The three-dimensional structure of fine-scale, vertical velocities inferred from SWOT and glider observations

Upper ocean vertical velocities intensify at scales where the dynamical constraints of Earth’s rotation weaken. Intensified vertical motions have been linked to mixed layer fronts in the ocean’s surface boundary layer, and recent studies indicate that these motions may extend below the mixed layer. Yet it remains a challenge to extrapolate these results to broader spatial scales and longer time periods. Here, we diagnose vertical velocities by exploiting the high resolution sea surface height observations collected by the Surface Water and Ocean Topography (SWOT) altimeter along with interior hydrographic measurements from ocean gliders. SWOT-derived density and velocity reconstructions allow an estimate of ocean vertical velocities through the quasi-geostrophic (QG) omega equation at finer spatial scales than previous studies. Vertical velocities are deep-reaching, commonly exceed 150 m day−1 throughout the upper 1000 m, and are localized to narrow regions of high vorticity and strain with horizontal scales as small as 10 km. Multiple SWOT passes reveal statistical relationships between vertical velocity, strain, and vorticity that are consistent with high resolution numerical models. This analysis is a step towards generating spatially and temporally resolved vertical velocity and tracer fluxes for the circumpolar Southern Ocean.