Recently, a study led by the National Aeronautics and Space Administration (NASA) revealed that certain coastal areas in California are sinking. Although the changes in elevation may be relatively small, researchers warn that it could ultimately increase the risk of flooding for coastal communities.
The report released on the 10th of this month highlighted that in the San Francisco Bay Area, particularly in San Rafael, Corte Madera, Foster City, and Bay Farm Island, the land is subsiding at a steady rate of over 0.4 inches (about 10 millimeters) per year, primarily due to sediment compression.
As the land sinks, the local sea levels are expected to rise at an accelerated pace.
Using precise satellite radar data, researchers identified the vertical movements of the land and sea level changes in coastal areas of California.
The report stated, “To capture local movements from space, the research team analyzed radar measurements from the European Space Agency’s Sentinel-1 satellite and compared them with motion velocity data from ground receivers of global satellite navigation systems.”
They further compared the observational results from the same locations between 2015 and 2023.
The fastest sinking area in California is the Central Valley region, with subsidence reaching up to 8 inches per year. This is attributed to the extraction of groundwater during dry or rainy periods, causing expansion or contraction of underground aquifers.
In Northern California, areas such as San Francisco, Monterey Bay, and the marshlands at the Russian River mouth in Sonoma County are subsiding, possibly due to erosion.
In other regions, like the Big Sur Mountains below San Francisco and the Palos Verdes Peninsula in Los Angeles, sinking is occurring due to slow-moving landslides.
Scientists also discovered that not all coastal areas in California are experiencing subsidence. For example, the terrain in Santa Barbara is rising a few millimeters each year due to the replenishment of groundwater basins.
Additionally, the report noted that the elevation in Long Beach is also increasing, attributed to fluid extraction and injection in oil and gas production.
The study predicts that by 2050, California’s sea levels will rise 6 to 14.5 inches higher than in 2000. The melting of glaciers and ice sheets is identified as the primary cause of rising water levels.
Marin Govorcin, a scientist at the Jet Propulsion Laboratory in Southern California, stated, “In many parts of the world, such as in land reclamation areas below San Francisco, the rate of sinking is faster than the rate of sea level rise.”
Researchers emphasized that due to human factors such as groundwater extraction and wastewater injection, along with natural factors like tectonic activity, the scale and speed of elevation changes may be challenging to predict.