The Reykjanes Ridge experiment and OVIDE plans

1. The Reykjanes Ridge experiment and OVIDE plans V. Thierry H. Mercier, P. Lherminier, B. Ferron, N. Daniault and the RREX and OVIDE groups LPO, Brest (France), CNRS/IFREMER/IRD/UBO LOCEAN, Paris (France), CNRS/UPMC IIM, Vigo (Spain)

2. The OVIDE project • Objectives • Quantify and understand the MOC variability • Understand storage mechanisms of anthropogenic CO2 in the Atlantic Ocean • Quantify and understand water mass properties variability • Means • Hydrographic section (2002, 04, 06, 08, 10, 12 + Fourex 1997) • Current meters, Argo, Altimetry • Modeling, data assimilation - Partners: LPO, IIM Vigo, S.B. Roscoff, LOCEAN Contribution to CLIVAR, IOCCP, Argo Funding: Ifremer, INSU, CSIC, CNES, Météo-France, LEFE, CarboChange Collaborations : SIO, WHOI, DFO, NOCS

3. Quantify and understand the MOC variability

4. Quantify and understand the MOC variability Red points: MOC from OVIDE and FOUREX hydrographic data Blue line: upper limb of the MOC computed from Altimetry Black lines: upper limb of the MOC computed from Altimetry + Argo or WOA Mercier et al 2013, Prog. Oceanogr.

5. Variability of EGIC transport: 2005-2006 Daniault et al, 2010, JPO

6. Variability of EGIC transport: 1993-2010 Daniault et al, 2011, GRL

7. Understand storage mechanisms of anthropogenic CO2 in the Atlantic Ocean Perez et al, 2010, Biogeosciences

8. Understand storage mechanisms of anthropogenic CO2 in the Atlantic Ocean Perez et al, 2013, Nature Geosciences

9. Reykjanes Ridge Mode Water variability PSAL SIG0 TPOT Thierry et al 2008, JGR, de Boissséson et al, 2012, JGR

10. Conclusions • Climate relevant indexes of the North-Atlantic Ocean variability are monitored: MOC, water mass properties, CO2 storage • Data from sustained observing systems (altimetry, Argo) have been used to compute proxies of those indexes • to extend the time series backward in time • to interpolate in between the hydrographic sections • to resolve time-scales that are not resolved by the hydrographic data (seasonal) • Hydrographic cruises remain mandatory • to acquire data that are not accessible by sustained observing systems and autonomous platform (pH, CO2, deep limb of the MOC, CO2 storage) • to resolve small spatial scales that are not resolved by sustained observing systems • to define and validate proxies (and the associated hypothesis) of the indexes • to calibrate Argo data

11. OVIDE plans High-frequency hydrographic data are required to capture interannual variability and long-term trends in the highly variable North-Atlantic Ocean • Continue the OVIDE time series on a 2 year basis : • GEOVIDE in 2014: funded (GEOTRACES + OVIDE) • OVIDE in 2016 • Ship time under IIM Vigo responsibility (BOCATS project) • Expected funding: Spain, France, Europe • OVIDE 2018 • Ship time under LPO/France responsibility • Expected funding: France, Spain, Europe

12. A process study to understand the role of the Reykjanes Ridge on the large scale circulation, water mass transformation and ultimately on the MOC The Reykjanes Ridge Experiment • Reykjanes Ridge is localized in a strategic place for the MOC • The flow along and above the ridge is poorly understood and its representation in ocean models is flawed.

13. Objective 1: Document and understand how does the Reykjanes Ridge control the large-scale circulation Summer mean 2002-2010 velocity across the Ovide section and salinity along the section • What are the dynamical flow regimes that prevail on the two sides of the ridge ? • How the RRMW and ISOW are transferred toward the Irminger Sea ?

14. Objective 2: Document and understand how does the Reykjanes Ridge influence, through turbulent mixing, water mass transformation • Turbulent kinetic energy dissipation is enhanced nearby the Reykjanes Ridge: near the bottom and at the base of the mode water layer. • We want to quantify the spatio-temporal varaibility of the mixing around the ridge and its influence on the currents and water-masses.

