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Widespread Greenland Melting A Sign of Things to Come

When 97 percent of Greenland’s ice experienced at least some melting in July 2012, scientists wondered if it was a one-time phenomenon. Now a new study in Geophysical Research Letters indicates it is a sign of things to come and by 2025, there is a 50-50 chance of it happening annually.

It’s not clear what the effects of such melting will be: the majority of Greenland’s ice loss, which has accelerated significantly over the past decade, comes from glaciers shedding more ice into the sea, and moving faster toward the sea, not from melting snow and ice at higher elevations of the ice sheet.

Extent of surface melt over Greenland’s ice sheet on July 8, 2012 (left) and July 12, 2012. In just a few days, the melting had dramatically accelerated and an estimated 97 percent of the ice sheet surface had thawed.
Credit: Nicolo E. DiGirolamo, SSAI/NASA GSFC, and Jesse Allen, NASA Earth Observatory

Nevertheless, such widespread melting indicates an overall warming in the region that could threaten the ice more generally, adding significantly to the threat of sea level rise.

The 2025 projection is based on two factors, according to lead author Dan McGrath, a glaciologist at the University of Colorado, Boulder. The first is a series of temperature measurements going back to 1950 at the Summit research station, at the highest — and on average, the coldest — point on the Greenland ice sheet. The mercury has been rising more or less steadily there for that entire time, with the fastest increase, of about .22° F per year, coming since 1992. “That’s six times faster than the global average,” McGrath said in an interview.

The highest parts of the ice sheet still remain below the freezing mark virtually all the time, but when unusual weather conditions set in — an especially warm air mass, or as in the case of the 2012 melting, an influx of clouds just thin enough to let sunlight through but thick enough to block heat from escaping — the thermometer can sneak above 32°F. “Only an hour above freezing is enough to start the surface melting,” McGrath said.

Another factor that went into the analysis involved what’s known as the equilibrium line — the altitude where the snow is neither piling up year to year nor shrinking. Over the past 20 years or so, that transition zone has been gradually moving up the ice sheet by about 115 feet every year, on average— another indication that temperatures on the frozen island are warming.

Greenland cumulative melt days. Jan. 1 - May 20, 2013.
Credit: NSIDC

It was this second effect that led McGrath and his colleagues to launch their study. “When our research camp was established, it was put as close as possible to the equilibrium line,” McGrath said.  “If they put it any lower, it would melt out every year, and if it was higher, it could get buried in snow.”

But when the team returned for the summer season in 2009, he said the surface had melted so much that “it was falling apart. It looked like someone had dropped a bomb on it.”

They relocated the camp, and things were fine in 2010, but the following summer it had melted out again. “That led us to look at things in more depth,” he said.

The findings broadly agree with earlier research by other groups. “This is clearly an interesting paper, although I think it’s dangerous to pinpoint such a specific date as 2025,” said Marco Tedesco, a glaciologist at City University of New York, who produced some of that research.

To Tedesco, there’s too little emphasis on how Greenland’s ice would respond to a variety of scenarios for emissions of greenhouse gases, the primary reason for the planet’s overall warming over the past half-century.

Tedesco also felt that the new paper didn’t look hard enough at some of the feedback mechanisms between the ice sheet and the atmosphere that could arise as melting ice gives rise to more clouds, for example.

Nevertheless, he agreed, the overall message is entirely consistent with what others have found: Greenland’s ice is under assault by rising temperatures, and whether or not 2025 will represent a milestone, the consequences over coming decades could be catastrophic. 

Related Content
Greenland's Ice Loss May Slow, But Coasts Still At Risk
Greenland Melt Sets Record Weeks Before Summer Ends
Clouds Helped Enhance Greenland's Record Melting
Smaller Glaciers Boost Sea Level as Much as the Giants
Exhibition Turns Climate Data into Artistic Experience
The Story Behind Record Ice Loss in Greenland

Comments

By Dave (Basking Ridge, NJ 07920)
on May 21st, 2013

The ice sheet peaks in the middle of Greenland at about 10,000 feet ASL. Simple math: A 100 plus feet per year average rate of change in elevation of the equilibrium line is 1000 plus feet per decade. According to what I have read the line is already at 3 or 4000 feet. This and Mt. Everest peak snow melting back?  Sure “…could be catastrophic” seems to sum it up.

