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Extreme Melting on Greenland Ice Sheet, Reports CCNY Team

Posted on 31 October 2011 by John Hartz

The following is a reprint of a news release posted by the City College of New York (CCNY) on Oct 13, 2011

Glacial Melt Cycle Could Become Self-Amplifying, Making it Difficult to Halt

The Greenland ice sheet can experience extreme melting even when temperatures don’t hit record highs, according to a new analysis by Dr. Marco Tedesco, assistant professor in the Department of Earth and Atmospheric Sciences at The City College of New York.  His findings suggest that glaciers could undergo a self-amplifying cycle of melting and warming that would be difficult to halt.

Marco Tedesco standing on the edge of one of four moulins (drainage holes) he and his team found at the bottom of a supraglacial lake during the expedition to Greenland in the summer, 2011. (Credit: P. Alexander) Marco Tedesco standing on the edge of one of four moulins (drainage holes) he and his team found at the bottom of a supraglacial lake during the expedition to Greenland in the summer, 2011. (Credit: P. Alexander)

(click thumbnail for larger-size image)


“We are finding that even if you don’t have record-breaking highs, as long as warm temperatures persist you can get record-breaking melting because of positive feedback mechanisms,” said Professor Tedesco, who directs CCNY’s Cryospheric Processes Laboratory and also serves on CUNY Graduate Center doctoral faculty.

Professor Tedesco and his team collected data for the analysis this past summer during a four-week expedition to the Jakobshavn Isbræ glacier in western Greenland.   Their arrival preceded the onset of the melt season.

Combining data gathered on the ground with microwave satellite recordings and the output from a model of the ice sheet, he and graduate student Patrick Alexander found a near-record loss of snow and ice this year. The extensive melting continued even without last year’s record highs.

The team recorded data on air temperatures, wind speed, exposed ice and its movement, the emergence of streams and lakes of melt water on the surface, and the water’s eventual draining away beneath the glacier. This lost melt water can accelerate the ice sheet’s slide toward the sea where it calves new icebergs. Eventually, melt water reaches the ocean, contributing to the rising sea levels associated with long-term climate change.

The model showed that melting between June and August was well above the average for 1979 to 2010. In fact, melting in 2011 was the third most extensive since 1979, lagging behind only 2010 and 2007. The “mass balance”, or amount of snow gained minus the snow and ice that melted away, ended up tying last year’s record values.   

Temperatures and an albedo feedback mechanism accounted for the record losses, Professor Tedesco explained. “Albedo” describes the amount of solar energy absorbed by the surface (e.g. snow, slush, or patches of exposed ice). A white blanket of snow reflects much of the sun’s energy and thus has a high albedo. Bare ice – being darker and absorbing more light and energy – has a lower albedo.  

But absorbing more energy from the sun also means that darker patches warm up faster, just like the blacktop of a road in the summer. The more they warm, the faster they melt.

And a year that follows one with record high temperatures can have more dark ice just below the surface, ready to warm and melt as soon as temperatures begin to rise. This also explains why more ice sheet melting can occur even though temperatures did not break records.

Professor Tedesco likens the melting process to a speeding steam locomotive. Higher temperatures act like coal shoveled into the boiler, increasing the pace of melting. In this scenario, “lower albedo is a downhill slope,” he says. The darker surfaces collect more heat. In this situation, even without more coal shoveled into the boiler, as a train heads downhill, it gains speed. In other words, melting accelerates.

Only new falling snow puts the brakes on the process, covering the darker ice in a reflective blanket, Professor Tedesco says. The model showed that this year’s snowfall couldn’t compensate for melting in previous years.  “The process never slowed down as much as it had in the past,” he explained. “The brakes engaged only every now and again.”

The team’s observations indicate that the process was not limited to the glacier they visited; it is a large-scale effect. “It’s a sign that not only do albedo and other variables play a role in acceleration of melting, but that this acceleration is happening in many places all over Greenland,” he cautioned. “We are currently trying to understand if this is a trend or will become one. This will help us to improve models projecting future melting scenarios and predict how they might evolve.”

Additional expedition team members included Christine Foreman of Montana State University, and Ian Willis and Alison Banwell of the Scott Polar Research Institute, Cambridge, UK.

