SPATIAL VARIABILITY OF TURBULENT MIXING IN THE ABYSSAL OCEAN

Ocean microstructure data show that turbulent mixing in the deep Brazi l Basin of the South Atlantic Ocean is weak at all depths above smooth abyssal plains and the South American Continental Rise. The diapycnal diffusivity there was estimated to be less than or approximately equa l to 0.1 x 10(-4) meters squared per second. In contrast, mixing rates are large throughout the water column above the rough Mid-Atlantic Ri dge, and the diffusivity deduced for the bottom-most 150 meters exceed s 5 x 10(-4) meters squared per second. Such patterns in vertical mixi ng imply that abyssal circulations have complex spatial structures tha t are linked to the underlying bathymetry.