PNNL

Abstract

Wind farms extract momentum from the atmospheric flow, generating wind speed deficits both within the plant, and extending downstream. When located offshore, these deficits modulate air-sea coupling, potentially impacting coastal upwelling in sensitive regions. We investigate potential impacts of wind plants on coastal upwelling using kilometre-scale, three-way-coupled simulations with the Coupled Ocean--Atmosphere--Wave--Sediment Transport (COAWST) system for the U.S. West Coast. Wind farm effects are represented by a generalized turbine drag formulation, a deliberately idealized, height-dependent body force whose magnitude is systematically varied. This approach isolates the leading-order fluid-dynamical response in a realistic coastal configuration. The atmospheric adjustment exhibits an approximately linear relation between drag force and wind-speed deficit, with wakes that expand downstream and increase in magnitude as drag increases. An Empirical Orthogonal Function analysis of sea-surface-temperature anomalies reveals the emergence of a canonical dipole pattern under strong drag forcing. Subsurface diagnostics show consistent shoaling of the mixed layer and suppressed upward velocities in areas close to wind farm region, accompanied by compensating enhancements of shoaling closer to the coast, indicating a spatial redistribution of the upwelling system. Together, these results identify turbine drag as a control parameter in assessing interactions between wind farm wake and coastal upwelling and provide scaling relationships for understanding offshore wind farm effects on coastal circulation dynamics.