From the City College of New York: Extreme Melting on Greenland Ice Sheet, Reports CCNY Team
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.
“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
http://greenland2011.cryocity.org
Cryospheric Processes Laboratory
Professor Tedesco Tracks Life and Death of Greenland Glacial Lake
http://www1.ccny.cuny.edu/advancement/news/Tedesco-Greenland-Glacial-Lake.cfm
Map of expedition location
Expedition Facebook page
http://www.facebook.com/pages/Cryocity/124269854300408
Expedition Twitter Feed
http://twitter.com/#!/Cryocity
Marco Tedesco profile
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Well, I’ll just get right on the panicking part.
I mean really… it was such a breeze to “halt” glacial melting before, but now that it’s self-amplifying, I don’t know.
Of course we have no reference period. Everything today that has to do with melting can therefore be blamed on CO2.
Does it get any better than that?
“The model showed that melting between June and August was well above the average for 1979 to 2010.”
Pretty much all you need to know about this study.
Modelled nonsense.
GIGO.
The conclusions are reasonable: melting cycles can be self-accelerating, and probably just as self-decelerating once the conditions are right. It seems quite possible that the whole island could melt eventually, in the sense that it is no longer covered by a permanant ice sheet, even if it continues to have hard winters.
There does not seem to be strong emphasis on blaming human activity for initiating the change, nor a strong statement that it is natural. As Greenland has been slowly melting since the end of the LIA I presume it will continue until the next ice age starts, mini or major.
This work advances our understanding of how ice sheets behave, at least some of the time.
As Fairbridge once concluded that sea level rises and falls by as much as (or more) than a metre in as little as 20 years (study of Eastern Australian shoreline change over the last 8000 years) perhaps this type of self-acceleration is not all that rare.
I always get the funny feeling when reading these types of findings that the report was probably written prior to the data collecting expedition. Why is that?
One point not mentioned in the article is how much new snow and ice is added to the glaciers. One would think it is zero or almost. Not true. The only such thing I found mentioned in an anecdote posted by a reader on Steve’s blog:
http://www.real-science.com/greenland-meltdown#comment-54428
Alarmists love them some positive feedback.
If there was increasing levels of positive feedback then why weren’t there record high temperatures?
I’d like to see their raw data. It doesn’t seem as if it would support any speculation about positive feedback caused melting. It seems as if they were desperate to publish something so that they didn’t have to admit that they wasted a year’s worth of work.
Did they figure out how much melting is due to black carbon?
Model involved. Ocean level dropping. Junk science.
“…….Combining data gathered on the ground with microwave satellite recordings and the output from a model of the ice sheet……..”
Model mentioned in study.
Enter sleep mode.
really nothing new…
just confirmation of what we already understood…
Danish researchers found that the annual Greenland ice melt was 191 til 240 billion metric tonnes a year from 2003 to 2008. http://www.dmi.dk/dmi/danske_forskere_maaler_og_vejer_indlandsisen
Not sure if there is any evidence that the melting was increased dramatically since then.
Wiki estimates the total Greenland ice sheet is 2,850,000 cubic kilometres. So dividing that mass with any number between 191 and 240 billion tons a year will yield over 10,000 years before we can inspect the whole of an ice free Greenland. By then we will assuredly have entered another ice age. Willis Eschenbach had a long article about this here some time ago coming to the same conclusions. It is amazing how this “non story” keeps surfacing again and again based on a cursory visit and a model. The Danes surely have a better understandig of what is going on there.
I wonder why there does not seem to be a sea-level rise signal from the accelerated melting?
http://sealevel.colorado.edu/
This will help us to improve models………
==================================
/snark
I wonder what caused the melting from 1850 – 1902, in this image from NASA?
http://www.nasa.gov/101948main_calvingstill_1850_2003.tiff
(7 MB file!)
Here is the full article from 2004. In this article NASA says, “Jakobshavn Isbrae holds the record as Greenland’s fastest moving glacier and major contributor to the mass balance of the continental ice sheet.”
http://www.nasa.gov/vision/earth/lookingatearth/jakobshavn.html
Sorry, I can’t put much faith in a study by someone without the common sense to NOT stand that close to the edge of a moulin. You fall in that thing, you’re done.
The averages are based on the years 1979 – 2010. Once again confirming that the Earth began in 1979.
@John Peter
“The Danes surely have a better understanding of what is going on there.”
There is a rumour they even use thermometers to determine the temperature of the Arctic!
How quaint!
If Greenland was basically glacier-free only 250,000 years ago, give or take, it can’t be all that unusual to have melting there. Self-acceleration is a very reasonable expectation. Watch the snowbanks melting in springtime. As soon as there is dry ground dust blows around changing the albedo. It may or may not change the sea level as prophesied – depends on what is happening elsewhere.
[snip – all caps – resubmit]
Have a look at this site how a couple of abandoned radar site are being swallowed by the Greenland ice cap. http://www.lswilson.ca/dye2pics.htm.
Ockham says:
October 26, 2011 at 8:41 am
I always get the funny feeling when reading these types of findings that the report was probably written prior to the data collecting expedition. Why is that?
The reason for the feeling may not be known, but the feeling exists, nonetheless. I liken it to the brain ‘needing’ a scientific sequence of events in order to properly integrate knowledge. When one reads one of these press releases, they all follow the same pattern: An assertion, a series of uncertain-language postulations, a leap of faith, and some wishy-washy conclusions, all watered down into layperson’s terms…and all some kind of link to ‘climate change’ as if it were some kind of dastardly anomaly beckoning for ‘science’ to unravel the cause. The queasy fealing is basically “I have the feeling I’ve read this before”, and as it unfolds, one is left with an empty hollowness. Climate science has become concrete-bound, making the same assertions over and over, to serve the juggernaut, while never leaving the safety of conventional wisdom. All of this, and tainted by alarmist untertones; “irreversible melting” in this case.
GIGO indeed.
From photo at top of article.
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)
So…where is the lake this is at the bottom of? A ‘supraglacial’ lake is on top of the glacier!?
In the period 1930-1950, summer temperatures of Greenland around the edges were as high to higher than today. The edges were melting as fast as now (if not faster). After that period, the glacier tongues advanced again, until the 2000’s…
Another “tipping point.” Positive melting feedback will lead to a “runaway” icecap melt and we’ll end up like Venus.
We noted a few posts ago that the Greenland ice sheet doesn’t record anything beyond the last interglacial, and the possibility that the Eemian melted it away. Might happen again, should the Holocene last long enough, fingers crossed. The Eemian was about 2 degrees warmer than ours for a couple thousand years, so it’s a question.
Once again, if positive feedbacks were dominant at any time in the last few billion years, why are we even alive?