Observing global ocean topostrophy

Abstract

Recent publications have evaluated topostrophy, τ Ξ f x V · ∇D where is f Coriolis, V is velocity, and ∇D is gradient of total depth, as a means of comparing models' circulations. Some results are striking. Comparing four global models, two with modest grid size and two with fine grids, Merryfield and Scott (2007) show that finer grid models are characterized by more positive τ, especially at greater depths and higher latitudes. Among nine Arctic Ocean models, Holloway et al. (2007) find τ in three of the models quite distinct from the other six, a result shown to depend upon subgrid eddy parameterization. From different choices of numerical method within the same model, Penduff et al. (2007) show that improved numerical representations support more positive τ. Can these model results be compared with observations? A global compilation has been prepared from 17120 current meter records, spanning 83087 current meter-months. The compilation tends to confirm modeling progress achieved by finer resolution, improved parameterizations and better representations. A new characterization of global ocean circulation emerges, with suggestive dynamical insights. Copyright 2008 by the American Geophysical Union.