Greenland ice melt spreads northwest

by Gareth on March 27, 2010

This animation shows Greenland’s ice mass loss over 2003 to 2009, estimated by combining data from NASA’s GRACE satellites with high precision GPS measurements of “rebound” in the underlying rock as the weight of ice is removed. The lightest blue shows low levels of mass loss, black the highest. From the University of Colorado press release:

“Our results show that the ice loss, which has been well documented over southern portions of Greenland, is now spreading up along the northwest coast,” said Shfaqat Abbas Khan, lead author on a paper that will appear in Geophysical Research Letters.

Khan goes on to suggest what this might imply for the future:

If this activity in northwest Greenland continues and really accelerates some of the major glaciers in the area — like the Humboldt Glacier and the Peterman Glacier — Greenland’s total ice loss could easily be increased by an additional 50 to 100 cubic kilometers (12 to 24 cubic miles) within a few years.

Another good reason to keep an eye on the Arctic this summer. Climate Progress has a very good overview of recent work on Greenland ice loss and its implications for sea level rise. Well worth a read, if not exactly comforting.

{ 14 comments… read them below or add one }

mspelto March 27, 2010 at 3:08 pm

The spread northward of the melt is indicative of the changes in the maximum anomaly of the melt season. In 2002 and 2003 the southern and western sections of the GIS had maximum melt in 2007 and 2008 the maximum shifted to the northwest section of the GIS. The impact of the northward shift has been enhanced melting and additional retreat of Petermann Glacier. This glacier has the longest floating tongue of any glacier in the Northern Hemisphere.
http://glacierchange.wordpress.com/2010/03/27/pet

Gareth March 27, 2010 at 10:24 pm

Thanks Mauri, interesting link. I blogged on Jason Box at the Petermann last (NH) summer. It's relatively straightforward to track events on the glacier tongue from space, using NASA's MODIS rapid response imagery: this shot (27/3/10) shows the glacier tongue clearly, and a great deal of open water in the Nares Strait

Steve Wrathall March 27, 2010 at 9:40 pm

"between April 2002 and February 2009, the Greenland ice sheet shed roughly 385 cubic miles of ice"
1605 km3 over 6.8 years =
235km3/yr
Volume of Greenland ice cap = 2 850 000 km3
Time for it to melt at this rate = 12 000 years.

Catastrophe Cancelled

Al Gore won't need to sell his $4M beachfront apartment anytime soon.

dappledwater March 28, 2010 at 2:09 am

"Volume of Greenland ice cap = 2 850 000 km3
Time for it to melt at this rate = 12 000 years." – S.Wrathall

Yes, on imaginary earth perhaps, but the ice loss is accelerating:

http://www.sciencedaily.com/releases/2009/11/0911

And, as linked to in the article above, is approaching a tipping point where it will rapidly disintegrate:

http://climateprogress.org/2010/03/23/greenland-i

"A new study has lowered the carbon pollution threshold or “tipping point” for collapse of the Greenland ice sheet to 400 to 560 ppm. We’re currently at about 390 parts per million atmospheric concentrations of CO2, rising about 2 ppm a year (and yes, total collapse would take a while)"

Steve Wrathall March 28, 2010 at 4:53 am

From your link:"At the same time that surface melting started to increase around 1996, snowfall on the ice sheet also increased at approximately the same rate, masking surface mass losses for nearly a decade. Moreover, a significant part of the additional meltwater refroze in the cold snowpack "

Yes, negative feedback, of exactly the sort, that will rule out the orders-of-magnitude increase in melt that would be required to be of concern, and to bring about the mythical "tipping points". The only tipping points that seem to be being reached are catastrophic rises in public skepticism of catastrophist claims.

Carol C March 28, 2010 at 7:34 am

Steve, have you never defrosted a freezer? The ice melts slowly for a few hours then suddenly, wham, it starts collapsing rapidly. And there are more factors at play in Greenland's situation than in your freezer – increasing air and sea-surface temperatures, melt-water seeping into crevasses, decreased albedo, etc etc. It's not logical to assume the same melt-rate today will apply throughout a decade, let alone a century.

dappledwater March 28, 2010 at 7:38 am

Sorry Steve, but what part of the lead-in don't you understand?

