SST fronts in the Southeastern Pacific

According to Fedorov et al. (1984) the Subtropical and Subantarctic frontal zones corresponding to the oceanic fronts out of the Peruvian and Chilean economic zones show some frontal lines which, like in other frontal zones of the planet, present climatic character. The basic analysis of the dynamics, and the classification of the fronts in this areas of the Southeastern Pacific, were done using satellite monitory data for the changes in the sea surface temperature (SST) over the period 1986-1996, and monthly mean data. To estimate the annual dynamics for the frontal dividing lines, monthly SST data for the period July 1989 to August 1990 were used, based on 1x1 squares over the region between 5-45º S and 100º W - American coast. The identification of the fronts and frontal zones was made analyzing all together the following characteristics: the SST gradient, the areas presenting maximum clustering for the isotherms, the temperature magnitudes, and the time-spatial dynamics for all these parameters. Contrasting with the previous classification, which presented the fronts for the Southeastern Pacific only as the Subtropical Convergence Zone, the data used in the present paper allow to distinguish four frontal zones and their corresponding fronts in the region under study: A - Principal Subtropical Front - PSTF (T=18º C), B- North Subtropical Front - NSTF (T=15º C), C- Subtropical Surface Front - STSF (T=12º C), and D - South Subtropical Front - SSTF (T=10º C). Moreover, from the changes in the frontal location, areas presenting along a year three of these fronts are distinguished. This area, where usually and during a year one other front (or A, or B, or C) is found, is the best concentration area for the Jurel (Trachurus symmetricus murphyi) in the Southeastern Pacific.