Data collected from a NASA ice-watching satellite reveal that the vast ice shelves extending from the shores of western Antarctica are being eaten away from underneath by ocean currents, which have been growing warmer even faster than the air above.
The animation above shows the circulation of ocean currents around the western Antarctic ice shelves. The shelf thickness is indicated by the color; red is thicker (greater than 550 meters), while blue is thinner (less than 200 meters).
Launched in January 2003, NASA’s ICESat (Ice, Cloud and land Elevation Satellite) studied the changing mass and thickness of Antarctica’s ice from its location in polar orbit. An international research team used over 4.5 million surface height measurements collected by ICESat’s GLAS (Geoscience Laser Altimeter System) instrument from Oct. 2005 to 2008. They concluded that 20 of the 54 shelves studied — nearly half — were losing thickness from underneath.
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Most of the melting ice shelves are located in west Antarctica, where the flow of inland glaciers to the sea has also been accelerating — an effect that can be compounded by thinning ice shelves which, when grounded to the offshore seabed, serve as dams to hold glaciers back.
Melting of ice by ocean currents can occur even when air temperature remains cold, maintaining a steady process of ice loss — and eventually increased sea level rise.
“We can lose an awful lot of ice to the sea without ever having summers warm enough to make the snow on top of the glaciers melt,” said Hamish Pritchard of the British Antarctic Survey in Cambridge and the study’s lead author . “The oceans can do all the work from below.”
The study also found that Antarctica’s winds are shifting in response to climate change.
“This has affected the strength and direction of ocean currents,” Pritchard said. “As a result warm water is funnelled beneath the floating ice. These studies and our new results suggest Antarctica’s glaciers are responding rapidly to a changing climate.”
ICESat completed operations in 2010 and was decommissioned in August of that year. Its successor ICESat-2 is anticipated to launch in 2016.
Read more on NASA’s news release here.
Animation credit: NASA/Goddard CGI Lab