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By James Wrightsman (Bronxville, NY 10708)
on May 22nd, 2013

THANK YOU FOR BRINGING EVIDENCE TO THE DISCUSSION ON GLOBAL WARMING.  KEEP IT UP.

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By Mouse (Lewes DE 19958)
on May 22nd, 2013

And now, allowing for equal time, a spokesperson for corporate polluters will deny that there is any glacier melting or increased CO2 in our atmosphere

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By Lewis Cleverdon
on May 22nd, 2013

Dave - your extrapolation somewhat understates the annual ascent of the melt line. The paper’s abstract reports that the average ascent has been 35m /yr (115ft) over the last 18 years, but 44m /yr (144ft) over the last 15 years. I’d like to know that average since the massive arctic sea-ice melt of 2007.

The fact that the gradient declines the higher the average melt-line rises means that the area switching from dry snow to percolation each year is multiplied both by the rising melt-line ascent per year and by the declining gradient. In parts of both the SW and the SE the melt line is already within the watershed of the bedrock’s encircling ring of high ground around Greenland’s central depression, meaning that the moulins from melt-lakes in those areas (of about 60,000kms2 and 20,000kms2 respectively) are draining their melt water into an arterial system under the ice sheet.

That water will have melted its way to the lowest point of the bedrock in a depression about 300km wide to the east of a low point in the ring of mountains at Jacobshaven. When the water table rises with new melt water inputs each summer, there is a notable acceleration of the glaciers under which it overflows. The fact that the arterial system must lead to the lowest point and only then to the outflow implies that the whole system is flushed each year with freshly warmed water, much of which will remain each winter after overflow stops, transferring its heat into the base of the ice sheet and thus expanding the voids for the next year’s inflow to fill.

Michael reports a critique of the paper that it could have paid more attention to feedbacks, which I assume refers to surface melt accelerants, such as the cryoconites’ surface darkening that tracks the ascent of the melt line, and the rising occurrence of the Greenland High that both raises insolation and cuts snowfall. But to my mind the internal decay of the ice sheet due to warming by melt water poses a potentially far greater source of change, given the accelerating ascent of the melt line. Up the W coast for about 1100kms the melt line at present is at around 2000ms and at a gradient of about 5ms per kilometre, meaning that a 50m ascent adds a melt area of around 11,000kms2 per year, with the new melt-lakes’ moulins mostly within the watershed and so rapidly raising the annual inflow of melt water. Additional areas with lower gradients, particularly the saddle right across the ice sheet in the south that doesn’t reach 2500ms, enlarge this dynamic significantly.

The base of the ice sheet receive heat energy from the geothermal source which keep it far less cold than the core of the ice sheet above it, and in being penetrated by thousands of moulins and a riverine melt-water arterial system along the bedrock to the central depression, its solidity is being reduced. With an overlying ice burden above the central depression of around 2,500Ts /m2 (3,500lbs /in2) the ice sheet’s progressive internal collapse seems predictable as its base is increasingly weakened. In clogging the arterial system, such a collapse would greatly raise the internal water table each summer, thus increasing the fraction of the melt water inflow’s heat energy that is transferred to the ice sheet, and accelerating its internal decay.

With the ice sheet being around 700kms wide and only 3.5kms deep, it seems entirely likely that, if we failed to undertake the commensurate mitigation measures including Albedo Restoration, we’d see a central lake that is ice-free to the bedrock appearing at the level of the water table, and expanding by the year due to its insolation warming its banks and melting them back. With the median of arctic ice loss models having been patently wrong by well over a century, due primarily to their exclusion of critical feedback dynamics, models of the rate of melt of the GIS that exclude the feedback of its internal melt-dynamics will predictably suffer the same massive optimism bias. The implications for abrupt sea level rise are troubling.

