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GLOBAL MELTDOWN
MASSIVE LOSS OF ARCTIC ICE MEANS GLOBAL WARMING IS NOW PAST THE POINT OF NO
RETURN, SAY SCIENTISTS
By Steve Connor
The Independent
September 16, 2005

http://news.independent.co.uk/world/science_technology/article312997.ece

A record loss of sea ice in the Arctic this summer has convinced scientists
that the northern hemisphere may have crossed a critical threshold beyond
which the climate may never recover. Scientists fear that the Arctic has now
entered an irreversible phase of warming which will accelerate the loss of
the polar sea ice that has helped to keep the climate stable for thousands
of years.

They believe global warming is melting Arctic ice so rapidly that the region
is beginning to absorb more heat from the sun, causing the ice to melt still
further and so reinforcing a vicious cycle of melting and heating.

The greatest fear is that the Arctic has reached a "tipping point" beyond
which nothing can reverse the continual loss of sea ice and with it the
massive land glaciers of Greenland, which will raise sea levels
dramatically.

Satellites monitoring the Arctic have found that the extent of the sea ice
this August has reached its lowest monthly point on record, dipping an
unprecedented 18.2 per cent below the long-term average.

Experts believe that such a loss of Arctic sea ice in summer has not
occurred in hundreds and possibly thousands of years. It is the fourth year
in a row that the sea ice in August has fallen below the monthly downward
trend -- a clear sign that melting has accelerated.

Scientists are now preparing to report a record loss of Arctic sea ice for
September, when the surface area covered by the ice traditionally reaches
its minimum extent at the end of the summer melting period.

Sea ice naturally melts in summer and reforms in winter but for the first
time on record this annual rebound did not occur last winter when the ice of
the Arctic failed to recover significantly.

Arctic specialists at the US National Snow and Ice Data Centre at Colorado
University, who have documented the gradual loss of polar sea ice since
1978, believe that a more dramatic melt began about four years ago.

In September 2002 the sea ice coverage of the Arctic reached its lowest
level in recorded history. Such lows have normally been followed the next
year by a rebound to more normal levels, but this did not occur in the
summers of either 2003 or 2004. This summer has been even worse. The surface
area covered by sea ice was at a record monthly minimum for each of the
summer months -- June, July and now August.

Scientists analysing the latest satellite data for September -- the
traditional minimum extent for each summer -- are preparing to announce a
significant shift in the stability of the Arctic sea ice, the northern
hemisphere's major "heat sink" that moderates climatic extremes.

"The changes we've seen in the Arctic over the past few decades are nothing
short of remarkable," said Mark Serreze, one of the scientists at the Snow
and Ice Data Centre who monitor Arctic sea ice.

Scientists at the data centre are bracing themselves for the 2005 annual
minimum, which is expected to be reached in mid-September, when another
record loss is forecast. A major announcement is scheduled for 20 September.
"It looks like we're going to exceed it or be real close one way or the
other. It is probably going to be at least as comparable to September 2002,"
Dr Serreze said.

"This will be four Septembers in a row that we've seen a downward trend. The
feeling is we are reaching a tipping point or threshold beyond which sea ice
will not recover."

The extent of the sea ice in September is the most valuable indicator of its
health. This year's record melt means that more of the long-term ice formed
over many winters -- so called multi-year ice -- has disappeared than at any
time in recorded history.

Sea ice floats on the surface of the Arctic Ocean and its neighbouring seas
and normally covers an area of some 7 million square kilometres (2.4 million
square miles) during September -- about the size of Australia. However, in
September 2002, this dwindled to about 2 million square miles -- 16 per cent
below average.

Sea ice data for August closely mirrors that for September and last month's
record low -- 18.2 per cent below the monthly average- - strongly suggests
that this September will see the smallest coverage of Arctic sea ice ever
recorded.

As more and more sea ice is lost during the summer, greater expanses of open
ocean are exposed to the sun which increases the rate at which heat is
absorbed in the Arctic region, Dr Serreze said.

Sea ice reflects up to 80 per cent of sunlight hitting it but this "albedo
effect" is mostly lost when the sea is uncovered. "We've exposed all this
dark ocean to the sun's heat so that the overall heat content increases," he
explained.

Current computer models suggest that the Arctic will be entirely ice-free
during summer by the year 2070 but some scientists now believe that even
this dire prediction may be over-optimistic, said Professor Peter Wadhams,
an Arctic ice specialist at Cambridge University.

"When the ice becomes so thin it breaks up mechanically rather than
thermodynamically. So these predictions may well be on the over-optimistic
side," he said.

As the sea ice melts, and more of the sun's energy is absorbed by the
exposed ocean, a positive feedback is created leading to the loss of yet
more ice, Professor Wadhams said.

"If anything we may be underestimating the dangers. The computer models may
not take into account collaborative positive feedback," he said.

Sea ice keeps a cap on frigid water, keeping it cold and protecting it from
heating up. Losing the sea ice of the Arctic is likely to have major
repercussions for the climate, he said. "There could be dramatic changes to
the climate of the northern region due to the creation of a vast expanse of
open water where there was once effectively land," Professor Wadhams said.
"You're essentially changing land into ocean and the creation of a huge area
of open ocean where there was once land will have a very big impact on other
climate parameters," he said.

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Published by David Sunfellow
NewHeavenNewEarth (NHNE)
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