A series of unprecedented storms over the Southern Ocean likely caused the most dramatic decline in Antarctic sea ice seen to date, a new study finds.
Antarctic sea ice – frozen ocean water that rings the southernmost continent – has grown over the past few decades but declined sharply in late 2016. By March of 2017 – the end of the Southern Hemisphere’s summer – Antarctic sea ice had reached its lowest area since records began in 1978.
In a new study, scientists puzzled by the sudden ice loss matched satellite images of Antarctica with weather data from the second half of 2016 to figure out what caused so much of the ice to melt. They found that a series of remarkable storms during September, October and November brought warm air and strong winds from the north that melted 75,000 square kilometers (30,000 square miles) of ice per day. That’s like losing a South Carolina-sized chunk of ice every 24 hours.
Antarctic sea ice is relatively thin – on average only 1 meter (3 feet) thick – making it extremely vulnerable to strong winds, said John Turner, a climate scientist with the British Antarctic Survey in Cambridge, United Kingdom, and lead author of the new study in Geophysical Research Letters, a journal of the American Geophysical Union.
Sea ice area is an important indicator of climate change, and sea ice loss in the Arctic has been linked to increased greenhouse gas emissions. But because sea ice records go back only four decades – when the satellite era began – it’s difficult to attribute Antarctica’s sea ice loss last year to human-caused climate change, Turner said. Whaling records provide scientists with hints of Antarctica’s past sea ice extent, but it’s tough to compare that data to satellite records, he said.