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Northeast Greenland is home to the 79° N Glacier—the country's largest floating glacier tongue, but also one seriously threatened by global warming. Warm water from the Atlantic is melting it from below. However, experts from the Alfred Wegener Institute have now determined that the temperature of the water flowing into the glacier cavern declined from 2018 to 2021, even though the ocean has steadily warmed in the region over the past several decades. This could be due to temporarily changed atmospheric circulation patterns.

In a study just released in the journal Science, the researchers discuss how this affects the ocean and what it could mean for the future of Greenland's glaciers.

Over the past few decades, the Greenland Ice Sheet has lost more and more mass, which has also lessened its stability. This is chiefly due to the warming of the atmosphere and oceans, which accelerates the melting of ice, contributing in turn to an increase in mean sea level. The Northeast Greenland Ice Stream alone, which feeds into the massive Nioghalvfjerdsfjorden Glacier—also known as the 79° N Glacier—could produce a meter of sea-level rise if it melted completely.

Beneath the glacier tongue lies a cavern, into which ocean water flows. Data gathered by the Alfred Wegener Institute, Helmholtz Centre for Polar and Marine Research (AWI) now indicates that the temperature of the water flowing into the cavern declined between 2018 and 2021.

"We were surprised to discover this abrupt cooling, which is a marked contrast to the long-term regional ocean warming we've observed in the influx to the glacier," says Dr. Rebecca McPherson, a researcher at the AWI and the study's first author. "Since the ocean water in the glacier cavern grew colder, it means less oceanic warmth was transported under the ice in this period—and in turn, the glacier melted more slowly."

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