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Greenland Ice Sheet “Could Undergo a Self-Amplifying Cycle of Melting and Warming … Difficult to Halt,” Scientists Find

By Joe Romm  

"Greenland Ice Sheet “Could Undergo a Self-Amplifying Cycle of Melting and Warming … Difficult to Halt,” Scientists Find"

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Greenland Ice Sheet Ties Record for Mass Loss in 2011

Another day, another amplifying feedback or vicious cycle.

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….

… 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.

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)

The photo on the right is “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.”

It’s not news that there are amplifying feedbacks at work on the great ice sheets.  Just this March, the U.S. Jet Propulsion Laboratory published its analysis that Polar ice sheet mass loss is speeding up, on pace for 1 foot sea level rise by 2050.  That study found:

The Greenland and Antarctic ice sheets are losing mass at an accelerating pace, according to a new NASA-funded satellite study. The findings of the study — the longest to date of changes in polar ice sheet mass — suggest these ice sheets are overtaking ice loss from Earth’s mountain glaciers and ice caps to become the dominant contributor to global sea level rise, much sooner than model forecasts have predicted.

But the new CCNY study, based on in situ observations “during a four-week expedition to the Jakobshavn Isbræ glacier in western Greenland,” lays out for the first time a very specific amplifying feedback occurring way up north:

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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….

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.

Tedesco has a good analogy — and he explains that this effect is widespread:

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.”

2011 Melting in Greenland report
http://greenland2011.cryocity.org

Have I mentioned that the time to act was a long time ago, but now is a lot better than later if one doesn’t want endlessly rising seas?

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15 Responses to Greenland Ice Sheet “Could Undergo a Self-Amplifying Cycle of Melting and Warming … Difficult to Halt,” Scientists Find

  1. Leif says:

    The last sentence of a report from U of Melbourne. I do not recall seeing a science report with this kind of language.

    “It is not that the 2°C target has slipped out of reach already, but if there is 10 years more of inaction, if there is 10 years of following only low ambition pathways, then we are very close to the point where we don’t know that there are technologies that would be able reduce the emissions fast enough to be able to reach the two-degree pathway,” says Meinshausen. “So we are very close to the cliff.”

    “Temperature targets slipping away”

    http://www.abc.net.au/science/articles/2011/10/24/3345614.htm

    • Yeah, right now the technologies look like kicking out the floorboard and trying to brake by digging in with your heels. In 10 years, the technologies look like tying off the steering wheel while you try to jump.

  2. Joan Savage says:

    It may seem like a side-bar at the moment, but the physics of water and ice includes spatial reorganization at temperatures other than well-known phase changes of ice to water, water to gas. Gelatinous sub-zero water is one of the more bizarre.

    As massive parts of the Greenland ice sheet change from deep cold to not-so-deep cold, it is hugely important to continue to have on-site monitoring of what the ice and water are doing.

  3. Steve Funk says:

    Maybe this study is a good heads up, but it is a press release, not a peer reviewed publication.

  4. prokaryotes says:

    So far Greenland is considered a long term feedback. But at the same time ice sheet dynamics are not completely understood. There have been in the past been abrupt melts recorded. Moulins will probably create instabilities for the Greenland Ice, within the coming years or decades.

    Changes recorded in the climate of Greenland at the end of the Younger Dryas, as measured by ice-cores, imply a sudden warming of +10°C within a timescale of a few years. http://en.wikipedia.org/wiki/Abrupt_climate_change

    Water from moulins may help lubricate the base of the glacier, affecting glacial motion. Given an appropriate relationship between an ice sheet and the terrain, the head of water in a moulin can provide the power and medium with which a tunnel valley may be formed. The role of water in lubricating the base of ice sheets and glaciers is complex. Difficulties modelling this process led to apparently over-optimistic predictions of sea level rise by the IPCC in the IPCC fourth assessment report. Recent research by Stefan Rahmstorf, released at the Climate Congress suggests that sea level rise will be greater than predicted in the IPCC’s report. http://en.wikipedia.org/wiki/Moulin_(geology)

    Periods of exceptional climate change in Earth history are associated with a dynamic response from the solid Earth, involving enhanced levels of potentially hazardous geological and geomorphological activity. This response is expressed through the adjustment, modulation or triggering of a wide range of surface and crustal phenomena, including volcanic and seismic activity, submarine and sub-aerial landslides, tsunamis and landslide ‘splash’ waves glacial outburst and rock-dam failure floods, debris flows and gas-hydrate destabilisation. Looking ahead, modelling studies and projection of current trends point towards increased risk in relation to a spectrum of geological and geomorphological hazards in a world warmed by anthropogenic climate change, while observations suggest that the ongoing rise in global average temperatures may already be eliciting a hazardous response from the geosphere.
    http://rsta.royalsocietypublishing.org/site/issues/climate_forcing.xhtml

  5. Lou Grinzo says:

    The drumbeat of “it’s worse than we thought” news continues.

