 April 2007 : Argo-Oxygen Program The white paper prepared by Nicolas Gruber and colleagues was presented to the Argo Steering Team at their 8th meeting (AST-8) at UNESCO-IOC, March 7-9. The white paper outlines the scientific motivations for adding O2 sensors to the Argo array, and addresses the numerous scientific and technological challenges associated with this expansion of Argo. Among the most important scientific motivations for measuring sub-seasonal to decadal variations in the ocean’s oxygen content is that O2 is a rather sensitive tracer for changes in oceanic circulation and biology, making it an ideal “bellwether” for climate change. Furthermore, subsurface O2 changes are a reliable indicator for oceanic export production, a key quantity of the global carbon cycle. Last but not least, measuring the oceanic outgassing of oxygen helps to interpret the atmospheric O2 budget, which can be used to understand the partitioning of the terrestrial and ocean CO2 fluxes.
The analyses of the performance of the more than 70 floats that have been deployed with oxygen sensors to date reveals that the technology has advanced to the state where a large-scale initial deployment has become feasible and scientifically justifiable. In particular, the white paper shows that O2 sensors can be deployed for several years with drift and accuracy remaining within the acceptable limits. Issues that remain to be addressed are sensor response time, and calibration routines. Initial estimates of the costs associated with the addition of the oxygen sensors to the Argo array suggest that it costs about 40% above the costs for the purchase and operation of a standard Argo float, or an additional about USD 7000 over 5 years.
The white paper was well received by the AST. They commended the quality of the document and welcomed Dr Gruber’s proposal for a pilot project of around 100 floats to be released in a region of specific interest for O2 observations. While the AST was positive about the project it was also cautious regarding the effects of the O2 sensors on battery life, potential for an increase in premature instrument failure, and the legal implications of adding an additional observation to the Argo array given the current international agreements. These issues would need to be understood and resolved before O2 measurements could be considered for integration into the operational Argo array.
 Download the White paper on the Argo-Oxygen Program by Nicolas Gruber et al. (version 5.1, Feb. 14, 2007).
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