Alaska: 'Graveyard' of old Arctic sea ice

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Alaska may have earned itself a new nickname in the grim annals of summer sea ice meltdown: The Graveyard of Old Ice.

First a recap: The summer destruction of the polar cap officially ended on Sept. 9 with the second smallest extent ever observed during the age of satellites, according to the newest analysis posted by the National Snow & Ice Data Center. Plunging polar temperatures have been refreezing the Arctic for weeks.

Ice covered about 1.78 million square miles during September -- more than 40 percent lower than the monthly average recorded between 1979 and 2000 and only 120,000 square miles above the minimum seen in 2007.

To put that data in perspective, it's as though a marine habitat almost the size of Alaska, Washington, Oregon and California combined has disappeared from the Arctic’s September world. But 2011 still retained more ice than the minimum seen in 2007 by NSIDC calculations, holding onto floes that would cover an area about the size of New Mexico.

Don't exhale with relief just yet, scientists say. Ice shrink in 2011 may have been more severe than it might appear (and a German team of scientists say the record did fall; more on that below).

Although sea ice melted at double the average rate during early summer -- opening the Northern Sea Route and Northwest Passage earlier than ever before -- 2011 still lacked the sort of unusual weather thought to have triggered the 2007 record. In fact, much of the late summer favored ice preservation, which raises some troubling questions about the true meaning of this year's second-place finish in the race to the bottom.

"Why did ice extent fall to a near record low without the sort of extreme weather conditions seen in 2007? One explanation is that the ice cover is thinner than it used to be," the NSIDC says here.

Ice that was less than two years old covered 80 percent of the Arctic basin last March -- much less than the long-term average. While new ice has generally been surviving summer melt since 2007, the polar sea has been steadily losing the oldest and thickest ice at the same time, especially in the Beaufort and Chukchi seas north of Alaska.

Thus, 2011 flirted with a new record partly because Alaska's royal blue, multi-year ice cap -- that frigid wilderness of epic floes that once wiped out Yankee whaling fleets and inspired the international rescue of trapped gray whales -- is almost gone.

"Continued loss of the oldest, thickest ice has prevented any significant recovery of the summer minimum extent," federal scientists concluded. "In essence, what was once a refuge for older ice has become a graveyard."

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The extent of summer ice in the Arctic -- defined as the area covered by at least 15 percent ice -- has been sliding for almost 30 years. Some scientists say the Arctic will lose virtually all of its summer ice cover within decades, and they blame this loss on rising temperatures and complex shifts in Arctic storm patterns. 

The ongoing summer meltdown stresses animals that need the solid floes for hunting and denning platforms. When sea ice melts out of existence, habitat necessary to maintain healthy populations of polar bears, walruses and seals simply disappears. The loss of summer ice in the Beaufort Sea led the United States to list polar bears as threatened under the Endangered Species Act and designate a span of ocean north of Alaska as critical habitat.