Late Spring 2023 Sea Ice
More than most recent years
April 2023 was, by recent standards, comparatively cool over the Arctic as a whole: poleward of 60N the April average temperature was the lowest since 2009 (ERA5 reanalysis), though that was still warmer than the late 20th century average. While temperatures relative to normal have rebounded in May, the impacts of the cool conditions on sea ice are still being felt.
The Arctic-wide sea ice concentration from the high resolution AMSR2 data is shown in Fig. 1. Ice melting and development of low concentration and open water areas is usually a piece-meal process in the spring, dependent on pre-existing ice quality, thickness and stability, water runoff from the land masses, winds and currents. As of May 25th this “Swiss cheese pattern” was especially prominent in parts of the Canadian Arctic and the northern Bering Sea. Overall, ice extent is above the long term normal in the Greenland Sea and northeast Bering Sea but below normal in the Barents Sea (east of Svalbard) and portions of the Canadian Arctic. From the National Snow and Ice Data Center (NSIDC) Sea Ice Index, the May 25th Arctic-wide sea ice extent was the 15th lowest since 1979, though only one year prior to 2004 had lower extent than this year.
The Beringia Sector
Sea ice near northeast Russia, Alaska and northwest Canada remains more extensive than most recent years but is slowing melting, with increasing areas of open water in the Bering Sea and the Chukchi Sea immediately north of the Bering Strait. As seen in the loop in Fig. 2, farther north leads have opened and closed back up, mostly due to shifting winds, though apparently the pack ice in the East Siberia Sea offshore of northwest Chukotka is now starting to spread out (last frame of the loop). The persistent area of open water in the Amundsen Gulf (far eastern Beaufort Sea south of Banks Island) is also of note.
Figure 3 shows the May 25th AMSR2 sea concentration for this year (left) compared to the 2013-2022 median concentration for the date (right). In that decade in the Bering Sea, only 2013 and 2021 had as much or more ice remaining at this point in the season, and the last time there was any significant amount of ice south of St. Matthew Island this late in May was in 2013. The May 25th Chukchi Sea sea ice extent in the NSIDC data was, by a tiny amount (not significant), the highest for the date since 2001, very slightly higher than the extent on May 25, 2005, 2012 and 2013.
Leads in Chukchi Sea ice typically develop in the spring along the northwest Alaska coast, due in part to climatologically frequent east to northeast winds. That’s why the northwest Alaska coast has been home to people for thousands of years: spring leads make for reliably good marine mammal hunting. However, that has not been the case so much this spring. Figure 4 shows that since April 1st, low level easterly winds across much of the Chukchi Sea and southern Beaufort Sea have been significantly weaker than average: that is, there has more of a west wind component than usual. In the eastern Chukchi Sea this has resulted in only transitory leads developing and then closing off. Stronger than normal west winds were also prominent in the Barents Sea region and in the Canadian high Arctic.
NSIDC Arctic Sea Ice information and data available at https://nsidc.org/arcticseaicenews/
AMSR2 data and images from U. Bremen at https://seaice.uni-bremen.de/sea-ice-concentration/amsre-amsr2/
NCEP/NCAR reanalysis from https://psl.noaa.gov/data/composites/hour/
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