Arctic ice falls to record winter low after polar 'heatwaves'

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Claire Parkinson, a senior sea ice researcher at Goddard said: "There's a lot of year-to-year variability in both Arctic and Antarctic sea ice, but overall, until last year, the trends in the Antarctic for every single month were toward more sea ice". A better understanding of natural variation's role could help scientists narrow that predicted time span.

Arctic sea ice melts and regrows in an annual cycle, with freezing throughout the winter months and melting in the spring and summer. The previous below maximum extent occurs in 1979. Compared to last year's record low, ice covering the Arctic Ocean lost about 100,000 square kilometers. NASA satellites also indicate that at the opposite end of the world, Antarctica sea ice hit record lows for the end of the summer.

Sea ice extent is, very simply, a measurement of how much ocean water contains at least 15 percent sea ice (other organizations use different thresholds but 15 percent is the one used by NASA). According to recordkeeping dating back to 1979, that is the smallest maximum extent of arctic ice on record. The ice is shrinking not only in area but also thickness, making it more vulnerable to breakup by the seas, winds and warmer temperatures, NASA said.

Another type of record low was set for the Antarctic.

The sea ice, generally, reaches maximum and minimum in September and March respectively in Arctic circle.

"We started from a low September minimum extent", said Walt Meier of Nasa's Goddard Space Flight Center in a statement.

"Since November, daily Antarctic sea ice extent has continuously been at its lowest levels in the satellite record", said the United States space agency.

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Sea ice levels shrink in the Arctic and Antarctic. This winter, several factors affected the sea ice growth.

After decades of moderate sea ice expansion, NASA is witnessing something it did not expect. The ice cover generally reaches its maximum extent sometime in late February or March. Scientists reported that this is about 35,000 square miles-an area about the size of Maine-below 2015's record. However, the data centre reports Antarctic ice is highly variable and was at its highest level 2 1/2 years ago.

Ice floes float in Baffin Bay between Canada and Greenland above the Arctic circle on July 10, 2008.

A relatively new idea-that still divides meteorologists-links the shriveling ice cap at the North Pole to a weaker polar vortex and weak and ambling jet stream, which can mean more extreme weather for a good part of the rest of the world. The top line shows the Arctic; the middle shows Antarctica; and the third shows the global, combined total.

On March 7, 2017, Arctic sea ice hit a record low wintertime maximum extent in 2017.

The Antarctic is another story; there's no clear trend yet.