DOI: 10.6075/j08g8mp6
title: Data from: Understanding regional pCO2 model biases and uncertainties in the Biogeochemical Southern Ocean State Estimate (B-SOSE)

description: The B-SOSE model domain extends from an open boundary at the equator to 78ºS, and our analyses focus on the solution poleward of 30ºS. The physical configuration is based on the MIT general circulation model and software developed by the consortium for Estimating the Circulation and Climate of the Ocean (ECCO; Wunsch & Heimbach, 2013). It has 52 vertical levels of varying thickness, a zonal grid resolution of 1/3º, and a meridional grid resolution that varies with latitude. Boundary conditions, initial conditions, and other configuration parameters are described by Verdy & Mazloff (2017). The biogeochemical model is the Nitrogen-based Biogeochemistry with Light, Iron, Nutrients, and Gases model (N-BLING) adapted from Galbraith et al. (2010). The version employed has nine prognostic tracers: iron (Fe), nitrate (NO3), phosphate (PO4), dissolved inorganic carbon, alkalinity, dissolved oxygen, dissolved organic nitrogen, dissolved organic phosphorus, and phytoplankton biomass. N-BLING and its carbonate system are described in detail by Verdy & Mazloff (2017) and Dutkiewicz et al. (2015), respectively. In the present study, the control run is initialized with ocean temperature (T), salinity (S) and current velocities from a B-SOSE run spun up from December 2012. The B-SOSE spin up run includes adjustments to initial conditions and atmospheric state to fit all observational data but did not systematically adjust the biogeochemical model parameters nor specifically target the fit to fCO2 observations. This model setup was previously used to estimate biological parameters to improve the model chlorophyll vertical structure patterns (Kuhn et al., 2025). Alkalinity and Dissolved Inorganic Carbon initial conditions are from the Global Ocean Data Analysis Project version 2 (GLODAPv2). The B-SOSE code is written in Fortran and input files are provided as binary files.
description: This item contains model code and initial conditions to run the Biogeochemical Southern Ocean State Estimate (B-SOSE) with a control run configuration and 32 model perturbation experiments. Each perturbation experiment modifies a single model biogeochemical parameter, initial condition or model forcing. These perturbations include 9 biogeochemical model parameters, 1 sea-ice parameter, scaling factors for the initial conditions of T, S and total alkalinity, as well as scaling factors for short-wave radiation, long-wave radiation, and wind (u and v). Parameters were perturbed by doubling and halving the a priori parameter value used on the control run. Initial conditions and scaling factors for forcing variables were perturbed between 1% and 10% throughout the entire domain. A full description of the model and model experiments is included in Kuhn et al.

The item also includes model - observations misfits estimated between simulated surface carbon dioxide fugacity (fCO2) from B-SOSE's control run and perturbation experiments and fCO2 observations from the Surface Ocean CO2 Atlas (SOCAT). These perturbed model results were used to estimate new model optimized parameters to reduce the misfits to SOCAT observations.