreat is one of the most impressive consequences of current climate change . Its societal and economical impacts stem from water availability to sea-level0rise issues and geological hazards. A deep understanding of the complex dynamics that modulate and govern ice melting and glacier retreat is still lacking. One of the less investigated points concerns the relationship between biotic and abiotic processes occurring on the surface of glaciers and their impact on ice reflectance. The latter is a key factor in determining the radiative balance of glaciers and thus they response to external factors. It is known that the ablation region of retreating glaciers is often affected by darkening processes. These processes can be related to the formation of cryoconite, the typical dark sediments forming on melting ice, but also to mineral dust deposition, to the accumulation of impurities entrapped within ice or to algal blooms during summer. Here, we present novel data gathered from the Alpine valley glacier Vadret da Mortertasch, Switzerland, during the summers of 2016 and 2017. Having assessed the impact of cryoconite and mineral dust on snow and ice radiative properties, we focus attention here on the role played by algal blooms. This phenomenon is well known to occur on snow fields, but few studies are available concerning their impact on bare ice and none in the Alpine context. We gathered extensive data from field spectroscopy, laboratory analysis and remote sensing (aerial photogrammetry using unmanned aerial vehicles). Combining all these pieces of information it will be possible to disentangle the different contributions related to cryoconite, mineral dust and algal blooms, giving a first comprehensive picture of ice darkening in the European Alps.
Microbe mobility in the near-surface ice of the Greenland Ice Sheet
Tristram Irvine-Fynn, Arwyn Edwards, Ian Stevens, Joseph Cook, Andrew Mitchell, Karen Cameron, Johnny Ryan, Alun Hubbard
Corresponding author: Tristram Irvine-Fynn
Corresponding author e-mail: firstname.lastname@example.org
Recent studies reveal that microbial activity across the ablation zone of the Greenland Ice Sheet and ice masses elsewhere in the Arctic are extremely high, and that this activity results in the associated export of biomass, organic carbon and nutrients in proglacial runoff impacting on downstream ecosystems. Meltwater produced from ice ablation is commonly assumed to reach supraglacial streams with a minimal time-lag. However, there is growing recognition of the role of the ‘weathering crust’ in delaying meltwater flow across a glacier’s surface to stream networks. The presence of this inefficient supraglacial meltwater transfer indicates a parallel regulating influence by the weathering crust on the transport of biotic and abiotic impurities. Yet, this hydrological and ecohydrological system, and the transfer of biomass and other impurities across a glacier surface, all remain poorly quantified. Here, we investigate these processes using piezometer tests at two sites on the western Kangerlussuaq (K-) sector of the Greenland Ice Sheet to define the hydraulic conductivity of the supraglacial weathering crust using the bail-recharge technique. These measurements were paired with samples of the recharge water in shallow (~40 cm) auger holes, which were analysed using flow cytometry to enumerate biotic and abiotic impurities in suspension. Our results provide the first quantification of microbial flux through the weathering crust including evaluation of microbial residence time in the supraglacial environment and the delivery of microbes and abiotic impurities to streams which descend to en-, sub- or pro-glacial environments.
