Melting Antarctic Berg
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Parts of Antarctica have recently been warming much faster
than the rest of the Earth, according to scientists in the U.K.
They believe this degree of warming is greater than it has
been for nearly two thousand years. The scientists, from the
British Antarctic Survey, reported their findings in the
magazine Science.
At Amundsen-Scott base at the South Pole annual air
temperatures have actually cooled since 1958. On the
Antarctic peninsula, though, they have warmed since reliable
records began in the 1950s.
Trends in annual air temperature for 1950-98 show three
areas of especially rapid regional warming: northwestern
North America and the Beaufort Sea; an area around the
Siberian plateau; and the Antarctic peninsula and the
adjoining Bellingshausen Sea.
The BAS scientists say the longest records show a warming in
the northwest of the peninsula ?considerably larger than the
mean Antarctic trend,? with shorter records suggesting that
the warming extends further south and east. The warming
has caused
flowering plants to extend their ranges, glaciers to retreat
and seasonal snow cover to shrink.
Penguin distribution is also changing. Adelie penguins, which
need access to winter pack ice, are declining around
Faraday. But chinstrap penguins, which usually need open
water, are increasing.
The authors say three of the four ice cores from the
peninsula show a rise in temperature over the last half
century. Rapid regional warming has also led to the loss of
seven ice shelves during the last 50 years. One, the Prince
Gustav Channel shelf, disappeared in 1995. It came into
existence 1900 years ago, when sedimentary cores show the
climate was as warm as it has been recently. The scientists
say, ?The recent rapid regional warming in the Antarctic
peninsula is thus exceptional over several centuries, and
probably unmatched for 1900 years.?
They suggest three possible causes: changing ocean currents
may have brought warmer deep water onto the continental
shelf, reducing sea-ice; warmer air may have come into the
region; or a unique sea-ice-atmosphere feedback may be at
work. Not knowing which theory is the correct one, the
authors say they cannot predict the future. But they
describe what has happened as ?a profound climatic change,
an order of magnitude greater than global mean warming.?
One of the authors, Dr. David Vaughan, says, ?The important
thing is predicting whether this change will continue. What?s
stopping us is that we can?t say which of these mechanisms
is responsible. The climate modelers have done an astounding
job in the last ten years. But we now need to develop more
sophisticated tools to enable us to predict regional climate
changes.?
Another group of scientists is embarking on a seven-year
research program tracking the effect of global warming on
Antarctica?s vast ice sheets, seeking clues to how much ice
could melt if temperatures continue to rise. The United
Nations Intergovernmental Panel on Climate Change has
predicted the global average surface temperature will
continue to rise, due to rising levels of carbon dioxide and
other greenhouse gases in the atmosphere.
If Antarctica lost its ice, ocean levels would rise as much as
211 feet and scientists want to know what happened last
time a similar bout of global warming occurred 20 million years
ago, according to Tim Naish of the Antarctica Drilling
Consortium (ANDRILL). Drilling to depths that will take
scientists back as far as 40 million years will enable them to
see what Antarctica was like when the world was last 3-4
degrees warmer.
Antarctica is the world?s fifth largest continent with an area
of 5.4 million square miles-- twice the size of Australia. Naish
thinks the current ice sheet on Antarctica is the biggest
ever, as the world has generally been cooling for 60 million
years. He says, ?It may be that it takes a few hundred to a
thousand or a few thousand years to completely de-glaciate
Antarctica... But what we do know is that it will happen if we
maintain those levels of carbon dioxide (gain) and
temperatures.?
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