"Satellite observations and a state-of-the art regional atmospheric model have independently confirmed that the Greenland ice sheet is losing mass at an accelerating rate, reports a new study in Science."

Or this:

"Professor Jonathan Bamber from the University of Bristol and an author on the paper said: "It is clear from these results that mass loss from Greenland has been accelerating since the late 1990s and the underlying causes suggest this trend is likely to continue in the near future."

Your negative feedback has already vanished, which you would know had you understood the article.

Gareth March 28, 2010 at 10:54 pm

If you look at the video, the green colouring is where there is no mass loss — ie where snow accumulation matches loss by melt and transport. That area used to show mass gain, but that changed a few years before the period shown in the animation.

C3P0 March 28, 2010 at 8:31 pm

I agree that accelerating melting of Greenland would be cause for concern.

Only having data since the mid 1990’s (or 2003 above) however leaves many questions unanswered. How does today’s ice level relate to past levels (ie 1000+ years ago)? Is today’s melt unusual in the historical record? If the sheet has been warmer in the past were tipping points reached?

Sorry if I do not share your alarm but for me looking at only 10+ years of climate data and then projecting the trend forward is not cause for alarm.

Gareth March 28, 2010 at 10:52 pm

For tipping points, go and read the discussion at the Climate Progress link.

During the last interglacial (Eemian), global average temps were a little higher than now (CO2 was only 300 ppm, remember), and sea level was about 6m higher at peak. It's thought that half of that rise came from Greenland and half from Antarctica. IIRC the Greenland ice sheet was about 25% smaller than at present, with trees growing on the southern part of the island.

You have to bear in mind that this was an equilibrium response: the climate system stayed warm long enough for the oceans and ice sheets to "catch up". That's not true at the moment. What we're seeing now is the early part of the transient response to warming. But the Eemian gives us an idea of where we're heading…

C3P0 March 28, 2010 at 11:02 pm

"Steve, have you never defrosted a freezer? The ice melts slowly for a few hours then suddenly, wham, it starts collapsing rapidly. " …"melt-water seeping into crevasses, decreased albedo"

So this didnt happen?

You note CO2 levels were 300ppm yet it was warmer than today. Interesting…. its as if something other than CO2 can influence temperature.

Gareth March 28, 2010 at 11:10 pm

Lot's of things other than CO2 influence the climate system, but the point with the Eemian is that it demonstrates that the equilibrium response to 300 ppm is a lot of ice sheet melt and sea level rise. We're already at 389 ppm, with some of the impact reduced by aerosol masking, and a lot of catching up to do. How fast that might happen is a very interesting question, particularly as there are tantalising hints of rapid surges in sea level during the warm parts of the Eemian.

C3P0 March 29, 2010 at 1:54 am

"Lots of things other than CO2 influence the climate system, but the point with the Eemian is that it demonstrates that the equilibrium response to 300 ppm is a lot of ice sheet melt and sea level rise"

How long was the Eemian in equilibrium for?

You state that other things can effect climate but then you say that the Eemian demonstates an equilibrium response to 300ppb CO2. If your first statement is correct the Eemian demonstrates a response to all the factors that existed at the time – not just the level of CO2.

Anyway… so the Eemian was 1-2C warmer than today and CO2 was 300 ppm, so how long until that catches up with us? Given CO2 was last at 300 ppm when? World war 2? If 300 ppm was going to cause 1-2C warming how long do we have to wait?

Gareth March 29, 2010 at 2:40 am

The Eemian lasted about 15,000 years, and yes of course it was a response to the balance of all climate influences at the time. The difference now is that those drivers include anthropogenic interventions — aerosols, GHGs, land use change etc — and that the majority of those have only had a limited time to have an impact.

Different parts of the climate system have different characteristic timescales. The most important near term is the response of the top layers of the ocean, which is usually said to be about 30 years — that's the "lag" in the system. Ice sheets take longer to reach equilibrium with a changed climate — hundreds, perhaps thousands of years — but may still exhibit rapid responses in shorter periods (see the link I provided above).

One major difficulty in projecting the full impact of current GHG levels is that we're offsetting their impact with aerosol pollution. If we clean up the atmosphere, we could increase the warming. Google Ramanathan & Feng, they have an important paper on the subject.

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