ESA CryoSat maps largest-ever flood beneath Antarctica

Location of the crater in Victoria Land, East Antarctica at about 73ºS and 156ºE. The colour scale shows height derived from CryoSat data. The crater is located within the white box. Credit: ESA/M. McMillan

ESA's CryoSat satellite has found a vast crater in Antarctica's icy surface. Scientists believe the crater was left behind when a lake lying under about 3 km of ice suddenly drained.

Far below the thick ice sheet that covers Antarctica, there are lakes of fresh water without a direct connection to the ocean.

These lakes are of great interest to scientists who are trying to understand water transport and ice dynamics beneath the frozen Antarctic surface – but this information is not easy to obtain.

One method is to drill holes through kilometres of ice to the water – a difficult endeavour in the harsh conditions of the polar regions.

But instead of looking down towards the ice, a team of European scientists is looking to the sky to improve our understanding of subglacial water and its transport.

By combining new measurements acquired by CryoSat with older data from NASA's ICESat satellite, the team has mapped the large crater left behind by a lake, and even determined the scale of the flood that formed it.

From 2007 to 2008, six cubic kilometres of water – about the same amount that is stored in Scotland's Loch Ness – drained from the lake, making it the largest event of its kind ever recorded.

That amount of water equals a tenth of the melting that occurs beneath Antarctica each year.

Since the end of 2008, the lake appears to be refilling but six times slower than it drained. It could take decades to reform.