The Arctic sea ice plunged to a minimum extent of 4.64 million square km in 2017 – the eighth-lowest seasonal level in nearly 40 years – according to a preliminary report by the National Snow and Ice Data Center.

The report released on Tuesday says that this year’s minimum was 1.58 million square km, well below the 1981 to 2010 median extent for the same day.

The layer of ice that blankets the Arctic Ocean and nearby regions shrinks during the warmer seasons. The lowest level of the ice cap during a year is the minimum extent, and the highest level is the maximum extent. The worst ever year for the ice caps was in 2012, when it had shrunk to 3.39 million square km.

Senior climate scientist at National Aeronautics and Space Administration’s Goddard Space Flight Center, Claire Parkinson, said that the amount of ice left at the end of a summer depends on the “state of ice cover” earlier in the year and the weather conditions affecting the ice.

“The weather conditions have not been particularly noteworthy this summer. The fact that we still ended up with low sea ice extents is because the baseline ice conditions today are worse than the baseline 38 years ago.” Nasa researchers have said that the heavy and slightly warmer summer rains in the Arctic this year may have also led to the melting of the ice cap.

National Snow and Ice Data Center scientists said the ice extent could further decrease because of changing winds or late-season melt.


Arctic sea ice is dropping by 2.8% each decade

Earlier, on February 13 this year, Nasa said that combined Arctic and Antarctic sea ice were “at their lowest point since satellites began to continuously measure sea ice in 1979”.

Its figures showed that a chunk of sea ice larger than the size of Mexico had been lost up to February. “Total polar sea ice covered 6.26 million square miles (16.21 million square kilometers), which is 790,000 square miles (2 million square kilometers) less than the average global minimum extent for 1981-2010”, Nasa said. It added that the maximum extent of sea ice in the Arctic has “dropped by an average of 2.8% per decade since 1979”.