Climate Variability of the Northern Argentinean Shelf Circulation: Impact on Engraulis Anchoita

Abstract

A high-resolution ocean model and hydrographic observations are used to characterize the shelf circulation of the northern Argentinean shelf during the study period (1993–2008) and ultimately to explore possible linkages among atmospheric, oceanic, and biological climatic variability. Abundance of larvae and eggs of the local anchovy species, Engraulis anchoita, exhibit a spatial and temporal variability similar to those stocks found in other parts of the world and that we interpret in the context of the particularities of the local circulation and hydrography. Two (statistically) coupled modes of wind stress-surface velocity are described and interpreted in terms of historical and new information. A complex picture emerges in which the intensity of both a thermal shelf front, the alongshore flow, and larvae abundance would be connected and forced by local wind stresses. For all areas examined on the shelf, the larvae/egg abundance would not be very sensitive to short-lived climatic fluctuations (e.g., year-to-year) but they would be indeed to regime shifts. The shallow shelf area bounded by the 39°S and 41°S parallels would expose a clearer linkage between physical and biological variables than that north of 39°S. We attribute this fact to the particular physical conditions found in the southernmost area, which would favor an increased habitat quality for Engraulis anchoita.