Flooding of Subterranean Lake in Antarctica Created Boston-sized Crater

Flooding of a sub-glacial lake in Antarctica likely caused some 6 billion metric tons of water to flow directly into the ocean and the drainage caused a vast crater to form on the continent's icy surface to fill the void.

Far below the surface of the White Continent, at least 400 sub-glacial lakes (SGLs) exist. The lakes stay in a liquid state from heat rising up from the rock beds below and the pressure of ice pushing down from above. SGLs are believed to continually fill up with water and then drain. Geologists are busy trying to better understand why this happens and what results from it. Their latest work relied on unprecedented data collected from satellites overhead.

Cook SGL in eastern Antarctica flooded during an 18-month period between 2007 and 2008. An absence of water beneath 1.6-mile-thick ice sheet on the ground created a crater roughly the size of Boston, which at its most extreme point sank about 230 feet deep .

European Space Agency's CryoSat satellite was used to collect the data and make the discovery.

ESA reports that about 6 cubic kilometers of water - about the same volume of Scotland's Loch Ness - drained from the lake, making the event the largest of its kind ever recorded. The huge amount of water is equal to one-tenth of the melting that occurs beneath Antarctica each year.

"This one lake on its own represents 5-10 percent of [Antarctica's] annual mass imbalance," University of Leeds' Andrew Shepherd, a co-author of the research, told BBC News.

"If there are nearly 400 of these sub-glacial lakes then there's a chance a handful of them are draining each year, and that needs to be considered."

The freshwater sub-glacial lake appears to be refilling, but at such a slow rate that it will take decades for it to reform.

Scientists study sub-glacial lakes in part because of interest in finding prehistoric marine life. However, the rapid draining and subsequent refilling of the lake suggests that it was not the first time the event occurred, according to an ESA report.

"It seems likely that the flood water - and any microbes or sediments it contained - has been flushed into the Southern Ocean, making it difficult to imagine that life in this particular lake has evolved in isolation," said Shepherd.

The study of the sub-glacial lake drainage and the satellite images of Antarctica is being heralded by scientists.

Helen Fricker from the Scripps Institution of Oceanography was not involved in the research. She told BBC "The lake drainage event reported here was quite staggering in its size and the 3D image we got of the crater in the surface after the lake drained is unprecedented."

The research is published in the journal Geophysical Research Letters.