Scientists: Greenland glaciers pick up speed because of warming
By ALICIA CHANG, AP Science Writer
Last Updated 8:54 am PST Thursday, December 8, 2005
SAN FRANCISCO (AP) - Climate warming is most likely to blame for the alarmingly fast retreat of two of Greenland's largest glaciers, scientists told a meeting of the American Geophysical Union.
But researchers at the group's annual meeting also presented studies of Alaska's Columbia Glacier that suggest more complexity in the processes of glacial melt.
One of the Greenland glaciers, Kangerdlugssuaq, is currently moving at about nine miles a year compared to three miles a year in 2001, said Gordon Hamilton of the University of Maine's Climate Change Institute.
The other glacier, Helheim, is speeding at about seven miles a year - up from four miles a year during the same period.
"It's quite a staggering rate of increase," Hamilton said during Wednesday's presentation.
Glaciers worldwide play a major role in discharging flowing water into oceans.
Sea levels have swelled globally an estimated 4 inches to 8 inches over the past century because of melting glaciers and polar ice - enough to cause some low-lying places to be awash at high tide or during severe storms.
Melting of Greenland ice and calving of icebergs from glaciers is responsible for about 7 percent of the annual rise in global sea level.
Global warming is frequently blamed for retreating glaciers around the world. The rapid retreat of Greenland glaciers suggest that climate change is a factor, Hamilton said.
Meanwhile, one of the fastest melting glaciers in North America has reached the halfway point of disintegration and will continue retreat for another two decades.
Alaska's Columbia Glacier - about the size of Los Angeles - has shrunk nine miles since the 1980s. It is expected to lose an additional nine miles in the next 15 to 20 years before the bed of the glacier rises above sea level.
The glacier, which moves about 80 feet a day, currently releases about 2 cubic miles of ice every year into the Prince William Sound on the south coast of Alaska.
Understanding what happens during Alaskan glacier retreat could help explain the phenomenon in Greenland, said Tad Pfeffer, associate director of the University of Colorado's Institute of Arctic and Alpine.
Pfeffer said climate change warming trends do not directly explain the shrinking Columbia Glacier and other tidewater glaciers. Instead, scientists think the retreat is triggered by a slow warming trend that began five centuries ago.
Significant thinning of the Columbia Glacier is thought to be caused by huge chunks of iceberg that break off into the sound as a result of seawater pressure rather than climate change, Pfeffer said.
The glacier, which is up to 3,000 feet thick, has thinned up to 1,300 feet in some places over the last two decades.
Since the 1970s, scientists have monitored the Columbia Glacier with satellites, lasers and aerial photography and found that the increase of its so-called calving rate might be dangerous to shipping lanes in the sound.