Antarctic Glacier Thinning Four Times Faster Than 10 Years Ago

LONDON, UK, August 14, 2009 (ENS) – The thinning of a gigantic glacier in Antarctica is accelerating, scientists warned today, calling the loss of ice “alarming.” The Pine Island Glacier in West Antarctica is losing ice four times as fast as it was a decade ago.

The glacier, which is twice the size of Scotland, is releasing more ice into the sea than any other glacier in Antarctica.

The research also reveals that ice thinning is now occurring much further inland. At this rate scientists estimate that the main section of the glacier will have disappeared in just 100 years, six times sooner than was previously thought.

“Accelerated thinning of the Pine Island Glacier represents perhaps the greatest imbalance in the cryosphere today, and yet we would not have known about it if it weren’t for a succession of satellite instruments,” says Professor Andrew Shepherd, a co-author of the research from the School of Earth and Environment at the University of Leeds.

The Pine Island ice shelf and the Amundsen Sea beyond, 2009. (Photo courtesy David Holland/National Science Foundation)

The Pine Island Glacier is located within the most inaccessible area of Antarctica – over 1,000 km (600 miles) from the nearest research base – and was for many years overlooked.

Now, scientists have been able to track the glacier’s development using continuous satellite measurements over the past 15 years.

“Being able to assemble a continuous record of measurements over the past 15 years has provided us with the remarkable ability to identify both subtle and dramatic changes in ice that were previously hidden,” Shepherd said.

Pine Island Glacier is a large ice stream flowing west-northwest along the south side of the Hudson Mountains into Pine Island Bay, Amundsen Sea, Antarctica.

Scientists believe that the retreat of glaciers in this sector of Antarctica is caused by warming of the surrounding oceans, though they say it is too early to link such a trend to global warming.

The 5,400 square kilometer (2,084 square mile) region of the Pine Island Glacier affected today is big enough to impact the rate at which sea levels are rising around the world.

“Because the Pine Island Glacier contains enough ice to almost double the IPCC’s best estimate of 21st century sea level rise, the manner in which the glacier will respond to the accelerated thinning is a matter of great concern,” says Professor Shepherd.

The IPCC is the Nobel Laureate Intergovernmental panel on Climate Change, a body of thousands of scientists convened by the United Nations to assess the scientific literature on climate change.

Published in the journal “Geophysical Research Letters,” the research was led by Professor Duncan Wingham at University College London, and was funded by the UK Natural Environment Research Council.

Pine Island Glacier from helicopter, 1985. (Photo courtesy of T. Kellog and T. Hughes, University of Maine at Orono)

In the study, Professor Wingham explained, “The region of lightly grounded ice at the glacier terminus is extending upstream, and the changes inland are consistent with the effects of a prolonged disturbance to the ice flow, such as the effects of ocean-driven melting.”

“If the acceleration continues at its present rate, the main trunk of the Pine Island Glacier will be afloat within 100 years, six times sooner than anticipated,” he warned.

In 2007, scientists with the British Antarctic Survey spotted a huge iceberg that broke off the Pine Island Glacier – an iceberg nearly half the size of Greater London.

The iceberg was detected on October 7 as a scientist was studying satellite images collected from the European Space Agency’s satellite Envisat using the Polar View monitoring programme.

This calving event is part of a natural cyclic process that is not a cause for concern, the scientists said. A 34-year long study of the glacier has shown that a large iceberg breaks off roughly every five to 10 years.

British Antarctic Survey scientists say the calving of large icebergs has no effect on sea level as the ice they contain is floating before they break away.

A study of historical satellite imagery extending back to 1973 by Dr. Robert Bindschadler at the U.S. National Aeronautics and Space Administration, NASA, shows the glacier front has fluctuated around its present position since that time. Dr. Bindschadler, principal investigator for a new study of the glacier, is scheduled to begin making direct observations in 2011-12.

The BAS scientists are monitoring the iceberg’s progress with collaborators in the United States at the National Snow and Ice Data Center and NASA. It has already moved more than one kilometer from the glacier edge.

The Pine Island Glacier is of great interest to scientists worldwide as it has been thinning at a rate of more than one meter per year and its flow rate has accelerated over the past 15 years.

The BAS scientists said, the wider region within which Pine Island Glacier lies is the most rapidly changing portion of the Antarctic ice sheet and its future impact on sea-level rise could be “very significant.”

“The fast recession of Pine Island Glacier, predicted to be a possible trigger for the disintegration of the West Antarctic Ice Sheet, is attributed to enhanced basal melting of the glacier floating tongue by warm ocean waters,” say NASA scientists who conducted radar studies of the glacier.

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