California Map Reveals Where State Is Sinking

A new map reveals where in the state of California the land is gradually sinking, exacerbating future risks related to rising global sea levels.

The work—undertaken by remote sensing specialist Marin Govorcin of NASA’s Jet Propulsion Laboratory in Southern California—reveals how vertical land motions can be unpredictable in both scale and speed.

These changes, driven by natural forces like tectonic activity as well as human influences like groundwater pumping, need to be considered alongside calculations of sea level rise driven by melting ice sheets and glaciers and warming (and thus expanding) ocean water. By the year 2050, sea levels in California are expected to increase by between 6 and 14.5 inches over the levels in 2000.

“In many parts of the world, like the reclaimed ground beneath San Francisco, the land is moving down faster than the sea itself is going up,” Govorcin said in a statement.

Current models of changing sea levels are often based only on measurements from tidal gauges, meaning that they cannot cover every location in a given region, nor all the dynamic land motion at play.

In their study, Govorcin and his colleagues instead used satellites to track how thousands of miles of land along the California coast had risen and fallen between 2015 and 2023.

Combining radar measurements made by the European Space Agency’s Sentinel-1 Earth observation satellites with motion velocity data from the Global Navigation Satellite System’s Earth-based receiver stations, the team captured local ground movements in precise detail.

From this, it was possible to pinpoint hotspots—among which are cities, beaches and aquifers—that will be at a greater risk from rising seas in the coming decades.

In the case of the San Francisco Bay Area (specifically, Bay Farm Island, Corte Madera, Foster City and San Rafael), the researchers found that the land is subsiding at a rate of more than 0.4 inch each year as a result of sediment compaction.

When this is considered for the lowest-lying parts of these areas, local sea levels could rise by more than 17 inches by 2050—more than double the regional estimate of 7.4 inches, which is based only on tidal gauge predictions.

In the Big Sur mountains to the south of San Francisco and the Palos Verdes Peninsula of Los Angeles, the team identified local zones of downward motion linked to slow-moving landslides.

Subsidence was also seen at marshlands and lagoons around Northern California’s San Francisco and Monterey bays, as well as in the Russian River estuary in Sonoma County, all likely associated with erosion.

The team also revealed how human-induced drivers of land motion—such as oil and gas production, as well as groundwater extraction—can introduce uncertainties into future sea level projections of up to 15 inches in parts of Los Angeles and San Diego counties that require ongoing monitoring.

Some parts of California’s Central Valley, for example, can see as much as eight inches of subsidence each year; this is influenced by groundwater fluctuations.

Aquifers in Chula Vista (in San Diego County), Santa Ana (Orange County) and Santa Clara (Bay Area) were seen to ebb and swell with periods, respectively, of drought and precipitation.

Not all of California is sinking, however, the researchers report. With the steady replenishment of the Santa Barbara groundwater basin since 2018, for example, the team detected areas of several millimeters of annual uplift. Similar things were seen in Long Beach, where fluid extraction and injection take place in association with gas and oil recovery.

With their initial study complete, the researchers’ findings are now being used to help inform California state guidance on sea level changes.

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Reference

Govorcin, M., Bekaert, D. P. S., Hamlington, B. D., Sangha, S. S., & Sweet, W. (2025). Variable vertical land motion and its impacts on sea level rise projections. Science Advances, 11(5). https://doi.org/10.1126/sciadv.ads8163