An inter-EBUS comparison of zonal patterns of phytoplankton diversity with a Meridionally Averaged Model of Eastern Boundary Upwelling Systems (MAMEBUS)

Eastern Boundary Upwelling Systems (EBUSs) exhibit strong coupling between atmospheric wind forcing, oceanic transport and mixing, and biogeochemical cycles. This interplay of physical and biological dynamics lead to differences between EBUSs, notably in overall biological productivity. Recent studies have highlighted the response of primary productivity to mesoscale eddies, which induce an overturning circulation that opposes wind-driven upwelling, subsequently burying nutrients below the euphotic zone via stirring along isopycnals.

To better understand the impact of these physical processes on biology, and the horizontal extent of the nearshore phytoplankton bloom, we 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 NPZD models with size structured ecosystems.

This idealized model configuration allows us to explore the physical and biogeochemical dynamics of EBUS across a wide range of parameters, while circumventing the computational limitations associated with eddy resolving regional models. In this study, we use MAMEBUS to explore a physical and biogeochemical parameter space through idealized configurations of four eastern boundary upwelling systems and discuss the impacts on lower trophic level ecosystems. Specifically, we vary the strength in the wind stress forcing and the bathymetry in order to explore the variability in the source depth of upwelled water on the shelf, and the response of the biogeochemistry in a hierarchy of ecosystem models. With our experiments, we show results in varying biogeochemical model complexity, from a single nutrient model to size structured ecosystem model.