The Influence of Topography on the Stability of Shelfbreak Fronts

Abstract

In an attempt to understand the degree to which the stability of a shelfbreak front, characterized by continuous horizontal and vertical shear, is affected by topography, a linear stability analysis was conducted for a range of frontal jets and bottom-slope configurations. Three-dimensional perturbations superposed on a continuously stratified shelfbreak front were investigated using linearized, hydrostatic primitive equations. For all model runs in the study, the frontal instability mode, which is the fastest-growing mode for a baroclinic flow, was not influenced by the bottom: Retrograde, prograde, and flat-bottom jets all share the same stability characteristics. In contrast, weakly baroclinic jets are strongly influenced by bottom topography. The presence of a bottom slope stabilizes prograde jets and destabilizes retrograde jets, a difference attributed to the orientation of the isopycnals relative to the bottom slope. Temporal and/or downstream changes in the bottom slope and/or background stratification are shown to produce sizeable changes in the instability of a weakly baroclinic jet.