Antarctica: Sea-level rise too big to be pumped away

Washington DC: Sea level rise is likely to be a problem too big to handle as a new study suggests that geoengineers will not be able to pump away the rising tides.

The idea of unprecedented geo-engineering such as pumping water masses onto the Antarctic continent has been investigated by scientists at the Potsdam Institute for Climate Impact.

While the pumped water would certainly freeze to solid ice, the weight of it would speed up the ice-flow into the ocean at the Antarctic coast. To store the water for a millenium, it would have to be pumped at least 700 kilometer inland, the team found. Overall that would require more than one tenth of the present annual global energy supply to balance the current rate of sea-level rise.

Lead-author Katja Frieler said, "We explored a way to at least delay the rise of sea level we can no longer avoid by even the strictest climate-change mitigation strategies. This is estimated to reach about 40 cm by the end of the century. Our approach is definitely extreme, but so is the challenge of sea-level rise."

Burning fossil fuels leads to greenhouse-gas emissions that drive up global temperatures. Consequently, the thermal expansion of ocean water and the melting of glaciers and ice-sheets slowly raise sea levels, which will continue for millennia. Under unabated warming, sea level rise may exceed 130 centimeters by 2100.

"This is huge. Local adaptation, for instance building dikes, will not be physically possible or economically feasible everywhere," Frieler says, adding "Protection may depend on your economic situation - so New York might be saved, but sadly not Bangladesh, and this clearly raises an equity issue."

She noted that they wanted to check whether sacrificing the uninhabited Antarctic region might theoretically enable them to save populated shores around the world. Rising oceans are already increasing storm surge risks, threatening millions of people worldwide, and in the long run can redraw the planet's coastlines.

The scientists addressed the problem from an ice-dynamics perspective, using state-of-the-art computer simulations of Antarctica. Since the ice is continually moving, ocean water put on its surface can only delay sea-level rise and if it is placed too close to the coast, ice-sheet mass loss and thus sea-level rise after some time could even increase, they found. As a consequence the water has to be pumped a long way inland onto the ice sheet.

The costs are expected to be much higher than those associated with local adaptation in other studies, though these measures by definition are limited in scope and scale, the scientists stated.

"The magnitude of sea-level rise is so enormous, it turns out it is unlikely that any engineering approach imaginable can mitigate it," concludes co-author Anders Levermann, adding "Even if this was feasible, it would only buy time - when we stop the pumping one day, additional discharge from Antarctica will increase the rate of sea-level rise even beyond the warming-induced rate. This would mean putting another sea-level debt onto future generations."

Also, the most sensitive coastal ecosystems of Antarctica would of course be seriously affected by this measure.