Study: Global Warming 5 Million Years Ago Raised Sea Levels by 20 metres

A latest study says that five million years ago global warming led to the melting of Antarctica's large ice sheets that were considered stable, causing a rise in sea levels by 20 meters approximately.

In order to gain more information about the ancient melting of the East Antarctic ice sheets, the researchers from Imperial College London, examined mud samples during which they discovered that there were multiple episodes of melting that occurred between five-three million years ago in the geological period known as Pliocene Epoch. They believe that this could have led to a rise in the sea levels by approximately ten metres.

The scientists have also stated previously that the ice sheets of West Antarctica and Greenland partially melted at the same time and that caused the sea levels to increase to a total of 20 metres. By studying the glacial melting that occurred during the Pliocene epoch the researchers will gain more insight into melting trends as the global warming increases.  This is because the levels of carbon dioxide during the Pliocene Epoch was similar to the present time, 400 parts per million.

The East Antarctic ice sheet that is the largest ice mass on Earth was formed 34 million years ago, is approximately the size of Australia.  It was considered to be more stable when compared to the smaller ice sheets in West Antarctica and Greenland.

"The Pliocene Epoch had temperatures that were two or three degrees higher than today and similar atmospheric carbon dioxide levels to today. 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," said Dr Tina Van De Flierdt, co-author from the Department of Earth Science and Engineering at Imperial College London.

The researchers determined that the ice sheet partially melted during the stable period and they came to this conclusion on studying the mud samples that were collected by drilling three kilometers below the sea level off the coast of Antarctica. The mud came from the rocks that are at present blanketed under the ice sheets. The only way mud could have deposited as sediments in the sea was when ice sheets melted and eroded the rocks.

"Our work now shows that the East Antarctic ice sheet has been much more sensitive to climate change in the past than previously realised. This finding is important for our understanding of what may happen to the Earth if we do not tackle the effects of climate change," Carys Cook, co-author and research postgraduate from the Grantham Institute for Climate Change at Imperial, said.

The study was published in the journal Nature Geoscience.