The Reason Antarctica Is Melting: Shifting Winds, Driven by Global Warming

https://www.scientificamerican.com/article/the-reason-antarctica-is-melting-shifting-winds-driven-by-global-warming/

In the remote, alien area of the world where the Amundsen Sea meets the coast of West Antarctica, tall, frozen cliffs loom over the water. They are the edges of massive glaciers—rivers of ice that spill into the ocean. In recent years, these icy rivers have been flowing and melting at an alarming rate, threatening to add a substantial amount of water to the sea that would eat away at global coastlines.

For a long time, scientists had suspected that man-made climate change was likely causing this area of West Antarctica’s ice to thin, but they had not established a direct connection or mechanism. The issue is critical because this is where the majority of the continent’s ice loss is occurring. Now a new study new study published this week in Nature Geoscience appears to have solved the puzzle. A team of researchers in the U.S. and U.K. found that global warming has caused a shift in wind patterns that are ultimately bringing more warm ocean water into contact with the region’s ice.

Climate scientists first began to notice that all was not right with West Antarctica’s ice a couple of decades ago, but its melt proved a bit enigmatic. For the most part, air temperatures are still too cold for surface melting to explain why the ice is thinning. That fact suggested the ocean was likely the culprit—yet the top layer of seawater is also too cold to thaw the ice. And while there is a deeper layer of warm ocean water that sometimes reaches the Amundsen Sea and laps away at the undersides of two giant glaciers in the region—called Pine Island and Thwaites—rising global temperatures were not directly warming that water.

“This is an area where the [warm] ocean waters that melt the ice have been out of contact with the atmosphere for thousands of years,” explains Paul Holland, an ice-ocean scientist at the British Antarctic Survey and one of the authors of the new study. “They're very old waters, so they wouldn’t have been [heated] by global warming.” Thus, the question for Holland and his team was if—and how—climate change had affected these deep-ocean waters. They suspected that wind might be the missing connection.

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