Climate: Arctic sea ice peaks for the year

Arctic sea ice extent is declining at 2.6 percent each decade.

March surge boosts extent late in the season

Staff Report

FRISCO — Arctic sea ice grew to its maximum extent for the year on March 21, reaching 5.70 million square miles. According to the National Snow and Ice Data Center, it was the fifth-lowest maximum extent in the satellite monitoring era, starting in 1978. The lowest maximum extent occurred in 2011, at 5.65 million square miles.

The average date for maximum sea ice extent is March 9, just a couple of weeks after the spring equinox, but the date varies from year to year. The latest maximum on record was in 2011, when sea ice extent expanded through March 31. Through 2014, the linear rate of decline for March ice extent is 2.6 percent per decade relative to the 1981 to 2010 average.

This year, Arctic sea ice expanded late in the season with a shift in the Arctic Oscillation during the second week of March. Unusually low sea level pressure in the eastern Arctic and the northern North Atlantic set up a pattern of surface winds that spread out ice in the Barents Sea and in the Bering Sea, where ice extent was low all winter.

But air temperatures remained unusually high throughout the Arctic during the second half of March, at 4 to 11 degrees Fahrenheit above the 1981 to 2010 average.

NSIDC scientists also noted an increase in the extent of thicker, multi-year ice in the Arctic. During the summer of 2013, a larger fraction of first-year ice survived compared to recent years. This ice has now become second-year ice. Additionally, the predominant recirculation of the multiyear ice pack within the Beaufort Gyre this winter and a reduced transport of multiyear ice through Fram Strait maintained the multiyear ice extent throughout the winter.

Overall, multi-year ice increased from 869,000 to 1,22 million square miles between the end of February in 2013 and 2014. This winter the multiyear ice makes up 43 percent of the icepack compared to only 30 percent in 2013. The percentage of the Arctic Ocean consisting of ice at least five years or older remains at only 7 percent, half of what it was in February 2007. Moreover, a large area of the multiyear ice has drifted to the southern Beaufort Sea and East Siberian Sea (north of Alaska and the Lena River delta), where warm conditions are likely to exist later in the year.

NSIDC now offers a new Web site, Satellite Observations of Arctic Change (SOAC)  with interactive maps of the Arctic based on NASA satellite and related data. The site allows visitors to explore how conditions in the Arctic have changed over time. Data sets include air temperature, water vapor, sea ice, snow cover, NDVI, soil freezing, and exposed snow and ice.

Time periods vary by data set, but range from 1979 to 2013. You can animate a time series, zoom in or out, and view a bar graph of anomalies over time. Links to the source data and documentation are also included. Additional pages provide brief scientific discussion, and overviews of the scientific importance of these data. SOAC was developed with support from NASA Earth Sciences.






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