Approaches to including forest effects in avalanche hazard indication maps in Norway
Dieter Issler, Peter Gauer, Kjersti Gleditsch Gisnås, Ulrik Domaas
Corresponding author: Dieter Issler
Corresponding author e-mail: email@example.com
Avalanche hazard indication maps (AHIM) delineate areas that – pending a detailed hazard assessment – should be considered endangered by avalanches. AHIMs can be an important and cost-effective tool for land-use planning. The present Norwegian AHIM was automatically generated based on a DEM with 25 m resolution, using a topographic–statistical run-out model and release areas within a certain slope-angle range. Experience shows that the potential hazard areas are much too large in many cases, yet too small in others. The shortcomings of these maps have significant economic consequences. More accurate maps should result from (1) using a higher-resolution DEM, (2) applying additional topographic criteria for release areas, (3) taking into account climatic conditions and forest cover for eliminating release areas with very low release probability, and (4) using a dynamical model for run-out calculation. A 10 m DEM and comprehensive forest-cover data on a 25 m raster have become available for the entire country. However, the forest data is based on somewhat outdated imagery and has fairly large uncertainties at the cell level. Curvature and connectivity criteria were found to improve the selection of release areas considerably. However, compelling criteria for dividing extremely large potential release zones still have to be identified. Work on downscaling interpolated climatic data from a 1 km2 grid to the DEM resolution is ongoing. Based on mechanical and statistical considerations, a method for estimating the release probability in forested and non-forested areas has been proposed. It appears to give plausible results, but needs to be tested extensively. For the run-out calculations, a simple depth-averaged 2-D Voellmy-type model proved to be sufficiently fast and robust. The model takes the braking effect of forests into account by making the friction parameters linear functions of the product of average tree diameter, forest density and flow depth. The preliminary code has been tested in a number of regions with different topography and climate where detailed hazard maps are available. In most cases, the new model predicts much more realistic run-out zones than the current aHIM, but particularly in high-mountain areas with continental climate, the predicted run-out distances may be too short with the adopted model calibration. Another important task of future work is to find a way to include the hazard due to powder-snow avalanches.
Microbial biomass, activity and diversity in basal ices from the Greenland Ice Sheet
Mark Skidmore, Wei Li, John Dore, Melody Lindsay, August Steigmeyer, Eric Boyd
Corresponding author: Mark Skidmore
Corresponding author e-mail: firstname.lastname@example.org
Debris-rich basal ices have been shown to harbor metabolically diverse microbes that can be cultured under oligotrophic conditions at low temperatures (0–4°C), including heterotrophs that respire oxygen, nitrate and sulfate, as well as methanogens. Microbes in these habitats are supported by chemical energy from entrained debris, with the majority of activity likely localized to unfrozen water films on particle surfaces that persist at sub-zero temperatures. A wide range in biomass abundance has been reported for these debris-rich basal ices, implying significant differences in habitat potential. Analysis of the biological properties of debris-rich ice sampled from the margin of the Greenland Ice Sheet and from a number of deep ice cores (>2000 m ice depth) from the continental interior has shown relatively low biomass in comparison with previous studies of debris-rich ice from deep ice cores. We have also conducted a comparative analysis of the habitat potential of these different environments using measurements of biomass, microbial activity and microbial diversity. Collectively our results suggest substantial heterogeneity in the microbial biomass in the basal ice of deep ice cores, and by inference, the basal ice sequences that underlie ice sheets. This is significant for both understanding the extent and activity of biomass that may be contained within ice sheets and also using these ices as potential analogs for extra-terrestrial icy systems that also may have debris-rich ices.
Extending the shelf life of cryosphere bryophytes: subglacial and permafrost environments of the Canadian High Arctic
Catherine La Farge
Corresponding author: Catherine La Farge
Corresponding author e-mail: email@example.com
Glacial ecosystems are increasingly recognized as biological reservoirs of microbial fauna and flora. Furthermore, it has also been demonstrated that basal land plants (bryophytes) significantly expand the diversity of preserved biota in these critical polar ecosystems. Bryophytes have a unique biology that permits desiccation and later reactivation following prolonged cryopreservation. Enabling this capacity, bryophytes have totipotent cells that dedifferentiate to reboot the life cycle, which jump-starts the recolonization of polar landscapes. Arctic bryophytes, adapted to extreme environments on northern Ellesmere Island, Nunavut, Canada, are now shown to have the capacity to regenerate following subglacial entombment since the Little Ice Age (300–400 years old), as well as from diaspores of much older Holocene peat (4000–6000 years old). Given this regenerative capacity, the concept of biological refugia for land plants must be fundamentally expanded beyond the long-accepted categories limited to sites above and beyond glacier margins. Refugia must now include subglacial populations and potential diaspore populations preserved within frozen peat that contribute to models of landscape evolution. The resilience of bryophytes reported here – notably their capacity to withstand glacier and permafrost entombment – is fully consistent with – and actually explains – previous reports that recognized the continuity of bryophytes within the Canadian Arctic Archipelago since the Neogene (23 ma).