GEOVIDE, An international GEOTRACES study along the OVIDE section in the North Atlanctic and the Labrador Sea – GEOVIDE

The project is based on a 44-day oceanographic cruise on the R/V “Pourquoi Pas?” (May-June 2014). 78 stations were achieved (plus one test station), including 46 Short, 17 Large, 5 XLarge, and 10 Super stations. In total, we deployed 163 times the classical rosette, 53 times the trace metal clean rosette (TMR), 25 times the in-situ pumps, 11 times the mono-corer, and 9 times the plankton net. We also collected 140 clean sea-surface water samples, 18 aerosol samples, and 10 rainwater samples. Finally, between stations, we deployed 60 XBT, 8 ARVOR, 2 ARVOR-deep, 2 PROVOR-DO, 2 PROVBIO, 1 ARVOR double DO, 2 APEX and 12 buoys, and realised 160 profiles of LADCP and continuous measurements (OS38, OS150, thermosalinograph, sea-surface fCO2). This is in perfect adequacy with the initial plan, with adjustments that took into account real-time data, Mercator ocean forecasts, technical difficulties and meteorological constraints. All shelves could be sampled, despite the very recent presence of sea ice close to Greenland. Lots of parameters are already acquired and have been published or presented in international and national conferences (see the 18-month report).

- First time that the subarctic front so much to the south and the branches of the NAC so concentrated geographically.
- The Iceland Basin marked by a strong presence of SAIW at about 350m depth.
- Recently ventilated water mass down to 1000m in the central Irminger Sea.
- The thickest layer of recent Labrador Sea Water found down to 1500m depth
- Total Hg in the “young” Labrador Sea Waters amongst the lowest ever measured.
- Dissolved aluminium strongly influenced by water masses and South to North / West to East (S-N / W-E) gradient in the sea-surface concentrations, consistent with the expected decrease in atmospheric inputs.
- S-N / W-E gradient also observed in the Fe concentrations in the aerosols, confirming the low atmospheric inputs in our study area.
- High inputs from benthic nepheloid layers (BNL) evidenced from the particulate Fe concentrations.
- Dissolved Fe concentrations influenced by BNL, atmosphere, weathering, exchanges with particulate phases, water masses and biological activity.
- Highest primary production observed in the Irminger Sea.
- Clear accumulation of biogenic particulate barium in the mesopelagic layer, suggesting high export and remineralization of organic matter.

Many parameters still need to be analysed and/or validated and will allow to have a comprehensive view of the studied area. Our next GEOVIDE meeting will be in June 2016.
At the Ocean Science meeting in New Orleans (Feb. 2016), we have 3 special sessions related to GEOVIDE:
1- Trace Elements and Isotopes at the Interfaces of the Atlantic Ocean. Primary Chair: Geraldine Sarthou, LEMAR.
2- The role of particles in the cycling of trace elements and their isotopes in the ocean. Primary Chair: Hélène Planquette, LEMAR.
3- Integrating approaches to understanding the distribution and transfer of trace elements in the upper water column. Primary Chair: Rachel Shelley, LEMAR.
Une issue spéciale dans un journal international de rang A sera planifiée courant 2016.
A special issue in an international peer-review journal is planned is 2016.

