Dependence of seafloor boundary layer thickness on the overlying flow direction: a large eddy simulation study

Using large eddy simulation (LES) incorporating the effect of the horizontal component of the earth’s rotation vector, we studied the seafloor turbulent boundary layer to investigate the dependence of the boundary layer thickness on the overlying geostrophic flow orientation. The thickest boundary layer appears for the westward geostrophic flow: it is almost twice that of the eastward flow. The turbulent disturbances in the boundary layer are elongated slightly leftward relative to the geostrophic flow. Linear stability analysis for the Ekman’s spiral flow showed that the growth rate is maximum for the westward geostrophic flow and the unstable roll-like mode appears, which points slightly leftward relative to the geostrophic flow. These properties correspond to the feature near the bottom of the developed turbulent layer.