Biogeochemical sensor performance in the SOCCOM profiling float array

TitleBiogeochemical sensor performance in the SOCCOM profiling float array
Publication TypeJournal Article
Year of Publication2017
AuthorsJohnson K.S, Plant J.N, Coletti L.J, Jannasch H.W, Sakamoto C.M, Riser S.C, Swift D.D, Williams N.L, Boss E., Haentjens N., Talley LD, Sarmiento J.L
JournalJournal of Geophysical Research-Oceans
Volume122
Pagination6416-6436
Date Published2017/08
Type of ArticleArticle
ISBN Number2169-9275
Accession NumberWOS:000410790600021
Keywordsanthropogenic; bio-optical sensors; carbon; dissolved inorganic carbon; global ocean; in-situ; net community; nitrate sensors; oxygen optodes; oxygen sensors; particulate organic-carbon; pH sensors; production; profiling floats; seasonal variability; Southern Ocean; southern-ocean; surface ocean pco(2)
Abstract

The Southern Ocean Carbon and Climate Observations and Modeling (SOCCOM) program has begun deploying a large array of biogeochemical sensors on profiling floats in the Southern Ocean. As of February 2016, 86 floats have been deployed. Here the focus is on 56 floats with quality-controlled and adjusted data that have been in the water at least 6 months. The floats carry oxygen, nitrate, pH, chlorophyll fluorescence, and optical backscatter sensors. The raw data generated by these sensors can suffer from inaccurate initial calibrations and from sensor drift over time. Procedures to correct the data are defined. The initial accuracy of the adjusted concentrations is assessed by comparing the corrected data to laboratory measurements made on samples collected by a hydrographic cast with a rosette sampler at the float deployment station. The long-term accuracy of the corrected data is compared to the GLODAPv2 data set whenever a float made a profile within 20 km of a GLODAPv2 station. Based on these assessments, the fleet average oxygen data are accurate to 1 +/- 1%, nitrate to within 0.5 +/- 0.5 mu mol kg(-1), and pH to 0.005 +/- 0.007, where the error limit is 1 standard deviation of the fleet data. The bio-optical measurements of chlorophyll fluorescence and optical backscatter are used to estimate chlorophyll a and particulate organic carbon concentration. The particulate organic carbon concentrations inferred from optical backscatter appear accurate to with 35 mg C m(-3) or 20%, whichever is larger. Factors affecting the accuracy of the estimated chlorophyll a concentrations are evaluated.

DOI10.1002/2017jc012838
Short TitleJ Geophys Res-Oceans
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