The Regional Oceanic Modeling System with Non-Conservative Surface Gravity Wave Effects on Currents (ROMS-NCWEC v1.0.0)

Abstract. We present ROMS-NCWEC, an updated and extended implementation of non-conservative Wave Effects on Currents (WEC) in the Regional Ocean Modeling System (ROMS). It is either one-way coupled to the spectral wave model WaveWatch3 (WW3) to resolve a broadband wave field or fully coupled to a spectrum-peak (WKB) wave model with Doppler-shift Current Effects on the waves (CEW). The implementation of three non-conservative (NC) effects includes the following: wave breaking and wave-induced bottom streaming, each represented as either a boundary stress or a 3D body force, and wave-enhanced bottom drag. The turbulent mixing from wave breaking is parameterized as a near-surface eddy viscosity enhancement to the K-Profile Parameterization (KPP) model. The bottom boundary layer mixing scheme is modified to account for the influence of wave streaming and wave-enhanced bottom drag. The implementation is validated against the Duck 1994 experiment, recovering the essential nearshore flow features with normalized RMS errors comparable to past studies. ROMS-NCWEC is then applied in a realistic regional setting near Pt. Arguello, CA. It uses an intermediate grid resolution (dx = 30 m) that is inner-shelf-resolving, surfzone-permitting that bridges the gap between coarse-grid regional models and more fully surfzone-resolving simulations. A momentum balance analysis reveals dynamically distinct offshore and nearshore regimes. Offshore, WEC amplifies the terms in the turbulent thermal wind balance while preserving it as the governing balance, consistent with prior findings on wave-enhanced frontogenesis. Nearshore, breaking stress emerges as the dominant WEC contribution, producing at times vorticity enhancements of order 20 times relative to a no-wave control case and shifting the balance from wind-versus-drag to breaking-plus-wind-versus-drag. Wave streaming is found to compete with bottom drag on the inner shelf (depths 10 m < h < 100 m). Just seaward of the breaking zone, streaming meets the wave-driven undertow return current; the resulting near-bed convergence drives upwelling that closes a wave-forced overturning cell and generates strongly sheared alongshore jets at the surface.