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Millions of years ago, frozen ice sheet in East Antarctica melted

Warming may have caused huge increase in sea level

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Not even stubbornly frigid East Antarctica can escape the heat. Millions of years ago, global warming melted the region’s ice sheet, a drilling expedition finds.

Scientists consider the Pliocene epoch, 5.3 million to 2.6 million years ago, a good analog for future climate change. Global average temperatures were 2 to 3 degrees Celsius warmer than in pre-industrial times, and carbon dioxide concentrations were similar to modern levels. Sea level was higher, but there hasn’t been much direct evidence that melting in East Antarctica contributed to the swelling seas.

New proof comes from seafloor sediments drilled 310 kilometers off the continent. In the sediment core are layers rich in algae, a sign that the ocean was warm. The chemistry of the sediments in these layers resembles that of rock on the continent that is now buried beneath the East Antarctic ice sheet. Carys Cook of Imperial College London and colleagues say the sediments washed into the sea as the ice sheet melted, retreated inland several hundred kilometers and eroded the landscape. That much retreat translates to as much as 10 meters of sea level rise, the team reports July 21 in Nature Geoscience. The results could be a good guide for what Antarctica’s future holds (SN: 7/27/13, p. 18).

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