A huge lake on the east coast of Antarctica has disappeared, causing 200 billion gallons of water to vanish without a trace.
In the winter of 2019 on the Amery Ice Shelf, the third-largest ice shelf on the continent, around 600 million to 750 million cubic metres drained really quickly into the ocean. The lake’s disappearing act was noticed the following summer when scientists were looking at satellite photos of the region. The findings are chronicled in a new study.
“We believe a large crack opened briefly in the floating ice shelf and drained the entire lake into the ocean within three days,” Roland Warner, a scientist at the Australian Antarctic Program Partnership at the University of Tasmania who first spotted the major drainage on satellite imagery, said in a release. “The lake held more water than Sydney Harbour and the flow into the ocean beneath would have been like the flow over Niagara Falls, so it would have been an impressive sight.”
In the paper published last week in Geophysical Research Letters, Warner and his coauthors found that the sudden drainage may have been caused by meltwater in the ice. They theorise that there was meltwater stored underneath the deep, ice-covered lake, which put pressure on the ice shelf and caused a crack to open that sent the water right to the ocean, in a process known as hydrofracturing. The drained lake left a huge depression in the ice — around 11 square kilometres — which quickly began to fill with meltwater again last summer.
Meltwater has been responsible for collapse and drainage on smaller ice shelves throughout the continent. But the Amery Shelf is around 1,400 metres thick, and this happened in the middle of winter. That makes this event pretty unusual. (Similarly leaky lakes have appeared in recent winters on the surface of Greenland’s ice sheet thousands of kilometres away in the Arctic as well.)
Attributing the lake’s disappearance totally to climate change is a little complicated. But what it does provide is a valuable case study for how surface ice melt in Antarctica — which is expected to increase as the planet warms — can impact ice shelf stability. Antarctic ice shelves also face threats from warm ocean water undercutting them, particularly in West Antarctica. The loss of ice in Antarctica affects coastlines around the world because it contributes to sea level rise.
“This abrupt event was apparently the culmination of decades of meltwater accumulation and storage beneath that insulating lid of ice,” said Jonathan Kingslake, a co-author on the study and researcher at Columbia University’s Lamont-Doherty Earth Observatory. “However, increasing amounts of meltwater flowing into deep, ice-covered lakes and causing hydrofracture of thick ice shelves should also be considered in assessments of Antarctica’s future.”