Surface horizontal kinetic energy sensitivity to numerical parameters in tidal-resolving North and Equatorial Atlantic simulations

Abstract. Surface horizontal kinetic energy (SHKE) reflects the distribution of ocean circulation across temporal and spatial scales, shaping energy transfer and mixing in the upper ocean. Quantifying both total SHKE and its frequency content helps characterize processes from low-frequency motions to tides and near-inertial waves, but SHKE variability is difficult to quantify with observations alone. High-resolution tidal-resolving ocean models can bridge gaps in our understanding, yet the modeling results depend on the realism of the configuration choices. In this study, we isolate the role of individual model parameters by comparing seven tidal-resolving HYbrid Coordinate Ocean Model (HYCOM) simulations of the North and Equatorial Atlantic, in which only one parameter is varied at a time. Surface drifters serve as the observational reference and numerical drifters are seeded in the reference experiment to quantify the distortion of the low frequency and tidal variance introduced by the Lagrangian sampling. This framework allows a controlled sensitivity analysis of the SHKE distribution across four frequency bands, separately for deep ocean and continental shelf waters. The experiments show that, within the range of configuration changes explored, horizontal resolution is the dominant control of offshore total SHKE whereas vertical refinement has a smaller impact offshore and a slightly stronger one on the shelf. Hourly wind forcing strongly amplifies the diurnal and near-inertial variability, finer bathymetry enhances the offshore semidiurnal energy, and internal wave drag controls the tidal-band energy equatorward of their critical latitudes while leaving the low-frequency motions nearly unchanged. Increasing the number of tidal-constituent from one (M2) to eight of the largest constituents sharply increases the diurnal SHKE and allows us to disentangle the tidal from the non-tidal fraction of the diurnal cycle. Taken together, these experiments show that the shelf and offshore subdomains respond differently to each parameter and that each frequency band is sensitive to a different set of parameters. These results quantify how the configuration choices shape the modeled total SHKE and its spectral distribution, and offer guidance for setting up high-resolution tide-resolving model experiments.