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Abstract Motivated by the phenomenon of Scotian Shelf Crossover events, the problem of a shelf flow that is interrupted by a strait is considered. Laboratory experiments in a rotating tank with barotropic and baroclinic flow over flat and sloping shelves confirm that the flow is steered by the bathymetric contours and mainly circumnavigates the gulf. In order to jump across the strait, as suggested by earlier theories, the flow must have unrealistically high Rossby numbers. However, the near bottom friction relaxes the bathymetric constraint and causes the formation of a peculiar jet crossing the strait diagonally. For the dissipation values such that a half of the transport goes around the gulf and half crosses the strait diagonally, the diagonal crossover jet becomes most evident. Numerical solutions for realistic values of the frictional parameter reproduce the results of the laboratory experiments and consideration of the actual Gulf of Maine bathymetry reproduces patterns similar to those observed by drift trajectories and in the satellite derived sea surface temperature fields. 

The problem of a geophysical western boundary current negotiating a gap in its supporting boundary is considered. For traditional straight, parallel gaps, such systems are known to exhibit two dominant states, gap penetrating and leaping, with the transitional dynamics between states displaying hysteresis. However, for more complex geometries, such as angled or offset gap configurations, the question of multiple states and hysteresis is unresolved. In such cases, the inertia of the western boundary current is oriented into the gap, hence the assumption that increased inertia promotes gap penetrating loop current states. Here we address the problem numerically in an idealized setting. It is found that despite the inertia of the current being directed into the gap, for large western boundary current transport values, leaping states will be present. That is, we show here that the presence of multiple states with hysteresis for gap-leaping western boundary current systems is robust to both angled and offset gap geometries. 

Abstract The dynamics of gap-leaping western boundary currents (e.g. the Kuroshio intrusion, the Loop Current) are explored through rotating table experiments and a numerical model designed to replicate the experimental apparatus. Simplified experimental and numerical models of gap-leaping systems are known to exhibit two dominant states (leaping or penetrating into the gap) as the inertia of the current competes with vorticity constraints (in this case the β -effect). These systems are also known to admit multiple states with hysteresis. To advance towards more realistic oceanographic scenarios, recent studies have explored the effects of islands, mesoscale eddies, and variable baroclinic deformation radii on the dynamical system. Here, the effect of throughflow forcing is considered, with particle tracking velocimetry (PTV) used in the lab experiments. Mean transport in or out of the gap is found to significantly shift the hysteresis range as well as change its width. Because of these transformations, changes in throughflow can induce transitions in the gap-leaping system when near a critical state (leaping-to-penetrating/ penetrating-to-leaping). Results from the study are interpreted within a nonlinear dynamical framework and various properties of the system are explored. 

The classic oceanographic problem of a 1.5-layer western boundary current evolving along a straight wall is considered. Here, building upon the previous work of Charney, Huang and Kamenkovich, we have derived, solved and validated a new numerical formulation for accounting for viscous effects in such systems. The numerical formulation is validated against rotating table experimental results. 

Beginning from the shallow water equations (SWEs), a nonlinear self-similar analytic solution is derived for barotropic flow over varying topography. We study conditions relevant to the ocean slope where the flow is dominated by Earth's rotation and topography. The solution is found to extend the topographic β-plume solution of Kuehl (2014) in two ways. (1) The solution is valid for intensifying jets. (2) The influence of nonlinear advection is included. The SWEs are scaled to the case of a topographically controlled jet, and then solved by introducing a similarity variable, η = cx^n_xy^n_y. The nonlinear solution, valid for topographies h = h₀ − αxy³, takes the form of the Lambert W-function for pseudo velocity. The linear solution, valid for topographies h = h₀ − αxy^−γ, takes the form of the error function for transport. Kuehl's results considered the case −1 ≤ γ < 1 which admits expanding jets, while the new result considers the case γ < −1 which admits intensifying jets and a nonlinear case with γ = −3.