Blog Archive

Monday, January 14, 2008

UGA climatologist studies rate of melt in Greenland ice sheet

by Lee Shearer (

Story updated at 11:11 p.m., on Sunday, January 13, 2008

A University of Georgia scientist's research has revealed a dramatic rise in the rate of melt in the vast ice sheet of Greenland -- 60 percent higher last year than ever before recorded.

UGA climatologist Thomas Mote didn't use a big bucket to measure the water coming off the ice -- enough ice covers Greenland, the world's largest island, to fill the Gulf of Mexico.

Instead of actually trying to measure the vast amounts of ice that melts in spring and summer, Mote used a nearly 40-year record of satellite data.

"What we found was quite remarkable," said Mote, a professor in UGA's department of geography and director of its Climatology Research Lab.

Satellites have been recording microwave radiation coming off the ice sheet since 1973, Mote explained.

When ice begins to melt, it begins to radiate a lot more microwave radiation than solid ice, Mote said.

"It looks a lot hotter where it's melting than where it isn't," Mote said.

The melting ice reflects less sunlight and absorbs more energy than unmelted ice.

So while it's not possible to measure the exact amount of water coming off the world's largest island, Mote was able to use the satellite data to measure how long the ice melted in a given year and over how big an area.

Mote's analysis showed the rate of melt for the past decade is sharply higher than the previous 25 years -- and that 2007's rate of melt was 60 percent higher than the previous high in 1998.

Scientists have been keeping an increasingly close eye on Greenland as worries over the effects of global warming have mounted in recent years.

Mote's research helps confirm other scientists' conclusions that the loss of ice from Greenland and the globe's other titanic ice masses has speeded up.

Satellite data has shown a decrease in sea ice across the Northern Hemisphere since 2000.

But all of Greenland's ice won't melt any time soon -- a good thing, since that much melted ice could raise the sea level by about 21 feet, Mote said.

"The ice sheet has been there thousands of years. We're looking at a very small slice of time," he said.

But the research lends weight to other researchers' conclusions that the extent of global ice is shrinking, and that the shrinkage stems from man-made climate changes that are melting the ice.

Some scientists believe we could see a sea level rise of 3 feet over the next century. Other scientists think the rise could be even more, as much as 7 feet.

Another concern is what the increasing melt could do to a vast ocean current system called the North Atlantic Deep Water formation, which affects global climate, particularly in Northern Europe.

"It keeps Northern Europe quite warm," at least compared to other areas that far north on the globe, Mote said.

Mote plans to shift his focus slightly in the next few months on a Fulbright Scholar grant, which will allow him to spend three months at the University of Rio Grande do Sul in Porto Alegre, Brazil, from March to July -- fall and winter in the Southern Hemisphere.

In Porto Alegre, Mote hopes to set up a research collaboration to study how the changes in Antarctic ice are influencing the climate of South America.

He and his colleagues also will be trying to understand questions such as exactly how the giant masses of cold air coming out of the Antarctic influence the climate, and how the continuing deforestation of the Amazon River basin is influencing the South American climate, he said.

Mote also will expand his Northern Hemisphere research, working with four other scientists, he said.

The five-member team, from NASA and four U.S. universities, recently learned they will get a five-year, $1.13 million grant from the space agency, Mote said.

"We will be assembling an integrated look at changes in snow and ice over the Northern Hemisphere," Mote said.

Published in the Athens Banner-Herald on 011408

Link to article:

No comments: