Bio-optical Instrumentation on ARGO Floats

Chairman:

Dr. Hervé Claustre
Observatoire Océanologique de Villefranche
Laboratoire d’Océanographie de Villefranche
UMR7093 B.P. 08, 06238 Villefranche-sur-mer
FRANCE
Email: claustre@obs-vlfr.fr

The international Argo project, which currently has an array of about 3,000 floats deployed in the world ocean, has proven to be an invaluable tool in modern physical oceanography. It provides, on a routine basis and with great detail, the heat and salt content of the upper ocean, as well as water mass circulation, and more generally it helps ocean monitoring and forecasting systems. The Argo Data Management Committee and the Argo Steering Team have full control of the project.

Recently, about 60 floats have also been instrumented with O₂ sensors, for the benefit of the biogeochemical community (see Argo Oxygen Program – White Paper). Bio-optical sensors are now being developed with a reduced size which is compatible for implementation on the Argo floats. Several successful attempts in this direction have already been made in the US. Some discussions are planned on the same topic within the Euro-Argo Group. In summary, an activity is emerging in this domain, and individual researchers as well as Agencies have recognized the fact that a Lagrangian platform array could provide 3-D information not attainable by satellite platforms (the missing vertical dimension), or can even determine near surface properties when cloud cover impedes observations from space, and can also help the validation of satellite data (e.g., Chlorophyll, Kd etc.)

It therefore seems useful and timely to coordinate these various initiatives to obtain a coherent data set for the validation of ocean-colour satellite-borne sensors, and for the interpretation of optical properties in terms of relevant biogeochemical parameters.

The first meeting of the BIO-ARGO working group took place in Villefranche, France from 7-9 February 2008, and the second meeting of the WG is scheduled to take place from 20-21 November 2008, also in Villefranche.

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Presentations:

Location of BIO-Argo floats:

Current location of Argo floats with bio-optical sensors

Members

Stewart Bernard University of Cape Town, South Africa
Jean-Francois Berthon EU Joint Research Centre, Italy
Jim Bishop EO Lawrence Berkeley National Laboratory, USA
Emmanuel Boss University of Maine, USA
Hervé Claustre (CHAIR) LOV, Villefranche, France
Christine Coatanoan Coriolis Data Center, IFREMER, France
Fabrizio D’Ortenzio LOV, Villefranche, France
Ken Johnson Monterey Bay Aquarium Research Institute, Moss Landing, USA
Aneesh Lotliker Indian National Centre for Ocean Information Services (INCOIS), India
Osvaldo Ulloa Universidad de Concepción, Chile

Terms of Reference

To define precisely the parameters required for Cal/Val activities and biogeochemical studies (e.g. modelling), with their significance and limitations;
To evaluate the technical specifications for optical sensors (passive and active), and the adaptations required for long-term, autonomous missions onboard a drifting float:
- miniaturisation, buoyancy
- consumption, energy constraints
- sensitivity, accuracy and precision, acquisition rate;
To evaluate the complementarities with other chemical sensors (O₂, nutrients);
To evaluate the optimal placement of bio-optical devices on the floats
- shadowing effects
- quality control issues: life time and bio-fouling, stability /drift over 2-4 years of deployment, parking depths and measurements at parking depths;
To provide recommendations for deployment strategy of the equipped floats:
- adhering to the standard protocol adopted for physical S-T parameters, vs using another specific, and more flexible, protocol (e.g. higher profiling frequency, shallower casts, near-surface cast at noon for matchup), or a combination of both approaches,
- evaluation of the various communication devices (ARGOS, ARGOS 3, Iridium; two-way (adaptative sampling) vs one-way communication,
- data acquisition frequency over the profile and related issues of sensor consumption;
To recommend unified processing techniques for meaningful comparisons of the data, and ultimately for merging them;
To make recommendations regarding organization of data storage, quality control and archiving capacities;
To elaborate on recommendations for the policy in terms of data distribution (real-time and quality controlled, delayed time data) and access for ensuring the best and unselfish use of these data, at international, and inter-Agencies, levels;
To provide recommendations for pilot studies before large scale implementation;
To implement links with space agencies about the capacity of such a deployment, and its cost;
To produce a white paper to promote the addition of bio-optical sensors to the international Argo float program.