Sack Lunch Seminar (SLS)

Nonlinear stratified spindown over a sloping bottom



On a stratified sloping bottom, the nonlinear spindown of an along-isobath flow gives rise to asymmetry in Ekman pumping and suction. We show that nonlinear advection of buoyancy weakens Ekman pumping to a greater extent than Ekman suction. This mechanism for asymmetry contrasts with previous studies of nonlinear homogeneous spindown over a flat bottom, in which nonlinear advection of momentum weakens Ekman pumping and strengthens Ekman suction. Theoretical and numerical calculations are performed for increasing Rossby number to examine the relative roles of nonlinear advection of buoyancy and momentum on the asymmetry in Ekman pumping and suction and its subsequent feedback into the vertical vorticity field. The results of this study are applied to flows on the continental slope.