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Historical note on glaciology and nanotechnology, by John F. Nye

June 17th, 2015

This personal note, addressed to the glaciological community, is an addition to my lecture "Glaciology Sixty Five Years Ago" which is available to watch here.  I am a former glaciologist who is now working on optics and waves.  The transition happened in a quite logical and natural way.  I was interested in the radio-echo sounding of the Antarctic ice sheet when it first started.  At first, of course, it was not done from an aircraft or spacecraft but from a sledge down on the snow.  As you well know, a pulse of waves is sent out and you time how long it takes for the echo from the bed to come back.

Blog_Pic1

But the pulse that comes back is not exactly the same as the one that was sent out;  it is drawn out, with a long tail.  If the outgoing pulse contains 4 crests the echo might have 12 or many more crests in it.  The reason is simply that the rock bed is not just a mirror;  it is rough.  The front of the echo comes from just underneath the sledge but signals also echo back – are scattered back – by the more distant parts of the bed.  That gives the tail of the echo.

We knew from published photographs that the tail had a fine structure which changed rapidly as the sledge was moved, but to understand the details of how it would change Michael Walford, with two undergraduates, Robert Kyte and David Threlford, built a laboratory-sized analogue model [1] with a transmitter and receiver that used ultrasonic waves instead of radio waves.  Sound in air travels about 10,000 times slower than radio waves in ice, and the Antarctic ice sheet is also about 10,000 times thicker than a laboratory model, 1 m or so in depth.  So it scales down into the laboratory very nicely.  We simulated the rough rock bed by using crumpled cooking foil.  When we displayed the outgoing ultrasonic pulse and its echo on an oscilloscope they looked very like the radio versions.  But there was a feature of the received pulse that drew my attention;  it is shown in simplified form in the following animation.

The received pulse is very short in this example and contains just 4 crests.  But if the transmitter/receiver (carried by the sledge on the ice surface) is moved sideways by less than a wavelength the number of crests increases by 1.

At first there are 4 crests but then there are 5.  The following figure shows what the crests in the returning wave must look like in space.   

Blog_Pic2

The pulse must contain a dislocation very like an edge dislocation in a crystal, where a plane of atoms comes to an end.  The crests of the waves are the crystal planes.  4 crests sweep past point A, but an observer who moves to point B sees 5, as in the animation.  In the real problem the amplitude of the returning echo is a function of the three space variables x, y, z and the time t.  This example simplifies it to a function of x, z, t.  One can deduce that trains of waves in nature can contain dislocations (of mixed edge-screw type, in general).  That is a very broad conclusion, but it is justified because the cooking foil bed is sufficiently representative of a general scattering object.  Similar observations had been made before, most notably in the discovery as long ago as 1833-1840 by Whewell [2] of amphidromic points in the tides.   The new point was that dislocations are features to be expected in all waves.

This idea, developed with Michael Berry [3], has proved to be extraordinarily fruitful.  We and many others continue to pursue the topic of wave dislocations in optics and in monochromatic waves, where they are called optical vortices.  This is an academic study undertaken for its own inherent interest.  But the historical thread I want to follow here branched into an application of some importance when, following theoretical work by L. Allen, it was demonstrated [4] that a laser beam containing an optical vortex can turn a tiny object by transferring angular momentum to it.  The helical shape of the wavefronts was the operative feature.  It was already known that light can move an object by transferring linear momentum but here was the possibility, using a single laser beam, of a microscopic device, operating on a subwavelength scale, that could both move and turn an object even as small as a single atom – true optical tweezers.  As is well known, laser beams are now used for nano-assembly.  Nano-technology has begun, with all the exciting things it implies for the creation of new materials, and the new vistas it opens in the life sciences (manipulating single cells) and for quantum communication.  Thus the lineage can be traced back, from the manipulation of single atoms, molecules or cells and the nano-assembly of new materials, via optical vortices and dislocations in ultrasonic and other waves, to a study of radio-echo sounding in Antarctica – a scale change by a factor of 109.  Glaciologists may be pleased to know of this historical connection between their subject and nano-technology.

Correspondence

45 Canynge Road, Bristol BS8 3LH, UK.

Email: john.nye@bristol.ac.uk

References

[1] J. F. Nye, R. G. Kyte and D. C. Threlfall 1972, Proposal for measuring the movement of a large ice sheet by observing radio echoes, J. Glaciol. 11, No. 63, 319-325.

[2] S. Ducheyne 2010, Whewell's researches; scientific practice and philosophical methodology, Studies in History and Philosophy of Science A 41, (1), March, pp. 26-40.

[3] J. F. Nye and M. V. Berry 1974, Dislocations in wave trains, Proc. Roy. Soc. Lond A336, 165-190.

