Arctic sea ice maximum hit a record low last year, but down south, Antarctic sea ice was as thick and extensive as ever.
A US team led by NASA's Jet Propulsion Laboratory's Son Nghiem suggests why sea ice at the poles is acting differently – a massive "great shield" built early in the growing season protects Antarctic sea ice. The Arctic, though, lacks such a protective boundary.
"Our study provides strong evidence that the behaviour of Antarctic sea ice is entirely consistent with the geophysical characteristics found in the southern polar region, which differ sharply from those present in the Arctic," said Nghiem.
Sea ice floats on the ocean and extends and contracts seasonally. In Antarctica, sea ice maximum is around September each year.
In recent decades, records for Arctic and Antarctic sea ice have toppled – but in opposite extremes. While the Arctic has seen sea ice maximums shrink, Antarctica enjoyed record sea ice extent in 2012, 2013 and 2014.
So what's going on?
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