Professor Tedesco and his team provide their preliminary results on the Cryospheric Processes Laboratory webpage. They will will be presenting further results at the American Geophysical Union Society (AGU) meeting in San Francisco on December 5 at 9 a.m. and December 6 at 11:35 a.m.

The research was supported by the National Science Foundation and the NASA Cryosphere Program. The World Wildlife Fund is acknowledged for supporting fieldwork activities.

On the Internet:

2011 Melting in Greenland report

Cryospheric Processes Laboratory

Professor Tedesco Tracks Life and Death of Greenland Glacial Lake

Map of expedition location

Expedition Facebook page

Expedition Twitter Feed!/Cryocity

Marco Tedesco profile

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Comments 1 to 8:

  1. And to think that a mere 9 months ago, some were arguing that this wasn't true: A Flanner in the works. As Earth warms, ice and snow melt and the loss of their shiny, reflective surfaces means more sunlight is absorbed and global warming receives a boost. That's the trouble with the 'no its not' crowd. Physics doesn't care.
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  2. This was also the case observed on the east coast of Greenland by Mernild and Hanna.
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  3. @mspelto #2: Thanks for the reference and link. Here's the summary of that study. "An international team of scientists has discovered that warming in the Arctic region has triggered the accelerated melting of a Greenlandic glacier. Presented in The Cryosphere journal, the findings reveal that the overall mass loss of the Mittivakkat Glacier for 2011 has amounted to 2.45 metres, 0.29 metres higher than what was recorded in 2010. The study was funded in part by the INTERACT ('International network for terrestrial research and monitoring in the Arctic') project, which has clinched EUR 7.3 million under Research Infrastructures of the EU's Seventh Framework Programme (FP7)."
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  4. Back last spring there was a paper on albedo loss (in geophysical letters I think) which cryosphere buffs will no doubt recall, which reported that albedo loss now imposes a forcing equivalent to around 30% of anthro CO2 emissions - i.e. around 9.0GtCO2e. This is the only feedback for which I've seen a current figure intelligible to the layman, and I'd like to know if this present report supports that finding or not. Given that we face at least seven interactive mega-feedbacks of which six have been accelerating for some decades, I'm getting increasingly skeptical of the lack of proportionate attention being focussed on them, and particularly of the lack of translation of their scientific evaluations into lay English. The report noted above was exceptional in describing the forcing as being 'equivalent to around 30% of anthro CO2 output' - but it could be still more effectively expressed as 'about one-and-a-half new America's worth of warming, and rising by the year'. I would like to think that the lack of public information on the trend-lines of accelerating feedbacks is due simply to the difficulty of their evaluation, and to a grievous lack of co-ordination across the scientific community. But neither point holds true. First, several of the feedbacks have a directly quantifiable track record - i.e.: - rising DOC in peat-bog outflow streams (~6%/yr) since '62 due to elevated CO2 feeding microbial peat-decay rates; - rising percentage of water vapour carried by a warming atmosphere; - declining cryosphere (recorded graphically since the '60s space program) and resulting albedo loss; - declining permafrost - with limited but significant monitoring of resulting emissions allowing a credible estimate of its rising contribution to warming. Second, the failure to assemble, translate and disseminate those feedback trends to the public cannot logically be explained by an accidental lack of co-ordination in the scientific community - there has never been an issue on which global scientific research has collaborated to the extent it has on climate, and the feedbacks have been known for decades to pose the most extreme hazard of the entire climate issue. Skepticism is not a comfortable state of mind - it opens concerns that there is, at some arcane level of society, an interest in steering scientific enquiry away from the issue of the feedbacks - that could radicalize public demand for action - in favour of the deficient focus on anthro-emissions' impacts generating a scant public pressure for action, that has proved easily deflectable by mounting a circus of denial at home and a theatre of nationalistic rivalry abroad. Some may dismiss this perspective as mere conspiracy theory - but then they must either ignore or answer the question as to why the Inter-Governmental Panel on Climate Change has failed to include updates on the progress of each of the mega-feedbacks in each of its reports? As a great many climate scientists would assert, being self-reinforcing hazards they most certainly warrant that degree of attention. It's my hope that SkS will help to remedy this lack of public information about the rising trends of the interactive feedbacks - as a crucial part of its seminal role in informing and educating society on the climate predicament it faces. To my knowledge neither the I(G)PCC, nor the great scientific academies and institutions, nor the NGOs are fulfilling this critical role - so Sks would actually be breaking new and very relevant ground in doing so. Regards, Lewis
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    [DB] "It's my hope that SkS will help to remedy this lack of public information"

