http://www.commondreams.org/headlines03/1115-04.htm
Published on Saturday,
November 15, 2003 by the Guardian/UK
Shrinking Ice in Antarctic Sea 'Exposes
Global Warming'
by David Fickling in Sydney
CAPTION:
"ON ANOTHER GLOBAL WARMING FRONT...
A large portion of Lake Superior is seen covered in ice
in this March 12, 2003 satellite image. In theory, global
warming should be a good thing for the Great Lakes, right?
Wrong. Global warming means more snow, not less, for the
snowbound region along the eastern border between Canada
and the United States, researchers said on November 4, 2003.
Their study of snowfall records in the Great Lakes region
and elsewhere suggests there has been a significant
increase in snowfall in the Great Lakes region since
the 1930s but not anywhere else. The team, at Colgate
University in Hamilton, New York, said that global warming
does not mean sunnier weather everywhere. Other researchers
have predicted that, as the climate gets warmer overall,
it could mean colder temperatures in some parts of the
world and more severe weather in general as weather
patterns change." Photo by Reuters
Australian scientists yesterday revealed new evidence of
global warming, suggesting that sea ice around Antarctica
had shrunk 20% in the past 50 years.
The research published
in the journal Science traced the
pattern of sea ice in the Southern Ocean as far back as 1840.
"Between 1841
and 1950 there was very little change but there
is a marked decline in sea ice distribution since 1950 of
around 20%," said the lead author, Mark Curran.
The change is important
because sea ice - the area around
the poles where seawater is frozen into layers no more than
a few meters thick - is regarded as a crucial indicator of
climate change.
Unlike the ice caps
over Greenland and Antarctica and the
icebergs they spawn, the size and thickness of the sea ice
have little direct effect on worldwide temperatures and sea
levels.
But scientists believe
it is responsible for the movement
of global ocean currents which ensure land masses such as
Britain (via its warming Gulf Stream) are kept at certain
temperatures.
In winter, pack ice
covers an area of more than 7 million
square miles around Antarctica, shrinking to 1.5 million
square miles during the southern hemisphere summer. At its
greatest extent, the ice field is bigger than Russia.
Several studies in
recent years have shown that sea ice
around Antarctica has increased since the 1970s, but
Dr Curran said that the short timescale of those studies
failed to take longer-term trends into account. "Until now,
records have relied to a large degree on satellite
observations since the 1970s. Thirty years is a very
short time over which to draw any conclusions," he said.
A Nasa satellite study
released last week showed that the
growth of pack ice since the end of the 1970s was preceded
by a period of shrinkage between 1973 and 1978. The break-up
of the Arctic pack ice in recent years has also highlighted
concerns about the implications of sea ice decline.
The evidence is taken
from ice cores bored out of the
Law Dome, a mound of compressed snow from the Antarctic
mainland more than half a mile deep, which carries a climate
record stretching back 90,000 years.
Compacted snowfall
forms annual layers in the ice similar
to tree rings. The scientists worked out the extent of past
sea ice by measuring the amount of methane sulphonic acid
(MSA), produced by marine algae, in the ice cores.
MSA-producing algae is linked to sea ice, so the quantity
of the chemical in any year's snowfall gives a clue to
the extent of that year's pack ice.
"We have only
just scratched the surface of this so far,"
said Dr Curran. "It's only when we start going back into
the earlier layers that we'll start to find out whether
the changes since 1950 are the norm or an exception."
The new findings are
startlingly similar to contentious
research published in 1997 based on whaling records.
Before the banning of commercial whaling in 1987, ships
often moored close to the Antarctic pack ice while taking
their catch, allowing researchers to retrace the extent
of the pack ice by examining the positions of whaling ships.
Scientists see Antarctica
as a barometer of climate trends,
with many of the indicators pointing towards global warming.
Average temperatures on the Antarctic peninsula have risen
3C in the past 50 years, and the Antarctic ice shelves have
retreated dramatically.
B15, which at more
than 4,000 square miles was as big
as Jamaica and the world's largest iceberg when it calved
from the Ross ice shelf in 2000, split apart during storms
last month, giving rise to two smaller bergs.
© Guardian Newspapers
Limited 2003
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