Arctic sea ice reaches maximum extent

The Arctic sea ice appeared to reach its maximum extent for the winter on March 31, despite a small, temporary decline in ice cover earlier in the month, the National Snow and Ice Data Center reported April 6. March 31 is the latest date for the winter maximum extent since satellite-based ice observations began in 1979, with the previous record of March 29 being set in 1999, NSIDC said.

Cold weather and northerly winds over the Bering and Barents Seas caused the unusual late-season spurt in ice growth, NSIDC said.

At 5.89 million square miles this year’s maximum came close below the average maximum extent since 1979. However, the ice cover varies between different regions, being higher than average in the Bering and Baltic Seas, below average in the Atlantic and average elsewhere. And the long-term trend for the sea ice maximum, including the data for this year, shows a decline rate of 2.6 percent per decade, NSIDC said.

The lowest ever maximum sea ice extent occurred in 2006, with a total area of 5.6 million square miles.

However, NSIDC says that the ice that formed late in the season this year is thin and will melt quickly when temperatures rise, thus having little impact on the summer ice extent. On the other hand, with unusual patterns of atmospheric pressures and winds in the Arctic this winter, less sea ice than usual drifted out of the region, so that there has been some replenishment of the relatively thick multiyear ice that plays a key role in determining the extent of the summer ice melt.

—Alan Bailey