Intrinsic oceanic variability in the Argentine basin

In order to analyze the oceanic variability of intrinsic origin in the Southern Ocean (SO), the sigma-coordinate “Princeton Ocean Model” has been implemented under steady climatological surface heat and momentum fluxes. The central role played by bottom topography and stratification in setting up a consistent mean circulation is evident. The simulations show several phenomena of both high and low-frequency variability that are, again, strongly sensitive to bottom topography, stratification and parameterization of frictional processes. Self-sustained oscillations are found to be particularly significant over a wide range of time scales in the Argentine Basin; recent observations suggest the existence of similar features. In particular, the Zapiola Rise, the main topographic feature in the Argentine Basin, appears to control such variability. The analysis of transport and sea surface height signals obtained from the model results shows a high-frequency variability that we interpret in terms of topographic Rossby normal modes, and a low-frequency variability (yielding rapid switches from a weakly variable regime and a highly variable one, and viceversa) that is affecting the high-frequency variability. Interesting agreement is found when comparing model results with altimeter data.