Transition from glacial periods punctuated by sudden surges of ice melt and sea level rise
FRISCO — Even without the addition of heat-trapping greenhouse gases from fossil fuel combustion, the Antarctica ice sheets may be vulnerable to sudden collapse and melting. One such episode, about 14,600 years ago, is thought to have caused sea level to rise by more than 12 feet in just 100 years.
Scientists are racing to understand the dynamics of the Antarctic ice sheets because of the potentially significant consequences of rapid changes, and in one of the newest studies, they’ve traced some of the big iceberg calving events between about 19,000 and 9,000 years ago by analyzing deep sea sediment cores extracted from the region between the Falkland Islands and the Antarctic Peninsula. The study in the May 28, 2014 issue of Nature documents an unstable Antarctic ice sheet that can abruptly reorganize Southern Hemisphere climate and cause rapid global sea level rise.
“One of the iceberg events in our data that is of particular interest took place 14,600 years ago and coincided with a huge ice-sheet melt, the famous Meltwater Pulse 1A, which according to previous studies led to a global sea level rise of about 4 meters within 100 years,” says lead author of the study, Michael Weber at the University of Cologne in Germany.
“This is the first direct evidence that instabilities of the Antarctic ice sheet caused rapid sea level rise during the last glacial termination,” says co-author Peter Clark, professor at Oregon State University.
To determine what brought about such huge ice-sheet collapses in Antarctica, the team conducted a series of climate modeling experiments.
“An unusually strong flow of warm water towards Antarctica may have triggered these events. Our model experiments reveal further that the associated melting in turn increased the warm water flow, thus providing a positive feedback. This is a perfect recipe for rapid sea level rise,” explains co-author Axel Timmermann, professor at the International Pacific Research Center of the University of Hawaii.
The new findings document that the Antarctic ice-sheet underwent rapid changes in an otherwise gradual transition from glacial to interglacial times in the Southern Hemisphere.
“Our paleo data of abrupt ice-sheet instabilities provide an important benchmark against which future projections of human-induced changes in Antarctic ice volume and global sea level can be evaluated,” says Gerrit Lohmann, professor at the Alfred Wegener Institute, Bremerhaven, Germany.