Study Fuels Worry Over Glacial Melting
The Washington Post, July 19, 2002
Alaska's glaciers are melting at more than twice the rate previously thought because of warming temperatures, 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 few 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 sea levels -- a seemingly small rise that nevertheless could eventually 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 today'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 phenomenon is an example of the kind of effects that can occur because of alterations in the Earth's climate.
"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 exemplifies 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, an academic research center.
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, Mass., 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 fingerprints 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."
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 glacial area in Alaska and neighboring Canada. The profiles developed were compared with 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," Echelmeyer said. "What we don't know is if it's due to increased temperature or less snowfall, but it's definitely due to climate change."
© 2002 The Washington Post Company
Alaskan glaciers melting faster
The loss is greatest at highest elevations
BBCNews.com, July 19, 2002
US scientists have found that glaciers in Alaska are retreating much faster than originally thought.
The researchers say the resulting melt waters are sufficiently large to drive up global sea levels by 0.14 millimetres per year.
The study by Dr Keith Echelmeyer, of the University of Alaska Fairbanks Geophysical Institute, and colleagues used laser altimetry to measure the volume changes of 67 Alaskan glaciers from the mid-1950s to the-mid 1990s.
Their work, published in the journal Science, adds to the growing evidence that the level of recent glacier wastage - from polar regions to the tropics - has been underestimated.
Short of data
"There is some historical evidence that at the turn of the last century glaciers were thinning but not so that people noticed it much," Dr Keith Echelmeyer told the BBC.
"What we see over the last 50 years is that they have thinned quite substantially and then over the last five to 10 years there has been an acceleration."
Scientists who suspect human activities such as the burning of fossil fuels are causing an unnatural global temperature rise believe glacier wastage may be a good indicator of what is happening.
But Dr Echelmeyer is hesitant to say the recent changes his team have seen are the result of a warmer climate because he feels there is currently insufficient data to come to firm conclusions.
"Climate is changing and this is affecting the glaciers - and they are being a good indicator of that," he said.
"Now, whether it's warming up of the climate or less snowfall, it is hard to say. That will take further investigation and an analysis of glacier flow, for example."
Glaciers in Alaska and neighbouring Canada cover 90 thousand square kilometres, or approximately 13% of the mountain glacier area on Earth.
Dr Echelmeyer's team surveyed the volume and area changes of part of this region from an aircraft equipped with a laser altimetry system. The researchers measured the volume loss by checking glacier elevation and volume data on US Geological Survey maps from the 1950s.
"Most glaciers have thinned several hundred feet at low elevations in the last 40 years and about 60 feet at higher elevations," Dr Echelmeyer said.
The team has calculated that Alaskan glaciers are responsible for at least 9% of the global sea-level rise during the past century, and Alaska's glaciers raise the level of Earth's oceans by more than one-tenth of a millimetre each year.
The study fits with a review of data by Professor Meier and Mark Dyurgerov, of the University of Colorado at Boulder, US.
They said glacier wastage had been seriously underestimated by the UN's Intergovernmental Panel on Climate Change, which is trying to assess humanity's influence on the global climate.
One of the reasons for this, they said, was that the IPCC had not had access to the latest Alaskan data.
"For the first time we have some hard data from these glaciers which we have suspected, but didn't know for sure, are major contributors to the sea level change caused by glacier melt," Professor Meier said after the Fairbanks study was published.
The contribution from Alaska's glaciers to the worldwide sea level rise "is even more that what we had expected," he added.
Currently, measured sea levels are going up by about 0.8 millimetres per year with no apparent acceleration in that increase.