Antarctic Coastal Permafrost Melting Faster Than Expected
August 7, 2013
I’ve set up a script where I just hit the F2 key and a wordpress page comes up starting with the phrase, “For the first Time..”.
F3 brings up “Melting Faster than expected…”
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.”
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.
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 melting 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.”
West Antarctica has warmed much more than scientists had thought over the last half century, new research suggests, an ominous finding given that the huge ice sheet there may be vulnerable to long-term collapse, with potentially drastic effects on sea levels.
A paper released Sunday by the journal Nature Geoscience reports that the temperature at a research station in the middle of West Antarctica has warmed by 4.4 degrees Fahrenheit since 1958. That is roughly twice as much as scientists previously thought and three times the overall rate of global warming, making central West Antarctica one of the fastest-warming regions on earth.
“The surprises keep coming,” said Andrew J. Monaghan, a scientist at the National Center for Atmospheric Research in Boulder, Colo., who took part in the study. “When you see this type of warming, I think it’s alarming.”