Average Arctic ice extent in April

Shell has been commenting that unusually heavy ice in the Chukchi Sea may slightly delay the start of its planned drilling operations in that sea this summer.

Meantime, the National Snow and Ice Data Center has reported an April Arctic sea ice extent that is close to the average for the 34 years since satellite ice observations began. But, although at first sight this recent data might appear to buck the trend towards an ever shrinking Arctic ice cap, the center cautioned that a plot of April data over that 34 year period still indicates an ice cover decline at a rate of 2.6 percent per decade. And although this year’s ice cover is relatively broad, the ice is relatively thin, so that the ice will likely melt quite quickly as Arctic temperatures rise during the spring and summer.

The center attributes this April’s relatively large sea ice extent to a combination of unusually low temperatures and persistent winds that pushed the ice south. The April ice cover in the Bering Sea was especially extensive, the center said.

—Alan Bailey