New York Seas to Rise Twice as Much as Rest of U.S.

Posted: March 17, 2009 in environment
Richard A. Lovett
for National Geographic News
March 15, 2009

nolaSea levels around New York City and much of the U.S. Northeast will rise twice as much as in other parts of the United States this century, according to new climate models (U.S. Northeast map). Driven by changes in ocean circulation, the rapid sea level rise will bring increased risk of damage from hurricanes and winter storm surges, researchers say.

“Some parts of lower Manhattan are only 1.5 meters [5 feet] above sea level,” said lead study author Jianjun Yin, a climate modeler at Florida State University.

“Twenty centimeters [8 inches] of extra rise would pose a threat to this region.”

Yet New York, Boston, and Washington, D.C., area seas will rise 14 to 20 inches (36 to 51 centimeters) by 2100, according to the study, published online today in the journal Nature Geoscience.

Other U.S. cities, such as Miami and San Francisco, are expected to see only half as big an increase in sea levels.

Gulf Stream Forces to Weaken?

The reason U.S. Northeast seas are expected to rise disproportionately is because the forces that generate the North Atlantic’s Gulf Stream ocean current are projected to weaken in the coming decades.

New climate models predict that global warming will reduce the sinking of the cold water that drives the Gulf Stream. As a result, the deep ocean will begin to warm in the North Atlantic, Yin said.

As water around the current warms, it will expand, adding to the sea level rise caused by global factors such as melting ice caps and icebergs, the study says. (Related: “Small Melting Glaciers Will Speed Sea Level Rise, Study Says.”)

Ice Free Arctic by 2100?

Adding to those global factors is an Arctic Ocean that appears to be melting rapidly, said Julien Boé, a postdoctoral researcher at the University of California, Los Angeles, in another climate study in today’s Nature Geoscience.

After comparing a range of models with actual observations, his team predicts that the Arctic Ocean will be ice free during September as early as the end of this century.

Such studies are vital, experts say, because they offer scientists a more precise idea of how different regions might prepare for potential damage due to global warming.

“In both papers,” Boé said in an email, “the objective is to improve the projections of important aspects of regional climate change.”

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