Watch out Bangkok: Sea level rise likely to be faster, higher than expected

Melting ice from Antarctica could raise oceans by a metre before 2100 at current rates of greenhouse gas emissions, doubling previous forecasts, according to a study released Wednesday.

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Antarctica alone may lift seas a meter by 2100: study

March 2016, AFP – Melting ice from Antarctica could raise oceans by a metre before 2100 at current rates of greenhouse gas emissions, doubling previous forecasts for sea level rise, according to a study released Wednesday.

Such an abrupt change would spell disaster for major cities and coastal areas across the globe, forcing hundreds of millions of people to seek higher ground.

Over a longer timescale, the study concluded, the picture is even grimmer: within 500 years, Earth's once-frozen continent will have lifted water lines by more than 15 meters, reconfiguring the planet's coastlines.

"Frankly, I hope we're wrong about this," Robert DeConto, lead author of the study and a climate scientist at the University of Massachusetts, told AFP.

But independent experts contacted by AFP said the study was probably on target.

Scientists have long struggled to understand the role the Earth's southern extremity played during earlier periods of global warming – 125,000 and three million years ago – when temperatures barely warmer than our own raised oceans to levels six-to-10 metres higher than today.

"In both cases, the Antarctic ice sheet has been implicated as the primary contributor, hinting at its future vulnerability," the study said.

But how, exactly, the planet's ice continent – far colder than the Arctic, and thus less subject to melting – disintegrated remained a mystery.

Building on earlier work, DeConto and David Pollard, a climate scientist at Pennsylvania State University, created computer models integrating for the first time two mechanisms that appeared to solve the puzzle.

Coastal erosion is already a major problem in Thailand. Here, in nearby Samut Prakan, Wat Khun Samut Chin's ordination hall is slowly sinking due to rising sea levels. THANARAK KHUNTON

One is a process called hydrofracturing.

As any teenage can tell you, if you put a sealed bottle of water or beer in a freezer, the liquid will expand and crack the container.

"That's what happened here," said Anders Levermann, an expert on the dynamics of ice sheets at the Potsdam Institute in Germany and a lead author of the chapter on sea levels in the most recent Intergovernmental Panel on Climate Change (IPCC) report.

"You have melt water going deep into crevices in the ice sheet, and then it expands and cracks the ice open," pushing it toward the sea, he told AFP, commenting on the study.

The other natural mechanism is the breakup of buttressing ice shelves, and the failure of ice cliffs, that both act as dams for the ice sheets behind them.

"The recent modelling now favours the view that continuing rapid warming will cause sea level rise to be larger, and perhaps much larger, especially if we look beyond the end of this century," said Richard Alley, also a scientist at Pennsylvania State University.

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