Development and evaluation of vertical turbulent mixing schemes for the ocean boundary layer in climate models

Abstract The paper presents a new ocean boundary layer framework developed for numerical simulation of vertical mixing processes. The framework includes turbulence closures of varying complexity: a prognostic k – ε scheme, the Pacanowsky–Philander closure, and its dynamic modification proposed by the authors. The turbulent coefficients for the conditions of neutral stratification depend on surface stress and mixed-layer depth in the modified closure. The framework is validated and tested in idealized and observation-based single-column experiments as a stand-alone model and in global simulations as a library implemented in the INM RAS climate model. In the single-column cases, the dynamic modification produces mixed-layer depth and upper-ocean temperature evolution closer to reference solutions than the standard Pacanowsky–Philander closure and shows reduced sensitivity to vertical resolution. In the CORE-II-forced global simulations, the framework implementation modifies zonal-mean temperature and salinity biases in the upper ocean and reduces the global-mean annual mixed-layer depth error.