Increasing vertical mixing to reduce Southern Ocean deep convection in NEMO3.4

摘要: Abstract. Most CMIP5 (Coupled Model Intercomparison Project Phase 5) models unrealistically form Antarctic Bottom Water by open ocean deep convection in the Weddell and Ross seas. To identify mechanisms triggering Southern Ocean models, we perform sensitivity experiments on model NEMO3.4 forced prescribed atmospheric fluxes. We vary vertical velocity scale of Langmuir turbulence, fraction turbulent kinetic energy transferred below mixed layer, background diffusivity run short simulations from 1980. All exhibit Riiser-Larsen Sea 1987; origin is a positive sea ice anomaly 1985, causing shallow layer depth, hence anomalously warm surface waters subsequent polynya opening. Modifying mixing impacts both climatological state associated anomalies. The with enhanced colder reduced convection. decreased give warmer waters, larger polynyas more saline have across until end. Extended reveal an increase Drake Passage transport 4 Sv each year occurs, leading to large at end simulation. North Atlantic not significantly affected changes parameters. As new climate overflow parameterisations are developed realistically, argue that would benefit stopping convection, for example increasing their mixing.