The velocity structure in the bottom boundary layer (BBL) in the Middle Atlantic Eight (MAB) is investigated using data derived from the Shelf Edge Exchange Processes (SEEP-II) experiment to test theoretical predictions of the effects of cross-shelf buoyancy flux on the BBL which are thought to contribute to frontogenesis at the shelfbreak. The cross-shelf how is bottom intensified with a direction veering consistent with that of a frictional boundary layer with rotation. The BBL thickness based on veering angle ranges from 8 to 40 m with a velocity dependence complicated by stratification that is dependent on frontal position. There is evidence of the asymmetry in the BEL thickness expected for the cross-shelf buoyancy flux during up- and downwelling events. However, the velocity structure does not define a sharp upper boundary to the BBL as given by simple one-dimensional model calculations and suggests that there must be other sources of turbulence in addition to bottom friction.
Qy893Times Cited:5Cited References Count:12