5 million years ago, the sea level rose 20 meters
A new report suggests global warming that occurred 5 million years ago may have melted the antarctic ice caps and led to a 20 meter rise in global sea levels.
Researchers at Imperial College London have been analyzing mud samples in order to study ancient melting of the Eastern Antarctic ice sheet. They discovered that the ice sheet melted rapidly during a period between 3 and 5 million years ago known as the Pliocene Epoch. The researchers believe that the melting caused a global sea-level rise of about ten meters, but combined with similar melting on the arctic and on Greenland, the sea levels are estimated to have risen closer to 20 meters.
The researchers have said that studying the Pliocene Epoch may be important to our own warming planet, as CO2 levels at the time were similar to today’s levels, and temperatures were close to what is expected at the end of this century. Dr Tina Van De Flierdt, who is co-author of the study and comes from Imperial’s Department of Earth Sciences and Engineering explains: “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.”
The Eastern Antarctic ice sheet, was formed around 34 million years ago. While it has varied in size, it is believed to have stabilized around 14 million years ago, and is today the worlds largest ice sheet with an area comparable to that of Australia.
The Eastern Antarctic ice sheet
When the scientists analyzed the mud, which came from sediment 3km below the surface off the coast of Antarctica, they found a unique chemical fingerprint that they used to identify where the mud came from. Their conclusion was that the mud came from rocks which are currently below the ice sheet. The only way deposits from the ice sheet could end up in mud off the coast, is if the ice retreated inland and eroded the rocks while doing so.
“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.” explains co-author Carys Cook, “Our work now shows that the East Antarctic ice sheet has been much more sensitive to climate change in the past than previously realized. This finding is important for our understanding of what may happen to the Earth if we do not tackle the effects of climate change.”