Coastal Antarctic permafrost melting faster than expected

Jul 24, 2013

For the first time, scientists have documented an acceleration in the melt rate of permafrost, or ground ice, in a section of Antarctica where the ice had been considered stable. The melt rates are comparable with the Arctic, where accelerated melting of permafrost has become a regularly recurring phenomenon, and the change could offer a preview of melting permafrost in other parts of a warming Antarctic continent.

Tracking data from Garwood Valley in the McMurdo Dry Valleys region of Antarctica, Joseph Levy, a research associate at The University of Texas at Austin's Institute for Geophysics, shows that melt rates accelerated consistently from 2001 to 2012, rising to about 10 times the valley's historical average for the present geologic epoch, as documented in the July 24 edition of Scientific Reports.

Scientists had previously considered the region's ground ice to be in equilibrium, meaning its seasonal melting and refreezing did not, over time, diminish the valley's overall mass of ground ice.

Instead, Levy documented through LIDAR and time-lapse photography a rapid retreat of ground ice in Garwood Valley, similar to the lower rates of permafrost melt observed in the coastal Arctic and Tibet.

"The big tell here is that the ice is vanishing—it's melting faster each time we measure," said Levy, who noted that there are no signs in the geologic record that the valley's ground ice has retreated similarly in the past. "This is a dramatic shift from recent history."

Ground ice is more prevalent in the Arctic than in Antarctica, where and ice sheets dominate the landscape. In contrast to glaciers and ice sheets, which sit on the ground, ground ice sits in the ground, mixed with or buried under layers of sediment. Antarctica's Dry Valleys contain some of the continent's largest stretches of ground ice, along the coast of the Ross Sea.

After Levy and colleagues noted visible effects of ground ice retreat in Garwood Valley, they began to monitor the valley, combining time-lapse photography and weather-station data at 15-minute intervals to create a detailed view of the conditions under which the ice, a relict from the last ice age, is being lost.

Rising temperatures do not account for the increased melting in Garwood Valley. The Dry Valleys overall experienced a well-documented cooling trend from 1986 to 2000, followed by stabilized temperatures to the present.

Rather, Levy and his co-authors attribute the melting to an increase in radiation from sunlight stemming from changes in weather patterns that have resulted in an increase in the amount of sunlight reaching the ground.

Sunlight tends to bounce off the white, reflective surfaces of glaciers and ice sheets, but the darker surfaces of dirty ground ice can absorb greater amounts of solar radiation. Thick layers of sediment tend to insulate deeply buried ground ice from sunlight and inhibit melting. But thin sediment layers have the opposite effect, effectively cooking the nearby ice and accelerating melt rates.

As the ground ice melts, the frozen landscape sinks and buckles, creating what scientists describe as "retrogressive thaw slumps." An acceleration in the prevalence of such slumps has been well documented in the Arctic and other permafrost regions, but not in Antarctica.

Levy's research shows that even under the stable temperature conditions of the Dry Valleys, recent increases in sunlight are leading to Arctic-like slump conditions.

If Antarctica warms as predicted during the coming century, the melting and slumping could become that much more dramatic as warmer air temperatures combine with sunlight-driven to thaw ground ice even more quickly.

Ground ice is not the major component of Antarctica's vast reserves of frozen water, but there are major expanses of ground ice in the Dry Valleys, the Antarctic Peninsula and the continent's ice-free islands.

Garwood Valley could tell the story of what will happen in these "coastal thaw zones," says Levy.

"There's a lot of buried ice in these low-elevation coastal regions, and it is primed to melt."

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User comments : 8

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NikFromNYC
1.4 / 5 (18) Jul 24, 2013
The closest temperature station is a mere hundred miles away, on Ross Island which is actually Mount Erebus, the southernmost *active* volcano in the world and that temperature station indeed shows a recent spike, as it has twice in the last century, on top of a linear trend seemingly unaffected by CO2:

DATA: http://berkeleyea...s/166913

MAP: http://s7.postimg...tion.jpg

CLOSE UP: http://ngm.nation...1600.jpg
NikFromNYC
1.4 / 5 (18) Jul 24, 2013
The ring of volcanoes that extends along the entire east coast of South America extends further down along the Antarctic Peninsula:

http://www.antarc...ie-1.jpg

This volcanic region represents a melt worthy hot spot in an otherwise steadily *cooling* continent which represents, overall, a sea level sink since it is terribly below the freezing point of water yet in a warming and thus more humid world more snow is created and collects there, according to the IPCC reports.

Deception Island is even a tourist spot:

http://www.travel...nd10.jpg
NikFromNYC
1.5 / 5 (17) Jul 24, 2013
Typo: ...the entire *west* coast of South America...
animah
4.4 / 5 (14) Jul 24, 2013
Nik, positing that a volcano would warm up the ground 100 miles away is pushing it very far don't you think? Just think of the thermodynamics.

Anyway having worked in a volcano-infested country for 8 years, I am unaware of any predictive in-situ thermometry further away than slopes or immediate base areas. And the Japanese take this stuff very, very seriously. Do you have any data? Heat transfer is not hard. Give us some math?
NikFromNYC
1.4 / 5 (18) Jul 24, 2013
Nik, positing that a volcano would warm up the ground 100 miles away is pushing it very far don't you think?


A volcano is merely a point where upwelling magma found a crack to spew to the surface in an overall region that enjoys underground warming. The west coast of Antarctica represents an abrupt hot spot so studying "global warming" there while promoting alarmist headlines about Antarctica is highly suspicious in a field of science that has failed to condemn even the following behavior:

"For your eyes only...Don't leave stuff lying around on ftp sites - you never know who is trawling them. The two MMs have been after the CRU station data for years. If they ever hear there is a Freedom of Information Act now in the UK, I think I'll delete the file rather than send to anyone....Tom Wigley has sent me a worried email when he heard about it - thought people could ask him for his model code. He has retired officially from UEA so he can hide behind that." - Phil Jones
NikFromNYC
1.5 / 5 (17) Jul 24, 2013
The e-mail I quoted was written to Michael "Hockey Stick" Mann who helps run the alarmist site RealClimate.org along with Eric Steig who are among the people most qualified in the world to know how to use statistics properly. However, Steig's Nature journal cover story study of Antarctica that garnered headlines since it smeared Peninsula warming over the cooling mainland was quickly debunked by a few skeptics who eventually published a peer reviewed correction. RealClimate.org was registered by a huge PR firm, Fenton Communications, the same one that promoted both the autism/vaccine scare and the junk science attack on silicone breast implants that bankrupted Dow Corning.

http://www.nature...ture.jpg
http://wattsupwit...g-et-al/

deepsand
3.8 / 5 (13) Jul 25, 2013
Nik the Chemist seems to have missed or ignored the paragraph in the article which reads
Rising temperatures do not account for the increased melting in Garwood Valley. The Dry Valleys overall experienced a well-documented cooling trend from 1986 to 2000, followed by stabilized temperatures to the present.
SteveS
5 / 5 (4) Jul 27, 2013
A volcano is merely a point where upwelling magma found a crack to spew to the surface in an overall region that enjoys underground warming. The west coast of Antarctica represents an abrupt hot spot so studying "global warming" there while promoting alarmist headlines about Antarctica is highly suspicious ...


From the paper
geological heat sources are unlikely to contribute to ground ice melting in Garwood Valley: mapping indicates that no active fault-directed hydrothermal features or volcanic features are present in the valley, and geothermal heat flux in the MDV is generally low (~ 50 mW/m2)

http://www.nature...269.html