Impact of latitudinal variations in vertical diffusivity on climate simulations

The currently available theoretical and observational evidence for a latitudinal structure of thermocline vertical diffusivity is synthesized and included in a state of the art coupled climate model. Compared to the standard background value of 0.1 cm² s⁻¹, the simulations with the latitudinal structure show only little change in the meridional overturning circulation or northward heat transport. However, two regions are identified which are sensitive to the value of vertical diffusivity: the equatorial band, where only small changes in sea surface temperature lead to precipitation responses with basin-wide teleconnections, and the North Atlantic, where diffusivity affects the spiciness of Labrador Sea water and subsequently the Gulf Stream path.