Ocean Science www.ocean-sci.net 1812-0784 1812-0792 1 1 2005 10.5194/os-1-45-2005 http://www.ocean-sci.net/1/45/2005/ http://www.ocean-sci.net/1/45/2005/os-1-45-2005.html http://www.ocean-sci.net/1/45/2005/os-1-45-2005.pdf 45 79 2005-09-12 Formulation of an ocean model for global climate simulations S. M. Griffies stephen.griffies@noaa.gov A. Gnanadesikan K. W. Dixon J. P. Dunne R. Gerdes M. J. Harrison A. Rosati J. L. Russell B. L. Samuels M. J. Spelman M. Winton R. Zhang NOAA Geophysical Fluid Dynamics Laboratory, Princeton, USA Alfred-Wegener-Institut für Polar- und Meeresforschung, Bremerhaven, Germany Program in Atmospheric and Oceanic Sciences, Princeton, USA This paper summarizes the formulation of the ocean component to the Geophysical Fluid Dynamics Laboratory's (GFDL) climate model used for the 4th IPCC Assessment (AR4) of global climate change. In particular, it reviews the numerical schemes and physical parameterizations that make up an ocean climate model and how these schemes are pieced together for use in a state-of-the-art climate model. Features of the model described here include the following: (1) tripolar grid to resolve the Arctic Ocean without polar filtering, (2) partial bottom step representation of topography to better represent topographically influenced advective and wave processes, (3) more accurate equation of state, (4) three-dimensional flux limited tracer advection to reduce overshoots and undershoots, (5) incorporation of regional climatological variability in shortwave penetration, (6) neutral physics parameterization for representation of the pathways of tracer transport, (7) staggered time stepping for tracer conservation and numerical efficiency, (8) anisotropic horizontal viscosities for representation of equatorial currents, (9) parameterization of exchange with marginal seas, (10) incorporation of a free surface that accomodates a dynamic ice model and wave propagation, (11) transport of water across the ocean free surface to eliminate unphysical ``virtual tracer flux" methods, (12) parameterization of tidal mixing on continental shelves. 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