2010 apparently tied 2008 for second lowest sea ice extent after a cool stormy July slowed the record rate of ice volume loss seen in spring 2010.



Source: IJIS

Weather patterns that trapped record heat in the Moscow region caused cool weather around the north pole in July and early August. However, since 2007, the year that hit the all time record minimum sea ice extent, thick multiyear sea ice has been lost. This year, large areas of thin broken sea ice were observed in the Arctic ocean.

Yellow area is thin broken sea ice, Source: NASA

Following 1967, a year like 2007 with exceptional melting of Arctic ice, rapid cooling of the northern hemisphere was observed. The cooling was apparently triggered by low salinity melt water that wouldn't sink.

...according to Mark Maslin of the Environment Institute at University College London, one possible culprit is the Great Salinity Anomaly – an unusually large discharge of ice from the Arctic Ocean in 1967 that caused a 10,000 cubic kilometre pool of fresh water to form off the coast of Greenland. Normally, surface water in the northern North Atlantic cools during the winter, sinking as it becomes denser. In turn, warm, deep water rises to the surface, releasing its heat into the atmosphere. It is possible that the Great Salinity Anomaly shut down this mixing process and triggered a cool period by dumping light, fresh water on the surface. It wouldn't have been the first time, said Mike Mann at Penn State University. Around 12,800 years ago, a similar event on a far greater scale may have triggered a mini ice age. "A sudden runoff of fresh water into the North Atlantic from melting ice ... suppressed the sinking of high-latitude North Atlantic ocean water that drives the thermohaline circulation."

However, the rate of Arctic warming may now be fast enough to cancel out the normal tendency of Arctic ice melting to cool the Arctic. Much warmer than normal water is entering the Arctic from both the Atlantic and Pacific Oceans. The meltwater released in the 2007 mixed and cooled with salty Atlantic Ocean water last winter in massive storms in the Labrador sea. Apparently it sank and was replaced by warm water transported by the Gulf stream and other Atlantic currents.

Source: Mercator Ocean

The exceptionally warm water surrounding Greenland threatens the stability of Greenland's ice cap.

As the helicopter headed toward the coordinates on the glacier where Hamilton wanted to land, he gazed out the window. His mind drifted absently across the landscape. The steep rock of the fjord rose above the dark, pooling water below, the glacier still miles upstream. Suddenly, Hamilton was startled out of his grogginess by a squawking in his headphones: The pilot was trying to tell him something. Hamilton asked the man to repeat himself. "We're here," the pilot said. Hamilton looked down. They were over open water. The glacier had vanished. Confused, Hamilton picked up the satellite image. Perhaps he had given the pilot the wrong coordinates. In the sketch, he could see two tributary glaciers that emptied into Kangerdlugssuaq right where he had wanted to land. He looked out the window. There were the two tributary glaciers. But they were emptying into the sea. In the few months since the image had been taken, the front end of Kangerdlugssuaq had disappeared. "It was here for more than 50 years," Hamilton says. "And now it was gone."

Warm ocean water, melting the toes of glaciers, can trigger rapid movement and even collapse of the whole glacier. It is like a dam break. When the glacier is the outlet of one of the world's largest ice caps the failure of the toe of the glacier is a potential catastrophe.

A report being put together at the time by the U.N.'s Intergovernmental Panel on Climate Change, a collection of the world's leading climate experts, estimated that global sea levels would rise no more than a foot and a half in the next century. But over the past five years, as more discoveries like Hamilton's have emerged, those numbers have come to seem obsolete. "The estimates are now clustering around a rise in sea level of three feet by the end of the century," says Richard Alley, a geoscientist at Pennsylvania State University — double the previous estimates. "Nature has begun to resolve some of these arguments for us." The new science indicates that by the end of the century, rising seas could turn as many as 153 million people into refugees. Most of New Orleans, and large swaths of Miami and Tampa, are likely to be underwater, along with some of the world's largest cities: Manila, Lagos, Alexandria. A full quarter of the developing world's coasts will be battered by more frequent hurricanes and tsunamis; roughly half of Bangladesh, a country of 160 million people, will be subject to regular flooding. If Hamilton was right, then within the ice sheets something truly cataclysmic had begun.

The loss of sea ice and the melting of glaciers will cause more light and heat to be retained by water and less to be reflected back to space by ice. This will amplify the rate of Arctic warming. That may trigger a catastrophic, massive release of methane and CO2 from melting permafrost and methane ice.

"I hate to say it but I think we are committed to a four- to six-degree warmer Arctic," Serreze said. If the Arctic becomes six degrees warmer, then half of the world's permafrost will likely thaw, probably to a depth of a few metres, releasing most of the carbon and methane accumulated there over thousands of years, said Vladimir Romanovsky of the University of Alaska in Fairbanks and a world expert on permafrost. Methane is a global warming gas approximately 25 times more potent than carbon dioxide (CO2). That would be catastrophic for human civilisation, experts agree. The permafrost region spans 13 million square kilometres of the land in Alaska, Canada, Siberia and parts of Europe and contains at least twice as much carbon as is currently present in the atmosphere – 1,672 gigatonnes of carbon, according a paper published in Nature in 2009. That's three times more carbon than all of the worlds' forests contain.

But Republicans threaten to roll back regulator efforts by EPA to control greenhouse gas emissions and no comprehensive climate legislation is likely to be passed in President Obama's first term.