NASA has recently revealed that the East Coast of the United States is facing a double threat – not only are rising sea levels posing a danger, but the coastline itself is sinking. Images shared by the space agency show that major cities such as New York and Baltimore are built on land that has been sinking rapidly, putting infrastructure, farmland, and wetlands at risk.
A team of scientists at Virginia Tech’s Earth Observation and Innovation Lab, funded by NASA, used satellite data and GPS sensors to monitor the motion of the coast. They discovered that between 2007 and 2020, the land in cities like New York, Baltimore, and Norfolk, Virginia, sank by an average of 1 to 2 millimeters per year. However, some counties in Delaware, Maryland, South Carolina, and Georgia experienced land subsidence at twice or three times that rate.
The problem is not limited to cities alone. Marshes are sinking at a rate of more than 3 millimeters per year, displacing forests and causing saltwater intrusion. In total, at least 897,000 structures, including highways and airports, are situated on sinking land along the coast.
The maps created by NASA using satellite data from the U.S., Japan, and Europe reveal that the Mid-Atlantic region is sinking at a higher rate due to the retreat of the Laurentide ice sheet 12,000 years ago. This ongoing sinking process also causes parts of the U.S. and Canada to rise. Charleston, one of the fastest-sinking cities, experiences subsidence of about 4 millimeters per year. With downtown sitting just 10 feet above sea level, the city is considering building an 8-mile seawall to protect against storm surges.
Leonard Ohenhen, a geophysicist at Virginia Tech, emphasized that subsidence is a major problem that often goes overlooked compared to rising sea levels. However, it poses significant risks to coastal residents, including damage to homes, infiltration of saltwater into farms and freshwater supplies, and other challenges.
While subsidence is a complex issue, it can be slowed down locally. Manoochehr Shirzaei, a co-author of the studies and director of the Virginia Tech lab, suggests that groundwater extraction and the construction of dams and other infrastructure can contribute to subsidence. The lab plans to extend its research techniques to the Gulf Coast and aims to map all coastlines worldwide.
The threat of sinking coastlines is a pressing issue that demands attention. As climate change continues to impact our planet, it is crucial to address both rising sea levels and subsidence to protect coastal communities and their valuable resources.
