In the photo: The largest thickness (over 550 m) is shown in red, the smallest (less than 200 m) in blue.
Warm sea currents undermining the bottom of ice shelves have been identified as the main cause of Antarctic ice loss.
An international team of scientists concluded that 20 of the 54 considered ice shelves are melting primarily due to currents. Most of them are located in West Antarctica, where the speed of internal glaciers feeding the shelf has increased recently. It is water that is responsible for the lion's share of the losses that the Antarctic Ice Sheet experienced during the study.
“We can lose a lot of ice even if summer temperatures don't rise high and the snow on the tops of the glaciers refuses to melt,” said lead author Hamish Pritchard of the British Antarctic Survey. "The ocean will do all the work."
Where did these warm currents come from? “The changes in the Antarctic wind rose are driven by climate change,” explains Mr. Pritchard. - It influenced the strength and direction of currents. As a result, warm water accumulated under the floating ice”.
A different picture is observed on the Antarctic Peninsula, directed towards South America. The thinning of the largest ice shelves of the peninsula is explained by warm winds, leading to the melting of snow on the surface of the glaciers in summer.
In order to map the thickness changes of almost all floating ice shelves around Antarctica, the scientists took into account the results of 4.5 million measurements made by the ICESat satellite from October 2003 to October 2008. Computer modeling was required in order not to interfere with those changes in ice thickness that occur due to natural accumulation and compaction of snow, as well as tidal waves.
Previous work used radar measurements, in this case, specialists resorted to laser measurements: they are more accurate in detecting changes in ice thickness. This is especially true in coastal areas. Low resolution radar altimeters do not do well on steep slopes where the ice shelf touches land.
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ICESat was the first satellite specifically designed to study the polar regions of the Earth using laser altimeters. He worked from 2003 to 2009. Its successor, ICESat-2, will only launch in 2016.
Currents of West Antarctica: