Wall Street set for another big dive  

The SMH has a report on global warming and rising sea levels - Wall Street set for another big dive.

A predicted slowdown in Atlantic Ocean currents will cause sea levels along the US north-east coast to rise twice as fast as the global average, exposing New York and other big cities to violent and frequent storm surges, according to a new study.

Manhattan's Wall Street, barely a metre above sea level, for example, will find itself underwater more often as the 21st century unfolds, said the study, published online on Sunday in Nature Geoscience.

Sea levels vary across regions by up to 24 centimetres, influenced in part by powerful currents that course around the globe in a pattern called the thermohaline circulation.

In the Atlantic, warm water moving north along the surface from the Gulf of Mexico helps temper cold winters in western Europe and along the US east coast, while frigid Arctic waters run south along the bottom of the sea.

The UN's Intergovernmental Panel on Climate Change (IPCC) concluded in early 2007 that expanding ocean water driven by climate change will drive up sea levels, on average, from 18 to 59 centimetres by 2100, depending on how successful we are at slashing greenhouse gas emissions.

This rising water mark will erase several island nations from the map, and is likely to cause devastation in Asian and African deltas home to tens of millions of people.

More recent studies, taking the impact of melting ice sheets in Greenland and the Western Antarctic into account, forecast an even higher increase of at least one metre over the same period.

Jianjun Yin of Florida State University and two colleagues wanted to find out what impact these sea level rises would have at a regional level, especially along the American eastern seaboard.

The researchers analysed the projections of nearly a dozen state-of-the art climate change models, under three different greenhouse gas scenarios.

They found that sea levels in the North Atlantic adjusted in all cases to the projected slowing of the Gulf Stream and its northward extension, the North Atlantic Current.

The weakened currents account for nearly half of a predicted sea rise - from thermal expansion alone - of 36 to 51 centimetres for the US north-eastern coast, especially near New York, they found.