A Rhode Island-size piece of the floating ice fringe along a fast-warming
region of Antarctica has disintegrated with extraordinary rapidity, scientists
said yesterday.
The loss of floating ice does not contribute to rising sea levels, just as
melting ice cubes floating in a glass do not cause it to overflow. But the
researchers said this was the first time in thousands of years that this part
of Antarctica -- the east coast of its arm-shaped peninsula -- had seen so
much ice erode and temperatures rise so much.
While it is too soon to say
whether the changes there are related to a buildup of the ''greenhouse'' gas
emissions that scientists believe are warming the planet, many experts said it
was getting harder to find any other explanation.
''With the disappearance of ice shelves that have existed for thousands of
years, you rather rapidly run out of other explanations,'' said Dr. Theodore
A. Scambos, a glaciologist at the National Snow and Ice Data Center at the
University of Colorado, which has been monitoring the loss of ice in the
Antarctic along with the British Antarctic Survey.
Other parts of Antarctica have experienced different trends, including a
cooling of the continent's interior in recent decades.
The latest ice breakup occurred in the Larsen B ice shelf, which has
probably existed since the last ice age. ''There's no evidence of any period
in the last 12,000 years where there was open water in the area that has now
been exposed,'' Dr. Scambos said.
For years, researchers hiking on the ice and using satellites have been
watching pieces of the shelf slowly break away, but the disintegration over
the last month was on a vastly greater scale, several experts said. ''The
speed of it is staggering,'' said Dr. David Vaughan, a glaciologist at the
British Antarctic Survey.
Starting in February, satellites recorded the event as the ice sheet
fragmented into thousands of floes.
Scientists say the likely culprit is rapidly warming summer air
temperatures. Along that part of the peninsula, temperatures have risen 4.5
degrees in five decades, and hundreds of small ponds of meltwater have formed
on the surface of the Larsen shelf and others nearby.
The surface water migrates into tiny cracks in the ice, steadily deepening
and widening them until the monumental structure starts to fall apart, Dr.
Scambos said.
Back to Earth Changes
