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Selected
Examples
Of Ice Melt
Around The World
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 he Earth's ice cover is melting in more places and
at higher rates than at any time since record keeping began.
Reports from around the world compiled by the Worldwatch Institute
(see table below) show that global ice melting accelerated during
the 1990s which was also the warmest decade on record.
 Scientists
suspect that the enhanced melting is among the first observable
signs of human-induced global warming, caused by the unprecedented
release of carbon dioxide and other greenhouse gases over the
past century. Glaciers and other ice features are particularly
sensitive to temperature shifts.
The Earth's
ice cover acts as a protective mirror, reflecting a large share
of the sun's heat back into space and keeping the planet cool.
Loss of the ice would not only affect the global climate, but
would also raise sea levels and spark regional flooding, damaging
property and endangering lives. Large-scale melting would also
threaten key water supplies as well as alter the habitats of
many of the world's plant and animal species.
Some of
the most dramatic reports come from the polar regions, which
are warming faster than the planet as a whole and have lost large
amounts of ice in recent decades. The Arctic sea ice, covering
an area roughly the size of the United States, shrunk by an estimated
6 percent between 1978 and 1996, losing an average of 34,300
square kilometers -- an area larger than the Netherlands -- each
year.
The Arctic
sea ice has also thinned dramatically since the 1960s and 70s.
Between this period and the mid-1990s, the average thickness
dropped from 3.1 meters to 1.8 meters -- a decline of nearly
40 percent in less than 30 years.
The Arctic's
Greenland Ice Sheet -- the largest mass of land-based ice outside
of Antarctica, with 8 percent of the world's ice -- has thinned
more than a meter per year on average since 1993 along parts
of its southern and eastern edges.
The massive
Antarctic ice cover, which averages 2.3 kilometers in thickness
and represents some 91 percent of Earth's ice, is also melting.
So far, most of the loss has occurred along the edges of the
Antarctic Peninsula, on the ice shelves that form when the land-based
ice sheets flow into the ocean and begin to float. Within the
past decade, three ice shelves have fully disintegrated: the
Wordie, the Larsen A, and the Prince Gustav. Two more, the Larsen
B and the Wilkins, are in full retreat and are expected to break
up soon, having lost more than one-seventh of their combined
21,000 square kilometers since late 1998 -- a loss the size of
Rhode Island. Icebergs as big as Delaware have also broken off
Antarctica in recent years, posing threats to open-water shipping.
Antarctica's
vast land ice is also melting, although there is disagreement
over how quickly. One study estimates that the Western Antarctic
Ice Sheet (WAIS), the smaller of the continent's two ice sheets,
has retreated at an average rate of 122 meters a year for the
past 7,500 years -- and is in no imminent danger of collapse.
But other studies suggest that the sheet may break more abruptly
if melting accelerates. They point to signs of past collapse,
as well as to fast-moving ice streams within the sheet that could
speed ice melt, as evidence of potential instability.
Outside
the poles, most ice melt has occurred in mountain and subpolar
glaciers, which have responded much more rapidly to temperature
changes. As a whole, the world's glaciers are now shrinking faster
than they are growing, and losses in 1997-98 were "extreme,"
according to the World Glacier Monitoring Service. Scientists
predict that up to a quarter of global mountain glacier mass
could disappear by 2050, and up to one-half by 2100 -- leaving
large patches only in Alaska, Patagonia, and the Himalayas. Within
the next 35 years, the Himalayan glacial area alone is expected
to shrink by one-fifth, to 100,000 square kilometers.
The disappearance
of Earth's ice cover would significantly alter the global climate,
although the net effects remain unknown. Ice, particularly polar
ice, reflects large amounts of solar energy back into space,
and helps keep the planet cool. When ice melts, however, this
exposes land and water surfaces that retain heat -- leading to
even more melt and creating a feedback loop that accelerates
the overall warming process. But excessive ice melt in the Arctic
could also have a cooling effect in parts of Europe and the eastern
United States, as the influx of fresh water into the North Atlantic
may disrupt ocean circulation patterns that enable the warm Gulf
Stream to flow north.
As mountain
glaciers shrink, large regions that rely on glacial runoff for
water supply could experience severe shortages. The Quelccaya
Ice Cap, the traditional water source for Lima, Peru, is now
retreating by some 30 meters a year -- up from only 3 meters
a year before 1990-posing a threat to the city's 10 million residents.
And in northern India, a region already facing severe water scarcity,
an estimated 500 million people depend on the tributaries of
the glacier-fed Indus and Ganges rivers for irrigation and drinking
water. But as the Himalayas melt, these rivers are expected to
initially swell and then fall to dangerously low levels, particularly
in summer. (In 1999, the Indus reached record high levels because
of glacial melt.)
Rapid glacial
melting can also cause serious flood damage, particularly in
heavily populated regions such as the Himalayas. In Nepal, a
glacial lake burst in 1985, sending a 15-meter wall of water
rushing 90 kilometers down the mountains, drowning people and
destroying houses. A second lake near the country's Imja Glacier
has now grown to 50 hectares, and is predicted to burst within
the next five years, with similar consequences.
Large-scale
ice melt would also raise sea levels and flood coastal areas,
currently home to about half the world's people. Over the past
century, melting in ice caps and mountain glaciers has contributed
on average about one-fifth of the estimated 10-25 centimeter
(4-10 inch) global sea level rise -- with the rest caused by
thermal expansion of the ocean as the Earth warmed. But ice melt's
share in sea level rise is increasing, and will accelerate if
the larger ice sheets crumble. Antarctica alone is home to 70
percent of the planet's fresh water, and collapse of the WAIS,
an ice mass the size of Mexico, would raise sea levels by an
estimated 6 meters -- while melting of both Antarctic ice sheets
would raise them nearly 70 meters. (Loss of the Arctic sea ice
or of the floating Antarctic ice shelves would have no effect
on sea level because these already displace water.)
Wildlife
is already suffering as a result of global ice melt -- particularly
at the poles, where marine mammals, seabirds, and other creatures
depend on food found at the ice edge. In northern Canada, reports
of hunger and weight loss among polar bears have been correlated
with changes in the ice cover. And in Antarctica, loss of the
sea ice, together with rising air temperatures and increased
precipitation, is altering the habitats as well as feeding and
breeding patterns of penguins and seals. 
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