How important are diapycnal mixing and geothermal heating for the deep circulation of the Western Mediterranean?

The dissipation rate of turbulent kinetic energy ε and the associated diapycnal turbulent mixing is inferred from a set of microstructure observations collected over several cruises from year 2012 to 2014. The geographical distribution of ε highlights several regions of enhanced levels of turbulence ranging from 10 −9 to 10 −6  W kg −1 : the Sicily Channel, the Corsica Channel, and the Ligurian Sea. Elsewhere, ε was small, often below 10 −10  W kg −1 . Below 1300 m, geothermal heating provides three‐fold more buoyancy than small‐scale turbulence. Geothermal heating and turbulent diffusion provide enough buoyancy to balance 15% to 50% of a mean yearly deep water formation rate of 0.9 to 0.3 sverdrup (10 6  m 3 /s), respectively. The remaining part has to eventually overflow through the Strait of Gibraltar.