New York City is experiencing sinking ground due to a combination of factors, including the long-lasting effects of the ice age and human activities, according to a new study. Researchers from NASA’s Jet Propulsion Laboratory and Rutgers University used a remote sensing technique called interferometric synthetic aperture radar (InSAR) to analyze vertical land motion in the metropolitan area from 2016 to 2023.
The study found that much of the observed motion occurred in areas where previous modifications to the Earth’s surface, such as land reclamation and the construction of landfills, made the ground looser and more compressible. Additionally, natural processes dating back to the most recent ice age, approximately 24,000 years ago, are contributing to the sinking. When a massive ice sheet covered New England, the land around New York City was raised and is now readjusting, causing subsidence.
On average, the metropolitan area is subsiding at a rate of about 0.06 inches per year. The researchers used radar data from the European Space Agency’s Sentinel-1 satellites to map the motion in detail and identify specific neighborhoods and landmarks that are sinking more rapidly than average.
The findings have important implications for flood mapping and planning purposes, particularly as rising sea levels due to climate change pose a greater risk of flooding and storm surges. By tracking local elevation changes and relative sea level, scientists can better understand and mitigate these risks.
The study also identified specific hotspots of subsidence in New York City. For example, LaGuardia Airport’s runway 13/31 is sinking at a rate of about 0.15 inches per year. The airport, which is currently undergoing a major renovation, aims to address flooding concerns caused by the rising waters of the Atlantic Ocean. Another notable hotspot is Arthur Ashe Stadium, which is sinking at a rate of about 0.18 inches per year. During its renovation, a lightweight roof was constructed to reduce its weight and the amount of subsidence.
The scientists also discovered areas of uplift, such as in East Williamsburg, Brooklyn, and Woodside, Queens. Further investigation is needed to understand the causes of these uplifts, which could be related to groundwater pumping and the treatment of polluted water through injection wells.
Overall, the detailed map of vertical land motion in the New York City area provides valuable insights for the city’s coastal defenses and infrastructure planning in the face of sea-level rise. The researchers hope that their ongoing project, OPERA (Observational Products for End-Users from Remote Sensing Analysis), will expand surface displacement monitoring across North America using InSAR data from ESA’s Sentinel-1 satellites and the upcoming NISAR mission from NASA and the Indian Space Research Organization.
Understanding and monitoring vertical land motion, along with other changes related to natural hazards, will aid in protecting coastal cities like New York from the increasing risks associated with climate change.
