information:extraction, structural:expansion, information:filtering
Turbulence and mixing

Diapycnal mixing is the process by which different layers of a stratified fluid mix. It directly affects vertical gradients, thus it is of great importance to all gradient-driven types of transport and circulation (including thermohaline circulation). Mixing drives the global thermohaline circulation; without internal mixing, cooler water would never rise above warmer water, and there would be no density (buoyancy)-driven circulation. However, mixing in the interior of most of the ocean is thought to be ten times weaker than required to support the global circulation. It has been hypothesised that the extra-mixing can be ascribed to breaking of internal waves (Lee waves). When a stratified fluid reaches an internal obstacle, a wave is created that can eventually break, mixing the fluid's layers. It has been estimated that the diapycnal diffusivity in the Drake Passage is ~20 times the value immediately to the west in the Pacific sector of the Antarctic Circumpolar Current (ACC). Much of the energy that is dissipated through internal wave breaking (around 20% of the wind energy put into the ocean) is dissipated in the Southern Ocean.

In short, without the coarse topography in the depths of the Drake Passage, oceanic internal mixing would be weaker, and the global circulation would be affected.