How a lake on an Antarctic ice floe disappeared in three days – .

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How a lake on an Antarctic ice floe disappeared in three days – .


TORONTO – In 2019, a lake on an East Antarctic ice cap completely disappeared within three days.

The strange event went unnoticed until the following summer, when Dr Roland Warner, a glaciologist with the Australian Antarctic Program Partnership at the University of Tasmania, noticed discrepancies in satellite images of the platform. Amery ice form.

As he deepened his research, he and other researchers concluded that something rare had happened: hydrofracture.

“We believe a large crack opened briefly in the floating ice shelf and drained the entire lake into the ocean in three days,” Warner said in a press release.

“The lake contained more water than Sydney Harbor and the flow into the ocean below would have been like the flow over Niagara Falls, so it would have been an awesome sight. “

Hydrofractures occur when the pressure of liquid water on ice causes it to separate due to the density of the water.

Amery Ice Shield is the third largest ice shelf that branches off from Antarctica on the east side of the continent, and at 1,400 meters thick, it is rare to see a hydrofracture completely crack it.

The researchers described the process of tracking this event in an article published last week in the journal Geophysical Research Letters.

The lake itself was unnamed and had resided inside the plateau, covered with an ice cap. When the platform opened under the lake and the water flowed out, it left a large depression in the ice shelf.

This is an ice “sinkhole” – a term for a naturally closed depression in the ground, usually referring to sinkholes.

The ice sinkhole was approximately 11 square kilometers in size and was strewn with some of the cracked remains of the ice cover that once stood on top of the lake.

It was a small lake in terms of length, but still about half the size of Lake Minnewanka in Alberta, or 12 times the size of Lake Louise.

And it was deep, containing about 600 to 750 million cubic meters of water, about double the volume of San Diego Bay, according to another release from the Scripps Institution of Oceanography. This far exceeds the amount of meltwater the platter normally sees.

How did the researchers calculate the amount of water? Losing a lake of this size made a marked difference in the elevation of the pack ice itself, something that can be seen from space if you look closely enough.

The researchers used a laser instrument on NASA’s ICESat-2 to calculate the exact change in elevation caused by the lake’s drainage.

“The ICESat-2 orbits with exactly repetitive ground tracks and comparing the elevations before and after the lake drained showed us the dramatic vertical scale of the disturbance,” said Helen Fricker, professor at the Scripps Institution of Oceanography and co-author of the press release study.

After the lake emptied, this region of the pack ice tipped over, with the platform surface rising “up to 36 meters around the lake,” Warner said.

“The loss of water from the lake locally reduced the weight on the floating ice shelf so that ocean pressure lifted it up to the sinkhole. “

The lake itself sank deeper into the plateau, with the cavity basin lying 80 meters below the lake’s original surface.

Satellite photos of the lake showing the before and after process show how the movement of the pack ice also created a new, smaller pool of water on what was once an arm of water moving away from the lake, with the original lake surface appearing visibly cracked and drained.

It’s possible that the sinkhole will fill with water again, or the hydrofracture could reopen and drain that water again, Warner said.

While this phenomenon is not necessarily directly related to climate change, the movement of ice caps to the outskirts of regions such as Antarctica is essential to track. The loss of an ice cap, or the fracturing of an ice cap far from the mainland, could accelerate the loss of ice from the landmass itself, which would contribute to sea level rise if it melted.

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