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Fwd: Glaciers and Sea Ice Endangered by Rising Temperatures

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  • Patrick Neuman
    ... wrote: January 22, 2004-1 2004 Earth Policy Institute Glaciers and Sea Ice Endangered by Rising Temperatures Janet Larsen By 2020, the snows
    Message 1 of 1 , Feb 1 12:28 PM
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      --- In Paleontology_and_Climate@yahoogroups.com, "Patrick Neuman"
      <npat1@j...> wrote:

      January 22, 2004-1
      2004 Earth Policy Institute

      Glaciers and Sea Ice Endangered by Rising Temperatures

      Janet Larsen

      By 2020, the snows of Kilimanjaro may exist only in old photographs.
      The glaciers in Montana's Glacier National Park could disappear by
      2030. And by mid-century, the Arctic Sea may be completely ice-free
      during summertime. As the earth's temperature has risen in recent
      decades, the earth's ice cover has begun to melt. And that melting is
      accelerating.

      In both 2002 and 2003, the Northern Hemisphere registered record-low
      sea ice cover. New satellite data show the Arctic region warming more
      during the 1990s than during the 1980s, with Arctic Sea ice now
      melting by up to 15 percent per decade. The long-sought Northwest
      Passage, a dream of early explorers, could become our nightmare. The
      loss of Arctic Sea ice could alter ocean circulation patterns and
      trigger changes in global climate patterns.

      On the opposite end of the globe, Southern Ocean sea ice floating
      near Antarctica has shrunk by some 20 percent since 1950. This
      unprecedented melting of sea ice corroborates records showing that
      the regional air temperature has increased by 2.5 degrees Celsius
      (4.5 degrees Fahrenheit) since 1950.

      Antarctic ice shelves that existed for thousands of years are
      crumbling. One of the world's largest icebergs, named B-15, that
      measured near 10,000 square kilometers (4,000 square miles) or half
      the size of New Jersey, calved off the Ross Ice Shelf in March 2000.
      In May 2002, the shelf lost another section measuring 31 kilometers
      (19 miles) wide and 200 kilometers (124 miles) long.

      Elsewhere on Antarctica, the Larsen Ice Shelf has largely
      disintegrated within the last decade, shrinking to 40 percent of its
      previously stable size. Following the break-off of the Larsen A
      section in 1995 and the collapse of Larsen B in early 2002, melting
      of the nearby land-based glaciers that the ice shelves once supported
      has more than doubled.

      Unlike the melting of sea ice or the floating ice shelves along
      coasts, the melting of ice on land raises sea level. Recent studies
      showing the worldwide acceleration of glacier melting indicate that
      the Intergovernmental Panel on Climate Change's estimate for sea
      level rise this century—ranging from 0.1 meters to 0.9 meters—will
      need to be revised upwards. (See table of selected examples of ice
      melt from around the world.)

      On Greenland, an ice-covered island three times the size of Texas,
      once-stable glaciers are now melting at a quickening rate. The
      Jakobshavn Glacier on the island's southwest coast, which is one of
      the major drainage outlets from the interior ice sheet, is now
      thinning four times faster than during most of the twentieth century.
      Each year Greenland loses some 51 cubic kilometers of ice, enough to
      annually raise sea level 0.13 millimeters. Were Greenland's entire
      ice sheet to melt, global sea level could rise by a startling 7
      meters (23 feet), inundating most of the world's coastal cities.

      The Himalayas contain the world's third largest ice mass after
      Antarctica and Greenland. Most Himalayan glaciers have been thinning
      and retreating over the past 30 years, with losses accelerating to
      alarming levels in the past decade. On Mount Everest, the glacier
      that ended at the historic base camp of Edmund Hillary and Tenzing
      Norgay, the first humans to reach the summit, has retreated 5
      kilometers (3 miles) since their 1953 ascent. Glaciers in Bhutan are
      retreating at an average rate of 30—40 meters a year. A similar
      situation is found in Nepal.

