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Arctic ice shelf splits

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  • npat1@juno.com
    The largest ice shelf in the Arctic has fractured, releasing all the water from the freshwater lake it dammed. The Ward Hunt Ice Shelf is located on the north
    Message 1 of 1 , Nov 13, 2003
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      The largest ice shelf in the Arctic has fractured, releasing all the
      water from the freshwater lake it dammed. The Ward Hunt Ice Shelf is
      located on the north coast of Ellesmere Island in Canada's Nunavut
      territory. The huge mass of floating ice, which has been in place for at
      least 3,000 years, is now in two major pieces.

      The scientists who report the break-up in the journal Geophysical
      Research Letters (GRL) say it is further evidence of ongoing and
      accelerated climate change in the north polar region.

      The researchers - Warwick Vincent and Derek Mueller of Laval University
      in Quebec City, Canada; and Martin Jeffries of the University of Alaska
      Fairbanks, US - have been studying the shelf onsite and through satellite
      radar imagery and helicopter overflights.

      Lost water
      The Ward Hunt Ice Shelf, which is 443 square kilometres in size, now has
      a major crack that runs right through it from north to south.

      The scientists say the fracturing - which has been developing since the
      spring of 2000 - is the end result of a three-decade-long decline.

      "We're now seeing some very extensive fractures in it that extend many
      kilometres horizontally across the ice-shelf; and they extend all the way
      through from the top to the bottom, many tens of metres through the ice
      shelf. And we've never seen fractures like this," Dr Jeffries told the
      BBC.

      They warn that major free-floating ice islands could pose a danger to
      shipping and to drilling platforms in the Beaufort Sea. The immediate
      consequence of the rupture has been the loss of almost all of the
      freshwater from the Northern Hemisphere's largest epishelf lake (a body
      of mostly freshwater trapped behind an ice shelf). The freshwater lay in
      the 30-kilometre- [20-mile] long Disraeli Fiord. At its deepest, the
      freshwater measured 43 metres [140 feet], and sat atop 360 metres [1,200
      feet] of denser ocean water.

      Other worlds
      The loss of fresh and brackish water has changed the environment for the
      microscopic animals and algae living in the area. "These are very rare
      and unusual ecosystems and they have been studied as possible analogues
      for life on a colder Earth and life on the planets," Dr Jeffries said.
      "And if we are losing them, we are losing the opportunity to study life
      earlier in Earth history and elsewhere in the Solar System." Scientists
      monitor continuously ice-shelf development in both the Arctic and the
      Antarctic.

      In the southern polar region, recent times have witnessed some dramatic
      changes.
      Last year, the 3,250-square-km Larsen B Ice Shelf on the Antarctic
      Peninsula shattered over a period of a month into thousands of icebergs.
      The peninsula is one of the three fastest-warming regions on Earth -
      temperatures have gone up 2.5 degrees in 50 years.

      Global change
      Mueller, Vincent, and Jeffries say their calculations suggest changes of
      a similar nature have been taking place in the Ellesmere Island area. A
      century ago, the entire northern coast of the island was reported to be
      fringed with a continuous ice shelf. About 90% of that ice area had been
      lost by 1982, the scientists say.

      The precise timing of the break-up of the remnant Ward Hunt Ice Shelf may
      have been influenced by freeze-thaw cycles, wind, and tides, they tell
      GRL. Other factors may include changes in Arctic Ocean temperature,
      salinity, and flow patterns, they add.
      "Computer models show quite convincingly that global climate change would
      be manifested first and amplified in the polar regions and in particular
      in the Arctic," Dr Jeffries said "Our observations at Ward Hunt Ice
      Shelf fit in with a broader picture of Arctic change which fits in with
      our understanding of how the Arctic climate would respond to global
      change."
      http://news.bbc.co.uk/2/hi/science/nature/3132074.stm

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