West Antarctica is warming almost twice as fast as previously
believed, adding to worries of a thaw that would add to sea
level rise from San Francisco to Shanghai, a study showed.
Annual average temperatures at the Byrd research station in
West Antarctica had risen 2.4degC since the 1950s, one of the
fastest gains on the planet and three times the global
average in a changing climate, it said.
The unexpectedly big increase adds to fears the ice sheet is
vulnerable to thawing. West Antarctica holds enough ice to
raise world sea levels by at least 3.3 metres if it ever all
melted, a process that would take centuries.
"The western part of the ice sheet is experiencing nearly
twice as much warming as previously thought," Ohio State
University said in a statement of the study led by its
geography professor David Bromwich.
The warming "raises further concerns about the future
contribution of Antarctica to sea level rise," it said.
Higher summer temperatures raised risks of a surface melt of
ice and snow even though most of Antarctica is in a
year-round deep freeze.
Low-lying nations from Bangladesh to Tuvalu are especially
vulnerable to sea level rise, as are coastal cities from
London to Buenos Aires. Sea levels have risen by about 20cm
in the past century.
The United Nations panel of climate experts projects that sea
levels will rise by between 18cm and 59cm this century, and
by more if a thaw of Greenland and Antarctica accelerates,
due to global warming caused by human activities.
The rise in temperatures in the remote region was comparable
to that on the Antarctic Peninsula to the north, which snakes
up towards South America, according to the U.S.-based experts
writing in the journal Nature Geoscience.
Parts of the northern hemisphere have also warmed at
similarly fast rates.
Several ice shelves - thick ice floating on the ocean and
linked to land - have collapsed around the Antarctic
Peninsula in recent years. Once ice shelves break up,
glaciers pent up behind them can slide faster into the sea,
raising water levels.
"The stakes would be much higher if a similar event occurred
to an ice shelf restraining one of the enormous West
Antarctic ice sheet glaciers," said Andrew Monaghan, a
co-author at the U.S. National Center for Atmospheric
The Pine Island glacier off West Antarctica, for instance,
brings as much water to the ocean as the Rhine river in
The scientists said there had been one instance of a
widespread surface melt of West Antarctica, in 2005.
"A continued rise in summer temperatures could lead to more
frequent and extensive episodes of surface melting," they
West Antarctica now contributes about 0.3 mm a year to sea
level rise, less than Greenland's 0.7 mm, Ohio State
University said. The bigger East Antarctic ice sheet is less
vulnerable to a thaw.
Helped by computer simulations, the scientists reconstructed
a record of temperatures stretching back to 1958 at Byrd,
where about a third of the measurements were missing,
sometimes because of power failures in the long Antarctic