Quantification of boundary mixing using expendable microstructure profilers for the deep ocean and its incorporation into the global thermohaline circulation model

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The global mapping of diapycnal diffusivities in the deep ocean is essential for accurate modeling of global thermohaline circulation. Nevertheless the global distribution of diapycnal diffusivities below a depth of ～2000 m remains unknown. In order to clarify this, we have deployed a free-fall multi-scale profiler VMP-5500 thatcan measure microscale turbulence as well as the background fine-scale shear and strain from the sea surface down to a depth of ～6000 m. Using a combination of the fine-scale and microscale data thus obtained simultaneously together with the aid of the concurrent numerical simulation of internal waves which are generated by tidal interaction with abyssal rough bottom and propagate through the background shear and strain fields, we have succeeded in developing an empirical formula for diapycnal diffusivities near abyssal rough sea beds expressed in terms of fine-scale parameters.