New York: New York City, one of the most populous and famous cities in the United States, is facing a serious threat of sinking into the ground, according to a new report by NASA. The report, published in Science Advances, reveals that some parts of the city are subsiding faster than others due to various factors, such as human activities and natural processes. The report also warns that the sinking land could worsen the impact of sea level rise and coastal flooding in the future.
The report is based on a detailed analysis of vertical land motion across the New York City metropolitan area from 2016 to 2023, using a remote sensing technique called interferometric synthetic aperture radar (InSAR). The technique combines two or more 3D observations of the same region from space to measure surface changes or topography. The researchers, from NASA’s Jet Propulsion Laboratory and Rutgers University, found that on average the metropolitan area subsided by about 0.06 inches (1.6 millimeters) per year – about the same amount that a toenail grows in a month.
However, some locations in the city showed much higher rates of subsidence, up to 0.18 inches (4.6 millimeters) per year. These locations include LaGuardia Airport, Arthur Ashe Stadium, and Coney Island, which are all built on former landfill sites that make the ground more compressible and prone to sinking. The researchers also identified some areas that showed modest uplift, such as parts of Queens and Brooklyn, which are located on more stable bedrock.
The report explains that some of the land motion in the city is related to human land-use practices, such as land reclamation, landfill construction, groundwater extraction, and building development. These practices can alter the load and stress on the ground, causing it to compact or rebound over time. Some of the land motion is also caused by natural processes dating back thousands of years to the most recent ice age. About 24,000 years ago, a huge ice sheet covered most of New England and northern New York, pushing down the Earth’s crust beneath it. After the ice sheet melted, the crust began to slowly rebound upward, while the areas around it that were raised by the ice sheet began to sink back down. New York City, which sits on the edge of this glacial rebound zone, is still experiencing this adjustment.
The report also highlights the implications of land motion for coastal flooding risk in New York City, which is already vulnerable to sea level rise and storm surges. The researchers estimate that by 2100, sea level could rise by about 2 feet (0.6 meters) in New York City relative to 2000 levels, depending on greenhouse gas emissions and ice sheet melt scenarios. This could increase the frequency and severity of flooding events in low-lying areas, especially during high tides and extreme storms. The report suggests that accounting for land motion is important for developing accurate flood maps and adaptation strategies for coastal communities.
The report is one of the first comprehensive studies of land motion in New York City using InSAR data from the Sentinel-1 satellites operated by the European Space Agency. The researchers hope that their findings will help improve the understanding and management of coastal hazards in New York City and other urban areas around the world.