Some evidence for boundary mixing in the deep Ocean

Profiles of salinity and potential temperature in the deep ocean are presented which suggest the characteristic signature of two complementary mixing processes: vertical mixing within ∼50‐m‐thick layers at boundaries and topographic features and lateral advection and eventual smearing of these mixed layers along iopycnal surfaces. The combined effect of these two processes is often parametrically disguised as a vertical eddy diffusivity in one‐dimensional models. An estimate shows that the two processes can account for all the vertical mixing in the deep ocean without any vertical diffusion in the interior.