New York City is sinking, but not to worry yet

New York City has yet another problem to worry about, in addition to rising oceans, as it is slowly sinking under the weight of its skyscrapers, homes, asphalt, and humanity. New research has found that the city’s landmass is sinking at an average rate of 1 to 2 millimeters per year, which is referred to as “subsidence.” The study, published in the journal Earth’s Future, sought to estimate how the weight of the city itself is affecting this natural process. While ground compression is a natural phenomenon everywhere, the massive weight of the city’s more than one million buildings, made up of concrete, metal, and glass, is adding up to about 1.7 trillion tons (1.5 trillion metric tons) of pressure on the Earth. This is equivalent to the mass of 4,700 Empire State buildings, as per the study’s calculations.

The rate of compression varies across the city, with the skyscrapers of Midtown Manhattan built largely on rock, which compresses very little, while some parts of Brooklyn, Queens, and downtown Manhattan are on looser soil and sinking faster. Although the process is gradual, lead researcher Tom Parsons, from the US Geological Survey, said that parts of the city will eventually be under water, and it is inevitable that the ground is going down, and the water is coming up.

New York City’s Risk of Flooding

The study notes that while buildings themselves are contributing, albeit incrementally, to the shifting landscape, it will take hundreds of years before New York becomes America’s version of Venice, which is famously sinking into the Adriatic Sea. However, parts of the city are more at risk, and “the average elevation in the southern part of the island is only 1 or 2 meters (3.2 or 6.5 feet) above sea level – it is very close to the waterline, and so it is a deep concern,” Parsons said, referring specifically to Manhattan.

Due to the ocean rising at a similar rate as the land is sinking, the Earth’s changing climate may speed up the timeline for parts of the city to disappear under water. New York City is already at risk of flooding due to massive storms that can cause the ocean to swell inland, or inundate neighborhoods with heavy rain. The resulting flooding could have destructive and deadly consequences, as demonstrated by Superstorm Sandy a decade ago and the still-potent remnants of Hurricane Ida two years ago.

Andrew Kruczkiewicz, a senior researcher at Columbia University’s Climate School, said that “from a scientific perspective, this is an important study.” Its findings could help inform policymakers as they draft ongoing plans to combat, or at least forestall, the rising tides. “We can’t sit around and wait for a critical threshold of sea level rise to occur because waiting could mean we would be missing out on taking anticipatory action and preparedness measures.”

New York City isn’t the only place sinking. San Francisco is also 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.

Parsons and his team of researchers reached their conclusions using satellite imaging, data modeling, and mathematical assumptions. They note that it doesn’t mean that buildings should stop being constructed as the buildings themselves are not the sole cause of the sinking city, as there are many factors involved. The study’s purpose was to point out in advance before it becomes a more significant problem.

Tracy Miles, a New Yorker, initially found the idea to be made-up, but on looking at sailboats bobbing in the water edging downtown Manhattan, she reconsidered and said, “We do have an excessive amount of skyscrapers, apartment buildings, corporate offices, and retail spaces.”

As New York City slowly sinks, its residents must be aware of the risks of flooding and take anticipatory measures. The city’s policymakers must also consider the impact of rising tides and take steps to combat or forestall them.