Three-dimensional response of the ecosystem to upwelling off the Oregon Coast

Time-dependent, three-dimensional response of the ecosystem to upwelling off the Oregon coast is studied using the Princeton Ocean Model (POM) and a coupled five-component ecosystem model (NNPZD) (Spitz et al., 2002). The spatial and temporal variability of the ecosystem during the summer 2001 on the Oregon shelf is investigated. High mean surface phytoplankton values are found near the coast and extend over Heceta Bank, with a pattern similar to the cold surface temperature. The standard deviations of phytoplankton are the largest on Heceta Bank, where northward currents associated with a cyclonic circulation are found near the coast during relaxations. Vertical sections show that higher standard deviations are found deeper on Heceta Bank (44.2 N) than at two northern sections (44.7 N and 45 N). This corresponds also to higher standard deviations of nitrate at depth. The maximum mean surface zooplankton is located offshore of the maximum phytoplankton. The low standard deviations of zooplankton found at the surface near the maximum mean zooplankton values indicate that this pattern is a quasi-permanent feature during the 2001 upwelling season. The highest standard deviations of zooplankton are found near the coast and near the 200 m isobath. A complete description of the relative contribution of physical and biological forcing to the ecosystem response will be presented.