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Arctic sea ice continues downward trend

Friday, August 23, 2013, 1:33 PM - Arctic sea ice continues its melt toward the annual "minimum" but scientists don't expect any records to be broken.

Sea ice in the arctic continues its summer melt and is on its way toward the annual minimum - when the floating ice cap covers less of the Arctic Ocean than at any other period during the year.

The ice is expected to melt until mid-September but scientists don't believe the summer low will break any new records. 

Despite no records broken so far, researchers are concerned by the melt rates - which follow the sustained decline of ice cover observed by NASA over the last several decades.

“Even if this year ends up being the sixth- or seventh-lowest extent, what matters is that the 10 lowest extents recorded have happened during the last 10 years,” said Walt Meier, a glaciologist with NASA’s Goddard Space Flight Center in a press release. “The long-term trend is strongly downward.”

Sea ice extent measures the area of the Arctic Ocean where ice covers at least 15 percent of the surface.

Ice cover at the Arctic Ocean was measured at 5.83 million square kilometres on August 21.

In comparison, the smallest cover on record for this date occurred in 2012 at 4.34 million sq km. The largest for this date was in 1996, when ice covered 8.2 million sq km of the Arctic Ocean. 

This year's melting season started with a rapid melt in the first half of July, as above average temperatures warmed the region. 

Things changed due to low atmospheric pressure and increased cloud cover over the central Arctic, halting the ice's rapid retreat.

According to Joey Comiso, senior scientist at Goddard, 2013 is unlikely to set any new lows.

“But average temperatures in the Arctic fluctuate from one week to another, and the occurrence of a powerful storm in August, as happened in 2012, could cause the current rate of decline to change significantly,” Comiso said in a press release.

A fair number of storms have gripped the Arctic this summer, but none were intense like the cyclone that struck in August 2012. 

“Last year’s storm went across an area of open water and mixed the smaller pieces of ice with the relatively warm water, so it melted very rapidly,” Meier said. “This year, the storms hit in an area of more consolidated ice. The storms this year were more typical summer storms; last year’s was the unusual one.”

The ice cap along the Arctic has thinned considerably over the last couple of decades, making it very vulnerable to melt.

A thinner first time ice will behave more erratically in the summer than a multi-year ice. Conditions this summer weren't favourable to substantially melt new ice.

Antarctic ice growing

In contrast, Antarctic ice is in its growth season and could set new records for size.

On August 21 it reached 19.3 million sq km. A year ago the extent of Antarctic sea ice for the same date was 18.33 million sq km.

Many research studies are currently investigating why there is such a large contrast between Arctic and Antarctic conditions. 

The rate Arctic is melting currently surpasses growth rates seen in the Antarctic. 

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