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Sea ice in the Arctic and Antarctic areas

Updated on 10 Apr. 2018
Global Environment and Marine Department




Notice: The long term trend in the annual mean sea ice extent in the Antarctic area is corrected from 0.015 x 106 km2 per year to 0.019 x 106 km2 per year on 11 May 2018.




The sea ice extent in the Arctic Ocean has shown a long-term trend of decrease since 1979. The change in the annual minimum sea ice extent is particularly notable, with a yearly reduction equivalent to the area of Japan's northern island of Hokkaido.
In the Antarctic Ocean, the annual maximum and annual mean sea ice extents have shown a long-term trend of increase since 1979.

The annual maximum sea ice extent in the Arctic Ocean and the annual mean and annual minimum sea ice extents in the Antarctic Ocean for 2017 were both at their lowest since 1979.

Sea ice extent (1979 -2017) in the Arctic Ocean
Sea ice extent (1979 -2017) in the Antarctic Ocean

Time-series representations of annual maximum, mean and minimum sea ice extents in the Arctic Ocean (including the Sea of Okhotsk and the Bering Sea) and the Antarctic Ocean from 1979 to 2017


The solid blue, brown and red lines indicate the annual maximum, mean and minimum sea ice extents, respectively. The dashed lines indicate the linear trends of each value. Sea ice extents are calculated from brightness temperature data provided by NASA and NSIDC (the National Snow and Ice Data Center).


Commentary

It is virtually certain that there has been a long-term trend of decrease in the sea ice extent in the Arctic Ocean since 1979. The change in the annual minimum sea ice extent is particularly notable, with a yearly reduction of 0.090[0.075-0.106] x 106 km2 up to 2017 (numbers in square brackets indicate the two-sided 95% confidence interval), which equates to the area of Japan's northern island of Hokkaido (0.083 x 106 km2). The annual maximum sea ice extent for 2017 was 14.55 x 106 km2, which was the lowest since 1979.

Meanwhile, it is virtually certain that there has been a long-term trend of increase in the annual maximum and annual mean sea ice extents in the Antarctic Ocean since 1979. The former has increased by 0.023[0.010-0.035] x 106 km2 per year and the latter by 0.019[0.008-0.030] x 106 km2 per year. The annual minimum sea ice extent exhibits no discernible trend.

The sea ice extents in the Antarctic Ocean for 2017 were lower than their normals (1981 - 2010 averages). The annual mean sea ice extent (11.09 x 106 km2) and the annual minimum sea ice extent (2.24 x 106 km2) were both at their lowest since 1979.

According to the Intergovernmental Panel on Climate Change Fifth Assessment report (IPCC, 2013), anthropogenic influences have very likely contributed to Arctic sea ice loss since 1979, and there is low confidence in the scientific understanding of the small increase observed in the Antarctic sea ice extent.