Preprints
https://doi.org/10.5194/gmd-2022-244
https://doi.org/10.5194/gmd-2022-244
Submitted as: model description paper
21 Nov 2022
Submitted as: model description paper | 21 Nov 2022
Status: this preprint is currently under review for the journal GMD.

Formulation, optimization and sensitivity of NitrOMZv1.0, a biogeochemical model of the nitrogen cycle in oceanic oxygen minimum zones

Daniele Bianchi, Daniel McCoy, and Simon Yang Daniele Bianchi et al.
  • University of California Los Angeles, CA

Abstract. Nitrogen (N) plays a central role in marine biogeochemistry by limiting biological productivity in the surface ocean, in- fluencing the cycles of other nutrients, carbon, and oxygen, and controlling oceanic emissions of nitrous oxide (N2O) to the atmosphere. Multiple chemical forms of N are linked together in a dynamic N cycle that is especially active in oxygen minimum zones (OMZs), where high organic matter remineralization and low oxygen concentrations fuel aerobic and anaerobic N transformations. Biogeochemical models used to understand the oceanic N cycle and project its change often employ simple parameterizations of the network of N transformations and omit key intermediary tracers such as nitrite (NO2-) and N2O. Here we present a new model of the oceanic N cycle (Nitrogen cycling in Oxygen Minimum Zones, or NitrOMZ) that resolves N transformation occurring within OMZs, and their sensitivity to environmental drivers. The model is designed to be easily coupled to current ocean biogeochemical models by representing the major forms of N as prognostic tracers, and parameter- izing their transformations as a function of seawater chemistry and organic matter remineralization, with minimal interference with other elemental cycles. We describe the model rationale, formulation, and numerical implementation in a one-dimensional representation of the water column that reproduces typical OMZ conditions. We further detail the optimization of uncertain model parameters against observations from the Eastern Tropical South Pacific OMZ, and evaluate the model ability to reproduce observed profiles of N tracers and transformation rates in this region. We conclude by describing the model sensitivity to parameter choices and environmental factors, and discussing the model suitability for ocean biogeochemical studies.

Daniele Bianchi et al.

Status: open (until 16 Jan 2023)

Comment types: AC – author | RC – referee | CC – community | EC – editor | CEC – chief editor | : Report abuse

Daniele Bianchi et al.

Data sets

NitrOMZv1.0 Model Code Daniele Bianchi, Daniel McCoy, Simon Yang https://zenodo.org/record/7106213#.Yzc0_OzMIUE

Model code and software

NitrOMZv1.0 Model Code Daniele Bianchi, Daniel McCoy, Simon Yang https://zenodo.org/record/7106213#.Yzc0_OzMIUE

Daniele Bianchi et al.

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Short summary
We present NitrOMZ, a new model of the oceanic nitrogen cycle that simulates chemical transformations within Oxygen Minimum Zones (OMZ). We describe the model formulation and its implementation in a one-dimensional representation of the water column, before evaluating its ability to reproduce observations in the Eastern Tropical South Pacific. We conclude by describing the model sensitivity to parameter choices and environmental factors, and its application to nitrogen cycling in the ocean.