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NSIDC: Arctic shortcuts open up; decline pace steady

By Joe Romm on August 26, 2008 at 1:14 pm

"NSIDC: Arctic shortcuts open up; decline pace steady"

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Fresh from its Olympic-record in denier debunking, the National Snow and Ice Data Center has released a new update:

Sea ice extent is declining at a fairly brisk and steady pace. Surface melt has mostly ended, but the decline will continue for two to three more weeks because of melt from the bottom and sides of the ice. Amundsen’s Northwest Passage is now navigable; the wider, deeper Northwest Passage through Parry Channel may also open in a matter of days. The Northern Sea Route along the Eurasian coast is clear.

NSIDC has put together a nice animation (click on figure):

Still shot of single frame of animation showing sea ice in Arctic from satellite

More details below:

Arctic sea ice extent on August 24 was 5.47 million square kilometers (2.11 million square miles), a decline of 1.85 million square kilometers (714,000 square miles) since the beginning of the month. Extent is now within 580,000 square kilometers (220,000 square miles) of last year’s value on the same date and is 1.84 million square kilometers (710,000 square miles) below the 1979 to 2000 average.

The NSIDC has a fascinating discussion of ice thickness, for all you surface and bottom melt buffs out there:

As discussed in a number of previous postings (July 17, April 7), sea ice thickness is a key measure of the health of the sea ice. While the NASA ICESat sensor can give an overall picture of ice thickness over the Arctic Ocean, the most accurate way to measure ice thickness is by taking point measurements on the ground [with autonomous buoys]…. The buoy data have indicated increased amounts of melt on the underside of the ice cover in recent years; bottom melt last year was particularly extreme.

The pattern for 2008 has been more mixed. The ice at some buoy locations has thinned by more than a meter through the melt season because of strong melt both on the surface and the underside of the ice. Other locations show strong thinning caused by surface melt, while only modest thinning is apparent in others. Differences in surface melt from location to location reflect factors such as air temperature, the ice albedo, and cloud conditions. The wide range in bottom melt points to variations in the amount of ocean heat absorbed. In recent days, the buoys have indicated sub-freezing temperatures with surface melt coming to an end; however, bottom melt will continue for at least two to three more weeks and the ice extent decline, while slowing, will also continue.

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10 Responses to NSIDC: Arctic shortcuts open up; decline pace steady

  1. Ron Broberg says:

    One of the political angles of attack I use against deniers is the political and economic implications of the opening of the NW Passage and future Oil/NG resource exploitation. The Russians and Canadians would like nothing more than for us to believe that nothing is changing in the Arctic and that its business as usual. Meanwhile, a growing number of Navy and Coast Guard Admirals and defense think-tanks are coming to the realization that there is open water in the Arctic. The Coast Guard beefed up two Arctic coast stations this year and the Navy is telling us it takes 12 years from decision point to the commissioning of a new ship.

    Of course, half of the deniers now just say – well sure its changing. Change is natural. But it mutes the other half who don’t believe that we’re warming.

  2. Jim O'Rourke says:

    Joe: I thought I read something yesterday about a giant crack appearing unexpectedly on the northern Greenland glacier – any news on that?

  3. John Hollenberg says:

    The line has gone down sharply in just the last few days and is now very close to the 2007 line (although still slightly above it):

    http://nsidc.org/data/seaice_index/images/daily_images/N_timeseries.png

  4. jorleh says:

    No big noise from the deniers just now. Is this the end of those idiots?

  5. Gareth says:

    And just to spice things up a little… more news on methane.

  6. Mauri Pelto says:

    Jim: The Petermann Glacier which is the largest outlet glacier in northwest Greenland, has a huge floating tongue within its fjord. It just experienced a significant collapse (29 square km) of a portion of the tongue for the second time in this decade. The glacier has retreated very little in the 20th century. There is a large crack well back of the ice front indicating the retreat will continue. This is the same story we have seen on the Wilkins Ice Shelf, Larsen Ice Shelf and Jakobshavns and Helheim glaciers. That is long term thinning leads to a reduction in backpressure from the pinning points, in this case fjord walls, that leads to more calving, which leads to more acceleration as the thinner ice is less connected. The crack well back of the front indicates the preconditioning of this glacier to further retreat just as the fissures in Wilkins Ice Shelf did six months ago. This glacier thins from 600 m thick at the grounding line 80 km from the former ice front to less than 100 m at the ice front.
    Note the glacier in 2003 http://earthobservatory.nasa.gov/Newsroom/NewImages/images.php3?img_id=17754
    adn 2008 http://earthobservatory.nasa.gov/Newsroom/NewImages/images.php3?img_id=17754

  7. David B. Benson says:

    Mauri Pelto — Both your links are the same. :-(

  8. Another recent study adds to the alarm we should all feel as the ice melts…

    http://afp.google.com/article/ALeqM5iurNRV6EfFYyVJTs8qHrgjte_3cA

  9. paulm says:

    there’s that tippy feeling again…

    Arctic ice ‘is at tipping point’
    http://news.bbc.co.uk/2/hi/science/nature/7585645.stm

  10. shop says:

    The pattern for 2008 has been more mixed. The ice at some buoy locations has thinned by more than a meter through the melt season because of strong melt both on the surface and the underside of the ice.