[4] R. Allen, M. W. Beijersbergen, R. C. J. Spreeuw and J. P. Woerdman 1992, Orbital angular momentum of light and the transformation of Laguere-Gaussian Modes, Phys. Rev. A45, 8185-8189.

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The Truth is not an option – part 5

May 31st, 2012

Part 5. No awards and no allowance for willful ignorance

 “A hallucination is a fact, not an error; what is erroneous is a judgment based upon it.”

—Bertrand Russell, On the Nature of Acquaintance: Neutral Monism (1914)

Bertrand Russell was a philosopher, a pacifist, anti-Stalinist, anti-Nazi, anti-religious, and anti-Vietnam War.  He was also a prisoner of conscience.

In these key cases, more damaging than the misinformation about one scientific issue can be the grave damage to public understanding of the legitimate, constructive roles of science in society.  Science and its applied engineering offshoots (along with the labor and entrepreneurial spirit of millions of citizens and the vision of many leaders) are what built America and other modern developed nations.  Science and engineering have propelled America and the world into the age of planetary exploration, where planetary climate change (all natural, of course) is one of the driving scientific foci of exploration.  The same methods of analysis, but with a far deeper database of observations, are utilized to understand climate change on Earth, where causes in recent decades are clearly both natural and man-made.  The man-made component of climate change on our planet is rising above magnitude of the natural oscillations in many parts of the world.  If there is one thing that planetary science has taught us, it is that planets have many climate tripwires, many nonlinear forcing-and-response functions, many climate change mechanisms that are a challenge to understand from the past and even more difficult to predict.  The ones we know about and understand, when put into physics-based global climate models, are doing a pretty good job replicating the actual recent climate trends; the same models project more rapid and severe climate changes in the future.  Empirical models based on climate and CO2 levels of the geologic past suggest that, compared to baseline models presented by the IPCC, far more severe climate change could be in store for us.  The heat storage capacity and heat conveyance of the oceans, for example, are loaded with both slow and rapid climate change mechanisms, and the slow ones are apt to cause climate to keep warming for centuries even if we could stop greenhouse gas emissions.

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The Truth is not an option – part 4

May 23rd, 2012

Part 4.  Denial, doubt, and fear

“Uncertainty is commonly misunderstood to mean that scientists are not certain of their results, but the term specifies the degree to which scientists are confident in their data.”

— Anthony Carpi and Anne E. Egger, Data: Uncertainty, Error, and Confidence

Science is a cooperative endeavor dedicated to produce the most accurate possible image of how

things are now, or once were, or will be. No clique can rig an inaccurate image of truth and perpetuate it. Science is about our understanding of the Cosmos and everything included within.   Competition among peers is relentless, and valid hypotheses that turn out to be wrong are identified, and those on the right track are reinforced. Science is never a one-track path of advance, but rather it is a web of thought. Scientists must simplify the web for the public so they may derive some tangible meaning from the complexity; however, scientists must not be so simplistic as to present science as a singular linear train of thought, as from ignorance to knowledge, from false to true, from evil to good.  It is rather a dispassionate construction of an image of reality that is never perfect but can be ignored or inverted only to one’s peril.

Being wrong is not the issue. Reality is always there and rather insistently will tend to correct any falsehoods and incorrect conceptions. A few activists among the climate skeptics appear to have sincere motives to get to the bottom of matters, which can be confusing and complicated (because the Earth is complicated). The climate-change science community has no worries about well-intending skeptics; we thrive on serious questions and rise to the challenge of developing better explanations, filling logical or observational gaps, and doing a better job at communicating the science.  Where we are weak, we need and thrive on criticism; identifying weaknesses in one another’s work, and our own, and then remedying the weaknesses, is what we do for a living.  The history of science is replete with examples of how nonscientists have contributed critical analysis that has strengthened or altered scientific ideas.  In climate change science, deep probing by some of the more able skeptics led to an improved attention to uncertainties by many climatologists.  This has improved the science (actually lending greater credence to the high side of climate sensitivities).  Likewise, scientists who have models that may be on an extreme low or high side of climate sensitivity to greenhouse gases, or glaciologists who have nonstandard models of glacier responses, have nothing to fear; they may be wrong, or they may be right. Ideas that rail against the status quo of general understanding can and do meet with some resistance, but ultimately those ideas are given a hearing.

 

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The Truth is not an option – part 3

May 18th, 2012

Part 3. Lessons learned

“I had the opportunity with regard to Galileo to draw attention … the exegete and the theologian must keep informed about the results achieved by the natural sciences.”

–Pope John Paul II

Before Saturday’s end, the tide of media coverage had shifted from reporting the erroneous 15% disappearance of ice, as though it was real fact, to reporting the scientists’ rejection of a false claim by an atlas publisher.  Only on a few blogs was it being played as a scientific blunder or a controversy among scientists, and even those people generally relied on scientists’ statements to point out the mistake. There was nothing controversial about it.  HC goofed up, plain and simple; that is what the media reported over the weekend and into the next week. This shift was made by the intervention of the scientific community to lay out the facts, and by the mainstream media clearly wanting to play the story as it should be—true to the facts.

