Drifter Observations Reveal Intense Vertical Velocity in a Surface Ocean Front

Measuring vertical motions represent a challenge as they are typically 3-4 orders of magnitude smaller than the horizontal velocities. Here, we show that surface vertical velocities are intensified at submesoscales and are dominated by high frequency variability. We use drifter observations to calculate divergence and vertical velocities in the upper 15 m of the water column at two different horizontal scales. The drifters, deployed at the edge of a mesoscale eddy in the Alboran Sea, show an area of strong convergence (O $\mathcal{O}$(f)) associated with vertical velocities of -100 m day(-1). This study shows that a multilayered-drifter array can be an effective tool for estimating vertical velocity near the ocean surface.