Effects of the Pacific Diapycnal Mixing and Wind Stress on the Global and Pacific Meridional Overturning Circulation

Abstract

Numerical experiments are conducted using an idealized basin to investigate roles of the deep vertical diffusivity and wind stress of the Pacific Ocean in the global and Pacific meridional overturning circulation. The Pacific middepth diffusivity is found to be enhancing the global meridional overturning circulation; when this part of diffusivity is reduced to the background value, not only is the layered circulation of the Pacific greatly weakened, but also the production of the North Atlantic Deep Water (NADW) and Antarctic Bottom Water (AABW) is significantly reduced. The deeper part of the Pacific diffusivity is found to be enhancing the production of the AABW in the model. When the wind stress is turned off in the Pacific, the deep meridional overturning circulation of the Pacific is reduced and the production of the NADW and AABW is also significantly reduced. This is likely due to the reduction of the wind-enhanced upwelling in the subpolar and equatorial regions. These results suggest the importance of the diapycnal diffusion and sea surface conditions in the Pacific not only to the circulation within the Pacific but also to the global meridional overturning circulation.