A recent NASA study has revealed significant land changes in several regions of California that are sinking. While these elevation changes may seem minor, they could have a profound impact on flood risk and wave exposure as sea level continues to rise.
NASA conducted a case study in California, where a team of researchers examined the factors contributing to these changes, including groundwater extraction, coastal erosion, and tectonic activity.
“In many parts of the world, such as reclaimed land in San Francisco, the ground is sinking faster than the sea is rising,” said Marin Govorcin, the study’s lead author and a remote sensing scientist at NASA’s Jet Propulsion Laboratory (JPL) in Southern California.
By 2025, sea levels in California are projected to rise between 6 and 7 inches (15-17 cm) compared to the levels recorded in 2000. This increase is largely attributed to melting glaciers, ice sheets, and the warming of ocean waters.
To track these changes, researchers from JPL and the National Oceanic and Atmospheric Administration (NOAA) used satellite radar to monitor 1,000 miles of California’s coastline, identifying critical areas most vulnerable to rising sea levels.
These California Coastal Cities Are Sinking
Using data from the European Space Agency’s Sentinel-1 satellites and the Global Navigation Satellite System (GNSS), researchers analyzed surface movement between 2015 and 2023 using interferometric synthetic aperture radar (InSAR).
Their findings revealed that the following areas are experiencing significant subsidence:
- San Rafael
- Corte Madera
- Foster City
- Bay Farm Island
The study found that the land in these regions is sinking at a steady rate of more than 0.4 inches (10 mm) per year. If this trend continues, sea levels could effectively rise more than 17 inches (45 cm) by 2050.
Additionally, human activities such as hydrocarbon and groundwater extraction contribute to uncertainties in sea level projections, with some areas in Los Angeles and San Diego counties potentially experiencing up to 16 inches (40 cm) of sea level rise.
While parts of California are sinking, some regions—like Long Beach—are experiencing land elevation. This phenomenon is linked to the extraction and injection of fluids related to oil and gas production.
Why Is California’s Coast Sinking?
According to Govorcin, the study highlights the combined impact of human activities, natural events, and tectonic movements on land subsidence along the California coast. After analyzing over 1,000 miles of coastline from 2015 to 2023, researchers found that compaction of sediments in the San Francisco Bay Area is causing the land to sink at a rate of about 10 mm per year. As a result, sea levels in the region could rise by 17 inches (45 cm) by 2025.
While coastal areas are sinking at a rate of 10 mm per year, Central California—particularly the Central Valley—faces an even greater challenge. Due to groundwater extraction, drought, and precipitation patterns that deplete underground aquifers, the land is subsiding at a staggering rate of 8 inches (20 cm) per year.
These findings emphasize the urgent need for mitigation strategies and continuous monitoring of land movement to better prepare for the growing risks associated with rising sea levels.
