Beneath the ice sheet of Antarctica, there is a network of lakes filled with water from melting glaciers. Between 2007 and 2008, one of these lakes burst its banks and released 6 billion tons of water directly into the ocean in the largest flooding event ever recorded on the continent.

That’s enough water to meet the needs of the United States over two days. The study was published in Geophysical Research Letters.

The Cook lake is located below 2,700 meters of ice on the eastern part of the continent. It is one of 379 subglacial lakes in Antarctica, and the most famous of them is Lake Vostok.

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Scientists got to know about these lakes when they noticed that parts of the ice sheet moved vertically, as though bobbing on water. Using modeling and satellite rada data, scientists deduced that the movement was caused by subglacial lakes. These are fed by the melting of glaciers, and sometimes the lakes overflow and drain into the surrounding ocean.

Scientists noticed between 2006 and 2008 that the ice sheet on top of Cook lake was subsiding.  Over two years, the ice sank by 70 feet to form a deep crater. This suggested to scientists that Cook lake was losing water.

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The scientists used data from two Earth observing satellites to determine the geometry of the crater and calculate the volume of the space caused by the subsidence. They assumed the volume would be equal to the amount of water lost by the lake.

Their calculations showed that the lake had lost between 1.2 trillion and 1.7 trillion gallons of water. That would have been a massive flood, causing a rapid flow of water to the ocean.

If the higher estimate of the flood size were true, the flow rate of the resulting ‘river’ would have been 42,000 gallons (160 cubic meters) per second. That is close to the flow rate of the Colorado River.

Photo: Antarctic sea ice. (NASA/Thorsten Markus)