Addressing the Cryolist and SPRI’s letter15, on Saturday, 17 Sep 2011, I captured some of the cryosphere community’s sense of the turning tide:  “This cartographic fiasco and sad journalistic event is a dark cloud made a little smaller, but there is the silver lining: everybody with striking results, especially new results, should push it to the media and use the Scott Polar letter as a hook.  Greenland itself is beautiful, the data are exquisite, the science is sound, the changes are profound, the meaning of it is important to people; and honest journalists– by far most of those who would be inclined to report on the "15% mistake"– will be wanting answers to the question of what IS happening.”

Many lessons stemmed from that sequence of events. Foremost for me was from John Vidal, a reporter for The Guardian, who first broke the story from the HC press release.  He responded to my initial criticism, which I had levied (wrongly on my part) equally on The Guardian and HC: “… It's actually quite hard to know what to do in these circumstances. We are not academically equipped to sort, sift and judge all the decisions made by Times's cartographers, … …  I am more than happy to write another piece saying that groups of eminent cryologists are in profound disagreement with the Times atlas … … But in this case please don’t blame the messenger!” 

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The Truth is not an option – part 2

May 14th, 2012

Part 2. Tackling misinformation in the 24-hour news cycle

“Lastly, I would address one general admonition to all; that they consider what are the true ends of knowledge, and that they seek it not either for pleasure of the mind, or for contention, or for superiority to others, or for profit, or fame, or power, or any of these inferior things; but for the benefit and use of life; and that they perfect and govern it in charity. For it was from the lust of power that the angels fell, from lust of knowledge that man fell; but of charity there can be no excess, neither did angel or man ever come in danger by it.”

–Francis Bacon, 1620, Franciscus de Verulamio Summi Angliae Cancellaris Instauratio magna, in: Bacon, F., The Works, Part IV, J. Spedding, R. L. Ellis, and D.D. Heath (eds.), London (1901).

Climate change denialism and trivialization, whether a result of scientific illiteracy and ignorance or something more willful (possibly conspiratorial among some practitioners), has its mirror in climate change exaggeration.  Both are harmful to public understanding of issues bearing on human well being, are harmful to the economy and national competitiveness, and are dangerous for the next generations. 

The formal story of the HC mistake and the response (including HC’s courageous and productive response) is told elsewhere,2  but it is worth adding to the record, mainly as guidance as to whether the scientific response to the bogus news story may serve as a model for the future. The upshot is that valuable lessons were learned and will be applied in the future, but future misinformation crises are not apt to be as ideally tailored to a speedy, positive outcome as this case was.  Indeed, the publisher has made amends with intensive consultations with scientists and a new map recently provided as an insert for their Atlas.  That is the happy end of the story.  It’s worth reviewing briefly a few details leading up to that ending which are not already covered in a formal peer-reviewed account.These details are primarily available in the semi-public record provided by the Cryolist (http://cryolist.org, a listserve, administered by glaciologist Todd Albert, for glaciologists and scientists in related fields, but available to reporters and other legitimate users and citizens who eschew abuse of the service).  I also add my personal perspective, which is mine only and does not necessarily reflect opinions of my employer, my funding source (NASA), my research colleagues, or the International Glaciological Society. 

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The Truth is not an option – part 1

May 10th, 2012

Part 1. The Truth is not an option (it’s mandatory)

By Jeffrey S. Kargel

Disclaimer: The following 5-part series represents my own opinions and responsibility. Quotations are likewise not necessarily my opinions, but are of those quoted. –JSK

“An error does not become truth by reason of multiplied propagation, 
nor does truth become error because nobody sees it.”

–Mahatma Gandhi, Young India, A Weekly Journal, 26 Feb. 1925.

On September 15, 2011, midnight London local time, the publisher HarperCollins (HC) released a marketing statement about their newly published 13th Edition of the Times Comprehensive Atlas of the World (henceforth, the Atlas). The company marketed their renowned atlas via a press statement claiming an alarmingly high rate of loss of ice cover in Greenland1; one-seventh of the microcontinent’s permanent glacial ice cover had melted, thus “turning Greenland green,” just in the 12-year interval since their previous Greenland mapping. HC had announced the most dramatic consequence of climate change yet documented; or so they thought. Unfortunately for HC’s book sales, but welcome news to everybody else who may have believed the news, the story was a grotesque (and accidental) exaggeration of a real retreat occurring roughly a factor of a hundred more slowly2

It was a big mistake, but we all falter and sometimes fail. HarperCollins has not only apologized (albeit awkwardly), but took immense measures to rectify their mistake3-5. For HarperCollins, surely the motive was to support their claims regarding the quality and time-vaunted credentials of their atlas6. Why then is this still a story and a vital lesson to heed and to be committed to full record? It is not for the debt of the mistake maker, but for the debt of those who would repeat the accidental mistake of exaggeration of climate change or its mirror opposite of trivialization of climate change.