Regards,

Lewis

PS If i were the first to posit the central lake’s development (which I doubt) I’d claim the right to name it Lake Povricide.

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By Gerald Wilhite (Austin, Texas 78703)
on May 22nd, 2013

The Greenland melt is certainly something to be carefully watched. We need to keep in mind, however, that according to researchers at the University of Wisconsin historical data indicates that this type of event happens about every 150 years, and this one appears to be right on time.

Here is an excerpt from the University of Wisconsin article (see link below):

“But the unusual-seeming event had nothing to do with hot air, according to glaciologists. It was actually to be expected.
Ice cores from Summit station [Greenland’s coldest and highest] show that melting events of this type occur about once every 150 years on average. With the last one happening in 1889, this event is right on time,” said Lora Koenig, a Goddard glaciologist and a member of the research team analyzing the satellite data.”


https://www.google.com/url?q=http://www.news.wisc.edu/21638&sa=U&ei=NCydUdW9O-m6yAG8uoCoCg&ved=0CAcQFjAA&client=internal-uds-cse&usg=AFQjCNH9QLsg4kdgEDbrI7r-WNeAUAZSEw

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By Tom Mallard (BELLEVUE, WA 98008)
on May 22nd, 2013

My recent focus in relation to the ice-sheet has been atmospheric circulations that are bringing much warmer air over it in all seasons, thus a hypothesis, that our jetstreams are warmer thus less dense thus less power per unit volume so can be altered more easily than previously and are now responding to thermal-forcing by transporting heat north and cold south more directly.

During the critical three months of cold, Jan-Mar, I now observe a flow from the Gulf that ends up over Greenland via New England, USA, this brings much warmer air than say prior to 30-years ago where a polar flow SE over the area from the pole was more the norm bringing very cold air and maintain status-quo on heat-balance.

At Disco Island 30-years ago it was dogsleds ... today hunters must use fishing boats; the average temps went from -30C to rarely below -10C a 20C/68F rise over that time the reason, the jetstreams the link to the thermal transfer of that much heat.

Therefore, the mechanism that’s working on the ice-sheet to accelerate melting beyond the global temperature rise is a localized, likely geographic circulation of the northern temperate jetstream with altered flow in all seasons vs prior to 50-years ago as a basis, it being less dense some critical amount to establish new flow patterns whereas a colder, more dense jetstream acts more like a river and in winter would be rather continuous at times with 4-lobes around the pole.

Recently you can see due-north, due-south pieces of jetstream from the latitude of Alaska to Hawaii, with smaller pieces that take great-circle routes from upper latitude warmer air, cooling over the pole and heading due south to disperse the cold; set 7-days, stop on 06Z 19 May to display this, it’s followed by others over the Atlantic but a perfect example: http://virga.sfsu.edu/scripts/nhemjetstream_model.html

Note also the very small pieces of jetstream all over the Arctic with not much coherence [hit faster some for this], this is novel in recent years to last as it does now to where to me it’s a “feature”, never happened like this. What the atmosphere is doing is moving heat to cold and cold to heat as fast as it can, due-north, due-south, much less eastward deflection, or, you get huge rotations between the Arctic and the Temperate air that just transfer heat & moisture, some really large high-pressure areas form as well,  the Midwest drought in the USA is tied to these types of circulations.

Overall, the thermal-forcing is just too strong now and the jetstream pieces document this.

As someone into glaciology for quite a while, we’ve lost the ice-sheet, we’re at 400-ppm CO2, we’ll be at 450-ppm in 18-years, 500-ppm in 35-years, unless we switch away from fossil fuels and stop ramping up the CO2, the ice-sheet is gone and sea-level rise will result.

Then, to speak to sea-level rise, my expectations are 1m within 50-years, 3m/10ft within a century due to our hyper-greenhousing a planet, it’s a geologic term, our thermal-forcing, this by changing CO2 43% in 200-years from 280-400-ppm.

This implies our measure of rise-rate is now a snapshot of an exponential curve until the forcing is removed, 3mm/yr today, so that keeps increasing yearly faster to beyond the interglacial rates allowed in the Pleistocene, for modelers.

