A NASA-led research team has analysed satellite data to study how vertical land motion could impact future sea levels. The study has found that aquifers have a significant influence.
The study, published in the journal Science Advances, used California as a case study, where sea levels are predicted to increase 15-37 cm by 2050.
Capturing inch by inch localised motion from space, the team analysed radar measurements from the European Space Agency’s Sentinel-1 satellites, along with motion velocity data from ground-based receiving stations in the Global Navigation Satellite System, comparing multiple observations of the same locations from 2015 to 2023, using an interferometric synthetic aperture radar (InSAR) processing technique.
In many parts of the world land is moving down faster than the sea is rising, due to both human-caused factors such as groundwater extraction and wastewater injection, as well as from natural ones like tectonic activity.
But not all of the studied coastline is sinking. Uplift hotspots of several millimetres per year were identified in the Santa Barbara groundwater basin, for example, which has been steadily replenishing since 2018. But periods of drought and precipitation can alternately draw down or inflate underground aquifers impacting vertical land motion.
The study illustrates how challenging it is to prepare for sea level rise due to the unpredictable nature of vertical land motion, which can alter at scale and speed according to human activity, necessitating ongoing monitoring.