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Atlasgate – the follow up!

May 10th, 2012

You all will recall the flurry of activity last autumn when the new Times Atlas of the World was published by HarperCollins and the unified response of the glaciological community to their marketing ploy. The publishers claimed to have spotted an alarmingly high rate of loss of ice cover in Greenland. This proved to be a mistake and a result of overzealous interpretaion of the publishers. Fortunately the glaciological community was 'on the ball' and the mistake was picked up immediately. Letters and e-mails were written and the end result was that HarperCollins apologized, and has taken measures to rectify their mistake. 

The glaciologists involded in pointing out the mistake and forcing the apology from HarperCollins banded together and wrote an article about the episode that was published in the online journal The Cryosphere last week. As a followup, the lead author, Jeff Kargel has written a five-part blog that will be published on the IGS web during the next few days.

The series is called 'The Truth is not an Option' with the subtitles 

Part 1. The Truth is not an option (it’s mandatory)
Part 2. Tackling misinformation in the 24-hour news cycle
Part 3. Lessons learned
Part 4. Have plenty of patience
Part 5.  No awards, no allowance for willful ignorance

I trust you will find this series informative and enlightening.

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Membership of the IGS

March 8th, 2012

I started this monolog initially intending to respond to Helen Fricker's question on the IGS Facebook site. But it turned out to be much too long for that venue so I moved it to the blog. 

Back in the seventies everyone in glaciology was 'expected' to join the IGS. My UW professor Charlie Raymond told us in no uncertain terms that if we were going to pursue a career in glaciology we really should be members.That is where the glaciology papers were published and if you wanted to have a copy of the papers, the only way was to join. Unfortunately or fortunately, depending upon how you look at it, that is no longer the case. People nowadays ask themselves, 'what is the benefit of joining?'.  

So we are looking at ways to give 'value added' to IGS membership. But what we can do is dependent on the membership. The more members we have the more we can do.

Membership started dropping off in the eighties with a slight surge upwards in the late eighties and then again a drop.  In the early nineties membership started climbing again and reached a peak in 2001 at 835. It then plummeted but we started crawling back in 2004/2005 and now we are getting close to the 'latter day maximum' in 2001. At the time of writing we are at 825. So get your colleagues to join to bring the number above the 2001 figure. We will then have to go back to 1987, when we had 907 members.

We are aiming to get above 900 this year and above 1000 within another 2-3 years. But it all depends on what we can 'give' to members. Right now we have all the back issues of the Journal and Annals available to members online. This is our main attraction. ICE is now online as well. Members also get a preferential rate at our symposia.

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I’ve attended my 5th IGS sponsored (or co-sponsored) meeting of my first year as president…

February 20th, 2012

Just back from New Zealand, where I attended the 2012 Annual Workshop of the Snow and Ice Research Group (NZ) held in Twizel, New Zealand. What a trip! (See the forthcoming report in ICE for more details.) This means that during the first year of my term as IGS president, I've attended meetings in La Jolla, California, Cambridge, UK, Oslo, Norway, Grenoble, France and now Twizel, New Zealand. The things I've learned at these meetings would have made my head spin, if it were not already spinning from the jet lag.

On my way to and from Twizel (located in the shadow of Aoraki/Mt. Cook), I passed through Christchurch. It was very disturbing to see the damage and suffering that the residents of Christchurch went through as a result of the recent earthquakes. However, I was delighted to have a "flat white" and a bit of shopping at the "container mall" on Cashel Street.

A free day at the end of the trip allowed me to see the blue penguins at the Antarctic Centre in the outskirts of Christchurch. Photos and a video are attached.

Doug MacAyeal

 

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Informal glaciologists meetings

February 5th, 2012

Just attended the 16th Alpine Glaciology Meeting in Zurich. These meetings are so productive and informative. The AGM is based on the same concept as the Northwest Glaciologists meetings in the US and Canada. As a young student at University of Washington in Seattle, under Charlie Raymond, we used to travel to Vancouver and Tacoma for those meetings every year, different venue every year. 
It was a great opportunity to meet up with fellow students and the famous names in glaciology like Barclay Kamb, Garry Clarke and Mark Meier and many others. It was a great opportunity for students to practise their presentation skills and learn how to answer probing questions from such greats as Barclay. Once you leaned how to respond to a question from Barclay Kamb you could handle anything. 30 years later these meetings are just as vibrant and stimulating and the students are still taking their first steps in the demanding world of public speaking.

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