Antarctic ice melts as sea warms but cause unknown

By Jeremy Lovell

LONDON (Reuters) – Antarctica is melting, adding to the
inexorable rise in global sea levels, endangering millions of
lives and whole economies, leading scientists said on Monday.

But while the effect is well known after years of
monitoring from land and space, the reasons for the sea warming
are not.

“We know sea levels will rise. We need to know by how much
and why,” Anthony Payne of the University of Bristol and one of
the organizers of a major scientific conference in London, told
Reuters on the sidelines of the meeting at the Royal Society,
Britain’s national academy of science.

“This has implications for the whole world — most people
and industries are in coastal areas,” he added.

Payne said there was a net loss of mass in Antarctica as
the snowfall in the center of the frigid landmass was more than
offset by sea ice melting around the edges.

The key was to find out whether the process was
accelerating, or whether it might stabilize or even reverse.

And the important factor was understanding the complex
interaction between ocean and wind currents and how much — if
any — of the warming of the seas was due to mankind’s
contribution to global warming.

“We know a lot more about the ice sheets than we did
before,” Payne said. “We know change is happening and that it
is rapid. What we don’t know is why or what is causing it —
what proportion is anthropomorphic.”

Scientists calculate that average world temperatures —
which have already risen by 0.6 degrees Celsius (1.1
Fahrenheit) since 1900 — could rise by at least two more
degrees this century, due in large part to greenhouse gases
from burning fossil fuels.

HIGH ECONOMIC COST

Bob Bindschadler, a glaciologist from U.S. space agency
NASA, said the West Antarctic ice sheet was reducing — albeit
patchily — but that if it all melted it would raise global sea
levels by 6 meters.

Putting it in context he said that a 1-meter rise in sea
levels would cost the United States alone $400 billion —
roughly twice the estimated cost of the destruction wrought by
hurricane Katrina in New Orleans last month.

“We don’t want to have too many New Orleans,” he told the
start of the two-day conference that will pool all Antarctic
knowledge and help shape the fourth assessment report of the
Intergovernmental Panel on Climate Change that is due in 2007.

Eric Rignot, a fellow NASA scientist, said marine ice on
the world’s coldest continent was in general retreat due to
rising sea temperatures.

“The Antarctic ice sheet is changing at a faster rate than
anticipated. The coastal changes are the most significant, with
the potential to reach far inland,” he told an audience of his
peers from around the world.

While the vast East Antarctic ice sheet, which is more than
double the size of its western neighbor, was more or less
stable except at the coastal fringes, there was no guarantee it
would remain so.

“The East Antarctic ice sheet is not immune to change,” he
said, noting that more than one third of the annual 1.8
millimeter rise in global sea levels came from Antarctica.