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With Arctic sea ice vulnerable, summer melt season begins briskly (+video)

The Arctic saw a record loss of summer sea ice in 2012, and the 2013 melt is off to a faster start than a year ago. Another record is uncertain, but warming has sapped the ice's staying power.

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In addition, a string of storms in February accelerated the fracturing already occurring in a large region of ice floes in the Chukchi and Beaufort Seas.

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Researchers have noted that ice frequently fractures in this area all the time. But this event was unusual for the large extent of ice affected, as well as the length and width of the cracks that opened.

It involved seasonal ice. And prior to the storms, a weather system had stalled over the area, sweeping relatively warm winds out of the southwest across the ice, slowly spinning the collection of relatively large ice floes and driving them en masse like a floating pinwheel toward the northwest corner of Alaska.

Indeed, the vulnerability of single-year, or seasonal, ice was a key factor in last year's record decline in summer ice extent – the combined effect of long-term preconditioning from global warming and a powerful storm that roared out of Siberia on Aug. 2, and over the central Arctic Ocean, only to weaken over the Canadian Archipelago 12 days later.

In what Parkinson and Goddard colleague Josephino Comiso describe as a polar version of "divide and conquer," the storm in effect bit off a 154,000-square-mile chunk of ice, which broke up and melted. This exposed a new ice edge to rough seas and once the storm passed, to more sun-warmed open water to melt the newly exposed floes to melting from underneath.

The storm, dubbed the Great Arctic Cyclone of 2012, was the strongest summertime storm to hit the region since 1979. It also ranked as the 13th strongest storm ever during that period.

The Goddard duo's analysis of the storm's impact on the ice was published last month in the journal Geophysical Research Letters.

Researchers have been tracking the continuing erosion of summer sea ice because of its potential impact on climate regionally, as well as globally. Less ice exposes more ocean to long hours of sunlight in the summer. The ocean absorbs the radiation and stores it as heat to be slowly released as air temperatures begin to cool.

Scientists have suggested that heat released from this expanding reservoir of relative warmth could well fuel storm systems that pass over the ocean, increasing the risk of storm surges along a coast with far less land-fast ice in the melt season and into the fall than it once had. This could represent an additional challenge to overcome for companies that aim to exploit resources beneath the Arctic coast.

A team led by Jesse Vermaire at Carleton University in Ottawa reported last month an increase in the level of storm-surge activity along the Mackenzie River Delta since the late 19th century. The evidence emerged from 1,200 years' worth of flooding and surge data recorded in sediment cores extracted from small lakes on the outer delta.

Surge activity was low until around 1910. Over the next 50 years, activity increased, then weakened again between 1960 and 1980. After that storm surge activity rose sharply, a change that coincided with rising temperatures and retreating sea ice.

One surge, in 1999, swamped an estimated 1.2 million acres in the low-lying delta, salting the soil, killing vegetation and turning some freshwater lakes brackish. The team notes that, a decade later, affected areas still haven't recovered.

While the region is sparsely populated, it is said to contain oil and gas reserves – raising the potential for additional development as the Arctic's climate continues to warm.

The team formally published its results last month in the journal Geophysics Research Letters.

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