    Science and scientists have been researching climate change and publishing that reaseach for more than a century.  There have been active calls by scientists and scientific bodies for the public and media to pay more attention to their findings for many decades (which is why, for example, President Nixon established the EPA).  So it is not for a lack of transparency, will and effort to reach the public that the message is not being delivered.  So hints at conspiracy on the part of science are vastly misplaced.

    That leaves the issue squarely in the laps of the media and the well-publicized and well-funded efforts of the anti-science community to block any efforts which may result in a declining usage of fossil fuels.  And that is far beyond the realm of this post.  It is my hope that any individuals willing to pursue this line of dialogue take it to a more appropriate thread (many exist), as it is off-topic here.

  5. LewisC wrote: "...why the Inter-Governmental Panel on Climate Change has failed to include updates on the progress of each of the mega-feedbacks in each of its reports?" WG1 Section 8.6 Enjoy.
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  6. LewisC #4: You state: "It's my hope that SkS will help to remedy this lack of public information about the rising trends of the interactive feedbacks ..." SkS has been doing just that since its inception. To see the results, insert the word "feedback" into the site's search box and click "GO".
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  7. It was not my intention to imply any conspiracy on the part of science in my comment above. I wrote specifically of 'steering' by political, not scientific interests. The lack of quantified trends of the six mega-feedbacks' acceleration to date being - a/ assembled and b/ translated into language and graphic form accessible to the public, is something I'd be delighted to find I was wrong on. Can anyone locate such information ? I wrote the comment here of SkS precisely because of its fine and consistent coverage of the feedback reports since its launch. But as far as I know, SkS has yet to publish those quantified trends-thus-far, as an assembly, in a form accessible to the layman. Thus I was hoping that there might be sufficient concern over the issue to consider a fresh suggestion. I still hope that I wasn't wrong on that. For those who choose to respond defensively and see no reason to raise the game, I suggest they try talking to ordinary people about the NOAA/NSIDC report on permafrost carbon emissions: "Permafrost melting will cause around 100 billion tonnes of carbon to be emitted by 2100, getting to about 500 million tonnes by 2020 and to 1,600 million tonnes in 2100, - but that doesn't account for the CO2-equivalent warming due to part of the carbon coming out as methane, which is 72 times as potent as a greenhouse gas as carbon dioxide, - and it doesn't include extra melting due to the warming caused by the permafrost greenhouse gas emissions; - or that due to the several other interactive mega-feedbacks that are now accelerating; - or that due to the foreseeable loss of the cooling sulphate pollution that ending our fossil fuel emissions will curtail." An ordinary person hearing such a litany of unquantified hazards is more likely to be turned off than concerned. The need for the clearest quantified overview achievable is thus very real - not for the minority who are still duped by fossil interests, but for the far larger numbers who accept AGW and see the need of action, but are not remotely well-enough informed of the scale and urgency of threat to demand action with implacable determination. Those who want to carry on tussling with deniers to chip away at their minority support are in my view entirely laudable in their efforts, but addressing the majority with information that can generate the demand for action is evidently the necessary precursor to action being achieved at the earliest possible date. I would hope that we can at least agree that achieving commensurate action on climate is our common goal. Regards, Lewis
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    [DB] Lewis, it is with the greatest of regret that I intervene here.  Not becuase of what you write isn't of interest or not needing further exploration; both are.  But because it is off-topic to this thread.

    With that in mind, I invite you to write this up as a guest post for consideration for publication here at SkS.  If you are interested, just respond to this here and I will email you the details.

    Again, if others want to explore portions of this on some of the other, more pertinent threads, feel free to do so & leave a pointer stub here.  Thanks!

  8. DB - my thanks for your response and my apology for straying too far off topic - I hadn't realised how rigorous are the thread parameters here on SkS. My thanks too for your invitation to write up these ideas for consideration as a guest post - which I'd be glad to make time for. Regards, Lewis
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