A Numerical Modeling Framework to Evaluate Effects of Offshore Wind Farms on California’s Coastal Upwelling Ecosystem

In California’s offshore waters, sustained northwesterly winds are a key energy resource that could contribute substantially to the state’s mandated renewable energy goals. However, the development of large-scale offshore windfarms could potentially reduce wind stress at the sea surface, which could then in turn affect wind-driven upwelling, which affects nutrient delivery and ecosystem dynamics. By linking atmospheric and ocean circulation models with simulated wind turbine installation scenarios spread across California wind energy areas of interest, this research concluded that turbines could reduce wind speed downwind of wind farms. This reduction of wind speed would enhance cross-shore changes in wind speeds, leading to reduced upwelling on the inshore side of wind farms and increased upwelling on the offshore side. These changes, when expressed in terms of widely used metrics for upwelling volume transport and nutrient delivery, show that while the net upwelling in a wide coastal band changes relatively little, the spatial structure of upwelling within this coastal region can be shifted outside the bounds of natural variability. Determining how those changes in upwelling patterns might affect the California Current’s rich ecosystem requires additional study.