Ice Cap Is Melting
At A Frighteningly Fast Rate
By David Perlman
11 August, 2006
San Francisco Chronicle
The vast ice cap that covers
Greenland nearly three miles thick is melting faster than ever before
on record, and the pace is speeding year by year, according to global
climate watchers gathering data from twin satellites that probe the
effects of warming on the huge northern island.
The consequence is already
evident in a small but ominous rise in sea levels around the world,
a pace that is also accelerating, the scientists say.
According to the scientists'
data, Greenland's ice is melting at a rate three times faster than it
was only five years ago. The estimate of the melting trend that has
been observed for nearly a decade comes from a University of Texas team
monitoring a satellite mission that measures changes in the Earth's
gravity over the entire Greenland ice cap as the ice melts and the water
flows down into the Arctic ocean.
"We have only been watching
the ice cap melt during a relatively short period," physicist Jianli
Chen said Thursday, "but we are seeing the strongest evidence of
it yet, and in the near future the pace of melting will accelerate even
The same satellites tracking
Greenland's ice cap also are monitoring the melt rate of Antarctica's
ice cover, and there too the melting is adding to the global rise in
sea level, according to another team of scientists.
Next to Antarctica, Greenland,
a self-governing Danish territory, is the largest reservoir of fresh
water on Earth and holds about 10 percent of the world's supply. The
increasing flow of fresh water -- most of it from glaciers melting on
Greenland's eastern coast -- is already beginning to change the composition
of the ocean's salt water currents flowing past Northwestern Europe,
the scientists say.
The result could be a critical
change in the composition of the main ocean current that flows past
Europe's northern edge, blocking off warmer waters that normally flow
there and -- ironically -- making Northern Europe's weather colder than
normal, at least temporarily, while the rest of the globe continues
The report on Greenland is
being published today in the on-line edition of the journal Science
by the University of Texas scientists at Austin, including Chen, aerospace
engineer Byron Tapley and geologist Clark Wilson.
According to the researchers,
surface melting of Greenland's ice cap reached 57 cubic miles a year
between April of 2002 and November of 2005, compared to about 19 cubic
miles a year between 1997 and 2003.
"The sobering thing
is to see that the whole process of glacial melting is stepping up much
more rapidly than before," said Tapley in a statement.
If the Greenland ice cap
ever melted completely -- a highly unlikely event, at least in the foreseeable
future -- the scientists estimate it would raise world's sea level by
an average of 6.5 meters, or about 21 feet, more than enough to drown
all the world's low-lying islands and even some entire nations, like
The possibility of future
sea level rises becomes even more evident when Antarctica's huge ice
sheets are considered.
Only last March two University
of Colorado physicists used the same satellite system to measure melting
of ice on the Antarctic continent. Although earlier evidence using other
techniques appeared to show that the East Antarctica ice sheet was actually
thickening, satellite data gathered by Isabella Velicogna and John Wahr
at Boulder found that melting -- primarily from the West Antarctic Ice
Sheet -- had turned at least 36 cubic miles of ice to fresh water each
year from 2002 to 2005.
A recent report from the
Intergovernmental Panel on Climate Change -- known as the IPCC -- estimated
that during all of the past century worldwide melting ice from global
warming had raised sea levels by only two-tenths of a millimeter a year,
or about 20 inches for the entire century.
But, according to Chen and
his Texas team, the melting of Greenland's ice cap is already raising
global sea levels by six-tenths of a millimeter each year, and the Colorado
group estimates that melting of the West Antarctic Ice Sheet alone is
adding up to four-tenths of a millimeter of fresh water to sea levels
each year. In other words, the global sea level, due to melting of the
ice in Greenland and Antarctica combined, is already rising 10 times
faster than the IPPC's tentative estimates, the two analyses indicate.
Both the Texas and Colorado
groups have been obtaining their data from two satellites known as GRACE,
the Gravity Recovery and Climate Experiment, which fly in orbit 137
miles apart and determine with extraordinary accuracy just how the mass
of even small regions of the Earth change as ice melts and flows away
from the land to the sea.
The GRACE satellite mission
is due to end next year, but the Texas team is awaiting NASA approval
for a new and improved satellite system to continue the work, using
laser beams rather than microwaves to measure ice cap melting, Chen
In a recent summary of the
ice cap melting problem and its effect on sea levels reported by Richard
Kerr in Science, geoscientist Michael Oppenheimer of Princeton said,
"The time scale for future loss of most of an ice sheet may not
be millennia," as glacier models have suggested, "but centuries."
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