Thursday, 04 August 2011 13:27 Written by Doug O'Harra, Alaska Dispatch

Alaska Dispatch.

Basking under clear, calm skies that delivered startling warmth to the Arctic Ocean, the polar ice cap shrank to the smallest extent ever recorded for the month of July, continuing a decades-long decline in the size of the summer floes.

Arctic ice cover averaged only about 3.06 million square miles during the month — about 81,000 square miles below the previous record low set in 2007, according to the latest update posted by the National Snow and Ice Data Center. That's about 842,000 square miles below the average for the month as recorded by satellites between 1979 and 2000.

This stunning loss of ice -- which has slowed dramatically in the last few weeks -- is at once a boon to commerce and a harbinger for future sea ice shrinkage.

"Shipping routes in the Arctic have less ice than usual for this time of year," the NSIDC reported. "And new data indicate that more of the Arctic's store of its oldest ice disappeared."

Northern Sea Route opens early

The retreat opened most of the Northern Sea Route over Russia earlier than ever before, making shipping between Europe and the Bering Strait more feasible than usual. Russian icebreakers plan to escort up to 15 ships between hemispheres before the summer ends, according to the Barents Observer. (Russia also announced plans to build six more icebreakers for the 2012 season.)

At least one Belgium-owned ship has already pounced, successfully hauling 70,000 tons of oil condensate over the Arctic through the Bering Strait to a port in China, according to this report.

"Taking advantage of the early retreat of sea ice in the Kara and Barents seas, the tanker Perserverance set sail on June 29, 2011 from Murmansk, Russia, aided by two icebreakers and completed the passage on July 14," the NSIDC added here. "The company plans to send six to seven more ships through the Northern Sea Route this summer."

Ice shrinkage in Northwest Passage ahead of average

But the fate of Arctic ice is never simple, and trends rarely move in a straight line.

Despite such a startling early season retreat of ice from the shores of Asia and Alaska, the Northwest Passage through the Canadian Archipelago remained "choked with ice" through late July, the NSIDC said. Still, the ice shrinkage in northern Canada was ahead of average and could end up rivaling the 2010 season, when ice in the fabled passage reached the lowest level since 1968.

"Whether a navigable channel does indeed open this year will depend on weather conditions through the next few weeks, but so far, it looks possible," according to the NSIDC.

Another complication: the weather has shifted and slowed the retreat. A series of low pressure systems and storms hammered the central Arctic during the last couple of weeks and substantially dialed back the melt rate. By the end of July, the total ice extent had slipped behind the 2007 season in the race to the bottom and — for a few weeks at least — was no longer setting daily records.

Sound like good news? A turnaround perhaps? Probably not.

"This change (in weather) brought cooler conditions and likely pushed the ice apart into a thinner but more extensive ice cover," the NSIDC explained.

Weather continues to affect ice

The remaining floes may be covering more territory than the same early August dates of 2007, but they appear to contain less of the thick, royal-blue sheets older than five years, the kind of ice that once formed the polar cap's bedrock.

"Until recently, the central Arctic Ocean and Canadian Archipelago served as refuges for some of the oldest, thickest ice," the NSIDC added. "However, the new data show that ice age is now declining in these areas."

Summer sea ice forms one of the Earth's most important ecological features and tracking its seasonal fate has become a sort of harbinger for climate change. The loss of summer ice directly contributes to climate change because darker open water absorbs more solar energy than glaring white floes. The exposed ocean heats up faster and then causes even more ice to melt.

But sea ice also provides habitat necessary to maintain healthy populations of polar bears, walruses and seals. When this summertime hunting and denning platform disappears, marine mammals must swim further or spend time on shore, making it harder for them to find enough to eat or avoid getting eaten by predators.

To put the latest data in perspective, the difference between July 2011 and the average ice cover seen in July during the 21 years between 1979 and 2000 is immense. It's as though a seasonal marine habitat the size of Alaska, Washington and Oregon combined has vanished from the Far North.

Originally posted August 3, 2011