July 24, 2013
Permafrost In Antarctica Melting At Fast Rate
Lee Rannals for redOrbit.com - Your Universe Online
Data from Garwood Valley in the McMurdo Dry Valleys region of Antarctica has shown that melt rates accelerated consistently from 2001 to 2012, rising to about ten times the valley's historical average for the present geologic epoch. Scientists previously thought the region's ground ice to be in equilibrium, meaning the seasonal melt and refreeze did not reduce the amount of ice overall. Instead, they documented through LIDAR and time-lapse photography a radii retreat of ground ice in Garwood Valley.
"The big tell here is that the ice is vanishing - it's melting faster each time we measure," said Joseph Levy, a research associate at The University of Texas at Austin's Institute for Geophysics. "This is a dramatic shift from recent history."
Antarctica's Dry Valleys, along the coast of the Ross Sea, contain some of the continent's largest stretches of ground ice. After the team noted visible effects of ground ice retreat in Garwood Valley, they started monitoring the valley and combining time-lapse photography and weather-station data to create a detailed view of the conditions under which the ice is being lost.
Levy and colleagues say the melting is due 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 bounces 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 these sediment layers insulate deeply buried ground ice from sunlight and inhibit melting. However, thin sediment layers have the opposite effect.
As ground ice melts, the frozen landscape sinks and buckles, which creates what scientists describe as "retrogressive thaw slumps."
The team'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.
"There's a lot of buried ice in these low-elevation coastal regions, and it is primed to melt," Levy said.
Scientists reported in February that Siberia is experiencing permafrost melt, which threatens the release of carbon from the soil. According to this study, if thawing of Siberia's permafrost occurs, it could release over 1,000 gigatons of greenhouse gases into the atmosphere.