In MOOSE, two river systems have been selected for high frequency monitoring of river loads. These are the Rhône River, nowadays the largest freshwater source for the Mediterranean Sea, and the Têt River, targeted as representative for the functioning of the numerous coastal rivers which discharge to the North-Western basin. Both rivers are equipped with automatic sampling stations close to the river mouths (station SORA at Arles on the Rhone, station POEM-River at Villelongue on the Tet), allowing them to be sampled in daily time steps during low water stages, and in hourly time steps during floods.
The MOOSE atmospheric stations are located all around the French NW Mediterranean coast (Cap Ferrat, Frioul, Cap Bear) providing an east-west gradient, ideal to study anthropogenic impacts and Saharan dust events. Consequently, the MOOSE project aims to maintain such atmospheric survey for the atmospheric inputs study in collaboration with the Working Group of ChArMeX “Deposition of nutrients and Hg”.
Marine observations all year round are accomplished by combining observations from moorings, lagrangian floats and gliders, ship surveys both in the coastal and open sea regions.
In addition to the Eulerian and Lagrangian observatories, ship transects are essential to acquire more parameters that cannot be obtained by autonomous technologies (glider, float, buoy, satellite) but still necessary for a complete marine environment observation. These in situ data concern essentially chemical (nutrients, CO2, pH) and biological (pigments, plankton description) variables.
The ship survey strategy is based on monthly cruises at 3 sites (MOLA, ANTARES, DYFAMED) using existing facilities during which CTD casts are carried out to record hydrodynamic characteristics of the entire water column (surface to bottom) using standard protocols and references that can be used to calibrate sensors installed on autonomous platforms (mooring lines, buoys, floats and gliders). Niskin bottles are also used during the CTD deployments to collect samples for discrete parameters acquisition (nutrients, oxygen, TCO2-alkalinity, pigments) as well as net sampling for plankton recording. The ship observations also implement modern technologies for having a 2D vision of biological community (size spectrum) by using autonomous instruments: Underwater Video Profiler, Laser Optical Plankton Counter.
An annual cruise MOOSE-GE covering the whole MOOSE domain is mainly dedicated to moorings maintenance. In addition to this maintenance, deep CTDs transects are also performed during this cruise in order to calibrate mooring sensors, to sample on a larger (sub-basin) scale and to measure variables only accessible with water samples (nutrients, dissolved inorganic carbon, phytoplanktonic pigments, zooplankton nets…). Such a CTD survey with cross-basin transects centered on the deep water formation area in the early summer allows to monitor the variability of the water masses of the basin (surface, intermediate and deep) and in particular the amount of the deep waters formed during the previous winter.
Grid of sampling hydrological sites during the annual cruise MOOSE-GE (MOOSE-Grande Echelle)
The observation of the coastal to offshore transfers along the shelf (canyon export) is represented by one dual station: MOLA station located 19 nautical miles offshore from Banyuls-sur-Mer on the northern flank of a canyon (600m depth) and Lacaze-Duthiers station located in the canyon axis (1,000m deep) and equipped with an instrumented mooring line (sediment traps, current meters) for the particulate flux transferred to the basin (program BILLION; Heussner et al., 2006). As well as Lacaze-Duthiers site, Planier site is equipped to record the occurrence and effects of dense shelf water cascades from the shelf of the Gulf of Lions.Concerning the deep basin, some key areas have been identified: the central part of the Ligurian Sea where atmospheric inputs are predominant (DYFAMED), the central zone in the Gulf of Lion for deep water formation (LION-42N5E/HC) and the ANTARES station located in the Northern Current pathway.
At present, the Eulerian observation is performed by 6 immerged mooring lines:
– Planier and Lacaze-Duthiers (sediment traps and hydrodynamic sensors) for dense water cascading and particle flux studies (since 1994, operated by CEFREM)
– LION (hydrodynamic sensors near the bottom) for hydrology monitoring of deep waters (since 2010, operated by LOCEAN and CEFREM)
– LIONCEAU (sediment traps and hydrodynamic sensors) in the convective zone of Gulf of Lion (operated since 2012 by LOCEAN, CEFREM)
– ANTARES (hydrodynamic sensors near the bottom) for hydrodynamic and organic matter remineralization in deep water (operated since 2004 by MIO)
– DYFAMED (sediment traps and hydrodynamic sensors) for atmospheric and marine flux transfer to the surface and deep waters (operated since 1988 by OOV)