The zonally symmetric inertial instability of oceanic near-equatorial flows is studied through high-resolution numerical simulations. In homogeneous upper layers, the instability of surface-confined westward currents implies potentially fast downward mixing of momentum with a predictable final equilibrium. With increasing Reynolds number, latitudinal scales along the surface associated with the instability become ever smaller and initially the motions are ever more concentrated underneath the surface. The results suggest that even if the upper layer is stratified, it may still be necessary to include the full Coriolis force in the dynamics rather than use the traditional beta-plane approximation.

}, keywords = {approximation, atmosphere, beta-plane, centrifugal-type instabilities, criterion, nonlinear instability, ocean processes, pacific-ocean, rotating flows, saturation, shear flows, symmetric stability, vertical scale selection}, isbn = {0022-1120}, doi = {10.1017/jfm.2017.377}, url = {