Submitted as: model description paper
23 Jan 2023
Submitted as: model description paper | 23 Jan 2023
Status: this preprint is currently under review for the journal GMD.

Ocean biogeochemistry in the coupled ocean-sea ice-biogeochemistry model FESOM2.1-REcoM3

Özgür Gürses, Laurent Oziel, Onur Karakus, Dmitry Sidorenko, Christoph Völker, Ying Ye, Moritz Zeising, and Judith Hauck Özgür Gürses et al.
  • Alfred-Wegener-Institut, Helmholtz-Zentrum für Polar- und Meeresforschung

Abstract. The cycling of carbon in the oceans is affected by feedbacks driven by changes in climate and atmospheric CO2. Understanding these feedbacks is therefore an important prerequisite for projecting future climate. Marine biogeochemical models are a useful tool there, but as any model is a simplification, need to be continually improved. In this study, we coupled the Finite-volumE Sea ice-Ocean Model (FESOM2.1) to the Regulated Ecosystem Model version 3 (REcoM3). FESOM2.1 is an update of the Finite Element Sea ice-Ocean Model (FESOM1.4) and operates on variable mesh resolution. Unlike standard structured-mesh ocean models, the mesh flexibility allows for a realistic representation of small-scale dynamics in key regions at affordable computational cost. Compared to the previous coupled model version FESOM1.4-REcoM2, the model FESOM2.1-REcoM3 utilizes a new dynamical core based on a finite volume discretization instead of finite elements, but retains central parts of the biogeochemistry model. As a new feature, carbonate chemistry including water vapor correction is computed by mocsy-2.0. Moreover, REcoM3 has an extended food web that includes macrozooplankton and fast-sinking detritus. Dissolved oxygen is added as a new tracer. In this study we assess the ocean and biogeochemical state simulated with FESOM2.1-REcoM3 in a global setup at relatively low spatial resolution forced with JRA55-do atmospheric reanalysis. The focus is on the recent period 1958–2021, to assess how well the model can be used for present-day and future climate change scenarios on decadal to centennial timescales. A bias in global ocean-atmosphere preindustrial CO2 flux present in the previous model version FESOM1.4-REcoM2 could be significantly reduced. In addition, the computational efficiency is 2–3 times higher than that of FESOM1.4-REcoM. Overall, it is found that FESOM2.1-REcoM3 is a skillful tool for ocean biogeochemical modelling applications.

Özgür Gürses et al.

Status: open (until 20 Mar 2023)

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Özgür Gürses et al.

Özgür Gürses et al.


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Short summary
This paper is assessing the biogeochemical model REcoM3 coupled to the ocean-sea ice model FESOM2.1. The model can be used e.g. to simulate the carbon uptake or release of the ocean on time scales of several hundred years. A detailed analysis of nutrients, ocean productivity and ecosystem is followed by the carbon cycle. The main conclusion is that the model performs well in simulating the observed mean biogeochemical state and variability, and is comparable to other ocean-biogeochemical models.