Large Sub-Glacial Lakes Beneath Greenland Ice Sheet Draining Rapidly - 1 Crater 2Km Across

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Scientists have discovered a crater, shown here, which had once been the site of a sub-glacial lake. Image credit: Ian Howat / DigitalGlobe Inc / Sci-News.com.

Recently, scientists have found direct evidence of concentrated, long-term storage and sudden release of melt water within sub-glacial lakes in Greenland. Two lakes were recently discovered.

One lake, described in the journal Cryosphere, once held billions of gallons of water and emptied to form a giant crater – 2 km across and around 70 m deep – in just a few weeks. Dr Howat and his colleagues detected the crater on a spot about 50 km inland from the southwest Greenland coast earlier in 2014.

There, previous aerial and satellite imagery indicates that a sub-glacial lake pooled for more than forty years. More recent images suggest that the lake likely emptied through a meltwater tunnel beneath the ice sheet some time in 2011. “The fact that our lake appears to have been stable for at least several decades, and then drained in a matter of weeks – or less – after a few very hot summers, may signal a fundamental change happening in the ice sheet,” Dr Howat said.

Dr Howat’s group calculated that the lake that formed it likely contained some 6.7 billion gallons of water. And it disappeared in a single season – remarkably quickly by geologic standards. The scientists characterized the sudden drainage as catastrophic. “We suspect that, as more meltwater reaches the base of the ice sheet, natural drainage tunnels along the Greenland coast are cutting further inland. The tunnels carry heat and water to areas that were once frozen to the bedrock, potentially causing the ice to melt faster,” Dr Howat said.

EDIT


A 'whirlpool' and crack on the Petermann glacier. Geophysicist Dr Richard Bates, of the Scottish Oceans Institute at the University of St. Andrews, takes 'casts' of temperature, pressure, current and salinity. He makes casts - dropping a CTD probe (Conductivity Temp Depth) into the pool and pulling it back up at a slow speed...

Much, much more at:

http://www.dailykos.com/story/2015/09/22/1421761/-Sudden-drainage-via-massive-chasm-of-Subglacial-lakes-in-Greenland-described-as-catastrophic