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Biogeochemical sensor performance in the SOCCOM profiling float array

Author(s): Johnson, Kenneth S; Plant, Joshua N; Coletti, Luke J; Jannasch, Hans W; Sakamoto, Carole M; et al

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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 µmol 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.
Publication Date: 5-Jul-2017
Citation: Johnson, Kenneth S., Joshua N. Plant, Luke J. Coletti, Hans W. Jannasch, Carole M. Sakamoto, Stephen C. Riser, Dana D. Swift et al. "Biogeochemical sensor performance in the SOCCOM profiling float array." Journal of Geophysical Research: Oceans 122, no. 8 (2017): 6416-6436. doi:10.1002/2017JC012838.
DOI: doi:10.1002/2017JC012838
EISSN: 2169-9291
Pages: 6416 - 6436
Type of Material: Journal Article
Journal/Proceeding Title: Journal of Geophysical Research: Oceans
Version: Final published version. This is an open access article.

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