Potential impacts of offshore wind energy development on physical processes and scallop larval dispersal over the US Northeast shelf

Abstract

This study examines the potential impact of offshore wind energy facilities on the local and regional circulation, stratification, and scallop larval dispersal and settlement over the U.S. Northeast continental shelf. A coupled high-resolution (up to ∼ 1.0 m), wind turbine-resolving hydrodynamical (NS-FVCOM) and scallop individual-based (Scallop-IBM) model was employed. Comparisons were made for scenarios with and without wind turbine generators (WTGs), encompassing three-dimensional flow fields, water temperature, bottom stress/vertical mixing, scallop larval dispersal, settlement, and distributions. The interaction of M₂ tidal currents with monopiles generates significant horizontal flow shear on the downflow lee side. The fluid–structure interaction-induced mesoscale currents deviate substantially from the idealized flow fields examined typically in the device-scale laboratory or coarse-grid hydrodynamical models with subgrid-scale explicit parametrizations. Stratification induces noteworthy changes in the flow around individual monopiles throughout the water column, with the maximum bottom stress primarily oriented in the onshore-offshore direction and vertical eddy viscosity occurring around all directions of individual monopiles. The deployment of a WTG array amplifies offshore low-frequency subtidal flow around 40 to 50-m isobaths, forming mesoscale eddies over the shelf. This enhanced flow contributes to offshore water transport, redirecting scallop larvae toward the Nantucket Lightship Closed Area (NLCA). The accumulation of larvae in the NLCA is attributed to eddy-induced retention.