The amount of Antarctic sea ice is falling fast Stephen Alvarez/Getty

Decades of expanding sea ice in Antarctica have been wiped out by three years of sudden and dramatic declines, leaving scientist puzzled as to why the region has flipped so abruptly.

A new satellite analysis reveals that between 2014 and 2017 sea ice extent in the southern hemisphere suffered unprecedented annual decreases, leaving the area covered by sea ice at its lowest point in 40 years. The declines were so big that they outstripped the losses in the fast-melting Arctic over the same period. “It’s very surprising. We just haven’t seen decreases like that in either hemisphere,” says Claire Parkinson at NASA’s Goddard Space Flight Center, who undertook the analysis.

However, researchers cautioned against pinning the changes on climate change and said it was too early to say if the shrinking is the start of a long-term trend or a blip.


“There was a period in the 1970s when the Antarctic also had a huge decrease in sea ice and then increased. So it could be this huge decrease over a few years [2014-2017] is going to reverse,” says Parkinson. There was a modest uptick between 2017 and 2018, but sea ice extent has since fallen again and today is at a near record low for this time of year.

The decline may just be natural variability, driven by shift in wind patterns which influence the extent of Antarctic sea ice, says Mark Serreze, director of the US National Snow and Ice Data Center. “To argue that this recent dip is evidence of the start of a longer term decline driven by greenhouse warming is premature.”

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Wind patterns, the hole in the ozone layer and the climate phenomenon El Niño all play key roles in affecting Antarctic sea ice which, unlike the Arctic, has been growing for decades. Researchers are trying to find out why the trend has flipped, says Kaitlin Naughten at the British Antarctic Survey.

Melting Antarctic sea ice does not add to sea level rise because the ice is already in the water. However, it is bad for wildlife such as penguins that rely on it. It also contributes to global warming because sea ice reflects much of the sun’s energy back into space, while dark water absorbs it. “The sea ice has a huge impact on climate in that respect,” says Parkinson.

Journal reference: PNAS, DOI: 10.1073/pnas.1906556116