Interactions Between Internal Tidal Bores and Submesoscale Currents on
the Continental Shelf
Abstract
Realistic simulations of Central California reveal interactions between
shoaling internal tidal bores and submesoscale currents on the
inner-shelf (30-60 m depth). These interactions comprise collisions
between internal tidal upwelling, ‘forward’ bores (FBs) with
submesoscale currents (SMCs) in the form of surface layer density fronts
or filaments with downwelling secondary circulation. Along-shore
oriented FBs collide with both cross-shore (perpendicular interaction)
or along-shore (parallel interaction) oriented SMCs. In perpendicular
interaction, FBs colliding into cross-shore oriented SMCs refract around
the offshore tip of the downwelling front or filament. SMCs generally
survive perpendicular interaction, despite partial disruption of
downwelling secondary circulation by FBs. An example of parallel
interaction demonstrates (1) blocking of FB propagation by elevated
mixing and dense filament formation on the inner-shelf and (2) the
subsequent destruction of the dense filament coincident with a decrease
in vertical mixing and FB propagation underneath it. For both
perpendicular and parallel interaction, FB propagation is modulated by a
varying medium introduced by SMC density and current structure. The
computational evidence of these interactions corroborates recent
observations of interactions between small-scale, nearshore currents in
the real ocean. This study motivates further exploration of interactions
between fronts, filaments, internal tidal bores, and vortices in the
nearshore.