15. Objective 3: Identify and quantify the key ocean model parameters involved in the representation of the dynamics of the flows around the Reykjanes Ridge • Ocean models show large discrepancies in the representation of the flow and water mass properties in the subpolar gyre of the North Atlantic • Part of the deficiencies comes from errors in the representation of the dynamics of the flows around the Reykjanes Ridge

16. The Reykjanes Ridge Experiment (RREX) Idealized experiment + new and existing datasets + realistic simulations understand mechanisms at play in the vicinity of the RR and incorporate them appropriately in large-scale models • Hydrographicsurvey : • 113 CTD-O2-ADCP casts • Water sample: S, O2 and nutrients • Mixing measurement (VMP profile) every other CTD casts • Argo floatsdeployment • Duringcruise • Every 3 monthsowing to the ASFAR device • Currentmetermeasurements

17. The Reykjanes Ridge Experiment (RREX) Idealized experiment + new dataset + realistic simulations understand mechanisms at play in the vicinity of the RR and incorporate them appropriately in larg-scale models • Hydrographicsurvey : • 113 CTD-O2-ADCP casts • Water sample: S, O2 and nutrients • Mixing measurement (VMP profile) every other CTD casts • Argo floatsdeployment • Duringcruise • Every 3 monthsowing to the ASFAR device • Currentmetermeasurements

18. The Reykjanes Ridge Experiment (RREX) Idealized experiment + new dataset + realistic simulations understand mechanisms at play in the vicinity of the RR and incorporate them appropriately in larg-scale models • Hydrographicsurvey : • 113 CTD-O2-ADCP casts • Water sample: S, O2 and nutrients • Mixing measurement (VMP profile) every other CTD casts • Argo floatsdeployment • Duringcruise • Every 3 monthsowing to the ASFAR device • Currentmetermeasurements

19. ASFARAutonomous System for Argo floats Release

20. The Reykjanes Ridge Experiment (RREX) Idealized experiment + new dataset + realistic simulations understand mechanisms at play in the vicinity of the RR and incorporate them appropriately in larg-scale models • Hydrographicsurvey : • 113 CTD-O2-ADCP casts • Water sample: S, O2 and nutrients • Mixing measurement (VMP profile) every other CTD casts • Argo floatsdeployment • Duringcruise • Every 3 monthsowing to the ASFAR device • Currentmetermeasurements

21. The RREX moorings

22. The RREX planning, funding and collaborations • RREX Planning • Summer 2015: Hydrographic survey and mooring deployment for 2 year • Summer 2016: Refill the 2 ASFAR • Summer 2017: Moorings recovery and 2nd realization of the survey • Funding: France, Spain, Europe • Ship time: priority 1 afterevaluation • Part of the fundingalreadyacquired (easternmoorings, hydrographiccruise) • Needfunding for western moorings and to maintainmoorings longer than 2 years • Partners: LPO, LOCEAN, LEGI, IIM Vigo • Collaborations : SIO Moscow, OSNAP partners

23. OSNAP vs. RREX moorings

24. Argo floats and Argo floats with oxygen sensor • Use ASFAR system (bottom or mooring) to deploy Argo floats on a regular basis in North-Atlantic • We aim at developing and sustaining a global Argo-O2 array to monitor changes in O2 content • Pilot experiment in the North-Atlantic • Monitor deep convection • Follow ventilation pathways of water masses • Follow OMZ • Biogeochemical studies • 12 deep Argo floats (0-4000m) with 02 sensors will have to be deployed in 2015 and 2016 Argo profiles with O2 sensor • We will look for ship of opportunity with O2 measurements to deploy some of those floats in the North-Atlantic and to validate the data

25. Thank you

26. The RREX moorings Kinetic energy dissipation along Ovide section

27. The RREX moorings

28. Deep-Arvor 6901468 DOXY_ADJUSTED = 1.003*DOXY + 41.3