    Jeffrey Davis mentioned above that soon we’ll be reduced to jumping out of the moving car. When one considers all the relevant time lags, from figuring out what’s really going on in the earth system to the very long atmospheric lifetime of CO2 to political and economic delays, I would contend that we’re already at the point of having to decide whether to jump from the moving car. I’m confident that a lot of people in positions of great political power know this and are choosing to kick the can down the street and tell themselves that the tiny changes they’re “able” to make “are enough, given political realities”.

    There’s been more talk again about the CIA refusing a FOIA request related to their analysis of climate change (presumably from a national security viewpoint). I’m not the least bit surprised by this, as I suspect they spoke with several scientific organizations and individuals, consulted all the latest research, and came to some absolutely hair-raising conclusions about water, food, climate refugees, and the knock-on effects of creating more terrorists and triggering decades of humanitarian crises and even failed states. If you had a report that said countries X, Y, Z, and W were headed for “natural” disasters like nothing we’ve seen in recorded human history, you probably wouldn’t be thrilled to see it made public, either, given the uproar it would cause. Much better to keep it under wraps, tell the right people in the government about your findings, and let the public continue to trundle blissfully along. (I am not saying I share this viewpoint, merely that I can very easily imagine people at the highest level of government seeing things that way.)

    I am more convinced than ever that we won’t see meaningful action to address climate change until the evidence of real world impacts is so great and so painful that it overcomes both our psychological resistance to the awful truth as well as the best efforts by the fossil fueled industries to deceive us. And by then, we’ll have certainly locked in a major dose of hell and high water.

  6. jyyh says:

    Then there’s the Grinstedt paper described here:
    http://www.skepticalscience.com/Sea-levels-will-continue-to-rise.html
    but as it’s said in the comments, I too find it hard to believe ice on a slope would stay there for long.

  7. Joan Savage says:

    Maps of Antarctic and Greenland bedrock elevations.

    http://nsidc.org/data/atlas/news/bedrock_elevation.html

    One surprise for me is a below-sea-level area in central Greenland that could become a freshwater inland sea.
    Another is how much of what we call Antarctica is profoundly below current sea level.

    • Joan Savage says:

      The inland depression in Greenland has a possible outflow channel to the Arctic Ocean.

      It seems improbable that under-glacier melt water could be flowing out of Greenland towards the north, but I haven’t yet found a paper on direction of melt water that might shed light on this.

    • Leif says:

      Thank you Joan for the informative link. I note that the orange is above current sea level. I would point out that the seas are rising and the orange will shrink and grays will increase. Also reminiscent of the Glacier Lake Missoula ice dam break up. When the water level behind the dam became deep enough to float the ice dam, (~2,000 feet on the first floods, with 4,000 foot of bottom head,) the ice stopper lost contact with the bottom and the whole collapsed in a matter of days and the 2,000 foot deep water flushed across the states of Washington and Oregon to a lesser degree. The whole in a matter of a few weeks or months at most. Not once but dozens of times.

      • Joan Savage says:

        Leif,
        I agree with an ice dam component as one of the Greenland scenarios. I hadn’t thought about the ~ 12,000 ybp Missoula ice dam break, but it is a catastrophe like the moraine break in the Hudson River Narrows around 13,350 YBP that unleashed proto-glacial Lake Iroquois water into the Atlantic.
        In Greenland an abrupt event like that could happen if an inland lake of ice melt accumulated above sea level and broke through an ice or sediment dam. For now, the moulins seem to be the main path of discharge, and the ice-surface lakes are transient, so I’m curious about water accumulating below the ice sheet and below current sea level.
        There’s plenty of room in the Greenland bedrock topography for lakes to form above sea level with a bedrock lake bottom, too.
        I also agree about the long view of the changing topo map, which is in 100 meter units. It would not not be expected to show much change in the 3 meter rise that seems to be horizon for people who want to talk about a single century, but it would surely change in a longer time scale towards the maximum sea level rise of 80 meters ( USGS fact sheet http://pubs.usgs.gov/fs/fs2-00/ )
        Over time a fresh water lake could burst into the sea and/or the sea could move into the depression. The Black Sea is thought to have enlarged as a post-glacial Mediterranean rose over a land barrier in the Bosporus.
        Too bad humans are speeding things up so ferociously. As you have pointed out before, our fascination with fire is a real problem.

        Thanks for sharing in the long view!

        • John McCormick says:

          Joan, you might be interested in a book written by Bill Ryan, at Columbia, who seems to have discovered the origin of the Black Sea. It is just as you said.

          Amazon.com: Noah’s Flood: The New Scientific Discoveries About the Event that Changed History (9780684810522): William Ryan,

    • Merrelyn Emery says:

      Yep, thats why the WAIS is almost certainly a goner, ME

  8. Mauri Pelto says:

    Moulins are and have been a key part of the GIS for sometime. Adding more is not going to lead to instability. It is the outlet glacier dynamics changing that is the key, along with expanding the melt zones to new areas in northern Greenland that will alter the dynamics in a region that had lacked this melting. Pay attention to the changing details from glacier to glacier. The thinning and recession is changing the geography, and that can change the terminus dynamics.