Mixing in stratified bottom boundary layers on the steep sloping walls of Monterey Submarine Canyon

Strong internal tide generated currents and rough topography lead to intense mixing at the bottom and the sloping sidewalls of Monterey Submarine Canyon. Estimates of mixing were made from measurements with SWIMS3, a depth-cycling towed body, at eleven cross-canyon transects and two along canyon-transects in upper Monterey canyon (at thalweg depths < 700 m) over the course of two spring tides and one neap tide. The Gooseneck Ridge and other topographic features in the sinuous canyon acted as roughness elements and hydraulic elements in the baroclinic flow, generating a stratified turbulent bottom boundary layer, similar to that observed by Kunze et al. (2012) elsewhere in the canyon, that was present throughout the measurement region. The cross-canyon transects show a layer of elevated mixing (K >10^(-3) m^2/s) over the canyon bottom, ranging from 70 m thick during neap tide to 300 m thick during spring tide over topographic features. The regions of elevated mixing extend up the canyon sidewalls, diminishing in thickness and magnitude of mixing as the shelf is approached. These sidewall boundary layers generated by the internal tide may be important for sediment resuspension and other transport processes in the canyon.