O 2 Minimum zone of the South East Pacific PRIMO international Project Chili, Pérou, France U. Concepcion, U. Chili (Santiago) IGP, IMARPE (Pérou) CNRS/IRD/Université

Role of physical and biogeochemical processes in the formation and dynamics of OMZ from daily to decadal time scale (Coutesy A. Chaigneau)

Physics in the OMZ of the ESP Main Research questions What is the transport of the PCU and what is its spatio-temporal variability?. What are the main mechanisms transporting oxygen to the OMZ?. Evaluation of advection associated with different flows of the ESPCS, the role of the turbulent diffusivity on the oxygen transport toward the OMZ. What prevents the southward extend of the ZMO and what is therefore the role of Chile-Peru Current? The tropic-subtropics connections in the SEP - Role of the Coastal Trapped Waves on the vertical structure of the OMZ. - Role of Rossby waves on the offshore extension of the OMZ.

Variability of upwelling in the OMZ How does the upwelling contribute to the vertical structure of the OMZ? Mesoscale activities and the OMZ Document processes associated with mesoscale eddies (eddy transports + lateral diffusion). Subducted intermediate waters and the OMZ Document vertical and horizontal mixing processes. - Does the strong salinity vertical gradient (low salinity water near the surface and high salinity at OMZ level) prevent the mixing of low O2 waters? - Which other mechanisms (e.g. thermal stratification) prevent the vertical mixing of surface oxic and low O2 subsurface waters? - What is the contribution of the horizontal mixing to the OMZ spatial heterogeneity?.

bio-geochemical Questions How the OMZ does control: –Communities (phytoplanctonic, bactériennes, trophiques…) –Production fluxes (primary and secondary) –Remineralization of organic matter and associate biogenetic elements –Export and sedimentation fluxes –Diagenetic processes –Sedimentary archives reconstruction  Implications for parameterization of the biogéochemical component in regional models  Implications for proxy calibration

Integrated Approach physical - biogeochemical coupled models –Study of processes to derive parametrization –Validation thanks to the cartography of « core parameters » => Contribution of physical and biogeochemical processes to OMZ dynamics (daily to interannual timescales) Proxies calibration: –Understanding of tracers cycle –Constitution of archives –Link with the Paleos for the long term variability (GALOPER project) => Study of the OMZ dynamics at interannual to interdecadal timescales

Strategy Step 1 : preliminary studies –Long-term observational component and historical data analysis –Laboratory experiments (in closed collaboration with modelers) (sensitivity experiments? or other?) –Physical-biogeochemical regional modeling: development for adjusting to OMZ (to adapt different model compartments to OMZ conditions ) Step 2 : work at sea: cruise, moorings etc. –Argo Profilers in Primo Step 3 : model data (data base, sharing data agreement)

Agenda Thursday, 2nd of June, morning 10h-10h45 : Progresses in the Primo scientific document since last meeting in March. 10' presentation per countries: - comments on Primo-V02.doc (what's good, what's wrong) - list of experts to be directly involved in the project and in which part 10h45-12h30: - Round table: discussions to highlight the caveats of the actual document (V02) Define groups to improve some parts of the document - Working groups at work -afternoon 13h30-15h30: Working groups at work h30- 15h45: break -15h45-17h00: Restitution -17h00-18h30: Define PRIMO strategy - start discussions on the implementation plan -Thursday night- 19h30 BBQ at Yves' place Friday, 3rd of June, morning -9h00: Implementation plan: Cruise: route, moorings, fixed stations, equipments... -afternoon Data sharing and policy....

Goals of the meeting Complete and discuss the scientific document Verify that we got all contributions and that nothing is missing Complete each part with names starting from chilean and peruvian partipation. Define cruise experiments, laboratory experiments Define long term strategy –thesis (co-tutelle?), –exchanges between countries…