Implementing biharmonic neptune in a global eddying ocean model

Results are presented from a pair of global ocean circulation simulations whose horizontal resolution is fine enough to allow spontaneous formation of eddies. The only difference between the two runs is inclusion of a parameterization for the “neptune effect” [Holloway, G., 2004. From classical to statistical ocean dynamics. Surv. Geophys. 25, 203–219] in one of them, which tends to force the flow along local topographic contours. A Laplacian operator form of this force has been used for numerous studies with coarse (non-eddying) resolution models. For eddying resolutions, however, a biharmonic friction operator is commonly used to avoid strong damping at small scales. Here we extend the neptune parameterization to a biharmonic operator, and test how inclusion of neptune affects the fidelity of simulation.