      As the glaciers melt they are rapidly filling glacial lakes, creating
      a flood risk. An international team of scientists has warned that
      with current melt rates, at least 44 glacial lakes in the Himalayas
      could burst their banks in as little as five years.

      Glaciers themselves store vast quantities of water. More than half of
      the world's population relies on water that originates in mountains,
      coming from rainfall runoff or ice melt. In some areas glaciers help
      sustain a constant water supply; in others, meltwater from glaciers
      is a primary water source during the dry season. In the short term,
      accelerated melting means that more water feeds rivers. Yet as
      glaciers disappear, dry season river flow declines.

      The Himalayan glaciers feed the seven major rivers of Asia—the
      Ganges, Indus, Brahmaputra, Salween, Mekong, Yangtze, and Huang He
      (Yellow)—and thus contribute to the year-round water supply of a vast
      population. In India alone, some 500 million people, including those
      in New Delhi and Calcutta, depend on glacier meltwater that feeds
      into the Ganges River system. Glaciers in Central Asia's Tien Shan
      Mountains have shrunk by nearly 30 percent between 1955 and 1990. In
      arid western China, shrinking glaciers account for at least 10
      percent of freshwater supplies.

      The largest aggregation of tropical glaciers is in the northern
      Andes. The retreat of the Qori Kalis Glacier on the west side of the
      Quelccaya Ice Cap that stretches across Peru has accelerated to 155
      meters a year between 1998 and 2000—three times faster than during
      the previous three-year period. The entire ice cap could vanish over
      the next two decades.

      The Antizana Glacier, which provides Quito, Ecuador, with almost half
      its water, has retreated more than 90 meters over the last eight
      years. The Chacaltaya Glacier near La Paz, Bolivia, melted to 7
      percent of its 1940s volume by 1998. It could disappear entirely by
      the end of this decade, depriving the 1.5 million people in La Paz
      and the nearby city of Alto of an important source of water and
      power.

      Africa's glaciers are also disappearing. Across the continent,
      mountain glaciers have shrunk to one third their size over the
      twentieth century. On Tanzania's Kilimanjaro, ice cover has shrunk by
      more than 33 percent since 1989. By 2020 it could be completely gone.

      In Western Europe, glacial area has shrunk by up to 40 percent and
      glacial volume by more than half since 1850. If temperatures continue
      to rise at recent rates, major sections of glaciers covering the Alps
      and the French and Spanish Pyrenees could be gone in the next few
      decades. During the record-high temperature summer of 2003, some
      Swiss glaciers retreated by an unprecedented 150 meters. The United
      Nations Environment Programme is warning that for this region long
      associated with ice and snow, warming temperatures signify the demise
      of a popular ski industry, not to mention a cultural identity.

      Boundaries around Banff, Yoho, and Jasper National Parks in the
      Canadian Rockies cannot stop the melting of the glaciers there.
      Glacier National Park in Montana has lost over two thirds of its
      glaciers since 1850. If temperatures continue to rise, it may lose
      the remainder by 2030.

      In just the past 30 years, the average temperature in Alaska climbed
      more than 3 degrees Celsius (5 degrees Fahrenheit)—easily four times
      the global increase. Glaciers in all of Alaska's 11 glaciated
      mountain ranges are shrinking. Since the mid-1990s, Alaskan glaciers
      have been thinning by 1.8 meters a year, more than three times as
      fast as during the preceding 40 years.

      The global average temperature has climbed by 0.6 degrees Celsius (1
      degree Fahrenheit) in the past 25 years. Over this time period,
      melting of sea ice and mountain glaciers has increased dramatically.
      During this century, global temperature may rise between 1.4 and 5.8
      degrees Celsius, and melting will accelerate further. Just how much
      will depend in part on the energy policy choices made today.

      Copyright © 2004 Earth Policy Institute

      http://www.earth-policy.org/Updates/Update32.htm

      Pat
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