Global Sea Level Rise Forecast to Flood Low-Lying Coastlines

LONDON, UK, October 18, 2005 (ENS) - "The melting of the ice contained in West Antarctica would lead to a sea level rise of five or six meters around the world, or sufficient to cause effects such as the inundation of much of the state of Florida," said Dr. Tony Payne Monday at a conference of Antarctic climate experts. A five to six meter rise means seas would rise 16 to 19 feet above their present levels.

At the Royal Society in London, the Antarctic climate scientists are examining the latest evidence for climate change on the icy continent and its effects on the southern ice sheet, at a two day scientific meeting that winds up today. The goal of the meeting is to determine whether recent rapid melting of the ice sheet can be attributed to climate change caused primarily by a rise in atmospheric concentrations of greenhouse gases.

Dr. Payne, a professor of glaciology at the University of Bristol and co-director of the UK's Centre for Polar Observation and Modelling, has organized the gathering, which he calls the most important such conference in over a decade.


Iceberg melting into the Davis Sea, East Antarctica. (Photo by Richard Dunbar)
“The future of the Antarctic ice sheet is critical to the amount of global sea level change that could occur over the coming centuries because it represents the largest potential source of ocean water on the planet," said Payne.

It is anticipated that the findings of these scientists will influence the Fourth Assessment Report from the Intergovernmental Panel on Climate Change (IPCC), which is due to be published in 2007. The IPCC is under the auspices of the World Meteorological Organization and operates through the United Nations Environmental Programme.

Among the speakers at the meeting is Richard Alley, professor of geosciences at Pennsylvania State University, who points out that rapid changes at the margins of the West Antarctic Ice Sheet may already be contributing to an increase in sea levels.

He has raised concerns about the conclusion of the 2001 Third Assessment Report by the IPCC that it was “very unlikely” to produce a substantial rise during the 21st century. The IPCC report indicated that the West Antarctic Ice Sheet contains enough ice to raise sea levels around the world by six meters.

"I am not an alarmist," Dr. Alley has said. "Essentially, the Intergovernmental Panel on Climate Change is very good and is doing a very good job. But what some policy makers are seeing as information on climate change looks nicer than what is likely to happen."

"Likely we will be surprised no matter how good our models are, and the IPCC and other governmental groups need to plan for this surprise and deal with resource conflicts in a progressive way," says the Penn State scientist.


Dr. Richard Alley is Evan Pugh Professor of Geosciences and associate of the EMS Environment Institute at Pennsylvania State University. He has spent three field seasons in Antarctica and five in Greenland. (Photo courtesy CIRES)
The computer climate models that predict the contribution of the Antarctic ice sheet to future sea levels may not be accurate, the scientists believe, because the most modern source of information - satellite data - has not yet been included in these models.

“Recent evidence strongly suggests that parts of the Antarctic ice sheet are losing mass, and contributing to sea-level rise, at rates far greater than has been previously thought," Payne said.

"Much of the evidence comes from satellite observations of the ice sheet, which have revolutionized the way in which we view the ice sheet and have highlighted a range of ways in which the ice sheet may respond to climate change over the period of years to decades, and much faster than previously thought," he said.

"These mechanisms are not included in the large-scale models currently used to predict the contribution of the Antarctic ice sheet to future sea levels," he said. "One of the major outcomes of this meeting will be new ideas about ways in which these models must be improved.”

A rise in global average temperatures due to an increase in greenhouse gas concentrations could cause sea levels around the world to rise for three main reasons, the scientists explain.

First, warming the water in seas and oceans will cause it to expand. Second, the melting of glaciers and ice sheets will increase the amount of water in seas and oceans. And finally, if ice on land breaks up and falls into the oceans and seas, it will displace water, like dropping ice cubes into a glass of water.

Scientists are using new satellites and observation systems to monitor disappearing ice shelves and moving glaciers. One 10,000 year old ice shelf in the Antarctic peninsula recently melted in just three weeks, according to NASA scientist Eric Rignot.

"These glaciers are melting much faster than we thought," said Rignot, principal scientist for the radar science and engineering section at NASA's Jet Propulsion Laboratory.


Dr. Eric Rignot is principal scientist for the Radar Science and Engineering Section at NASA’s Jet Propulsion Laboratory in Pasadena, California. (Photo courtesy NASA)
Rignot is a principal investigator on NASA funded projects to study the mass balance of the Greenland and Antarctic ice sheets using radar interferometry combined with other methods; the interactions of ice shelves with the ocean; and the retreat of Patagonian glaciers.

Rignot presented his latest findings, showing that sea levels could rise by one meter (39 inches) because of ice draining into the ocean from the Pine Island Sector of West Antarctica.

But some scientists have suggested that overall annual snowfalls on the Antarctic ice sheet appear roughly to be balanced by the loss of ice due to melting or the breakup into icebergs.

Rignot presented data that shows ice shelves and glaciers in East Antarctica are thinning and losing mass, even though ice in that area is thought to be thickening overall due to increased amounts of snow and rainfall.

Richard Hindmarsh, an ice sheet modeller at the British Antarctic Survey, presented the results of his calculations about the stresses inside Antarctic ice sheets. They imply that the removal of ice shelves due to climate change will cause more ice to flow off the Antarctic land mass and into the ocean, leading to a significant rise in sea levels across the globe.

The scientists hope that this meeting will help to produce more accurate forecasts of how sea levels will be affected by Antarctic climate change and allow policymakers to address more effectively this threat arising from rising greenhouse gas concentrations in the atmosphere.