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SeaQUEST cruise

6-10 April 2016

Meso- and Sub-mesoscale Physico-biogeochemical Dynamics in a Coastal NW Mediterranean Sea: Quantifying and Understanding Ecosystem Structure and Transport

Brief Scientific Rationale and Socio-Economic Relevance

Shelf and coastal regions are at the interface between continents (impacted by human activities) and the open ocean (the main regulator of our planet’s climate and its biogeochemical cycles). The shelf-sea carbon pump largely relies on lateral transport to remove atmospheric
Schematic
Figure 1: Map of the study area showing the main oceanographic features as well as dominant winds (T=Tramontane, M=Mistral, SE=Southeaster) and the upwelling zones (CB=Côte Bleu and C=Calanques).
CO2 from the ventilated surface waters and sequester it at depth. A good understanding of the physical transport processes in coastal regions and their impact on the ecosystem dynamics is therefore not only important for future climate predictions but also has a more immediate relevance (e.g., knowledge of local transport is necessary for the creation of marine protected areas, the management of spills, or the mitigation of harmful blooms events, etc.).

The Rhône River/GoL area offers a typical system for studying river/shelf-sea interactions. The GoL is one of the most productive areas in a mostly oligotrophic Mediterranean Sea and is home to the French Mediterranean fishing fleet, with over 500 aquaculture farms in the Sète region alone. Its high productivity is due to Rhône River inputs and coastal upwelling activity. It therefore is an important feeding area for fish, birds, and mammals, both resident and migratory.

Principal Goal

SeaQUEST aims to investigate the horizontal transport and cross-shelf exchange processes including their effect on the biogeochemistry in the coastal zone around the Gulf of Lion (GoL, Fig. 1).

The circulation in the GoL is forced mainly by wind, freshwater run-off and seasonal heating–cooling. The dominant circulation feature is the Northern Current (NC, Fig. 1),a slope current that passes along the continental slope off the GoL, where it bounds and controls shelf circulation. In fact, the NC can constitute an effective dynamical
Chlorohphyll a
Figure 2: Satellite (MERIS) image of chlorophyll-a concentration. The dashed area shows the location of the NC. The sharp drop in Chl-a concentration near the shelf edge (arrows) illustrates how the horizontal dispersal of Chl-a beyond the shelf edge is blocked by the NC.
barrier to cross-shelf transport, locking the coastal waters in the GoL (Fig. 2).

The main goal of SeaQUEST is to examine the role of the Northern Current as a physical barrier to cross-shelf transport and the effect of its seasonal variability on the local biogeochemistry and plankton dynamics at meso- and sub-mesoscales. This will be achieved through a highly interdisciplinary approach employing a range of methods and data (numerical simulations, in situ and satellite observations). SeaQUEST will provide new insights into the ecosystem functioning and biological-physical interactions in a highly productive and economically important coastal area which is also one of the main tourist destinations worldwide. The results will therefore be of broad relevance to a variety of stakeholders including decision makers and local managers.

Cruise Plan

Vessel and Dates

Tethys2
Figure 3: RV Tethys II.

Deploying the MVP
Figure 4: The MVP

Deploying the CTD
Figure 5: The CTD rosette.
The cruise will take place aboard RV Tethys II (Fig. 3) and is scheduled to depart from La Seyne-sur-Mer on 6 April 2016 with a total duration of 5 days. Underway sampling will be continuous whereas fixed-station sampling is limited to daylight hours (0800h-2100h approx).

Scientists on board

Name Affiliation Role on board
Oliver Ross MIO P.I. & cruise leader
Andrea Doglioli MIO SPASSO & MVP
Iva Talaber NIB-MBP biogeochemical sampling & analyses
Katja Klun NIB-MBP biogeochemical sampling & analyses
Dorian Guillemain MIO operating CTD, rosette, LOPC, LISST
Louise Rousselet MIO physics & assistance to biogeochemical sampling
Joan Fremon Genavir operating MVP

Scientists lending support on land

Name Affiliation Role
Christel Pinazo MIO 3D modelling
Christophe Yohia MIO Operational modelling & forecasting, IT support
Anne Petrenko MIO expertise on NC and physics
Christian Grenz MIO SAM oceanographic equipment pool
François Carlotti MIO expertise on zooplankton and LOPC/LISST

Instruments on board

Underway (continuous) measurements Fixed-station measurements

 

Cruise track (subject to change)

The
cruise track
Figure 6: Possible cruise track for the SeaQUEST campaign and satellites crossing the study area during the cruise period. Black boxes indicate the military ZONEX locations (requires permission from French navy to carry out any sampling activity).
underlying idea is to criss-cross back and forth over the Northern Current (NC) in order to characterize the fluxes and the biogeochemical environments on each side of the current and in the current itself (cf. Fig. 6). The actual location of the cruise track will therefore depend on the location of the NC at the time of the cruise and will be adapted in response to in situ conditions using the SPASSO software (see below).

The cruise track will also try to follow some of the AltiKa satellite tracks which will pass over the region during the cruise period:

The JASON2 tracks are plotted for reference only. They are too far out from the study area and it will most likely not be possible to use them.

Support

SPASSO

SeaQUEST will make use of the SPASSO software. Remote sensing images of SSH, SST and Chl-a will be posted here in near real time to allow for the cruise design to be adapted to in situ conditions.

3D biogeochemical modelling

Prior to as well as during the cruise, SeaQUEST will be supported through 3D biogeochemical modelling (MARS3D-ECO3M) with daily images posted on this website as they become available.

Mars3D animation
Figure 7: Example 48h animation of output of SST and sea surface current velocities from operational modelling using Mars3D. The Northern Current is clearly visible entering the domain from the NE, both in the current velocities and the temperature signature.

Links

Acknowledgements

SeaQUEST is made possible through financial support from the People Programme (Marie Curie Actions) of the European Union's Seventh Framework Programme FP7/2007-2013/ under REA grant agreement n° 624170 and through a collaboration with the NIB - Marine Biology Station Piran. Thanks also to Isabelle Pujol (CLS) for her help with satellite tracks.

 


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