High latitude internal tides

The interaction of the barotropic tide with a tall, two-dimensional ridge is examined analytically and numerically at latitudes where the tide is subinertial (generating evanescent internal tides), and contrasted to when the tide is superinertial (generating radiating internal tides). Unlike superinertial internal tides, the energy density of subinertial tides close to topography grows with latitude due to increasing oscillatory along-ridge flows and isopycnal displacements. Nonlinear processes lead to the formation of rectified along-ridge jets, which become faster at high latitudes. When the tide is subinertial, dissipation and mixing is larger, and these peak later in the tidal cycle compared to when the tide is superinertial. Mixing occurs mainly on the flanks of the topography in both cases, though a superinertial tide may additionally generate mixing above topography arising from convective breaking of radiating waves.

Subinertial internal tides may provide a relatively important pathway leading to mixing along continental shelves at high latitudes.