May 11, 2007  North America Still Bouncing Back From Ice Age

Sheets of ice almost two miles thick once covered most of Canada and the northeastern U.S. And although the ice retreated thousands of years ago, a new study finds that the gravitational field over North America is still undergoing changes as a result of the ice sheets having been there. The study appears in the May 11 issue of the journal Science and is the result of four years of data from two satellites that measure the Earth’s gravitational field. 

The purpose was to examine the gravitational field to find any subtle changes in the distribution of the planet’s mass. And the researchers did uncover evidence that parts of the Earth’s crust are still rebounding from being crushed down by the incredible weight of the massive Laurentide Ice Sheet. The gravitational evidence yields information about the geometry of the ice, which helps our understanding of the ice age climate. It’s also important for improving the climate database that comes into play when interpreting modern climate records.  One of the researchers involved in the study put it poetically: “The ghost of the Ice Age still hangs over North America.”