PROJECTIONS OF FUTURE WAVE CONDITIONS OFFSHORE OF PACIFIC ISLANDS

Robust projections of future wave conditions along Pacific Island coastlines are essential for assessing coastal flooding hazards and morphodynamic change over the next century. Through a dynamical downscaling effort, deep-water wave conditions offshore of Hawai’i and 22 other Pacific Islands were projected for historical (1976-2005) and future (2026-2045; 2081-2100) time periods. Near-surface winds from four separate Global Climate Models under two climate change scenarios forced a global ocean wave model over the Pacific Ocean to generate ensemble predictions of mean and extreme wave height, period, and direction. Climate change scenarios included Representative Concentration Pathway (RCP) 4.5 and RCP 8.5, which characterize a stabilizing global climate (i.e., curbed emissions) and continued rates of high emissions, respectively. Changes to wave conditions relative to the historical period were analyzed by season. Though spatial patterns and trends are alike under both climate change scenarios, magnitudes of change are larger under RCP 8.5. December-February extreme wave heights are projected to decrease by ~10% by the end of the 21^st century. Boreal summer extreme wave heights are projected to increase and mean wave directions at most locations are projected to rotate clockwise. Though inconsistent over the study area, the frequency of extreme events that produce damaging waves is projected to decrease under both climate change scenarios. Results corroborate widespread agreement amongst other studies regarding increasing magnitude of Southern Ocean winds and swell, which will affect these islands during boreal summer. Shifts of wave energy distributions across seasons has implications for coastal flooding and management along previously protected, lower energy coastlines in the Central Equatorial Pacific.