Peer-review publications
- Zunino et al., Submitted to Geophys. Res. Lett
International Conferences
- Cossa et al, 2015, 12th International Conference on Mercury as a Global Pollutant, Jeju, Korea.
- Gourain et al., 2015, ASLO meeting, Granada, Spain.
- Heimburger et al., 2014, AGU Fall Meeting
- Heimbürger et al., 2015, 12th International Conference on Mercury as a Global Pollutant, Jeju, South Korea.
- Lemaître et al., 2015, Goldschmidt Conference, Prague.
- Le Roy et al., 2015, Goldschmidt Conference, Prague.
- Lherminier et al., 2015, Our Common Future Under Climate Change, Paris,
- Lherminier et al., 2015, EGU General Assembly 2015.
- Menzel et al., 2015, ASLO meeting, Granada, Spain.
- Sarthou et al., 2015, Goldschmidt Conference, Prague.
- Shelley and Sarthou, 2015, Aquatic Sciences Meeting, Granada, Spain.
- Sutton et al., 2015, IBiS 2015, London, UK.
- Tonnard et al., 2015, Goldschmidt Conference, Prague
- Zhang et al., 2014, 12th International Conference on Mercury as a Global Pollutant, Jeju, Korea
- Zunino et al. 2015, 26th IUGG General Assembly 2015, IAPSO Symposia P09, Prague (CZ)
National meetings:
- 2014, Pre-cruise GEOVIDE meeting : 19 présentations, www.geovide.obs-vlfr.fr/kick-off-pre-cruise-67-february-2014/
- 2015, Post-cruise GEOVIDE meeting : 17 présentations, www.geovide.obs-vlfr.fr/post-cruise-meeting-25-26-may-2015/
- Cossa et al., 2014, Reunion des Sciences de la Terre, Pau

Trace elements and their isotopes (TEIs) play a crucial role in the ocean and can be used as tracers for past and modern oceanic processes. Studying their biogeochemical cycles has direct implications in diverse research areas such as carbon cycling, climate, ocean ecosystems and environmental contamination. In this context, GEOVIDE proposes to undertake an integrated oceanographic transect in the North Atlantic and Labrador Sea. This area is crucial for the Earth climate and the thermohaline circulation as it represents a major overturning area of the so-called Meridional Overturning Circulation (MOC). Moreover, TEI distribution is poorly constrained in this area. GEOVIDE is an international collaborative programme which aims at better constraining the uncertainties on water and heat fluxes across the cruise section, notably by adding information on the deep water mass export and circulation, but also in providing new information on chemical element fluxes. GEOVIDE will allow the quantification of processes that influence the distribution of key TEIs in this area, in particular advective and scavenging processes, biological uptake, exchanges with the margins, and atmospheric deposition.
The main scientific objectives of GEOVIDE are to:
1- Better know and quantify the MOC and the carbon cycle in a decadal variability context, adding new key tracers
2- Map the TEI distribution with their physical and chemical speciation along a full-depth high resolution ocean section
3- Characterize the TEI sources and sinks and quantify their fluxes at the ocean boundaries
4- Investigate the link between the TEIs, and the production, export and remineralisation of particulate organic matter
5- Better understand and quantify the paleoproxies 231Pa/230Th, Nd isotopes, and Si isotopes.
The project is based on a 44-day oceanographic cruise on the R/V “Pourquoi Pas?” (summer 2014). We will use a series of novel techniques and state-of-the-art instrumentation. The strength of the project resides in its interdisciplinarity: physical oceanography, geochemistry and biogeochemistry will be coupled, merging observation and modelling. GEOVIDE gathers highly qualified scientific teams from five different countries. This project will be the French contribution in the North Atlantic to the Global GEOTRACES TEI survey (official GA01 GEOTRACES section) and will provide essential information, notably for the modelling of the present and past ocean, on TEI distributions in this key area of the thermohaline circulation. GEOVIDE will also actively contribute to other international programmes, such as SOLAS, IMBER, CARBOCHANGE and CLIVAR. GEOVIDE is part of the axis 2 of the LabexMER “A changing Ocean” and is linked to the Equipex NAOS “Novel Argo Ocean observing System”, in particular to the WP5 “Deep oxygen floats in the North Atlantic”. GEOVIDE is also a strong international and original action of the UPEE Pole in the framework of the IDEX UNITI in Toulouse.
Finally, GEOVIDE has an educational component at various academic levels and the results of the project will be incorporated into materials for web dissemination and public outreach, as well as through scientific publications and presentations at international conferences. Five young scientists (three research associates and two PhD students) will be trained during this project. The results obtained during this project will be available through various databases (SISMER, LEFE-CYBER, and the GEOTRACES International Data Assembly Centre).