Previous Greenland Ice Sheet Collapse Rose Sea Level up to 6 Meters

More than 400,000 years ago, a warming period pushed Greenland's ice sheet past its limit and raised global sea levels up to 6 meters, according to new research. The results may give us a glimpse as to what may happen as a result of Greenland's current climate-induced melting dilemma.

Known as the Marine Isotope Stage 11, this exceptionally long warming period between ice ages resulted in a global sea level rise of about 6-13 meters above present, caused by changes in the Earth's orbit around the Sun.

This study, published in the journal Nature, is one of the first to zero in on how the vast Greenland ice sheet responded to such warming temperatures.

"The climate 400,000 years ago was not that much different than what we see today, or at least what is predicted for the end of the century," co-author Anders Carlson, an associate professor at Oregon State University, said in a statement.

"This may give us a better sense of what may happen in the future as temperatures continue rising," he added.

Researchers examined sediment cores collected off the coast of Greenland from what is called the Eirik Drift. Based on their distinct "fingerprints," they can determine differences in the terrain as well as how old the samples are, and whether or not ice was present at the time.

"Not only can we estimate how much ice there was," Carlson noted, "but the isotopic signature can tell us where ice was present, or from where it was missing."

Analysis of these "ice sheet tracers" suggests that ice loss and deglaciation in southern Greenland 400,000 years ago would have accounted for at least four meters - and possibly up to six meters - of global sea level rise. Other studies have shown, however, that sea levels during that period were at least six meters above present, and may have been as much as 13 meters higher.

But scientists are unsure of how much Greenland contributed to this event and how much may have resulted from the melting of Antarctic ice sheets or other causes.

"This is the first step toward more complete knowledge of the ice history," Carlson said, "but it is an important one."