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A new study has found that New York City is sinking at a rate of 1-2 millimeters per year due to the weight of its skyscrapers. Some parts of the city are sinking even faster, which could pose challenges for the low-lying city, home to more than 8 million people. The study highlights the need for mitigation strategies to counter rising flood risk and sea levels. The researchers calculated the combined mass of over 1 million buildings in the city to be 764 billion kg or 1.68 trillion pounds, and converted it into downward pressure, taking into account gravity.
New York is slowly sinking under the weight of huge skyscrapers
New York is sinking and its skyscrapers are tearing it down. This is the discovery of a new study that has modeled the geology beneath the city and compared it to satellite data. The publication Science Alert told in more detail.
Technically referred to as subsidence, this is the gradual subsidence or sudden subsidence of the earth’s surface. It occurs when soft sediments are displaced or ground loads push the earth’s surface deeper. The reasons are many, but the weight of the cities themselves is rarely studied.
The study showed that New York is sinking at a rate of 1-2 millimeters per year under the weight of its skyscrapers. A few millimeters may not seem like much, but some parts of the city are sinking much faster.
The deformation could pose challenges for the low-lying city of more than 8 million people, so the results should spur further efforts to develop mitigation strategies to counter rising flood risk and rising sea levels.
“The goal of the study is to raise awareness that each additional high-rise building built on a coast, river or lakeside could increase the risk of future flooding,” write geologist Tom Parsons of the US Geological Survey and his colleagues at the University of Rhode Island.
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It is also reminiscent of the totality of human constructs. As of 2020, scientists estimate that everything humans have ever created was close to or already exceeded the dry weight of every living thing on Earth. Buildings and roads weigh more than all the trees and shrubs put together; plastics weigh as much as twice the weight of animals.
In this study, Parsons and colleagues calculated the combined mass of over 1 million buildings in New York City to be 764,000,000,000 kg or 1.68 trillion pounds. They then divided the city into a 100-by-100-meter grid of squares and converted the mass of the building into downward pressure, taking into account gravity.
Their estimates only include the mass of buildings and their contents, not the roads, sidewalks, bridges, railroads, and other paved sections of New York City. Even with these limitations, these new calculations refine past observations of subsidence in the city, given the complex surface geology beneath New York City, which is composed of sand, silt, and clay lake deposits.
By modeling the behavior of these substrates, studies have shown that clay-rich soils and artificial embankment are particularly prone to subsidence. More elastic soils bounce back after construction, while the bedrock on which many skyscrapers are anchored does not move as much.
By comparing these models with satellite data that measures the height of the earth’s surface, the team mapped subsidence estimates across the city. The researchers warn that increased urbanization, including draining and pumping groundwater, could only exacerbate New York’s subsidence problem.
New York is certainly not alone in its decline. A quarter of Indonesia’s capital, Jakarta, could be underwater by 2050, and parts of the city are sinking nearly 11 centimeters a year due to groundwater pumping. More than 30 million Jakarta residents are currently considering relocating the city or doubling down on climate change efforts.
By comparison, New York is the third most prone to flooding in the future. Most of lower Manhattan is only 1 and 2 meters above present-day sea level. The 2012 (Sandy) and 2021 (Ida) hurricanes also showed how quickly a paved city can be inundated with water.
“New York City is a symbol of growing coastal cities around the world that have been observed to subside, meaning that there is a common global issue of the need to mitigate the effects of rising flood risk,” the researchers conclude.
A 2022 study of 99 coastal cities around the world found that subsidence may actually be a bigger or at least underestimated problem than sea level rise. In most of the cities studied, land is sinking faster than sea levels are rising, meaning residents will experience flooding sooner than climate models predict.
Although tons of skyscrapers have already been built, the future trajectory of our planet is not predetermined, and reducing greenhouse gas emissions is the best way to limit future risks, whether it be sea level rise or hurricanes.
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