New York City areas are sinking and rising

Scientists using space-based radar have found that the ground in New York City is sinking at varying rates due to human and natural factors. Some points are rising.

Scientists have discovered that parts of the New York City metropolitan area are sinking and rising at different rates due to factors ranging from land use practices to long-lost glaciers. While elevation changes seem small — fractions of an inch per year — they can enhance or reduce local flood risks associated with sea level rise.

The new study was published on September 27 Advancement of science By a team of researchers from NASAjet propulsion laboratory (Jet Propulsion Laboratory) in Southern California and Rutgers University in New Jersey. The team analyzed the ups and downs Vertical ground movement — also known as the rise and fall — across the metropolitan area from 2016 to 2023 using a remote sensing technology called interferometric synthetic aperture radar (InSAR). This technique combines two or more 3D observations of the same area to detect surface or terrain movement.

By mapping vertical land movement across the New York City area, the researchers found that the land is sinking (indicated in blue) by about 0.06 inches (1.6 mm) per year on average. They also detected a modest increase (shown in red) in Queens and Brooklyn. White dotted lines indicate county/town boundaries.
Image source: NASA/JPL-Caltech/Rutgers University

Factors affecting the movement of the Earth

Most of the movement they observed occurred in areas where previous modifications to the land surface — such as land reclamation and the construction of landfills — had made the ground looser and more compressible under later buildings.

Some of the movement is also caused by natural processes dating back thousands of years to the most recent Ice Age. About 24,000 years ago, a massive ice sheet spread across much of New England, and a wall of ice more than a mile high covered what is today Albany in upstate New York. The Earth’s mantle, which is a bit like an elastic mattress, has been slowly resetting since then. New York City, which sits on high ground beyond the edge of the ice sheet, is now sinking again.

Detailed results and implications

Scientists found that the metropolitan area thins on average about 0.06 inch (1.6 mm) per year, the same amount a toenail grows in one month. Using existing radars at the European Space Agency (ESA)European Space Agency) Sentinel-1 satellites, combined with advanced data processing techniques, have mapped detailed movement and identified neighborhoods and landmarks — down to an airport runway and a tennis court — that are receding more quickly than average.

The team identified hotspots: On the left, Runway 13/31 at LaGuardia Airport in Queens, receding at a rate of about 0.15 inches (3.7 mm) per year; On the right, part of Newtown Creek, a Superfund site in East Williamsburg, Brooklyn, is rising unevenly at about 0.06 inch (1.6 mm) per year.
Image source: NASA/JPL-Caltech/Rutgers University

“We produced a detailed map of vertical ground motion in the New York City area, where features that had not been observed before emerged,” said lead author Brett Buzanja, a postdoctoral researcher at JPL.

Tracking local elevation changes and Relative sea level They can be important for flood mapping and planning purposes. This is especially important because Earth’s changing climate is causing oceans to rise around the world, creating more frequent phenomena. Annoying flood Destructive events and storm surges.

Important hotspots

The team identified two notable landing hotspots at a site co-located with landfills in Queens. The first, Runway 13/31 at LaGuardia Airport, is falling at a rate of about 0.15 inches (3.7 mm) per year. Scientists noted that the airport is undergoing an $8 billion renovation aimed in part at mitigating flooding caused by rising water levels in the Atlantic Ocean. They also identified Arthur Ashe Stadium, which is sinking at a rate of about 0.18 inches (4.6 mm) per year and required the construction of a lightweight roof during the renovation to reduce its heaviness and the amount of subsidence.

Other subsidence hotspots include the southern portion of Governors Island — built on 38 million square feet (3.5 million cubic meters) of rock and dirt from early 20th-century Underground excavations — as well as the near-ocean sites of Brooklyn’s Coney Island and Arverne by the Sea. In Queens which was built on artificial infill. Similar levels of subsidence have been observed below Route 440 and Interstate 78 in suburban New Jersey, which traverse historic fill sites and, at Rikers Island, expanded to their present size by landfilling.

Scientists also found previously unquantified elevation in East Williamsburg, Brooklyn — where it rose by about 0.06 inches (1.6 mm) per year — and in Woodside, Queens, which rose by 0.27 inches (6.9 mm) per year between 2016 and 2019 before leveling off. Co-author Robert Cobb of Rutgers University said groundwater pumping and injection wells used to treat contaminated water may have played a role, but more research is needed. “I’m fascinated by the potential of using high-resolution InSAR to measure these types of relatively short-lived environmental modifications associated with elevation,” Cobb said.

Cities like New York, which are investing in coastal defenses and infrastructure in the face of sea level rise, could benefit from high-resolution estimates of ground motion, the scientists said.

Monitoring and future projects

Led by JPL Opera (Monitoring Products for End-Users of Remote Sensing Analysis) will detail surface displacement across North America in a future data product. To do this, it will make use of InSAR data from ESA’s Sentinel-1 and from forthcoming Nazar The NASA/ISRO Synthetic Aperture Radar mission is scheduled to launch in 2024. Information from OPERA will help scientists better monitor Earth’s vertical motion along with other changes associated with natural hazards.

Reference: “Local uplift, large-scale subsidence, and the implications of sea level rise in the New York City metropolitan area” by Brett Buzanga, David B. S. Pickart, and Benjamin D. Hamlington, and Robert E. Cope, Marin Govorcin, and Kenneth J. Miller, September 27, 2023, Advancement of science.
doi: 10.1126/sciadv.adi8259