As rising oceans threaten NYC, study documents another risk: The city is sinking

NEW YORK (AP) — If rising oceans aren’t worry enough, add this to the risks New York City faces: The metropolis is slowly sinking under the weight of its skyscrapers, homes, asphalt and humanity itself.

New research estimates the city’s landmass is sinking at an average rate of 1 to 2 millimeters per year, something referred to as “subsidence.”  That natural process happens everywhere as ground is compressed, but the study published this month in the journal Earth’s Future sought to estimate how the massive weight of the city itself is hurrying things along.

More than 1 million buildings are spread across the city’s five boroughs. The research team calculated that all those structures add up to about 1.7 trillion tons (1.5 trillion metric tons) of concrete, metal and glass — about the mass of 4,700 Empire State buildings — pressing down on the Earth.

The rate of compression varies throughout the city. Midtown Manhattan’s skyscrapers are largely built on rock, which compresses very little, while some parts of Brooklyn, Queens and downtown Manhattan are on looser soil and sinking faster, the study revealed.

While the process is slow, lead researcher Tom Parsons of the U.S. Geological Survey said parts of the city will eventually be under water.  But no need to invest in life preservers just yet, Parsons assured.

The study merely notes buildings themselves are contributing, albeit incrementally, to the shifting landscape, he said. Parsons and his team of researchers reached their conclusions using satellite imaging, data modeling and a lot of mathematical assumptions.

It will take hundreds of years — precisely when is unclear — before New York becomes America’s version of Venice, which is famously sinking into the Adriatic Sea.  But parts of the city are more at risk.  New York City isn’t the only place sinking. San Francisco also is putting considerable pressure on the ground and the region’s active earthquake faults.

In Indonesia, the government is preparing for a possible retreat from Jakarta, which is sinking into the Java Sea, for a new capital being constructed on the higher ground of an entirely different island.

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