Influence of numerical schemes on current-topography interactionsin 1/4° global ocean simulations

[摘要] The combined use of partial steps and of an energy-enstrophy conserving momentum advection schemewas shown by Barnier et al. (2006)to yield substantial improvements in the surface solution of the DRAKKAR¼° global sea-ice/ocean model. The present study extends this investigation below the surfacewith a special focus on the Atlanticand reveals many improvements there as well: e.g. more realistic path, structure and transports of major currents(Gulf Stream, North Atlantic Current, Confluence region, Zapiola anticyclone), behavior of shedded rings,narrower subsurface boundary currents, stronger mean and eddy flows (MKE and EKE) at depth, beneficialenhancement of cyclonic (anticyclonic) flows around topographic depressions (mountains).Interestingly, adding a no-slip boundary condition to this improved model setup cancels most of theseimprovements, bringing back the biases diagnosed without the improved momentum advectionscheme and partial steps (these biases are typical of other models at comparable or higher resolutions).This shows that current-topography interactions and full-depth eddy-admitting model solutionscan be seriously deteriorated by near-bottom sidewall friction, either explicit or inherent to inadequatenumerical schemes.

[学科分类] 海洋学与技术