Upwelling and cross-shelf transport dynamics along the Pacific Eastern Boundary

Abstract

The upwelling and cross-shelf transport dynamics along the Pacific Eastern Boundary is explored using a high resolution ocean model for the last 60 years. Three ocean circulations have been modeled. From North to South, we investigate the dynamics of the Gulf of Alaska (GOA), the California Current System (CCS) and the Humboldt Current System (HCS, also known as the Peru-Chile Current System). The statistics of coastal waters transport are computed using a model passive tracer, which is continuously released at the coast. By looking at the passive tracer concentration distribution, we find that the Pacific Decadal Oscillation modulates the coastal variability of the GOA, the North Pacific Gyre Oscillation controls the upwelling of the CCS, while the El-Niño Southern Oscillation affects the upwelling of Peru and Chile mainly through coastally trapped Kelvin waves. Results also emphasize the key role of the mesoscale eddies in the offshore transport of coastal waters masses. The passive tracer experiments, performed in this study in the GOA, CCS, and HCS, therefore could provide a dynamical framework to understand the dynamics of the upwelling/downwelling and offshore transport of nutrient rich coastal water and to interpret how it responds to atmospheric forcing. This also could reinforce our interpretation (and therefore predictions) in the changes in vertical and offshore advection of other important biogeochemical quantities, essential in understanding ecosystem variability.