The ANR MEDSALT project aims to consolidate and expand a scientific network recently formed with the purpose to use scientific drilling to address the causes, timing, emplacement mechanisms and consequences of the largest and most recent 'salt giant' on Earth: the late Miocene (Messinian) salt deposit in the Mediterranean basin. After obtaining the endorsement of the International Ocean Discovery Program (IODP) on a Multiplatform Drilling Proposal (umbrella proposal) in early 2015, the network is planning to submit a site-specific drilling proposal to drill a transect of holes with the R/V Joides Resolution in the evaporite-bearing southern margin of the Balearic promontory in the Western Mediterranean - the aim is to submit the full proposal before the IODP dealine of April 1st 2017, following the submission of a pre-proposal on October 1st 2015. Four key issues will be addressed: 1) What are the causes, timing and emplacement mechanisms of the Mediterranean salt giant ? 2) What are the factors responsible for early salt deformation and fluid flow across and out of the halite layer ? 3) Do salt giants promote the development of a phylogenetically diverse and exceptionally active deep biosphere ? 4) What are the mechanisms underlying the spectacular vertical motions inside basins and their margins ? Our nascent scientific network will consit of a core group of 22 scientists from 10 countries (7 European + USA + Japan + Israel) of which three french scientists (G. Aloisi, J. Lofi and M. Rabineau) play a leading role as PIs of Mediterranean drilling proposals developed within our initiative. Support to this core group will be provided by a supplementary group of 21 scientists that will provide critical knowledge in key areas of our project. The ANR MEDSALT network will finance key actions that include: organising a 43 participants workshops to strengthen and consolidate the Mediterranean drilling community, supporting the participation of network scientists to seismic well site-survey cruises, organising meetings in smaller groups to work on site survey data and finance trips to the US to defend our drilling proposal in front of the IODP Environmental Protection and Safety Panel (EPSP). The MEDSALT drilling initiative will impact the understanding of issues as diverse as submarine geohazards, sub-salt hydrocarbon reservoirs and life in the deep subsurface. This is a unique opportunity for the French scientific community to play a leading role, next to our international partners, in tackling one of the most intellectually challenging open problems in the history of our planet.

The Southern Ocean (oceans south of 30°S) plays a key role in global biogeochemical cycles. Vertical exchange in the Southern Ocean is indeed responsible for half of the oceanic uptake of anthropogenic carbon dioxide and for supplying nutrients that fertilize three-quarters of the biological production in the global ocean. Both roles are tied to the variability of water mass transport and primary production in the Southern Ocean. Indeed, the upwelling branch of the Southern Ocean overturning circulation returns carbon and nutrients to the surface ocean, while downwelling branches transport heat, carbon, nutrients and other properties into the ocean interior. The balance between upwelling and release of CO2 versus carbon uptake into the ocean interior determines the strength of the Southern Ocean sink of CO2. But large environmental changes are ongoing in the Southern Ocean physical and biogeochemical properties. These changes reflect widespread environmental changes that are occurring throughout the southern hemisphere and over the Southern Ocean (changes in surface winds, solar radiation, sea ice cover and glacial melt from Antarctica). How the Southern Ocean primary production and carbon cycle will respond to these changing climate stressors is a matter of concern in the climate science community. New observing networks and also the major step-change in the realism of ocean carbon cycle components of CMIP6 Earth System Models (ESMs) will improve our understanding of the response of the Southern Ocean biogeochemistry to changing climate stressors. In this perspective, we here intend to study the integrated response of Southern Ocean biogeochemistry to multiple changing stressors and the ability of ocean component of CMIP6 ESMs to capture this response. We will particularly focus on the role of small scale oceanic processes and on the impact of the change in melt and glacial sources of freshwater and iron on Southern Ocean productivity and carbon cycle. The project will also quantify the impact of the sources of uncertainty due to oceanic scale interactions in the CMIP6 ESMs projection. To this purpose, our 4-years project will use a strategy based on a hierarchy of model studies with various levels of complexity and grid resolution, at global and regional scale, all based on the community model NEMO-PISCES. We will in particular use an unprecedented series of ensemble simulations of a global « eddying » ocean carbon cycle model. The set-up and the analysis of the model simulations will be coordinated with observations teams and on-going observation programs. Our project team is a unique consortium of physical oceanographers, biogeochemists and climate scientists coming from leading climate research and operational institutions. SOBUMS project will allow a breakthrough in our understanding of the role played by ocean mesoscale turbulence and changing Antarctic cryosphere on Southern Ocean biogeochemistry and prepare the analyses of future CMIP6 simulations. The project also offers a unique opportunity for tightening the links between operational and research institutions in the prospect of future EU green services.