Sensitivity of a Coarse‐Resolution Global Ocean Model to a Spatially Variable Neutral Diffusivity

Abstract Motivated by recent advances in mapping mesoscale eddy tracer mixing the ocean we evaluate sensitivity of a coarse‐resolution global model to spatially variable neutral diffusion coefficient κ n ( x , y z ). We gradually introduce physically motivated models for horizontal (mixing length theory) and vertical (surface mode structure along with suppression mean flows. Each structural feature influences ocean's hydrography circulation varying extents, flows being most important factor relatively unimportant. When utilizing full theory (experiment “FULL”) interhemispheric overturning cell is strengthened 2 Sv at 26°N (a ∼20% increase), bringing it into better agreement observations. Zonal biases are also reduced FULL. Neutral impacts through surface temperature‐induced changes buoyancy fluxes nonlinear equation state effects. Surface forcing anomalies largest Southern Ocean where decreased diffusivity FULL leads cooling enhanced dense‐to‐light water mass transformation, reinforced reductions cabbeling thermobaricity. The increased transformation midlatitude stratification overturning. spatial as enhances without degrading Antarctic bottom cell, unlike uniform reduction . These results highlight modeled motivate use physics‐based its structure.