NASA Study Reveals East Coast Sinking Threatens 2.1 Million People

The future of the U.S. East Coast is under threat not just from rising sea levels but also from the sinking of the land itself, as revealed by NASA images. Some regions are experiencing land subsidence of several millimeters annually. Utilizing satellite data and ground-based GPS sensors, a team of scientists from Virginia Tech’s Earth Observation and Innovation (EOI) Lab, funded by NASA, discovered that areas including major cities like New York, Baltimore, and Norfolk, Virginia, witnessed land sinking by 1 to 2 millimeters yearly between 2007 and 2020.

According to a study published in the journal PNAS Nexus, certain counties in Delaware, Maryland, South Carolina, and Georgia experienced double or triple the average sinking rate. The study highlights that the subsidence, reaching rates of 2 mm per year, affects around 2.1 million people, 867,000 properties, and essential infrastructure along the East Coast, posing a significant threat to metropolitan areas directly intersecting with rising seas.

This phenomenon could exacerbate the impacts of projected sea level rise, estimated to surpass one foot along most U.S. coasts by 2050, leading to heightened tidal flooding and infrastructure damage.

Leonard Ohenhen, a Virginia Tech geophysicist and co-author of the study, emphasized that subsidence, though often overlooked compared to global sea level rise, plays a crucial role in elevating water levels in many eastern U.S. regions.

The map provided illustrates the variability in land movement across the East Coast between 2007 and 2020, with blue areas indicating subsidence, particularly darker shades representing faster sinking, while dark red areas depict rising land. The satellite data used in the map, with an average spatial resolution of 50 meters per pixel, offers superior detail compared to previous ground-based sensor maps.

Manoochehr Shirzaei, another paper co-author and director of the EOI Lab, noted that while subsidence presents a challenge, it’s a problem that can be mitigated to some extent at local levels.

The mid-Atlantic coast is experiencing more significant sinking compared to the northeastern coast due to past ice sheet movements. Glacial isostatic adjustment, where land shifts in response to ice sheet melting, likely contributes to much of the observed sinking along the coast. Factors such as groundwater withdrawal and sediment blockage by dams may also drive subsidence in certain areas.

Cities like Charleston, South Carolina, are particularly vulnerable, sinking at a rate of about 4 mm annually, compounded by rising sea levels. Shirzaei pointed out that the situation on the Atlantic Coast is more severe than on the Pacific Coast due to its proximity to sea level and infrastructure.

Charleston’s increased tidal flooding frequency has prompted discussions about constructing an 8-mile seawall for storm surge protection.

Looking ahead, researchers aim to expand their mapping efforts to cover more of the U.S. coast, with the Gulf Coast next on their agenda. Shirzaei expressed the long-term goal of mapping global coastlines using their technique to empower cities worldwide in enhancing coastal resilience.

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