Bio-Optical Profiling Floats as New Observational Tools for Biogeochemical and Ecosystem Studies: Potential Synergies with Ocean Color Remote Sensing

摘要

Profiling floats now represent a mature technology. Inparallel with their emergence, the field of miniature, lowpower bio-optical and biogeochemical sensors is rapidlyevolving. Over recent years, the bio-geochemical andbio-optical community has begun to benefit from theincrease in observational capacities by developingprofiling floats that allow the measurement of key bioopticalvariables and subsequent products ofbiogeochemical and ecosystem relevance likeChlorophyll a (Chla), optical backscattering orattenuation coefficients which are proxies of ParticulateOrganic Carbon (POC), Colored Dissolved OrganicMatter (CDOM). Thanks to recent algorithmicimprovements, new bio-optical variables such asbackscattering coefficient or absorption by CDOM, atpresent can also be extracted from space observations ofocean color. In the future, an intensification of in situmeasurements by bio-optical profiling floats wouldpermit the elaboration of unique 3D / 4D bio-opticalclimatologies, linking surface (remotely detected)properties to their vertical distribution (measured byautonomous platforms), with which key questions in therole of the ocean in climate could be addressed. In thiscontext, the objective of the IOCCG (InternationalOcean Color Coordinating Group) BIO-Argo workinggroup is to elaborate recommendations in view of afuture use of bio-optical profiling floats as part of anetwork that would include a global array that could be¿Argo-relevant¿, and specific arrays that would havemore focused objectives or regional targets. The overallnetwork, realizing true multi-scale sustainedobservations of global marine biogeochemistry and biooptics,should satisfy the requirements for validation ofocean color remote sensing as well as the needs of awider community investigating the impact of globalchange on biogeochemical cycles and ecosystems.Regarding the global profiling float array, therecommendation is that Chla as well as POC should bethe key variables to be systematically measured. A firsttarget would be to implement 20% of the Argo floatswith these measurements within a five-year term. Theyearly additional cost is estimated to 1.5 M$, includingadditional management structure in each of the twoGlobal Data Assembly Centers.