Weatherdem's Weblog

Bridging climate science, citizens, and policy

State of the Arctic – 4/27/09


The Arctic ice sheet areal extent has slowly decreased in the month since my last post.  It has done so at a rate that is less than the climatological norm as well as less than the melt seen during March and April the past couple of seasons.  This should be good news for the areal extent of ice later this season, barring anomalous weather conditions this summer and fall.  I want to point out that areal extent does not equal volume extent.  The Arctic ice sheet’s volume is lower this year than in past years due to the extensive summer melts that have occurred in consecutive years.  As the NSIDC notes, thin ice is more susceptible to summer melting than is thick ice, which makes perfect sense.  So to update my last post, here are the corresponding graphs showing the state of the arctic ice sheet as of yesterday:

The extent of the ice sheet graphically looks like this:

The recent La Nina that hung around for the better part of two years has recently ended.  As we move toward neutral El Nino conditions this year, what kind of storm systems will the Arctic experience?  How long will one-year ice last under even climatological conditions?  Will weather conditions this summer and fall only be “normal” or will they be as warm or warmer than recent summers and falls?  I’ll keep an eye on developments.


2 thoughts on “State of the Arctic – 4/27/09

  1. My old Stat Professor used to instruct us … “When looking at data, first use the “Interocular Test” …. see if it hits you between the eyes!” Applying that rule:

    I look at the graph provided and see that the 2009 extent is higher than the 2007 average and is approaching and may exceed the 1979-2000 average in future months.

    As to thinning of the ice sheet I recently came across this information:

    American Sub breaks through very thin Arctic Ice at North Pole

    Skate (SSN-578), surfaced at the North Pole, 17 March 1959.

    Image from NAVSOURCE

    “the Skate found open water both in the summer and following winter. We surfaced near the North Pole in the winter through thin ice less than 2 feet thick. The ice moves from Alaska to Iceland and the wind and tides causes open water as the ice breaks up. The Ice at the polar ice cap is an average of 6-8 feet thick, but with the wind and tides the ice will crack and open into large polynyas (areas of open water), these areas will refreeze over with thin ice. We had sonar equipment that would find these open or thin areas to come up through, thus limiting any damage to the submarine. The ice would also close in and cover these areas crushing together making large ice ridges both above and below the water. We came up through a very large opening in 1958 that was 1/2 mile long and 200 yards wide. The wind came up and closed the opening within 2 hours. On both trips we were able to find open water. We were not able to surface through ice thicker than 3 feet.”
    – Hester, James E., Personal email communication, December 2000

    I think that we should look at decades of past data and ice fluctions over extended times before we once again ring alarm bells.

    And there is this recent report on Antarctica:

    Ice Gains in East Antarctica

    Revealed: Antarctic ice growing, not shrinking

    ICE is expanding in much of Antarctica, contrary to the widespread public belief that global warming is melting the continental ice cap.

    The results of ice-core drilling and sea ice monitoring indicate there is no large-scale melting of ice over most of Antarctica, although experts are concerned at ice losses on the continent’s western coast.

    Antarctica has 90 per cent of the Earth’s ice and 80 per cent of its fresh water. Extensive melting of Antarctic ice sheets would be required to raise sea levels substantially, and ice is melting in parts of west Antarctica. The destabilisation of the Wilkins ice shelf generated international headlines this month.

    However, the picture is very different in east Antarctica, which includes the territory claimed by Australia.

    East Antarctica is four times the size of west Antarctica and parts of it are cooling. The Scientific Committee on Antarctic Research report prepared for last week’s meeting of Antarctic Treaty nations in Washington noted the South Pole had shown “significant cooling in recent decades”.

    Australian Antarctic Division glaciology program head Ian Allison said sea ice losses in west Antarctica over the past 30 years had been more than offset by increases in the Ross Sea region, just one sector of east Antarctica.

    “Sea ice conditions have remained stable in Antarctica generally,” Dr Allison said.

    The melting of sea ice — fast ice and pack ice — does not cause sea levels to rise because the ice is in the water. Sea levels may rise with losses from freshwater ice sheets on the polar caps. In Antarctica, these losses are in the form of icebergs calved from ice shelves formed by glacial movements on the mainland.

    Last week, federal Environment Minister Peter Garrett said experts predicted sea level rises of up to 6m from Antarctic melting by 2100, but the worst case scenario foreshadowed by the SCAR report was a 1.25m rise.

    Mr Garrett insisted global warming was causing ice losses throughout Antarctica. “I don’t think there’s any doubt it is contributing to what we’ve seen both on the Wilkins shelf and more generally in Antarctica,” he said.

    Dr Allison said there was not any evidence of significant change in the mass of ice shelves in east Antarctica nor any indication that its ice cap was melting. “The only significant calvings in Antarctica have been in the west,” he said. And he cautioned that calvings of the magnitude seen recently in west Antarctica might not be unusual.

    “Ice shelves in general have episodic carvings and there can be large icebergs breaking off — I’m talking 100km or 200km long — every 10 or 20 or 50 years.”

    Ice core drilling in the fast ice off Australia’s Davis Station in East Antarctica by the Antarctic Climate and Ecosystems Co-Operative Research Centre shows that last year, the ice had a maximum thickness of 1.89m, its densest in 10 years. The average thickness of the ice at Davis since the 1950s is 1.67m.

    A paper to be published soon by the British Antarctic Survey in the journal Geophysical Research Letters is expected to confirm that over the past 30 years, the area of sea ice around the continent has expanded.

  2. Pingback: State of the Arctic – 5/26/09 « Weatherdem’s Weblog

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