Configuration and validation of an oceanic physical and biogeochemical
model to investigate coastal eutrophication: case study in the Southern
California Bight
Abstract
The Southern California Bight (SCB), an eastern boundary upwelling
system, is impacted by global warming, acidification and deoxygetation,
and receives anthropogenic nutrients from a coastal population of 20
million people.
We describe the configuration, forcing, and validation of a realistic,
submesoscale resolving ocean model as a tool to investigate coastal
eutrophication. This modeling system represents an important achievement
because it strikes a balance of capturing the forcing by U.S. Pacific
Coast-wide phenomena, while representing the bathymetric features and
submesoscale circulation that affect the vertical and horizontal
transport of nutrients from natural and human sources.
Moreover, the model allows to run simulations at timescales that
approach the interannual frequencies of ocean variability, making the
grand challenge of disentangling natural variability, climate change,
and local anthropogenic forcing a tractable task in the near-term. The
model simulation is evaluated against a broad suite of observational
data throughout the SCB, showing realistic depiction of mean state and
its variability with remote sensing and in situ physical-biogeochemical
measurements of state variables and biogeochemical rates. The simulation
reproduces the main structure of the seasonal upwelling front, the mean
current patterns, the dispersion of plumes, as well as their seasonal
variability. It reproduces the mean distributions of key biogeochemical
and ecosystem properties. Biogeochemical rates reproduced by the model,
such as primary productivity and nitrification, are also consistent with
measured rates. Results of this validation exercise demonstrate the
utility of fine-scale resolution modeling in support of management
decisions on local anthropogenic nutrient discharges to coastal zones.