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Climate: New clues for West Antarctic ice sheet melting

New data shows warm ocean currents melting the ice from below

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Antarctic sea ice has expanded slightly in recent years, but the continental ice shelves are losing mass. Bob Berwyn photo.

By Summit Voice

FRISCO — New data from sensors in the Amundsen Sea suggest more strongly than ever that warm ocean currents are causing extensive ice loss from the West Antarctic Ice Sheet.

Ice in the area is melting faster than expected and could contribute significantly to sea level rise, but there’s been very little data from the region. The latest observations by oceanographers from the University of Gothenburg (Sweden) were recently published in the journal Nature Geoscience.

Previous research by the British Antarctic Survey showed that rising air temperatures in the region will break down a hydrological boundary of cold water, allowing warmer water to infiltrate beneath the ice.

“There is a clear reduction in the ice mass in West Antarctica, especially around the glaciers leading into the Amundsen Sea,” said researcher Lars Arneborg from the Department of Earth Sciences at the University of Gothenburg. Arneborg carried out the study with co-researchers Anna Wåhlin, Göran Björk and Bengt Liljebladh.

One reason why West Antarctica is particularly sensitive is that the majority of the ice rests on areas that are below sea level. Warm sea water penetrates beneath the ice, causing increased melting from underneath.

“It is therefore probably a change in the ocean circulation in the Amundsen Sea that has caused this increased melting,” Arneborg said. “But there have been very few oceanographic measurements from the Amundsen Sea to confirm or contradict the results from the computer models. Nor has there been any winter data. Sea ice and icebergs have made it impossible to get there in the winter, and it isn’t easy to have instruments in place all year round.”

Until now, researchers have been referred to studies that use high-resolution computer models. But the Swedish researchers placed instruments in the Amundsen Sea in 2010, enabling them to measure the inward flow of warm sea water towards the glaciers

The observations show that the warm sea water flows towards the glaciers in a more or less constand current all year round, in contrast to the model results which suggested a strong seasonal cycle.

“This shows just how important observations are for investigating whether the models we use describe something that resembles reality,” Arneborg said. “Warm ocean currents have caused much more melting than any model has predicted, both in West Antarctica and around Greenland.

The researchers want more and longer time series of oceanographic observations in order to improve the models and achieve a better understanding.

“Only then will we be able to say something about how the ice masses of the Antarctic and Greenland will change in the future,” he concluded.

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