Inconvenient Ice Thickening

This was big news back in September of 2007:

..."Record melting of the Arctic polar ice cap this summer has seen it shrink to an area one million square miles more than normal, scientists claim.
Arctic sea ice - which melts and re-forms depending on the season - reduced by an area the size of 10 Britains during the warmer months, according to the US National Snow and Ice Data Centre.

And the astonishing shrinkage - plummeting to a total ice cap area of 1.59 million square miles - has shattered the the previous 2005 record by 460,000 square miles.

Arctic sea ice 10 times the size of Britain has melted during the summer, setting a new record

The centre believes the sea ice has reached its minimum area for 2007, measured over a five-day average, and ice is now beginning to re-form for the winter.

At its lowest point during the summer melting season, which stretches from around March to September, sea ice coverage in the Arctic plummeted to 1.59 million square miles, compared with the previous low of 2.05 million square miles in 2005, and 2.60 million square miles for the long-term average between 1979 and 2000.

The ice shrank so much this year that the fabled Northwest Passage route around the top of North America between the Atlantic and Pacific opened up and became fully navigable for around five weeks.

The Northeast Passage, over the top of Siberia, remains closed by just a narrow band of ice, the scientists said.

A combination of higher temperatures, clear skies, warm winds from Siberia and thinner ice have all contributed to the record-breaking sea ice melt this year.

Earlier this month scientists at the NSIDC warned that at current rates, the Arctic could be ice-free in the summer by 2030 and pointed the finger at climate change for the record melting."



Now:

Recent cold snap helping Arctic sea ice, scientists find
Last Updated: Friday, February 15, 2008 | 10:17 AM ET
CBC News

There's an upside to the extreme cold temperatures northern Canadians have endured in the last few weeks: scientists say it's been helping winter sea ice grow across the Arctic, where the ice shrank to record-low levels last year.

Temperatures have stayed well in the -30s C and -40s C range since late January throughout the North, with the mercury dipping past -50 C in some areas.

Satellite images are showing that the cold spell is helping the sea ice expand in coverage by about 2 million square kilometres, compared to the average winter coverage in the previous three years.

"It's nice to know that the ice is recovering," Josefino Comiso, a senior research scientist with the Cryospheric Sciences Branch of NASA's Goddard Space Flight Centre in Maryland, told CBC News on Thursday.

"That means that maybe the perennial ice would not go down as low as last year."

Canadian scientists are also noticing growing ice coverage in most areas of the Arctic, including the southern Davis Strait and the Beaufort Sea.

"Clearly, we're seeing the ice coverage rebound back to more near normal coverage for this time of year," said Gilles Langis, a senior ice forecaster with the Canadian Ice Service in Ottawa.

Winter sea ice could keep expanding

The cold is also making the ice thicker in some areas, compared to recorded thicknesses last year, Lagnis added.

"The ice is about 10 to 20 centimetres thicker than last year, so that's a significant increase," he said.

If temperatures remain cold this winter, Langis said winter sea ice coverage will continue to expand.

But he added that it's too soon to say what impact this winter will have on the Arctic summer sea ice, which reached its lowest coverage ever recorded in the summer of 2007.

That was because the thick multi-year ice pack that survives a summer melt has been decreasing in recent years, as well as moving further south. Langis said the ice pack is currently located about 130 kilometres from the Mackenzie Delta, about half the distance from where it was last year.

The polar regions are a concern to climate specialists studying global warming, since those regions are expected to feel the impact of climate change sooner and to a greater extent than other areas.

Sea ice in the Arctic helps keep those regions cool by reflecting sunlight that might otherwise be absorbed by darker ocean or land surfaces.