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Study: Melting Greenland ice sheets could cause trouble

Roughly 145 million people worldwide could be displaced if water levels from a melting Greenland rise as quickly as they did at the end of the last ice age, according to a report released this week from a University of Wisconsin geologist.

UW geology professor Anders Carlson led the team that did the research and, published it this week in the journal Nature Geoscience.

During the last ice age, an ice cap covered much of North America. In a period of about 2,500 years, it rapidly melted to the north, raising water levels by seven to 13 millimeters a year.

Serious damage will be done if sea levels rise at those rates. If, for example, the oceans rise by just one meter, about 2.2 million square kilometers of land will be overtaken by water, causing over $1 trillion in damage.

“New Orleans is below sea level, all big cities are by the coast, New York, Boston, Florida doesn’t look so great, the Netherlands, Dubai,” Carlson said. “And then there are these various tropical islands that are basically just little coral reefves or volcanoes coming out into the sea.”

The possibility of that drastic of a rise is higher than previously expected by the United Nations’ Intergovernmental Panel on Climate Change.

“They left the question rather open as to how much sea level rise we could get from the melting of the Greenland ice sheet or the Antarctic ice sheet,” said Allegra LeGrande of the NASA Goddard Institute of Space Studies at Columbia University in New York City, who worked with Carlson on the study.

To determine how fast the old North American ice sheet melted, Carlson looked at the details on the edge of the current ice sheet and other climate indicators, including tree rings and some types of fossils.

Temperatures in Greenland will continue to rise due to greenhouse gases, which will inevitably raise the rate of melting.

By 2100, the average summer temperature in Greenland will be two to four degrees Celsius higher, nearly identical to summer conditions over North America 9,000 years ago.

LeGrande said the study does not guarantee anything, just that it is possible for ice to melt that quickly and with dire consequences.

“I would say that we weren’t really in disagreement with the IPCC report;, our study was directed by something that had been an area of relative uncertainty in the IPCC report,” LeGrande said.

The IPCC will look further into rising sea levels for its next report. Research simulations for that report will begin in spring 2009, Legrande said.