A 45-year high-resolution wave hindcast for the Fijian archipelago: mean climate, spectral characteristics, and long-term trends

Fiji’s coastal communities are highly exposed to ocean waves that drive erosion, inundation and shoreline change. Yet the Fijian archipelago lacks a comprehensive, wave-climate assessment at a resolution that represents island effects appropriately. To address this gap, we present a 45-year (1979–2023) wave hindcast from the unstructured SWAN model, refined to 500 m near the coast, forced by ERA5 reanalysis, and validated against satellite altimetry and in situ wave buoys. The hindcast resolves a distinct south-to-north energy gradient, persistent wave corridors, and island shadowing that govern coastal wave exposure across the archipelago. Spectral analysis identifies three dominant wave sources, namely, the extratropical storms in both hemispheres, and the Southeast Trade Winds. On interannual timescales, the Antarctic Ocean Index (AAO) is the dominant driver of long-period swell variability to the south, while the Oceanic Niño Index (ONI) modulates wave energy to the north. Over 45 years, the offshore wave height (Hs) increase is significant at + 2.4 ± 2.8 cm, as is the peak period (Tp, + 0.2 ± 0.13 s). Together, these findings provide a critical resource for coastal planning, wave energy assessments, and climate adaptation for vulnerable Fijian coastal communities. Fiji’s coastlines are highly exposed to ocean waves that can erode shorelines, flood communities, and damage infrastructure. Using 45 years of high-resolution wave model data, this study provides a clear picture of Fiji’s wave climate, its seasonal patterns, and long-term changes. We identify the main sources of waves as distant storms and the trade winds, and show how large-scale climate cycles such as El Niño influence them. Results reveal a gradual increase in wave height and period in Fiji’s offshore regions with potential implications for coastal erosion and inundation. These findings provide essential information for communities, planners, and policymakers to strengthen coastal adaptation in Fiji.