Six billion tonnes of water vanishes from underground Antarctic lake — leaves behind city-sized ice crater
Six billion tonnes of water may have been dumped into the ocean all at once after an underground Antarctic lake overtopped, causing the ice sheet above it to slump into a giant 260 square-kilometre crater.
“The crater’s a big feature,” said Dr. Malcolm McMillan, the lead author of a report on the phenomenon. ”It covers an area of about 260 sq km, which is about the size of Edinburgh, and was as much as 70 m deep.”
The crater was highlighted in a recent study published in the scientific journal Geophysical Research Letters.
The crater is above the Cook Subglacial Lake, which is in the Cook Ice Sheet. The crater was likely caused when the water flowed away underground and the ice above moved into the vacated space. The loss took place over an 18 month period between 2008 and 2009.
The size and depth of the crater was key to the scientists being able to figure out how much water there was underground. They used readings from a pair of satellites — NASA’s ICESAT and Europe’s CyroSat — to gauge the dimensions, and then use those numbers to determine how much water must have spread away from the underground lake.
“Thanks to CryoSat, we can now see fine details that were not apparent in older satellite data records,” McMillan said in a release from the European Space Agency.
Antarctica loses approximately 50 to 100 billion tonnes of mass each year, most of which is ice melting into the ocean. The loss of six billion tonnes of water all in one go is one of the largest single water losses.
“This one lake on its own represents 5-10% of [Antarctica’s] annual mass imbalance,” Prof. Andy Shepherd a co-author of the report 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.”
It is possible, however, that the water wasn’t lost directly to the ocean. Antarctica has a large number of underground water flows, recently mapped by NASA. It’s possible that the water could have flowed though those underground channels and could return to the lake at some point.
“Further downstream, there was an inflation of the ice,” Hugh Corr from the British Antarctic Survey told the BBC. “But whether all that water reaches the ocean, or re-freezes onto the underside of the ice, or even melts more ice with its heat — we just don’t know. It will, though, change the lubrication.”
The crater itself does seem to be rising, but at a rate six times slower than it went down.
Sadly, the rapid dispersment of the lake means that any life it contained likely followed the water, whereever it went.
“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,” Andrew Shepherd, a co-author of the study, told the ESA.
The underground lakes are kept liquid by a combination of heat from the rocks below and pressure from the ice above.
- Largest sub-glacial flood ever recorded, leaves massive ice crater in Antarctica ice sheet (theextinctionprotocol.wordpress.com)
- Large Antarctic Crater Created by Underground Flood (livescience.com)
- Deluge from sub-glacial lake’s burst (bbc.co.uk)