New York is sinking, or rather, the city is being drowned by its skyscrapers. That’s the conclusion of a new study that modeled the geology beneath the city by comparing it with satellite data.
Manhattan Bridge, New York. Image credit: Patrick Tomasso via Unsplash, free license
There are many reasons for the gradual sinking of the Earth’s surface, but the weight of the cities themselves is rarely studied.
The study found that New York is sinking 1-2 millimeters per year due to the weight of tall buildings. A few millimeters may not seem like much, but some parts of the city are sinking much faster.
The deformation could spell trouble for the low-lying city of more than 8 million people. These results should encourage further efforts to develop climate change mitigation strategies to combat increased flood risk and sea level rise.
New York. Image credit: Thomas Habr via Unsplash, free license
In this new study, researchers calculated the combined mass of about 1 million buildings in New York City to be 764,000,000,000,000,000 kilograms. They then divided the city into a 100 x 100 meter square grid and, taking into account the force of gravity, converted the mass of the buildings into downward pressure.
Their calculations only include the mass of buildings and the things inside them, not New York’s roads, sidewalks, bridges, railroads, and other paved areas. Even with these limitations, these new calculations refine previous observations of the city’s collapse by taking into account the complex surface geology beneath New York City, which includes deposits of sand, silt, and clay, as well as rock outcrops.
By comparing these models with satellite data that describes the land surface elevation, the team determined the city’s subsidence. The researchers warned that increasing urbanization, including the draining of groundwater, could only add to New York’s problem of “sinking” into the ocean.
New York at night. Image credit: Andre Benz via Unsplash, free license
New York is certainly not the only such city in the world. A quarter of Indonesia’s capital, Jakarta, by 2050 could end up underwater as parts of the city sink almost 11 cm a year due to groundwater extraction. More than 30 million Jakarta residents are now considering relocating.
By comparison, New York City ranks third in terms of future flood risk. Much of lower Manhattan is only 1 to 2 meters above the current sea level. The hurricanes in 2012 and 2021 also showed how quickly the city can be flooded.
In 2022, a study of 99 coastal cities around the world found that subsidence may actually be bigger than estimated. In most of the cities surveyed, the land is sinking faster than the sea level is rising, meaning residents will face flooding sooner than climate models predict.
Written by Alius Noreika
