New production in the upwelling center at Point Conception, California: temporal and spatial patterns

Abstract

As part of the Organization of Persistent Upwelling Structures (OPUS) 1983 study of the Point Conception upwelling system, a station (G-1) at the cold center between Points Conception and Arguello was occupied almost daily, a section measuring biological variables was made regularly along a line (the C-line) extending south from Point Arguello, and a series of drifter-following experiments were made on the R.V. Velero IV. Water upwelled at 5-1 follows either a cyclonic or anticyclonic flow pattern and in both cases usually crosses the C-line to enter the Santa Barbara channel. As seen in previous upwelling studies, the ability to take up nitrate increased with time and along with the circulation pattern, this “shift-up” determined the pattern of new production. Weak upwelling was associated with the cyclonic path, longer travel time to the C-line, and higher new production rate at the south end of the C-line. High wind stress and strong upwelling was associated with the anticyclonic mode, short travel time, and low production rates at the north end of the C-line. Comparisons with the 15°S, Peru upwelling center and with the Cap Blanc (northwest Africa) upwelling system showed similarities with both. The highest new production rates at Point Conception and Cap Blanc were associated with relaxation events and the sequence of biological processes during upwelling at Point Conception closely followed the Peru pattern. New production rates in 1983 at Point Conception fell at the low end of the spectrum of these upwelling centers.