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Glacier melt rate a surprise [Southeast Alaska]

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  • Mike Neuman
    Glacier melt rate a surprise Ice in Southeast vanishing twice as fast as expected The glaciers of Southeast Alaska are shrinking twice as quickly as scientists
    Message 1 of 1 , Aug 4 11:47 AM
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      Glacier melt rate a surprise

      Ice in Southeast vanishing twice as fast as expected

      The glaciers of Southeast Alaska are shrinking twice as quickly as
      scientists had previously estimated, according to a new study.
      The findings from Fairbanks and Juneau glaciologists are slated for
      publication in a leading scientific journal.

      During a 52-year period, the Panhandle lost ice in 95 percent of its
      glacier-covered areas, said Roman Motyka, of Juneau, one of the
      study's co-authors.

      The scientists participating in the study pinpointed the amount of
      ice loss by analyzing changes in the elevation of Southeast Alaska's
      glaciers between 1948 and 2000.

      Their measurements show Southeast Alaska lost an average of roughly
      14.6 cubic kilometers of ice per year during that time period.

      A cubic kilometer roughly equates to 264 billion gallons of water -
      about a quarter more than Los Angeles consumes in one year, according
      to estimates by NASA.

      "It's a pretty substantial loss of ice," Motyka said, noting the
      melting of Panhandle glaciers raised global sea levels by roughly
      0.04 millimeters per year. In all of the years combined, Panhandle
      ice loss caused the world's oceans to rise roughly 2.4 millimeters,
      according to the study.

      Scientists involved in the study said this week the Panhandle's ice
      reservoirs have retreated more drastically during the past couple of
      years.

      The study's lead author, Chris Larsen, also of the Geophysical
      Institute, plans further measurements this month at Panhandle
      glaciers, ranging from Petersburg's Stikine Icefield to the St. Elias
      Mountain Range.

      Scientists aren't the only ones noticing the wastage of most of the
      Panhandle's glaciers.

      Juneau residents and tourists visit the retreating Mendenhall Glacier
      daily. Some of the most dramatic ice losses in the Panhandle are
      underway at lake-terminating glaciers, such as the Mendenhall, fed by
      the Juneau Icefield, according to the study.

      "I just few over the Juneau Icefield three days ago. I was absolutely
      shocked by how dry and shrunken it looked," said Nick Jans, a Juneau
      author, on Tuesday.

      Further to the south, the amount of ice loss at Tracy Arm's South
      Sawyer Glacier is "not even conceivable," said Juneau photographer
      Mark Kelley.

      Kelley has photographed the glacier for the past 25 years and
      recently collaborated with Jans on a 40-page book about Tracy Arm's
      glaciers. In 2004, the South Sawyer Glacier retreated approximately
      one-half mile, clogging the water with icebergs.

      "Just think about that volume. The glacier was 1,100 feet thick and a
      mile across," Kelley said.

      Motyka is concerned a runaway process - initially triggered by
      climate warming but now controlled by glacial calving dynamics - may
      already be underway in Southeast Alaska.

      More of the same could be in store for world's other coastal
      glaciers, he said.

      "We have a lot of ice (in Southeast Alaska), but Greenland has more,"
      Motyka said.

      In Greenland, Motyka and other Geophysical Institute scientists are
      attempting to learn how dramatic loss of ice at the base of a large
      tidewater glacier, the Jakobshavn, is affecting the ice sheet at the
      top.

      "I worry that these (tidewater) glaciers will bring down the ice
      sheet, no matter what happens with climate," Motyka said.

      "If Greenland goes unstable, a lot more water will be going into the
      ocean. This could cause problems with ocean currents," Motyka
      explained.

      The Panhandle study - now under review by third-party scientists - is
      the first to measure ice loss at all major Panhandle glaciers.

      The study measured changes in glacial elevation at 74 individual
      glaciers. "It's total coverage," Larsen said.

      A previous study, published in 2002, profiled ice loss at 12 glaciers
      in Southeast Alaska. When those results were extrapolated to the rest
      of the Panhandle, the result was a significant underestimate of
      regional ice loss, Motyka said.

      The new study was enabled by a 2000 NASA Endeavour space shuttle
      project called the Shuttle Radar Topographic Mission. Among other
      duties, the shuttle mission produced a new three-dimensional radar
      map of Southeast Alaska.

      Motyka and his colleagues collected the NASA maps and compared them
      to topographical maps and high-resolution photographs of Southeast
      Alaska dating back to 1948.

      After final revision, a paper describing the Panhandle study will be
      published in the Journal of Geophysical Research.

      • Elizabeth Bluemink can be reached at
      elizabeth.bluemink@....
      Click here to return to story:
      http://www.juneauempire.com/stories/080206/loc_20060802017.shtml
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