Handbook of best practices

The subsurface core variables to be measured at the FixO3 observatories includes variables
mentioned for the surface core such as temperature, salinity current and phytoplankton, in
addition to other variables such as nutrients (usually nitrate) and dissolved oxygen. Nutrient
measurements are essential biogeochemical information, and provide critical links between
physical climate variability and ecosystem variability. Manufacturers for this kind of sensor
are Satlantic, EnviroTech or TriOS optical sensors. Dissolved oxygen is an excellent tracer
for ocean circulation and ocean biogeochemistry. The main current manufacturers are
Seabird electronics and Aanderaa.
The seafloor core variables to be measured should be those already defined in the
deliverable D68 in the ESONET European Seas Observatory Network project
(http://wwz.ifremer.fr/esonet_emso/content/download/42247/574588/file/Deliverable_D68_es
onet-label-definition_1.0.pdf) where in the table 1 page 18 suggests the variables and the
specific characteristics of the sensors. These “generic” variables are conductivity (salinity),
temperature, pressure, dissolved oxygen, turbidity, current and passive acoustic.
The list of “specific” instruments in this document is of a very high importance as it provides
the multidisciplinary time series collection essential to FixO3 objectives.
1.3.1.2 Other parameters
Among other variables to be included, we can consider the sea state (swell period and
height or wave direction and significant height), sound and light, in addition to
photosynthetically active radiation and precipitation. Observations of sea state are
particularly relevant because affect the air-sea exchanges and can also provide
complementary information of relevance to monitoring changes in the marine environment.
In mid-latitudes wave height is an indicator of storm track and strength. The distribution of
long period swell also reflects the maximum wind speed (fetch and duration) in the
generating storms. Changes in wave climate reflect changes in the atmospheric circulation.
Waves also play a dynamic role in the climate system, influencing air-sea interaction, albedo
and mass exchange across the air-sea interface. The sound is used to obtain information
from the ocean interior (bathymetry, fishery, tomography, etc.…) but also for the sea surface
(acoustic rain detection). The penetration depth of shortwave radiation is of interest to
biologists and related to the photosynthetic activity of phytoplankton and algae and links to
behavior of zooplankton and fish. The Absorbed Photosynthetically Active Radiation (PAR)
refers to the fraction of the incoming Photosynthetically Active Radiation (PAR) that is
effectively used in photosynthesis. PAR is a primary variable controlling the photosynthetic
activity of phytoplankton. PAR varies in space and time due to differences in species and
ecosystems, weather and climate processes.
The above mentioned “specific” ESONET-EMSO parameters are measured by sets of
instruments (“modules”). (updated from Ruhl et al. 2011).
Specific modules can be set up in varying combinations according to site-specific objectives.
For example, measuring synchronously seismic motion, gravity, magnetism, seafloor
deformation (acoustic geodesy), sedimentation, pore-water properties, gas hydrates, and
fluid dynamics will provide a great opportunity to make advancements in geosciences and
geo-hazard early-warning capability. Specific observatory applications in physical and
biogeochemical oceanography require full water depth moorings that allow recording of longterm,
high resolution time-series of hydrography, current sand biogeochemical state
variables (oxygen, fluorescence, nutrients) throughout the water column. A suite of
biogeochemical and physical sensors mounted on moored profilers can allow for highresolution
vertical profiling in the upper part of the water column. Instrumentation for
particularly extreme conditions are needed for some applications such as hydrothermal vent
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