Surface Kinetic Energy Distributions in the North and Equatorial Atlantic Derived from Surface Drifter Observations and High-Resolution Numerical Models with Tidal Forcing

Abstract. Surface kinetic energy (KE) reflects the distribution of ocean circulation across temporal and spatial scales, shaping energy transfer and mixing in the upper ocean. Quantifying both total KE and its frequency content helps characterize processes from low-frequency motions to tides and near-inertial waves, but KE 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. Focusing on the North and Equatorial Atlantic, we compare surface drifter observations to seven HYCOM high-resolution simulations. We assess model parameters that influence KE across the frequency bands. We first quantify the impact of a Lagrangian versus Eulerian framework in interpreting the KE variability and then perform a series of experiments to quantify the sensitivity of the KE distribution to parameter choices. These experiments show that horizontal resolution is the dominant control for the offshore KE, strongly increasing total and semidiurnal KE, while vertical refinement has a smaller impact offshore, and a stronger impact on the shelf. High-frequency wind forcing amplifies the diurnal and near-inertial variability, while finer bathymetry increases the semidiurnal energy. In contrast, adding wave drag reduces the offshore energy only below the critical latitudes. Overall, the in-depth quantification of the sensitivity of the modeled total KE and its spectral distribution to the parameters offers guidance for setting up high-resolution tide-resolving model experiments.