Antarctic sea ice is shrinking rapidly after decades of growth. Scientists aren't sure why. - NBCNewsMACH
Get the Mach newsletter.The amount of ice floating in waters off Antarctica has declined significantly since 2014, a new study shows. But the same research — a detailed analysis of 40 years of satellite data about sea ice — shows that the amount of
grew unexpectedly for almost four decades before the steep decline, even as sea ice in the Arctic region declined.“There’s a lot of interannual variability in both Arctic and Antarctic sea ice, but, which is consistent with what we’d expect,” said study author Claire Parkinson, a climatologist at NASA’s Goddard Space Flight Center in Greenbelt, Maryland. “What was happening in Antarctica could not be so easily explained.
Researchers have long struggled to explain the unusual behavior of Antarctic sea ice, which forms when seawater surrounding the southernmost continent freezes in winter. Whereas Arctic sea ice has been in steady decline over the past four decades, the amount of Antarctic sea ice increased from 1979, when scientists first had access to routine satellite observations of the area, to 2014, when the ice began its retreat.
“It was just three years later that we had a record low, which is quite a rapid shift,” Parkinson said. “The magnitude of that decrease from 2014 to 2017 was more than the decrease that has happened in the Arctic over more than 30 years.” But what caused the initial expansion and subsequent speedy retreat remains a mystery. Researchers have some hypotheses, but so far there is no scientific consensus., Parkinson said. During the 1980s and ’90s, heavy use of aerosol sprays, refrigerants and other products containing compounds known as chlorofluorocarbons thinned the ozone layer in Earth's atmosphere and allowed more warming ultraviolet rays from the sun to reach the planet’s surface.
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