Parts of New York City are sinking, while others are rising

A study led by NASA scientists has found that certain regions of New York City are either sinking or rising, and it’s not just due to modern human intervention – some of the reasons trace back to the last Ice Age.

While the elevation changes are just fractions of inches per year, the experts noted that they can increase or diminish local flood risks associated with sea level rise.

How the research was conducted 

The detailed analysis was conducted by experts from NASA’s Jet Propulsion Laboratory in California and Rutgers University in New Jersey.

The researchers used interferometric synthetic aperture radar (InSAR) data from 2016 to 2023. This advanced remote sensing technique merges multiple 3D observations of an area to expose surface movements or changes in topography.

Profound implications 

A considerable amount of the movement was detected in areas previously altered by human activity, such as land reclamation or the establishment of landfills. 

Such activities made the underlying ground more susceptible to compression, especially under the weight of new constructions.

Heavy ice burden

However, not all of the alterations were recent. The last ice age, which peaked around 24,000 years ago, saw vast parts of New England blanketed in ice. 

This heavy ice burden impacted the Earth’s mantle. Areas like New York City, which were located just outside the ice sheet’s periphery, have been undergoing a “rebalancing” of sorts, leading to the current sinking pattern.

Vertical land motion 

On average, the metropolitan area saw a decline of approximately 0.06 inches (1.6 millimeters) per year. To put it in perspective, that’s roughly the pace at which a toenail grows monthly. 

But certain landmarks and neighborhoods in New York have been sinking faster than this average. 

Brett Buzzanga, the study’s lead author, expressed excitement at the granularity of the data. 

“We’ve produced such a detailed map of vertical land motion in the New York City area that there are features popping out that haven’t been noticed before,” said Buzzanga.

Understanding these local elevation shifts is pivotal for flood mapping, especially given the global climate crisis and rising sea levels, noted David Bekaert, a JPL scientist.

Zones of change

A significant finding from the study highlights two regions in Queens, both associated with landfills, which are subsiding at alarming rates. 

One such area is runway 13/31 at LaGuardia Airport, descending at approximately 0.15 inches per year. The other notable location is the Arthur Ashe Stadium, sinking about 0.18 inches each year.

Other affected zones include parts of Governors Island, areas near Brooklyn’s Coney Island and Queens’ Arverne by the Sea built on artificial fill, and parts of New Jersey crisscrossed by Route 440 and Interstate 78.

Upward movement

Yet, not all areas are on a downward trajectory. Surprisingly, regions in East Williamsburg, Brooklyn, and Woodside, Queens, showed uplift. 

Woodside rose a notable 0.27 inches annually between 2016 and 2019. 

Further research is needed 

Study co-author Robert Kopp of Rutgers University said that 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 modifications associated with uplift,” said Kopp.

The scientists noted that cities like New York, which are investing in coastal defenses and infrastructure in the face of sea level rise, can benefit from high-resolution estimates of land motion.

With billions invested in coastal defenses and infrastructural adaptations, understanding and accounting for these subsiding and rising zones might just be the blueprint they need for a more resilient future.

The research is published in the journal Science Advances.

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