Starting date : T0 duration : 18 months

Main contributors : R. Person, C. Perruche, C. Lo Monaco

• The purpose of this task is (i) to identify and gather key observation databases for the project and (ii) to gather model-data inter-comparison tools available within the consortium.
• The tools and database will be made available to the project team through the project information system at LGGE. The database will in particular (but not only) include: ARGO profiles, elephant seals data, GLODAP, SOCAT and satelllite ocean color data. The tools will in particular include DRAKKAR monitoring procedure and the tools developed during ANR CONVERGENCE. The tools will be coherently assembled in a hierarchical model assessment procedure.
• The expected outcome is the preparation of an integrated evaluation procedure to be used throughout the project.

Starting date : T0 duration : 4 months

Main contributors : R. Person, O. Aumont, L. Bopp, I. Merino

• The purpose of this task is to revisit the formulation and the parameters of Iron sources in PISCES biogeochemical model.

• The work will be carried out with eORCA1 model configuration and then ported to eORCA025. The first step will include gathering existing information on iron distribution (with in particular GEOTRACES IDP2014 and KEOPS2 profiles) and sources (including sea ice and glacial/iceberg melt). The work will mostly consist in a series of sensitivity experiment carefully compared with observations with the tools from WP1.1.

• The expected outcome is an improved primary production distribution and seasonality in the Southern Ocean in PISCES simulations.

Starting date : T0 + 4 duration : 8 month

Main contributors : R. Person, O. Aumont, C. Ethé, M. Vancoppenolle

• The purpose of this task is to adapt the parameters of PISCES biogeochemical model to Southern Ocean condition in the revisited model configuration eORCA1 (extended grid and new iron sources).
  

• The work will consist in a series of model experiments with eORCA1 model configuration with the new iron sources. The model validation will mostly focus on the representation of the carbon cycle and in reducing the adjustment trends due to the adequation between initial conditions and model parameters. Possible adjustments of the model vertical physics are also planned.
  

• The expected outcome is a improved model representation of Southern Ocean biogeochemical cycles in PISCES. This will be presented in paper to be prepared for Geophysical Model Development.

Starting date : T0 duration : 6 months

Main contributors: G. Maisant, J. Deshayes, R. Person, C. Ethé

• The purpose of this task is to prepare eORCA025 physical model configuration to be run with coupled biogeochemistry.

• The work will consist in a series of sensitivity test performed within the frame of OMIP forcing protocol and based on the expertise of the DRAKKAR group (physics) and of LSCE (physics + BGC). The tests will allow to define a choice of parameters for vertical physics and also to improve the representation of vertical velocities in the model solution.

• The expected outcome is an improved physical model solution that is well adapted to coupling with PISCES to be used in WP3 and WP4.
  

Starting date : T0 + 6 duration : 6 months

Main contributors: C. Ethé, R. Person, C.Bricaud

• The purpose of this task is to integrate eORCA025 with PISCES and the online coarsening capability.

• The work will first consist in a series of calibration tests with eORCA025 and an age tracer including the online coarsening capability. Second, based on the results of 1.2, we will perform a series of test simulations that will be carefully compared with observations for both the physics (including sea ice) and the biogeochemistry components.

• The expected outcome is model solution (i) that compares favorably with observations and (ii) that is produced with reduced cost thanks to the coarsening capability. The model solution and development will be presented in a paper to be prepared for Geophysical model Development and will serve as a baseline configuration for OMIP inter-comparison.

Starting date : T0 + 12 duration : 12 months

Main contributors: E. Alekseenko, C. Ethé

• The purpose of this task is to produce the series of ensemble sensitivity experiments that will be the base material for WP3 and WP4.2.

• Based on the recommendations of WP3.1, we will perform a series of multi-decadal simulations with reference and perturbed forcings with eORCA1 and eORCA025. We will in particular explicitly modify the forcing in order to account for changes in surface winds, in radiative forcing and in glacial input of iron and freshwater.

• The expected outcome is the scientific material for WP3.3 and WP4.2.

Starting date : T0 + 6 duration : 6 months

Main contributors :  L. Bopp, B. Barnier

• The purpose of this task is to design the set of perturbations of the reference forcing that will be used in WP2 .3 and WP4.1

• Several perturbations will be considered : surface winds, air temperature and specific humidity, radiative fluxes and glacial/melt input. For winds, air temperature and specific humidity, the perturbation will be built from the trends of atmospheric properties that are consistently reproduced by atmospheric reanalysis over the last decades. The perturbation of short wave radiation will be built from the analysis of a series of CMIP5 simulation because atmospheric reanalysis do not show consistent trends in radiations. The perturbation of glacial input will be built from an AIS evolution scenario.

• The expected outcome is the forcing scenario that will be used in WP2.3 and WP4.1.
  

Starting date : T0 + 18 duration : 12 months (+ 6 months for publication)

Main contributors : M. Vancoppenolle, O. Aumont, Postdoc-LGGE, N. Jourdain

• The purpose of this task is to study how changes in Southern Ocean cryosphere affect biogeochemistry.

• In eORCA025 and eORCA1 simulations, sea-ice will respond to perturbations in the forcing fields (esp. to winds and glacial melt). How changes in sea ice affect biological production is still unclear because changes in sea-ice will affect both light availability and iron supply. We will here study in detail these processes in eORCA025 an eORCA1 model simulations. In addition, a series of 1D-water column idealized model experiments will be performed with prescribed sea-ice in order to investigate a range of parameter regimes.

• The expected outcome is a series of guidelines for the analysis of WP3.3. The results will be presented in a dedicated scientific paper.

Starting date : T0 + 24 duration : 18 months (+ 6 months for publication of results).

