Revisiting the parameterization of dense water plume dynamics in geopotential coordinates in NEMO v4.2.2

Abstract. Based on analytical study of the physics of dense overflow plumes, we suggest a new version of the bottom boundary layer parameterization of dense water plumes for geopotential vertical coordinates models. This parameterization is implemented in the NEMO ocean engine, based on a modification of the already existing tools to represent dense water plumes, and for the case of dense plumes that can be considered as geostrophic or quasi-geostrophic flows. A test case is designed to test the performance of the parameterization on a critical area of the North Atlantic Ocean, the Iceland-Scotland ridge, that includes the Faeroe Bank Channel. A comparison with the existing parameterizations already implemented in the NEMO ocean engine show that our approach increases the bottom density along the plume pathway. A sensitivity experiment of the different possible stages of this new parameterization shows their gradual effects. The addition of a downslope bottom pressure gradient term in the primitive equations is its most important feature to boost the bottom dense plume advection, although the parameterization of the downslope advection of the dense plume also contributes.