Flaws Identified in California’s Sea Level Projections
California’s coastal cities are facing a growing risk from rising sea levels. However, recent research shows that the situation might be worse than what was previously thought. A team of scientists from NASA’s Jet Propulsion Laboratory (JPL) discovered that the sinking of land, known as subsidence, is more significant than earlier estimates indicated.
According to their study, certain areas along the California coast are sinking much faster than expected. This means that in some locations, sea levels could rise more dramatically than current forecasts predict, leading to greater dangers for coastal communities.
To gather this information, researchers used satellite radar data from the European Space Agency’s Sentinel-1 satellites, along with ground sensors. They looked at over 1,000 miles of California’s coastline and compared new satellite data collected between 2015 and 2023 with older records. Their findings, published in the journal Science Advances, highlighted some alarming trends.
For instance, the San Francisco Bay Area is sinking at a rate of more than 0.4 inches (10 mm) per year. This slow decline is largely due to sediment compaction, a process where loose soil gets compressed over time. The study points out that low-lying regions like San Rafael, Corte Madera, Foster City, and Bay Farm Island could see local sea levels rise by over 17 inches (45 cm) by the year 2050, which poses a serious threat to residents and infrastructure.
Human activities also contribute to this worrying situation. For example, extracting groundwater can lead to land sinking above, as can drilling for oil and gas. In areas such as Los Angeles County and San Diego County, the effects of these actions could increase the uncertainty around sea level projections by up to 15 inches (40 cm). This uncertainty complicates efforts to create accurate models for predicting future flooding risks along the coast.
Interestingly, while some coastal areas are sinking, others are experiencing upward movement. In regions like Santa Barbara’s groundwater basin and Long Beach, land is rising by several millimeters each year. This disparity illustrates the complexity of land shifts and the variety of factors affecting different regions.
To address these issues, NASA is launching the OPERA project, which stands for Observational Products for End-Users from Remote Sensing Analysis. This initiative will complement the NISAR mission, a joint project with India’s space agency, ISRO. Together, these efforts will provide more detailed elevation data across North America, allowing scientists to track subsidence, uplift, and other surface changes in real-time.
Having access to more accurate data will help city planners and policymakers better prepare for the changes in land conditions. This information is essential in designing infrastructures like roads, bridges, and levees that can withstand the impacts of both rising seas and sinking land.
The findings from this study highlight an urgent need for California’s coastal communities. Although these areas are already investing in climate resilience measures, relying on outdated sea level predictions could leave them vulnerable to real threats. As subsidence accelerates in critical urban areas, city officials may need to revise current flood maps, building regulations, and emergency plans to better reflect the current status of their coastline, which is not only being threatened by rising waters but also by the sinking ground below.
