Sea level rise cannot be pumped away

Paradise Harbour, Antarctica, on March 4.

BURNING fossil fuels leads to greenhouse gas emissions that cause global warming. The consequent thermal expansion of ocean water and the melting of glaciers and ice sheets raise sea levels, which will continue for millennia. Under unabated warming, sea level rise may exceed 130 cm by 2100. Climate scientists at the Potsdam Institute for Climate Impact (PIK), Germany, explored whether unprecedented geoengineering such as pumping water masses on to the Antarctic continent could be used to mitigate the effects of climate change. “Our approach is definitely extreme, but so is the challenge of sea level rise,” said Katja Frieler, the lead author of the PIK study. “We explored a way to at least delay the rise of sea level we can no longer avoid.”

“Local adaptation, for instance, building dykes, will not be physically possible or economically feasible everywhere,” she pointed out. “Protection may depend on the nation’s economic situation..., and this clearly raises an equity issue,” she added. “Hence the interest in a universal protection measure. We wanted to check whether sacrificing the uninhabited Antarctic region might theoretically enable us to save populated shores around the world.”

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, at least 700 km, inland on to the Antarctic ice sheet. But the ice sheet is up to 4,000 m high. Pumping so much water that high up would require enormous amounts of energy (more than one-tenth of the present annual global energy supply to balance the current rate of sea level rise). Antarctica is very windy, so the power for the pumping could in principle be generated by wind turbines; yet this would require building roughly 850,000 wind energy plants. The costs would be much higher than those associated with local adaptation studies, though these by definition are limited in scope and scale, the scientists stated. So, rapid greenhouse gas emission reductions are indispensable if sea level rise is to be kept manageable.

Compiled by R. Ramachandran