RAPIDLY RISING SEA LEVEL CAUSE FOR ALARM: Scientist

The sea level on a stretch of the US
Atlantic coast that features the cities of New York, Norfolk and Boston is rising up to four times faster than the global average.

This increases the flood risk for one of the world's most densely-populated coastal areas and threatens wetland habitats, said a study reported in the journal Nature Climate Change.

Since about 1990, the sea level along the 1,000-kilometre (620-mile) "hotspot" zone has risen by two to 3.7 millimetres (0.08 to 0.15 inches) per
year.

The global rise over the same period was between 0.6 and one millimetre per year, said the study by the US Geological Survey (USGS). If global temperatures continue to rise, the sea
level on this portion of the coast by 2100 could rise up to 30 centimetres over and above the one-metre global surge projected by scientists, it added.

The localised acceleration is thought to be caused by a disruption of Atlantic current circulation. "As fresh water from the melting of the Greenland Ice Sheet enters the ocean, it disrupts this circulation, causing the currents to slow down,"

USGS research oceanographer and study co-author Kara Doran explained. "When the Gulf Stream current weakens, sea levels rise along the coast and the greatest amount of rise happens north of where the Gulf
Stream leaves the coast (near Cape Hatteras).

"Extreme water levels that happen during winter or tropical storms, perhaps once or twice a year, may happen more frequently as sea level rise is added to storm surge," Doran told AFP.
"Scientists predict that this will lead to increased beach erosion and more frequent coastal flooding."

Another study has shown a one-metre sea level rise to increase New York's severe flooding risk from one incident every century to one every three years.

The USGS report was based on actual tide level measurements, said Doran.

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