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Glaciers Melting at Accelerated Pace
By Eric Pianin Washington Post Staff Writer Thursday, July 18, 2002; 2:00 PM
Alaska's glaciers are melting at more than twice the rate previously assumed because of warming temperatures, a disturbing phenomenon that is dramatically altering the majestic contours of the state and driving up sea levels, according to a new study.
Scientists using highly precise airborne laser measurements of 67 Alaskan glaciers from the mid 1950s to the mid 1990s discovered that the glaciers are melting an average of six feet a year – and in some cases a couple hundred feet – and that the rate has accelerated in the past seven or eight years.
As one measure of the severity of the problem, the researchers calculated that the glaciers are generating nearly twice the annual meltage of the Greenland Ice Sheet, which is the largest ice mass in the Northern Hemisphere and second only to the Antarctic. That would mean the Alaskan melt is adding about two-tenths of a millimeter a year to the sea levels – an unprecedented development that could have long-term implications for flooding on Pacific islands and along coastal areas, the researchers concluded.
The study by a team of researchers from the University of Alaska in Fairbanks, published in Friday's issue of the journal Science, offers a vivid and troubling picture of the potential adverse impact of climate change on the United States and the rest of the world.
"The change we are seeing is more rapid than any climate change that has happened in the last 10 to 20 centuries," said Keith A. Echelmeyer, one of the five researchers who prepared the study.
Scientists can't say whether the extraordinary melting is the result of man-induced global warming, the slow natural advance and rapid retreat of the glaciers, or dramatic but natural variations in weather patterns. But the effects are illustrative of what some scientists and environmentalists predict will happen at home and abroad unless the United States and the rest of the world undertakes a more aggressive effort to reduce carbon dioxide and other heat-trapping gases.
"We're getting to the point that this melting is affecting human society," said Janine Bloomfield, a climate expert with Environmental Defense, an advocacy group. "Until now it was just warning signs and signals that the earth was warming."
Indeed, the study has provided fresh evidence for Alaskan officials, researchers and environmentalists who say their state has become the poster child for the ills of global warming. Over the past 30 years alone, the annual mean temperature in Alaska has risen 5.4 degrees Fahrenheit--four times the average global increase, according to the University of Alaska's Center for Global Change and Arctic System Research.
Some scientists theorize that the effects of climate change are most extreme in the northern part of the Northern Hemisphere because of a quirk in the way gases and the earth's radiation get trapped in the atmosphere.
As the state's pervasive permafrost begins to thaw, the consequences are dramatic and alarming: sagging roads, crumbling villages, sinking pipelines, the proliferation of insects that are destroying spruce forests and the possible disruption of marine wildlife. Some Alaskans talk about "drunken trees" that list and show their roots because of the rapid decline of the permafrost.
"I see it as a trend that has to be taken seriously," said Gunter Weller of the center for global change. "If these kinds of occurrences continue . . . it will have consequences around the world."
However, Sallie L. Baliunas of the Harvard-Smithsonian Center for Astrophysics in Cambridge contends that the Alaskan melting is due to a dramatic but temporary shift in Pacific Ocean warm water and wind patterns that began in 1976. "It doesn't have the finger prints of enhanced greenhouse gas concentrations," she said.
Sen. Ted Stevens (R-Alaska), who chaired public hearings in Fairbanks last year on global climate change, said, "Regardless of cause, many changes predicted worldwide appear to be happening first and with greater severity in arctic regions, including Alaska."
Early this year, an Antarctic ice shelf the size of Rhode Island shattered and collapsed into the sea after an unusual warming period, stunning some scientists who said they had never seen such a large loss of ice mass in the remote Antarctic Peninsula. The 1,260-square mile ice shelf is believed to have existed for as long as 12,000 years before regional temperatures began to rise, yet it disintegrated over a 35-day period that began Jan. 31.
A second research paper published today in Science offers further evidence that the polar ice caps are melting. Columbia University researchers found that, over the past four decades, water in the Ross Sea has become less salty for a variety of reasons, including the increased melting of the West Antarctic Ice Sheet.
Past efforts to measure the decline of the Alaskan glaciers have been imprecise because they were largely based on observations and model simulations of glacier mass. Glaciers that were monitored routinely were often chosen more for their ease of access and manageable size than for how well they represented a given region or how large a contribution they might make to changing sea level.
The University of Alaska research team--including Anthony A. Arendt, William D. Harrison, Craig S. Lingle, Virginia B. Valentine and Echelmeyer--used laser devices aboard airplanes to measure the volume and area changes of the 67 glaciers, representing about 20 percent of the glacerized area in Alaska and neighboring Canada. The profiles developed were compared to contours on U.S. Geological Survey and Canadian topographic maps made from aerial photographs taken in the 1950s to early 1970s.
The study found that, during the past five to seven years, glacier thinning averaged about six feet a year, or twice as fast as that measured on the same glaciers from the mid-1950s to the mid-1990s. (Because the glaciers are land based, their meltage displaces water and pushes up the level of the ocean.) The annual meltage totaled 52 cubic kilometers and contributed about 9 percent of the observable rise in the sea level over the past half century.
"Glaciers in Alaska are thinning quite rapidly . . . and it is due to climate change," said Echelmeyer. "What we don't know is if it's due to increased temperature or less snowfall, but it's definitely due to climate change."
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-- Martin (Martin@aol.com), July 19, 2002