July 22, 2013
Ancient Antarctic Ice Melt Raised Sea Levels 66 Feet
Brett Smith for redOrbit.com - Your Universe Online
A large team of international researchers has looked millions of years into the Antarctic past and found evidence that massive sections of the continent's eastern ice sheet once melted to raise sea levels by around 66 feet.
"Scientists previously considered the East Antarctic ice sheet to be more stable than the much smaller ice sheets in West Antarctica and Greenland, even though very few studies of East Antarctic ice sheet have been carried out," said Carys Cook, a postgraduate researcher at Imperial College London and co-author of a report on the team's findings that was published in Nature Geoscience.
"Our work now shows that the East Antarctic ice sheet has been much more sensitive to climate change in the past than previously realized," Cook said. "This finding is important for our understanding of what may happen to the Earth if we do not tackle the effects of climate change."
According to the report, an analysis of Antarctic mud samples revealed new detail about the ancient melting of the East Antarctic ice sheet that took place between three and five million years ago. The melting ice sheet would eventually contribute 33 feet of sea level rise during the Pliocene Epoch, when sea levels rose by a total of 66 feet.
Because the Pliocene Epoch had atmospheric carbon dioxide levels similar to today and global temperatures similar to those predicted for the end of this century, scientists are particularly interested in the time period that saw both Antarctic ice sheets and the Greenland ice sheet melt significantly.
"The Pliocene Epoch had temperatures that were two or three degrees higher than today and similar atmospheric carbon dioxide levels to today," said co-author Tina Van De Flierdt from the Department of Earth Science and Engineering at Imperial College London. "Our study underlines that these conditions have led to a large loss of ice and significant rises in global sea level in the past. Scientists predict that global temperatures of a similar level may be reached by the end of this century, so it is very important for us to understand what the possible consequences might be."
The research team came to their conclusion by analyzing the chemical content of mud samples taken from around 1.9 miles under the sea off the coast of Antarctica.
The sediment analysis found a chemical fingerprint that indicated where each individual sample had come from on the continent. The coastal samples were determined to have originated from rock now under the ice sheet. The team said these sediments were probably deposited after the ice sheet had retreated inland and their source rocks had been eroded.
The scientists noted the fact that some of the ice sheet rests in basins below sea level. This direct contact between ice and seawater makes the sheet vulnerable to melting when the ocean warms, as it did during the Pliocene.
The team said they expect to expand on this study by analyzing sediment samples to see how rapidly the ice sheet melted during the Pliocene.