The extent of Arctic sea ice covered the third smallest area ever recorded by satellite for the month of May, continuing the frozen pack's decades-long decline in volume and extent, according to the most recent post by the National Snow and Ice Data Center.
"Air temperatures averaged for the month of May were 4 to 5 degrees Celsius (7 to 9 degrees Fahrenheit) warmer than normal in the Beaufort and Chukchi seas, western Siberia, and in the Kara Sea," the NSIDC says. "The areas with high air temperatures correspond to locations where ice retreated and polynyas formed."
Sea ice generally disintegrates fast this time of year, and the NSIDC satellite jockeys say the polar floes shrank back almost 20,000 square miles per day over the month. The Arctic was losing a frozen habitat slightly larger than Vermont and New Hampshire combined during every horizon-lapping circuit of the midnight sun.
Such a rate of decline is typical for the Arctic spring, and pretty close to average, according to the NSIDC. But because the ice cap began the 2011 melt season much depleted, the overall size of the cap ended May covering only about 4.94 million square miles — 313,000 square miles below the average extent recorded from 1979 to 2000.
It's a mind-numbing disconnect. It's as though a seal-and-bear ecosystem the size of the U.S. West Coast states combined – California, Oregon and Washington – has simply vanished from the Arctic's May world. And it gets worse: The latest total was only about 81,000 square miles ahead of May's record minimum set in 2004 – about the same amount of ice that has been disintegrating every four days or so.
For a glimpse of breakup in progress, check out the Geophysical Institute's webcam, which showed shore-fast ice speckled with melt ponds off Barrow in mid-June.
More detail from NSIDC:
Ice extent remained lower than average in the Atlantic sector of the Arctic, including the Kara and Barents seas and the Labrador Sea. During May, areas of open water known as polynyas continued to develop in the Beaufort, Chukchi, and Laptev seas, and Hudson Bay. Those open water areas absorb the sun's energy, which will likely help to hasten further ice melt.
So what does this low extent — but not yet record low extent — say about our polar cap prospects for the rest of the summer, and the lead in to the climatic annual minimum ice pack we'll see by September?
"Arctic weather in the next few months will be a critical factor in how much ice remains at the end of the melt season," the NSIDC explained. "Years with dramatic ice loss, such as 2007, have been associated with comparatively warm, calm, and clear conditions in summer that have encouraged ice melt. Summers with slow melt rates are opposite and tend to be stormier than average. The number of storms influences how warm, windy and cloudy the Arctic summer is."
Contact Doug O'Harra at doug(at)alaskadispatch.com.