[A-CG36] Dynamics of Oceanic and Atmospheric Waves, Vortices, and Circulations

[ACG36-05] On the missing mixing in the abyssal Indian Ocean

*Lei Han¹ (1.Xiamen University Malaysia)

Keywords:Indian Ocean, Overturning circulation, Diapycnal mixing, Abyssal recipe

As a subject of enduring debate, the dichotomy of vertical diffusivity (also known as the “missing mixing”) in general refers to that the global average value of diffusivity inferred from advective-diffusive balance for the maintenance of ocean’s abyssal stratification, which is near 1e-4 m2/s, is one order of magnitude larger than the observed diffusivity. A similar problem occurs in the Indian Ocean. From a new perspective of sloshing mode of overturning circulation (attached figure), the author makes an attempt to mitigate the “missing mixing” problem in the deep Indian Ocean (Han, 2021 JPO). It is argued that the ‘‘missing mixing’’ in the deep Indian Ocean is (at least partially) due to the overestimated diapycnal volume fluxes upwelled to the upper layers.