Offshore wind farms are increasingly shaping coastal ocean dynamics, yet their cumulative physical impacts remain poorly quantified. Using decade-long, high-resolution simulations of the North Sea, we show that large-scale offshore wind development can reduce current velocities by up to \(20 \%\) and reshape local tidal energy distributions. Wind and tidal wakes exert distinct but interacting influences on ocean physics: wind speed anomalies drive far-field hydrodynamic impacts, while structure-induced drag intensifies local turbulence and mixing. Turbine spacing emerges as a key control on wake interactions, governing the formation of high-turbulence hotspots. The near- and far-field wake effects affect vertical mixing and surface heat fluxes – primarily driven by large-scale wind stress reductions – leading to shallower mixed layers and long-term surface warming of up to \(0.2\,^{\circ} \,{{{\rm{C}}}}\) in wind farm areas. Our findings reveal a basin-scale physical footprint of offshore wind energy and highlight the need to account for hydrodynamic impacts in future offshore wind farm planning.
