So far considered “a sleeping giant” the East Antarctic Ice Sheet could melt if carbon dioxide levels keep increasing a new study warns. Carbon dioxide levels above 600 parts per million could induce a rapid melting of the East Antarctic Ice Sheet adding several tenths of meters of sea level rise a new study says.

Glaciers drain the large ice sheet of Antarctica, in West Antarctica they are already melting in response to current global warming, but the much larger East Antarctic Ice Sheet, which sits mostly on rock above sea-level, was thought to be more stable. New research shows that it will melt if CO2 levels of 600ppm or above are reached and sustained for centuries to millennia. Picture: Katja Riedel
Glaciers drain the large ice sheet of Antarctica, in West Antarctica they are already melting in response to current global warming, but the much larger East Antarctic Ice Sheet, which sits mostly on rock above sea-level, was thought to be more stable. New research shows that it will melt if CO2 levels of 600ppm or above are reached and sustained for centuries to millennia. Picture: Katja Riedel

Scientists have identified a carbon dioxide “danger zone” for the demise of the East Antarctic Ice Sheet by assembling a detailed timeline surrounding the ice sheet’s inception around 34 million years ago. The research has led to a warning from a leading Antarctic expert that the world is on track for massive sea level rises resulting from the melting of an ice sheet.
The research, involving scientists from Victoria University of Wellington, New Zealand, has revealed that if carbon dioxide levels in the atmosphere continue increasing as predicted, the giant East Antarctic Ice Sheet will melt. “Our study shows that this ice sheet becomes unstable and melts if carbon dioxide levels in the atmosphere reach 600 parts per million—levels which may be reached by the end of the century if emissions reductions targets agreed to recently in Paris are not met,” says Professor Tim Naish, Director of Victoria University’s Antarctic Research Centre. “If the Antarctic ice sheet completely melted, global sea level would rise about 60 metres. It’s a sleeping giant.”
The research, published in March in the international journal Science, documents the growth of the first continent-wide ice sheet on Antarctica 34 million years ago. Led by Italian scientist Professor Simone Galeotti from the University of Urbino, the research is based on geological drill cores taken from the Ross Sea near New Zealand’s Scott Base 16 years ago by the international Cape Roberts Drilling Project.

Drilling rig of the Cape Roberts Project on the Ross Sea ice. The rig was used for three years to recover sediment cores for the geological reconstruction of Antarctic glaciation history. (Photo: Hans Grobe, AWI/CPR)
Drilling rig of the Cape Roberts Project on the Ross Sea ice. The rig was used for three years to recover sediment cores for the geological reconstruction of Antarctic glaciation history. (Photo: Hans Grobe, AWI/CPR)

The Cape Roberts Project: Between 1997 and 1999 the international Cape Roberts Project (CRP) has recovered up to 1,500 m long drill cores in the Ross Sea, Antarctica to reconstruct the glaciation history of Antarctica. The cores, ranging in age from 34 to 17 million years old, represent a period when the Victoria Land coast of Antarctica changed from a cool temperate to a subpolar climate. Differences in sediment layers record advances and retreats of the East Antarctic ice sheet that are caused by changes in Earth’s orbit around the sun, known as Milankovitch cycles. Orbital changes affected the distance between Antarctica and the sun and were the main reason why earth had moved in and out of ice ages and warm period naturally.

Lowermost sections of the Cape Roberts Project sediment core, segments have a length of 1 m and consist of sandstone (Photo: Hans Grobe, AWI/CRP)
Lowermost sections of the Cape Roberts Project sediment core, segments have a length of 1 m and consist of sandstone (Photo: Hans Grobe, AWI/CRP)

”The drill cores show that the first Antarctic ice sheet was quite dynamic. It advanced and retreated many times between 34 to 35 million years ago before finally stabilising at its largest extent when atmospheric carbon dioxide levels dropped below a threshold of 600 parts per million,” says Tim Naish, who participated in the original drill core expedition and is a lead author on the paper.
Concentrations of the greenhouse gas reached 400 ppm last year, well above its 280 ppm preindustrial level. “With present-day emission rates, it’s expected that we’ll reach 600 ppm before the end of this century,” says Simone Galeotti. Based on CO2 levels when the ice sheet formed, the researchers report that Antarctica’s ice will be “dramatically” more vulnerable to melting once CO2 surpasses 600 parts per million in the atmosphere
“We know that parts of the ice sheet sitting below sea-level in West Antarctica are already melting in response to current global warming, but the much larger East Antarctic Ice Sheet, which sits mostly on rock above sea-level, was thought to be more stable,” says Professor Naish. “We found it is vulnerable, and was much smaller the last time atmospheric carbon dioxide levels matched those predicted before the end of the century.”

Source: Antarctic Research Centre, Victoria University Wellington