A Meridionally Averaged Model of Eastern Bounday Upwelling Systems: An Ecosystem Overview

Eastern Boundary Upwelling Systems (EBUSs) exhibit strong coupling between atmospheric wind forcing, biogeochemical cycles, oceanic transport, and mixing. This complex interplay between physical and biological dynamics lead to variations in primary productivity as a result of a changing climate. To better understand the impact of these physical processes on biology, we have developed a Meridionally-Averaged Model of Eastern Boundary Upwelling Systems (MAMEBUS) - a quasi-2D physical model cast in terrain following coordinates, coupled with biogeochemical models ranging from a single nutrient-cycling model to more complex NPZD models with size structured ecosystems. This hierarchy of models is coupled with prognostic oxygen and carbon tracers, and allow us to study hypoxia and acidification in an efficient and idealized manner. Studies have shown that feedbacks from increasing acidification in coastal waters support increased phytoplankton uptake rates and carbon export to depth. The increased carbon export, in turn, decrease the oxygen concentration at depth. While the oxygen and carbon cycling of the ecosystem have been regularly studied, the effects of physics on biology are not well understood. As a result, we have run our model focusing on the California Current System with a wide range of climate forcings including increased surface buoyancy restoring via an increased heat flux, increased upwelling-favorable winds, and the protrusion of hypoxic waters from the subtropical oxygen minimum zone and the the transport of anoxic waters in the undercurrent from the North Pacific. We discuss the implications of our findings to characterize the variability of primary productivity, ecosystem feedbacks, oxygen concentration, and DIC, as a response to physical forcings due to a changing climate. Our results, though regional in scope, can be used to inform 3D regional models, and can be used to extrapolate the higher impacts on fisheries.