This brings up the interglacial we are in, expectations for it to end some 1,200-years from now our conditions astronomically matching those some 700k-years ago so indicate we would need less than 245-ppm to begin to fall into a full glacial again. Due to that we should expect to see cooling-warming cycles on a cooling trend that after 8k-10k years gets CO2 low enough for a full glacial to happen, from 285-ppm that was quite possible.

So here we are at 400-ppm gaining 3-ppm/year expecting the ice-sheet to remain, it’s more like how fast will it go away.

The outlet creeks and streams are putting out 10-20% more volume than 15-years ago for all of Greenland, everyone knows what Jakobshavn is doing.

When trying to calibrate remote sensing for snow cover recently it was found that melt pools existed 5m below the surface cover in late December along a lot of SE Greenland’s coast, this fits into the air circulation patterns I’ve been watching, and implies it’s not cold enough to freeze the summer melt, key issue on wasting the ice-sheet speed, call it a red flag. [http://nsidc.org/greenland-today/2013/03/an-early-spring-calibration-for-melt-detection/]

Meltwater always finds a way down, a way out.

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By Chris
on May 22nd, 2013

Re the linked article…

“What we do not know is what role clouds are going to play in the future.” http://www.climatecentral.org/news/clouds-helped-cause-greenlands-record-melting-last-summer-15824


“May 5, 2013 — University of Manchester scientists, writing in the journal Nature Geoscience, have shown that natural emissions and humanmade pollutants can both have an unexpected cooling effect on Earth’s climate by making clouds brighter.” http://www.sciencedaily.com/releases/2013/05/130505145839.htm


Greenland melt maps
http://www.greenlandmelting.com/browse-maps-and-plots.html

Re warmer air / current intrusion

Freak Current Takes Gulf Stream to Greenland http://www.dailykos.com/story/2010/01/06/822520/-Freak-Current-Takes-Gulf-Stream-to-Greenland

NASA: Arctic Ocean Currents Changed http://climatestate.com/2013/05/02/nasa-arctic-ocean-currents-changed/

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By Joseph Meyer (Denver CO 80202)
on May 24th, 2013

During the Medieval warming period the Norse settlers did not find the melting of the Greenland ice sheet to be a threat. They took advantage of the warmer temperatures to raise crops and livestock. It was when the temperature went back down that they found their crops, livestock, and ultimately themselves dying off. I am sure they went into their churches to   ask God what it was they were doing wrong to cause the climate to turn against them.

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By Robert J Molineaux, Sr. (Redfield, New York, 13437)
on May 25th, 2013

Has anyone looked into the possibility of an upward shift in the Greenland bed rock by tectonic forces as it is relieved of the weight of the ice pack?

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By Lewis Cleverdon
on May 26th, 2013

Robert - the rate of rebound upwards of the underlying bedrock is orders of magnitude too slow to significantly affect the slope down which the ice sheet fringes descend, but the incidence of minor earth tremors under the GIS has reportedly risen massively in the last 15 years. If efforts for effective global mitigation are blocked, these will at some point predictably fracture the ice mass where its base is softened by internal warming and pierced by melt-water arteries and voids, thereby initiating internal collapse and its feedback process, via: - choked meltwater arteries - raised watertable - longer meltwater residence - raised internal warming - accelerated internal collapse.

Regards,

Lewis

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By Donald H. Campbell (Dodgeville, Wisconsin 53533)
on May 29th, 2013

I concluded many years ago that ice melts three-dimensionally—-top, bottom, and sides simultaneously—as in ordinary chemical dissolution, with increasing surface area and rate of reaction. Glacial Ice seems to be no exception. Jagged microscopical surfaces on ice testify to the process of surficial dissolution, eventually undercutting and removing the solids as surface area increases on an ionic scale.

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By Dean Kallander (Hamilton, Ohio)
on May 30th, 2013

Consider also the possibility, even though remote, that all this fresh water pouring off Greenland might stop the Gulf Current.  Would the Arctic turn very cold again, stopping the ice melt.

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