Study finds glaciers melting faster than believed
WASHINGTON (AP) An estimated 24 cubic miles of ice
are disappearing annually from Alaskan glaciers, turning some imposing ice mountains
into minor hills and adding to the steady rise in global sea level, a study
in Friday's edition of the journal Science shows.
Researchers at the University of Alaska surveyed 67 major
glaciers using an airborne laser system and found that the rate of melting in
the last five years is rapidly growing.
"From the mid-1950s to the mid-1990s, the glaciers lost
about 52 cubic kilometers (13 cubic miles) a year," said Anthony A. Arendt,
first author of the study appearing in the journal Science. "In the last five
years, that rate has almost doubled."
Over almost a half century, he said, the glaciers have
lost some 500 cubic miles of ice.
The new measurements show that the glaciers of Alaska are
contributing about half of the water worldwide flowing into the oceans from
shrinking mountain glaciers, said Arendt.
Studies have suggested that the global sea level has risen
about 7.8 inches over the last 100 years, and some experts say the rate is increasing.
Arendt said that would be consistent with what he and his co-authors have found
in their study of the Alaskan glaciers.
"The next question is what has been causing this glacier
thinning. Is it because there is less snowfall in the winter or are the summers
warmer?" said Arendt. "Glacier changes are linked to the climate, so this indicates
that something has changed about the Alaskan climate."
Alaska's glaciers grow if they receive more snow in the
winter than is melted in the summer. Since the glaciers are shrinking, then
one end of ice equation has changed and Arendt said that more study is needed
to find out the causes.
Mark F. Meier, a glacier expert at the University of Colorado,
Boulder, said that the study by Arendt and his co-authors is an important advance
in the efforts of science to understand the global climate.
"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," Meier said.
The contribution from Alaska's glaciers to the worldwide
sea level rise "is even more that what we had expected," said Meier. Although
Alaska contains 13% of the world's glacier-bound ice, the melt from its glaciers
is greater than all the other glacier fields put together, excluding the ice
fields in Greenland and Antarctica.
"Greenland is actually contributing less runoff than are
these Alaskan glaciers," said Meier. "Greenland is much bigger, but it is much
Experts have attributed sea level rise to two primary effects:
run off from the melting of ancient ice fields, such as the Alaskan glaciers,
and an ocean expansion due to warming. Some have attributed the warming of the
ocean to a general global trend caused by human action.
Several indications show the Earth has warmed since early
in the 20th century and most climate scientists agree that a combination of
natural and human causes are responsible. Natural causes include things such
as a slight increase in the heat from the sun and fewer large volcanoes that
put light-blocking substances into the than in earlier times. The human cause
is the addition of gasses that tend to trap heat to the air, especially carbon
dioxide from burning coal, oil, as and other fuels.
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