Saturday, July 27, 2013

Cyclone Chewing up Arctice Sea Ice





 It is clear that we are not breaking any records this year although we are on track to be well in the recent ice coverage channel and open seaways.  Now we have a cyclone chewing things up that just could change things.  Recall that what made 2007 work so well was a major shift in the winds to accelerate ice removal.  If that were to happen again we would experience a major ice collapse throughout the Arctic.

My sense is that we have a stable climate regime that can be strongly disturbed downward on random years.  A bookmaker could almost play this.  Now we are watching a cyclone rip up the badly decayed ice.

It may still be interesting this year.

Stronger Arctic cyclones rapidly chewing up weak sea ice

BOB WEBER

Jul. 25 2013,


Arctic scientists are watching in awe this week as a raging summer cyclone tears up what could become a record amount of rotting northern sea ice.

“We’re really watching this year with a lot of fascination,” said Matthew Asplin, an Arctic climatologist at the University of Manitoba.

Arctic cyclones are driven by low-pressure systems in which winds of up to 100 km/h blow counter-clockwise in spirals more than 1,000 kilometres across. They occur in both winter and summer, but are usually stronger in winter.

Cyclones are not unusual in the Arctic, but seem to be changing in recent years, said David Barber, one of Canada’s top sea-ice experts.

“These cyclones are not getting more frequent, but they are getting deeper – which means stronger,” he said.

And they are getting harder on sea ice, which they break up through wave action associated with high winds and through rainfall, which darkens the ice and makes it absorb more solar energy. The storms also bring up water from the depths, which is actually warmer than surface water.

Cyclones can destroy large amounts of ice very quickly.

“In 2009, we actually documented one of these events in which large, multiyear ice floes – Manhattan-sized – broke up in a matter of minutes,” Dr. Barber said.

Last year, a particularly powerful cyclone is thought to have wiped out 800,000 square kilometres of ice. That contributed to record low sea-ice levels at the end of the 2012 melt year.

This year’s storm over the Beaufort Sea formed about midweek and is expected to die out on the weekend.

It is not as strong as last year’s, but the ice is thinner and weaker. As well, the ice was pummelled by earlier storms.

“The effects of [the storm] are nowhere near what we saw last August,” Mr. Asplin said. “But because the ice is thinner and it’s already been preconditioned, and because there’s less volume, it’s much more vulnerable to impacts from this sort of thing.”

Dr. Barber said the ice is getting so weak that new categories have had to be created for it.

“We have a whole new class of sea ice in the Arctic, which we’re calling ‘decayed ice,’” he said. “We started seeing it in 2009. It’s extremely weak.”

Dr. Barber said the research icebreaker CCGS Amundsen can do 13.5 knots in open water. Through decayed ice, it can do 13 knots.

Changing sea-ice cover is increasingly being linked to southern weather patterns. The jet stream, which strongly influences weather at mid-latitudes, is driven by temperature differences between the Arctic and the equator, a difference that shrinks with the sea ice.

Ice coverage is slightly above last year’s record low, but still well below the 30-year average.

Much remains unknown about the role of Arctic cyclones in the annual freeze-thaw cycle. Back when the sea ice was thick and lasted for years, cyclones tended to spread the ice out and actually increase its extent, said Julienne Stroeve of the National Snow and Ice Data Center in Boulder, Colo. Now, when ice gets spread out, it simply breaks up and disappears.

“As our ice cover has thinned, some of our old rules are changing,” Dr. Stroeve said.

Mr. Asplin said cyclones will be a big part of the research agenda when the Amundsen sets sail for the Arctic again later this month.

“This year has been very stormy. The month of August is definitely one to watch in the Arctic.”




Current State of the Sea Ice Cover

J. C. Comiso, C. L. Parkinson, T. Markus, D. J. Cavalieri and R. Gersten


The sea ice cover is one of the key components of the climate system. It has been a focus of attention in recent years, largely because of a strong decrease in the Arctic sea ice cover and modeling results that indicate that global warming could be amplified in the region by a factor of about 3 to 5 times on account of ice-albedo feedback. This results from the high reflectivity (albedo) of the sea ice compared to ice-free waters. A satellite-based data record starting in late 1978 shows that indeed rapid changes have been occurring in the Arctic, where the perennial ice cover has been declining at the rate of about 13% per decade and the ice cover as a whole has been declining at the lesser rate of about 5% per decade. In the Antarctic, the trend is opposite to that in the Arctic, with the sea ice cover increasing at about 1 to 2 % per decade. This is despite unusual warming in the Antarctic Peninsula region and declines in the sea ice cover in the Amundsen/Bellingshausen Seas of about 6% per decade. In the Arctic, a slight recovery in the sea ice cover has been observed in 2008 and 2009, following a major decline of the ice in 2007, while in the Antarctic, the sea ice cover was more extensive than normal in 2007, 2008, and 2009. Shown below are up-to-date satellite observations of the sea ice covers of both the Arctic and the Antarctic, along with comparisons with the historical satellite record of more than 30 years. The plots and color coded maps are chosen to provide information about the current state of the sea ice cover and how the most current daily data available compare with the record lows and record highs for the same date during the satellite era..



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