Interannual Wave-Driven Shoreline Change on the California Coast

Our understanding of how wave climate variability drives shoreline evolution has advanced substantially in recent decades with increasing satellite imagery, wave buoy records, and wave hindcast models. While severe beach erosion with extreme El Niño waves is well documented on Pacific coastlines, the broader link between interannual wave energy and shoreline response has remained less clear. Here, we show nearly half of California's interannual Landsat shoreline change is a coherent response to wave power anomalies originating from a specific central North Pacific swell generation region, which in turn is weakly correlated with the Niño3.4 index. Positive wave power anomalies (beach loss) are strongly associated with El Niños, but the negative anomalies (beach recovery) are not similarly tied to La Niñas. Cumulative change in the CA statewide mean shoreline position is small over the 37-yr Landsat era but an 83-yr wave hindcast suggests a statewide wave-driven retreat of ~ 4m loss since 1941. These results provide additional insight into the role of the North Pacific wave climate in modulating beach width retreat and recovery over interannual to multi-decadal timescales, with implications for long-term coastal resilience planning.