The land beneath the New York City region, including the borough of Queens, pictured here, moves fractions of an inch each year. These movements are a legacy of the Ice Age and are also due to human land use. Credit: NASA/JPL-Caltech
Scientists using space radar have discovered that New York City’s land is sinking at varying rates due to human and natural factors. A few places go up.
Parts of the New York metropolitan area are sinking and rising at different rates due to factors ranging from land use practices to long-lost glaciers, scientists have found. Even if elevation changes seem small – fractions of centimeters per year – they can increase or decrease local flood risk from sea level rise.
The new study was published September 27 in Scientists progress by a team of researchers at NASA’s Jet Propulsion Laboratory (JPL) in Southern California and Rutgers University in New Jersey. The team analyzed vertical up and down ground movement – also known as uplift and subsidence – in the 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 to reveal surface movement or topography.
By mapping the vertical movement of land in the New York area, the researchers found that the land was sinking (shown in blue) by about 0.06 inches (1.6 millimeters) per year on average. They also detected a slight increase (shown in red) in Queens and Brooklyn. White dotted lines indicate county and borough boundaries.
Credit: NASA/JPL-Caltech/Rutgers University
Factors influencing land movement
Much of the observed movement occurred in areas where earlier changes to the Earth’s surface – such as land reclamation and landfill construction – made the soil softer and more compressible under later buildings .
Some of this movement 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 stretched across most of New England, and a wall of ice more than a mile high covered what is now Albany, in northern New York State. The earth’s mantle, a bit like a bent mattress, has slowly readjusted itself since then. New York City, located on high ground just outside the edge of the ice sheet, is sinking again.
Detailed findings and impacts
Scientists found that, on average, the metropolitan area has subsided about 0.06 inches (1.6 millimeters) per year, or about the same amount as a toenail grows in a month. Using ESA (European Space Agency) radars Sentinel-1 satellites, combined with advanced data processing techniques, mapped movement in detail and identified neighborhoods and landmarks – down to a track airport and a tennis stadium – which are sinking faster than average.
The team identified hot spots: At left, Runway 13/31 at LaGuardia Airport in Queens is sinking at a rate of about 0.15 inches (3.7 millimeters) per year; at right, part of Newtown Creek, a Superfund site in East Williamsburg, Brooklyn, is rising unevenly by about 0.06 inches (1.6 millimeters) per year.
Credit: NASA/JPL-Caltech/Rutgers University
“We produced such a detailed map of vertical land movement in the New York region that there are features that had not been noticed before,” said lead author Brett Buzzanga, a postdoctoral researcher at JPL.
David Bekaert, a JPL scientist and principal investigator on the project, said tracking local elevation changes and relative sea level can be important for mapping and flood planning purposes. This is particularly critical as Earth’s changing climate pushes oceans higher around the world, leading to more frequent nuisance flooding and exacerbating destructive storm surges.
Important hotspots
The team identified two notable subsidence hotspots located adjacent to landfills in Queens. One of them, Runway 13/31 at LaGuardia Airport, is sinking at a rate of about 0.15 inches (3.7 millimeters) per year. Scientists noted that the airport is undergoing an $8 billion renovation, designed in part to alleviate flooding from rising Atlantic Ocean waters. They also identified Arthur Ashe Stadium, which is sinking at a rate of about 0.18 inches (4.6 millimeters) per year and required the construction of a lightweight roof during the renovation to reduce its heaviness and its 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 earth from early 20th century subway excavations – as well as sites near the ocean at Coney Island and Arverne in Brooklyn. the Queens Sea which were built on an artificial embankment. Similar levels of subsidence have been observed beneath Route 440 and Interstate 78 in suburban New Jersey, which pass through historic infill sites, and at Rikers Island, enlarged to its current size by landfilling. .
Scientists also found a previously unidentified increase in East Williamsburg, Brooklyn – increasing about 0.06 inches (1.6 millimeters) per year – and in Woodside, Queens, which increased by 0.27 inches (6. 9 millimeters) per year between 2016 and 2019 before stabilizing. Co-author Robert Kopp of Rutgers University said groundwater pumping and injection wells used to treat polluted water may have played a role, but further investigation is needed. “I’m intrigued by the potential of using high-resolution InSAR to measure these kinds of relatively short-lived environmental changes associated with uplift,” Kopp said.
Scientists said cities like New York, which invest in coastal defenses and infrastructure in the face of rising sea levels, can benefit from high-resolution estimates of land movement.
Monitoring and future plans
The JPL-led OPERA (Observational Products for End-Users from Remote Sensing Analysis) project will detail surface movement across North America in a future data product. To do this, it will leverage InSAR data from ESA’s Sentinel-1 and the upcoming NISAR (NASA-Indian Space Research Organization Synthetic Aperture Radar) mission, scheduled for launch in 2024. The information from OPERA will help scientists to better monitor the vertical movement of the ground along the Earth. with other changes linked to natural hazards.
2023-10-12 17:08:38
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