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3.11 Ocean Gyre Advection Schemes

(in directory: verification/tutorial_advection_in_gyre/)

Author: Oliver Jahn and Chris Hill

This set of examples is based on the barotropic and baroclinic gyre MITgcm configurations, that are described in the tutorial sections 3.9 and 3.10. The examples in this section explain how to introduce a passive tracer into the flow field of the barotropic and baroclinic gyre setups and looks at how the time evolution of the passive tracer depends on the advection or transport scheme that is selected for the tracer.

Passive tracers are useful in many numerical experiments. In some cases tracers are used to track flow pathways, for example in Dutay et al. [2002] a passive tracer is used to track pathways of CFC-11 in 13 global ocean models, using a numerical configuration similar to the example described in section 3.20.5). In other cases tracers are used as a way to infer bulk mixing coefficients for a turbulent flow field, for example in Marshall et al. [2006] a tracer is used to infer eddy mixing coefficients in the Antarctic Circumpolar Current region. In biogeochemical and ecological simulations large numbers of tracers are used that carry the concentrations of biological nutrients and concentrations of biological species, for example in .... When using tracers for these and other purposes it is useful to have a feel for the role that the advection scheme employed plays in determining properties of the tracer distribution. In particular, in a discrete numerical model tracer advection only approximates the continuum behavior in space and time and different advection schemes introduce diferent approximations so that the resulting tracer distributions vary. In the following text we illustrate how to use the different advection schemes available in MITgcm here, and discuss which properties are well represented by each one. The advection schemes selections also apply to active tracers (e.g. $ T$ and $ S$ ) and the character of the schemes also affect their distributions and behavior.



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