Main contributors : Postdoc-LGGE, XX, J. Orr

• The purpose of this core task is to study the response of Southern Ocean biogeochemistry to changes in climate stressors.

• We will study in detail how the Southern Ocean biogeochemical system respond to changing stressors in the series of eORCA025 simulations. We will in particular quantify the response of primary production, the response of the carbon cycle (air-sea CO2 fluxes, carbon subduction, … ) and the response of the carbonate system (acidification). We will study the impact of each changing stressors and also the impact of the combined change in all the stressors. A particular focus will be put on contrasting the response of eORCA1 and the response eORC025 in order to assess the representation of the response in coarse resolution climate models.

• The expected outcome is a improved understanding of the mechanisms involved in the future evolution of Southern Ocean biogeochemistry and guidance for the analysis of coupled CMIP6 simulations (see WP5.2). The results will be presented in scientific papers.

Starting date : T0 + 18 duration : 24 months

Main contributors : Postdoc-LOCEAN, M. Levy, X. Capet

• The purpose of this task is to quantify how the scale that are not resolved in eORCA025 affect nutrient supply and productivity in the Southern Ocean.

• The study will focus on the region of Kerguelen plateau because of the relatively high density of observations in this regions. The region downstream the plateau will here be considered as representative of Southern Ocean bloom regimes downstream ACC obstacles. We will use ZKERG36 model configuration and the simplified iron model of Wadley et al. (2014). We will produce a series of short simulation (5 years) with the reference forcing and the perturbation due to winds. The simulations will be reproduced at several other model grid resolutions (1/2°, 1/4°, 1/12°). The simulations will be used to quantify how small scale dynamics contribute to transporting iron both laterally from the plateau and vertically to the surface layers. A key question is in particular to contrast the role of small scale dynamics versus large scale advection by the ACC or versus seasonal entrainment to the mixed layer. The response of submesoscale dynamics to changes in winds will also be carefully quantified.
  

• The expected outcome is the first quantitative assessment of the role of sub-mesoscale dynamics on Southern Ocean productivity. This study will provide indications of the limitations of ocean components of CMIP6 ESMs in the Southern Ocean. The results will be presented in a dedicated science paper.
  

Starting date : T0 + 18 duration : 18 months

Main contributors : Postdoc-LSCE, J. Orr, XX, M. Gehlen , T. Penduff,

• The purpose of this task is to quantify how «eddy-driven » intrinsic low frequency variability of physical variables affect Southern Ocean biogeochemistry.  

• This study will be carried out on the basis of the material produced in WP2.3. We will mostly focus on the ensemble of references simulations (2 to 5 members). We will first quantify systematically the fraction of the interannual variability of biogeochemical variables that is not driven by the forcing. This will be done using the metrics developed by OCCIPUT project. We will focus in particular on primary production and air sea CO2 fluxes with a specific focus on the impacts at large scale. Then we will study what are the routes for the intrinsic variability of physical variables to imprint Southern Ocean biogeochemistry. We will in particular study how the changes in surface stratification and surface temperature actually drive changes in primary production.

• The expected outcome is the first quantification of the magnitude of « eddy-driven» intrinsic low frequency variability of Southern Ocean biogeochemistry. This will provide error bars for WP3.3 and material for WP5.3. The results will be presented in a dedicated science paper.

 Leader: James Orr

Starting date : T0 duration : 48 months

Main contributors : J. Orr, E. Alekseenko

• The purpose of this task is to set-up the internal and external communication tools for the project and to ensure that relevant material is always available through these tools over the course of the project.

• We will set up a state-of-the-art information system for the project. This will in particular comprise a project web site for both internal exchanges of scientific and technical material and external communication. We will extensively use a version control system for sharing numerical codes (svn). An automated monitoring of model simulations will also be available to the project team. All the members of the project team will therefore always have access to up-to-date information about ongoing activities. In addition, we will prepare a series of animations with model data band synthetic BIO-ARGO floats, for outreach and communication purposes.
  
• The expected outcome is (i) to ensure a high level of interactions among consortium institutions and (ii) to attract good postdoc candidates for the science studies.

 Starting date : T0 + 12 duration : 36 months

Main contributors : L. Bopp, XX, J. Orr

• The purpose of this task is to ensure that the relevant outcome and results of the project are seamlessly transferred to OMIP groups and CMIP6 community

• As mentioned above the baseline configuration obtained in WP2.2 will be used for participating in OMIP inter-comparison experiments. In addition, we intend to investigate the response of Southern Ocean biogeochemistry in IPSL-CM and CNRM-CERFACS-CM CMIP6 simulations in light of the results of our project. This activity will be carried out in collaboration with H2020-Crescendo project. Furthermore, we propose to organize a workshop on « eddying biogeochemical components in CMIP6 » at T0+36.

• The expected outcome is an optimal dissemination of the project results and a first analysis of Southern Ocean trends in NEMO based CMIP6 simulations. This will be presented in a dedicated science paper.

Starting date : T0 + 36 duration : 12 months

Main contributors : M. Gehlen , P. Brasseur, J.B. Sallée, C. LoMonaco

• The purpose of this task is to understand how the presence of eddy-driven low frequency variability can affect our future observation strategies.

• We will focus on the question of whether the Southern Ocean observing system is well-adapted to detecting trends due to climate stressors. To this purpose, we will map the structure and amplitude of the intrinsic variability (primary production, pCO2,…) as seen by the observing systems (inc. Bio-Argo and ocean color). A dedicated workshop will be organized at T0+48 in year 4.

• The expected outcome is the dissemination of our results to observing teams. A dedicated science paper will also be prepared.