Mesoscale Eddy Effects on the Subduction of North Pacific Eastern Subtropical Mode Water

Abstract

AbstractThe effects of mesoscale eddies on the subduction of the North Pacific eastern subtropical mode water (ESTMW) are studied by comparing observations with results from the Ocean Model for the Earth Simulator (OFES). Both observations and the OFES show that mesoscale eddies exist in the ESTMW subduction region. Compared to the observations, the OFES reproduces the characteristics of the ESTMW and subduction quite well. Subduction of the ESTMW mainly occurs within a low‐density advection region, which leads to the formation of low potential vorticity water. The eddy subduction rate accounts for nearly 56% of the total subduction rate, creating high peaks in the ESTMW subduction volume histogram. Case study results show that the propagation of eddies is responsible for the shallowing of the mixed‐layer depth, which allows low potential vorticity water to subduct under the mixed‐layer bottom and prevents it from being entrained back into the mixed layer. The eddy subduction process investigated here has important implications for the further study of ESTMW subduction and transport, which is helpful for better understanding the interior transportation between the tropics and subtropics.