February 16, 2009

Scientist ponders ice sheet melting

A U.S. geoscientist says although it's known the Greenland and Antarctica ice sheets are melting, how much ice will melt is undetermined.

Penn State Professor Richard Alley said if Greenland's ice sheet melts, sea level will rise about 23 feet, which will inundate portions of nearly all continental shores. However, Antarctica, containing much more water, could add another 190 feet to sea level.

We do not think that we will lose all, or even most, of Antarctica's ice sheet, said Alley. But important losses may have already started and could raise sea level as much or more than melting of Greenland's ice over hundreds or thousands of years,

Alley said those who study ice sheets have long modeled ice sheet behavior but simulations of the whole Earth system typically haven't included ice sheets along with the atmosphere, oceans and clouds. He said past atmospheric modelers usually treated the ice sheets simply as white mountains.

They are not white mountains and they need to be modeled, said Alley. We need to have them in the models to figure out how the system works.

Alley notes a collaboration of government and academic scientists created the atmospheric and ocean models but collaborations to model the ice are only just being developed.

He spoke Monday in Chicago during the annual meeting of the American Association for the Advancement of Science.