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Physical and biogeochemical drivers of alongshore pH and oxygen variability in the California Current System

Citation

Fiechter, Jerome; Cheresh, Julia (2021), Physical and biogeochemical drivers of alongshore pH and oxygen variability in the California Current System, Dryad, Dataset, https://doi.org/10.7291/D1D96Q

Abstract

In the California Current System (CCS), the nearshore environment experiences natural exposure to low pH and reduced oxygen in response to coastal upwelling. Anthropogenic impacts further decrease pH and oxygen below biological thresholds, making the CCS particularly vulnerable to ocean acidification and hypoxia. Results from a coupled physical-biogeochemical model reveal a strongly heterogeneous alongshore pattern of nearshore pH and oxygen in the central CCS, both in their long-term means and trends. This spatial structuring is explained by an interplay between alongshore variability in local upwelling intensity and subsequent primary production, as well as changes in the vertical density structure modulated by meanders in the regional ocean circulation. The model solution suggests that the progression of ocean acidification and hypoxia will not be spatially homogeneous, thereby highlighting the need to consider sub-regional processes when assessing natural and anthropogenic impacts on coastal ecosystems in eastern boundary current upwelling regions.

Methods

This dataset is a subset of a coupled physical-biogeochemcial model for the central California Current upwelling system. The physical model is an implementation of the Regional Ocean Modelling System (ROMS; www.myroms.org) coupled to NEMUCSC, a customized version of the North Pacific Ecosystem Model for Understanding Regional Oceanography (NEMURO). The NEMUCSC biogeochemical model includes three limiting macro-nutrients, two phytoplankton functional groups, three zooplankton size-classes, and three detritus pools. To better represent the combined effects of regional circulation patterns and local upwelling intensity on alongshore biophysical properties, the model downscales a data-assimilative physical reanalysis at 1/10° (~10 km) resolution for the broader California Current system to a higher 1/30° (~3 km) resolution domain for the central California Current region. A subset of variables were extracted from the full daily model output at various depths and subsequently averaged monthly for 1988-2010 using Ferret V7.1 (http://ferret.pmel.noaa.gov/Ferret). The dataset is in NetCDF4 format (CF-1.4 compliant) with metadata describing each variable name and associated units on the native ROMS grid.

Usage Notes

All necessary information to use this dataset is contain in the metadata (variable name, units, missing value flag, etc).

Funding

National Science Foundation, Award: OCE1566623

National Science Foundation, Award: OCE1635315