Contrast and Predictability of Island-Scale El Niño Influences on Hawaii Wave Climate

The El Niño-Southern Oscillation (ENSO) influences ocean wave activity across the Pacific, but its effects on island shores are modulated by local weather and selective sheltering of multi-modal seas. Utilizing 41 years of high-resolution wave hindcasts, we decipher the season- and locality-dependent connections between ENSO and wave patterns around the Hawaiian Islands. The north and west-facing shores, exposed to energetic northwest swells during boreal winters, experience the most pronounced ENSO-related variability, with increased high-surf activity during El Niño years. While the year-round trade wind waves exhibit moderate correlation with ENSO, the basin-wide climate influence is masked by locally accelerated trade winds in channels and around large headlands. The remarkable global-to-local pathway through the high-resolution hindcast enables development of an ENSO-based semi-empirical wave model to statistically describe and predict severe wave conditions on vulnerable shores with potential application in coastal risk management and hazard mitigation for Pacific Islands and beyond.