2013
DOI: 10.1175/jtech-d-12-00221.1
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Long-Term Nitrate Measurements in the Ocean Using the in situ Ultraviolet Spectrophotometer: Sensor Integration into the APEX Profiling Float

Abstract: Reagent-free optical nitrate sensors [in situ ultraviolet spectrophotometer (ISUS)] can be used to detect nitrate throughout most of the ocean. Although the sensor is a relatively high-power device when operated continuously (7.5 W typical), the instrument can be operated in a low-power mode, where individual nitrate measurements require only a few seconds of instrument time and the system consumes only 45 J of energy per nitrate measurement. Operation in this mode has enabled the integration of ISUS sensors w… Show more

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Cited by 99 publications
(106 citation statements)
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“…The more recently developed optical sensor, the in situ ultraviolet spectrophotometer (ISUS) (Johnson and Coletti, 2002), has facilitated the high-resolution in situ measurement of nitrate. By outfitting APEX autonomous profiling floats with such sensors, Johnson et al (2013) are able to offer detailed sampling of the vertical distribution of nitrate in time . Such a growing database of nitrate measurements offers the opportunity to explore the vertical distribution of nitrate in space and time and the regional variability in the shape and depth of the nitracline.…”
Section: Introductionmentioning
confidence: 99%
“…The more recently developed optical sensor, the in situ ultraviolet spectrophotometer (ISUS) (Johnson and Coletti, 2002), has facilitated the high-resolution in situ measurement of nitrate. By outfitting APEX autonomous profiling floats with such sensors, Johnson et al (2013) are able to offer detailed sampling of the vertical distribution of nitrate in time . Such a growing database of nitrate measurements offers the opportunity to explore the vertical distribution of nitrate in space and time and the regional variability in the shape and depth of the nitracline.…”
Section: Introductionmentioning
confidence: 99%
“…The spectral measurements of the SUNA were post-processed using Satlantic's SUNACom software, which implements a temperature and salinity dependent correction to the absorption (Sakamoto et al, 2009). The SUNA sensors' light source is subject to aging which results in an offset NO − 3 concentration (Johnson et al, 2013). To determine the resulting offset, NO − 3 concentrations measured on bottle samples by the standard wet-chemical method were compared against the SUNA-based concentrations.…”
Section: Glider Sensor Calibrationsmentioning
confidence: 99%
“…The SUNA sensor allows quantifying the nitrate concentration (NO3 -) from light absorption at ultraviolet wavelengths (Johnson et al, 2010(Johnson et al, , 2013Johnson and Coletti, 2002). As recommended by , NO3 -is calculated using the algorithm developed by Sakamoto et al (2009).…”
Section: Biogeochemical-argo Measurementsmentioning
confidence: 99%