There is a series of lakes beneath Thwaites Glacier, part of an extensive network of meltwater drainage channels. In 2013, seven subglacial lakes, that were more than 2 km beneath Thwaites Glacier, suddenly all drained at the same time, releasing around 7 cubic kilometres of freshwater into the Amundsen Sea.

The new research, based on CryoSat data and published in Nature Communications, underscores the Antarctic ice sheet’s sensitivity to subglacial dynamics and its complex interactions with ocean conditions. 

The freshwater in these lakes is lighter than the salty ocean, when it drained through the grounding line of Thwaites in 2013, at a depth of roughly 1 km below sea level, it triggered a turbulent upwelling of warm, deep ocean water all the way to the ocean surface. This influx of warmer water accelerated melting at the base of the Thwaites Ice Shelf and contributed to the melt of offshore sea ice, opening a polynya. Crucially, this took place in an area of the ice shelf that controls the rate at which the ice inland flows, the buttressing effect of ice shelves. By thinning and melting, the ice shelf lost some of its ability to hold inland ice causing it to speed up into the ocean.

Read full story: How hidden lakes threaten Antarctic ice sheet stability

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