By now, most people have heard about polar ice melting due to global warming. But the coming and going of the sea ice surrounding Antarctica still leaves scientists puzzled. Recent research has shed light on changes in sea ice.

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sea ice in the Antarctic, white patches of ice against deep blue water

Antarctica is known for its dynamic sea ice, which contracts and extends seasonally, yet unpredictably. The drop in sea ice from 2015 to 2016 was staggering — 463,322 square miles, about twice the size of France. The following year, a Netherlands-sized hole melted within the sea ice. Geologists call this unfrozen expanse of open water within ice a polynya.

Related: New map exposes secrets of Antarctica’s green snow

So, what is happening to Antarctica’s sea ice? Recently, Geophysical Research Letters published new satellite research paired with data collected from ocean-faring floats. This research suggests that extremely powerful storms in the Weddell Sea whipped up warm winds, which lashed the icepack and brought on the 2015-2016 France-size melt. Storms started in September 2015, and the heat continued, causing the region’s hottest November on record. This weather created Antarctica’s first polynya in almost forty years. The polynya’s dark water absorbed more solar heat, leading to more melting. Then, another storm struck in December, further shrinking the ice.

On March 24, 2015, Antarctica experienced its then-highest ever recorded temperature of 63.5 degrees. This February, the icy continent broke that record when it hit 65 degrees.

“Variability in Antarctic sea ice extent is very large, and detecting an anthropogenic signal is going to be difficult,” said John Turner, a climate expert with the British Antarctic Survey, as reported by Earther. “The increase up to 2014 was a surprise, considering the ice loss in the Arctic, and the rapid drop in 2016 added to the long list of questions about Antarctic sea ice. It’s unclear whether the sea ice extent will recover to 2014 values or if this the start of the long-term decline expected as greenhouse gas concentrations increase.”

+ Earther

Images via Pexels and NASA Goddard Space Flight Center