New York City is sinking, but some parts of it are sinking faster than others and are causing flooding risks as sea levels continue to rise, say researchers who published their study on Wednesday.
“If you’re an average citizen in a coastal city, I think it’s important that you understand what the vertical land motion component does and how it can change the susceptibility to flooding, even from one neighborhood to the next,” said Brett Buzzanga, lead author of the study and a coastal scientist at NASA’s Jet Propulsion Laboratory.
The researchers - who hail from NASA’s Jet Propulsion Laboratory in Southern California and Rutgers University in New Jersey - made their discovery using space-based radar technology. Officials analyzed upward and downward vertical land motion across the metropolitan area from 2016 to 2023 using the interferometric synthetic aperture radar (InSAR).
“We highlight with really unprecedented detail the differences throughout the region and that some spots can be sinking faster than others and that can cause more flooding in some spots,” said Buzzanga. “This is going to be the same in any city.”
The study found that a runway at LaGuardia Airport, Arthur Ashe Stadium, Interstate 78, and Highway 440 are sinking at more than 2 millimeters a year. But on average, the entire city sinks at 1.6 millimeters per year.
But the study found shocking numbers in other US locations as well, including parts of Lousisiana's New Orleans, which has experienced 40 millimeters of sinking per year. The study also found some instances of rising land, including Brooklyn, where East Williamsburg’s Newton Creek rose about 2 millimeters every year.
It's suggested that a large-scale project in which they are treating and recovering polluted groundwater from the creek’s aquifer could be what is causing the land to rise.
While there are a few different reasons as to why land would sink, according to the researchers, these sites all have one thing in common: they used to be landfills in the past. And therefore, are more likely to compress at a faster speed than “something built on more solid ground”, says Buzzanga.
Meanwhile, some of the motion can also be attributed to natural processes that date back thousands of years to the most recent ice age. According to NASA, about 24,000 years ago a large ice sheet spread across most of New England while a mile-high wall of ice sat on top of what is now known as Albany, New York. The ice caused Earth’s crust to stretch and sag, but lifted New York upward. Since then, New York City had been readjusting to sink back down after the ice age.
But either way, land in New York City is sinking, and with rising sea levels, damage caused by flooding and other extreme weather will have adverse effects. One study estimated that about $8 billion in damages were caused by sea level rise during Superstorm Sandy in 2012.
“There’s more damage that can be done with higher sea levels and lower land together,” said Buzzanga. “It’s kind of adding to the background state on which these storms act. There’s more water to slosh around.”
He adds that he and his team are planning to create an updated version of their algorithm, which will be shared publicly so information about sinking and rising land can be used to help communities prepare for the future.
The team's findings were published in the journal Science Advances.