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Melting of ice from Antarctica represents the largest uncertainty in future sea-level projections, says a new study.
According to the study by scientists at Germany's Potsdam Institute for Climate Impact Research (PIK), discharge of ice into the ocean from East Antarctica's shore could trigger an unstoppable rise in sea levels for thousands of years to come.
The study follows the most recent report by the Intergovernmental Panel on Climate Change (IPCC) that projects Antarctica's total sea level contribution to be up to 16cm within this century itself.
The findings published in the journal Nature Climate Change suggest that East Antarctica may cause a large global sea-level rise of 300-400cm on timescales beyond a century.
This will happen if Wilkes Basin, the region holding the largest volume of marine ice in East Antarctica, starts losing ice to warming oceans.
"East Antarctica's Wilkes Basin is like a bottle on a slant, once uncorked, it empties out," the study's lead author Matthias Mengel said in a statement.
"The full sea-level rise would ultimately be up to 80 times bigger than the initial melting of the ice cork," co-author Anders Levermann added.
The findings are based on computer simulations of the Antarctic ice flow. The simulations show that it would take five thousand to ten thousand years for the complete discharge of ice from the basin.
But once started, the discharge would slowly continue until the whole basin is empty, even if climate warming stopped.
"This is the underlying issue here. By emitting more and more greenhouse gases we might trigger responses now that we may not be able to stop in the future," Mengel said.
Such extensive sea level rise would put coastal cities such as Mumbai, Tokyo or New York at risk, the scientists said.
Earlier research considered only West Antarctica as unstable but the latest findings suggest that East Antarctica, which holds marine ice more than five times that of West Antarctica, might also be at risk.
"If half of that ice loss occurred in the ice-cork region, then the discharge would begin. We have probably overestimated the stability of East Antarctica so far," said Levermann.