Coastlines retreat tipping point under storm climate changes

Projected changes in ocean–atmosphere coupling under global warming suggest an intensification of storm climates, which, combined with sea-level rise, poses profound challenges to the resilience of sandy shorelines. Therefore, the definition of relevant indicators assessing beach response regimes to wave climate is crucial for future forecasts Here, we analyze 23 years of satellite-derived shoreline positions together with offshore wave data to quantify storm-induced erosion and post-storm recovery tendencies at synoptic scales. Our approach integrates statistically robust storm composites, compared against in situ observations from six sites worldwide, and demonstrates that daily storm-induced shoreline dynamics can be inferred from monthly global shoreline datasets. By extending the analysis using 60-year of wave reanalysis, we identify a critical threshold beyond which shoreline evolution shifts from a seasonal to a storm-dominated regime, leading to persistent erosion trajectories. Since the late 1950s, the proportion of storm-dominated beaches has increased by 2% globally, with pronounced hot-spots emerging. While local beach morphology remain essential to fully resolve coastal dynamics, our findings reveal coherent large-scale tendencies that complement site-specific surveys and provide a global framework to guide targeted field efforts. These results highlight the pivotal role of storm regime shifts in shaping the future evolution of sandy shorelines.