A new NASA-led study has revealed that many of the world’s coastal cities are sinking, making them more vulnerable to rising sea levels than previously thought. Researchers found that in some regions, land is subsiding so rapidly that flood risks could double by 2050, far exceeding earlier projections.
Published in Science Advances, the study used satellite data from ESA’s Sentinel-1 mission to track vertical land motion along California’s coast from 2015 to 2023. The findings show that in areas like San Francisco Bay, land is sinking by over 10 millimeters per year, potentially leading to more than 45 centimeters of local sea level rise by mid-century.
While melting ice caps and climate change have long been blamed for rising seas, the study highlights that human activities such as excessive groundwater extraction, oil drilling, and rapid urbanization are accelerating land subsidence. This means coastal defenses designed to withstand projected sea level rise may already be outdated, putting cities at risk of earlier and more frequent flooding.
Researchers also identified areas where land is rising, such as Santa Barbara and Long Beach, due to groundwater recharge and industrial water injection. However, these changes remain unpredictable, complicating climate models.
With millions of people living in sinking coastal cities, scientists stress the need for immediate action. NASA’s OPERA project is now using satellite-based monitoring to track land movement across North America, helping governments and city planners develop better strategies for coastal resilience.