Think or swim: Can we hold back the oceans?

Not even massive geoengineering projects will stop the seas’ relentless rise. Maybe it’s time we found somewhere to put all that excess water

By Stephen Battersby 

FOR some, the end may come slowly, as the seas creep a little higher each year. That was the fate of the ancient cities of Herakleion and Eastern Canopus, which took centuries to be swallowed up. Elsewhere, the land may be eroded by waves and swept away by currents, as happened to the medieval English port of Dunwich. Or disaster could strike almost overnight, when a storm joins forces with the tides to create a surge that overwhelms flood defences, leaving the survivors wondering if there is any point in rebuilding.

As the world gets warmer, sea levels are rising. It has been happening at a snail’s pace so far, but as it speeds up more and more low-lying coastal land will be lost. At risk are many of the world’s cities and huge areas of fertile farmland. The sea is set to rise a metre or more by the end of this century, swamping much vital intrastructure and displacing hundreds of millions of people (New Scientist, 1 July 2009, p 28). And that’s just the start. "Unless there is a rapid and dramatic about-face in emissions – which no one expects – the next century will be far worse than this century," says glaciologist Bob Bindshadler of NASA’s Goddard Space Flight Center in Greenbelt, Maryland.

Throwing trillions of dollars at the problem could probably save big cities such as New York, London and Shanghai, but the task of defending all low-lying coastal areas and islands seems hopeless. Or is it? What if, instead of fighting a rearguard action against the encroaching oceans, we stopped sea levels rising at all? Could we find a way to slow the accelerating glaciers, drain seas into deserts or add more ice to the great ice caps of Greenland and Antarctica? …

… One of the reasons why the great ice sheets of Greenland and Antartica are already shrinking is that the ice is draining off the land faster. Ice floating on the surrounding seas usually acts as a brake, holding back glaciers on land, so as this ice is lost the glaciers flow faster. The acceleration of the Jakobshavn glacier in Greenland is thought to be the result of warm currents melting the floating tongue of the glacier. Other outlet glaciers are being attacked in a similar way.

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