| Popis: |
Oceanic cross-density (diapycnal) mixing helps sustain the ocean den- sity stratification and its Meridional Overturning Circulation (MOC) and is key to global tracer distributions. The Southern Ocean (SO) is a key region where different overturning cells connect, allowing nutri- ent and carbon rich Indian and Pacific deep waters, and oxygen rich Atlantic deep waters to resurface. The SO is also rife with localized intense diapycnal mixing due to breaking of internal waves induced by the interaction of energetic eddies and currents with rough topogra- phy. SO diapycnal mixing is believed to be of secondary importance for the MOC. Here we show that changes to SO mixing can cause sig- nificant alterations to Atlantic biogeochemical tracer distributions over short and long timescales in an idealized model of the MOC. While such alterations are dominated by the direct impact of changes in diapycnal mixing on tracer fluxes on annual to decadal timescales, on centennial timescales they are dominated by the mixing-induced variations in the advective transport of the tracers by the Atlantic MOC. This work sug- gests that an accurate representation of spatio-temporally variable local and non-local mixing processes in the SO is essential for climate mod- els’ ability to i) simulate the biogeochemical cycles and air sea carbon fluxes on decadal timescales, ii) represent the indirect impact of mixing- induced changes to MOC on biogeochemical cycles on longer timescales. |
