Fig. 1
From: Self-sharpening induces jet-like structure in seafloor gravity currents
Schematic velocity profiles of two different geophysical flows. A standard model for seafloor gravity currents (a), where turbulent fluctuations diffuse momentum down the vertical gradient of primary flow velocity, resulting in a concave upwards velocity profile (solid black line) in the inner and outer regions of the lower shear layer. The size of the lower and upper shear layers is not drawn to scale, varying with flow and environment conditions11. Depicted by background shading, turbulent mixing causes the scalar quantities transported by the flow (e.g., heat, solutes or particulates) to take on a smooth gradient. In contrast, in an idealised zonal jet (b), the self-organisation of turbulence, by dispersive waves, results in up-velocity-gradient momentum transport whilst irreversible wave breaking transfers wave momentum into the mean flow26. Breaking dispersive waves drive homogenisation of the potential vorticity profile, reinforcing flow sharpening, as denoted by red dashed to solid line. Strong gradients in potential vorticity, mixed by dispersive wave breaking act as an eddy transport barrier, preventing the mixing of the scalar quantities transported by the flow, resulting in a strongly stratified flow (depicted by background shading)
