The role of eddies on pathways, transports, and entrainment in dense water flows along a slope

Abstract

The flow of dense water along slopes has been investigated in several numerical investigations based on the Dynamics of Overflow Mixing and Entrainment (DOME) setup. In the present study, we try to obtain further insight into the pathways, transports, dynamics, and entrainment of such flows by performing numerical model studies with horizontal grid sizes of 10 km and 2.5 km. It is found that the rates of descent of the plumes along the slope are robust to the horizontal resolution. With a high vertical resolution and a bottom boundary condition that facilitates the representation of Ekman drainage, the plumes will follow a deeper path than when using quadratic bottom drag with a constant drag coefficient. In the results from the studies with 2.5 km horizontal grid, ambient lighter water inside anticyclonic eddies is sucked downward. Due to Ekman drainage, this water flows outwards near the bottom and underneath denser plume water. The water column around the core of the anticyclonic eddies becomes unstable, and ambient water is entrained into the plume. Due to the increased mixing and entrainment in the eddy-permitting regime, there is a substantial increase in the along slope plume transports when we reduce the grid size from 10 km (the laminar case) to 2.5 km (the eddy-permitting case).