WP3 : Response of Southern Ocean biogeochemistry to changing climate stressors

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.