Near-Surface Ocean Current and Its Response to Wind Forcing

Abstract

Ocean currents near the air-sea interface are critical for understanding boundary layer processes and advancing coupled models. The near-surface currents mediate air–sea fluxes and govern the transport of buoyant materials, yet the uppermost meter of the ocean remains sparsely observed and poorly represented in models. This study reconstructs ocean current profiles within the uppermost centimeters of the ocean using multiple remote-sensing techniques collected during the ASIT-2019 field campaign. The retrieved flows span three distinct layers: (a) the viscous sublayer O(10 μm); (b) the top of the logarithmic layer O(1 mm–1 cm); and (c) a 2-m reference layer. This unique data set enables examination of wind–wave–current interactions in the ocean surface boundary layer. We revisit the wind-driven near-surface current parameterizations. The along-wind skin drift is found to be 3.70% ± 0.34% of the wind speed; and the quasi-Eulerian current at the top of the logarithmic layer reaches 2.45% ± 0.56% of the wind speed. From the reconstructed profiles, we quantify near-surface shear and infer viscous stress, which are consistent with previous laboratory measurements. These results highlight the importance of resolving vertical flow structure for future data assimilation and modeling in the near-surface layer. In addition, the cross-wind near-surface flow is found to be, on average, of the same order of magnitude as the along-wind component, and its forcing reflects a complex interplay of multiple potential processes.