Delayed-Mode Quality Control of Oxygen, Nitrate, and pH Data on SOCCOM Biogeochemical Profiling Floats

Maurer, Tanya L.; Plant, Joshua N.; Johnson, Kenneth S.

doi:10.3389/fmars.2021.683207

Cited by 34 publications

(44 citation statements)

References 56 publications

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“…Similar to previous studies that have estimated uncertainty in observation-based biogeochemical data products (e.g., Landschützer et al, 2014;Gregor and Gruber, 2021;Keppler et al, 2020), we combine uncertainty from three separate sources measurement, representation, and algorithmto estimate uncertainty in GOBAI-O2 (section 3.2.4). datasetstated to be 1% (Lauvset et al, 2021) and the approximate accuracy of BGC Argo float observationsestimated as about 3 μmol kg -1 (Johnson et al, 2017;Maurer et al, 2021), which is close to 2% of average ocean [O2]. We recognize, however, that even 2% is a rather optimistic estimate for the accuracy of float [O2] sensors, especially when crossing steep vertical gradients (Bittig and Körtzinger, 2017;Bittig et al, 2018).…”

Section: Uncertainty Estimationmentioning

confidence: 77%

GOBAI-O₂: temporally and spatially resolved fields of ocean interior dissolved oxygen over nearly two decades

Sharp

Fassbender

Carter

et al. 2022

Preprint

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Abstract. Over a decade ago, oceanographers began installing oxygen sensors on Argo floats to be deployed throughout the world ocean with the express objective of better constraining trends and variability in the ocean’s inventory of oxygen. Until now, measurements from these Argo-mounted oxygen sensors have been mainly used for localized process studies on air–sea oxygen exchange, biological pump efficiency, upper ocean primary production, and oxygen minimum zone dynamics. Here we present a four-dimensional gridded product of ocean interior oxygen, derived via machine learning algorithms trained on dissolved oxygen observations from Argo-mounted sensors and discrete measurements from ship-based surveys, and applied to temperature and salinity fields constructed from the global Argo array. The data product is called GOBAI-O2 for Gridded Ocean Biogeochemistry from Artificial Intelligence – Oxygen (Sharp et al., 2022; https://doi.org/10.25921/z72m-yz67; last access: 30 Aug. 2022); it covers 86 % of the global ocean area on a 1° latitude by 1° longitude grid, spans the years 2004–2021 with monthly resolution, and extends from the ocean surface to two kilometers in depth on 58 levels. Two machine learning algorithms — random forest regressions and feed-forward neural networks — are used in the development of GOBAI-O2, and the performance of those algorithms is assessed using real observations and Earth system model output. GOBAI-O2 is evaluated through comparisons to the World Ocean Atlas and to direct observations from large-scale hydrographic research cruises. Finally, potential uses for GOBAI-O2 are demonstrated by presenting average oxygen fields on isobaric and isopycnal surfaces, average oxygen fields across vertical–meridional sections, climatological cycles of oxygen averaged over different pressure intervals, and a globally integrated oxygen inventory time series.

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Section: Uncertainty Estimationmentioning

confidence: 77%

GOBAI-O₂: temporally and spatially resolved fields of ocean interior dissolved oxygen over nearly two decades

Sharp

Fassbender

Carter

et al. 2022

Preprint

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“…After quality control adjustments, the mean sensor nitrate concentration difference from bottle samples collected when floats were launched (n = 2,644) was 0.2 μmol kg −1 with a standard deviation of 1 μmol kg −1 . The mean sensor pH differed from discrete samples (n = 1,262) by 0.002 with a standard deviation of 0.015 (Maurer et al, 2021).…”

Section: Profiling Float Measurementsmentioning

confidence: 89%

“…This is discussed further below. The accuracy of the float pH data does not appear to degrade in time (Johnson, Plant, Coletti, et al, 2017;Maurer et al, 2021), suggesting that the DIC estimates should retain similar accuracy values over time.…”

Section: Profiling Float Measurementsmentioning

confidence: 96%

Carbon to Nitrogen Uptake Ratios Observed Across the Southern Ocean by the SOCCOM Profiling Float Array

et al. 2022

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Measurements of pH and nitrate from the Southern Ocean Carbon and Climate Observations and Modeling array of profiling floats were used to assess the ratios of dissolved inorganic carbon (DIC) and nitrate (NO3) uptake during the spring to summer bloom period throughout the Southern Ocean. Two hundred and forty‐three bloom periods were observed by 115 floats from 30°S to 70°S. Similar calculations were made using the Takahashi surface DIC and nitrate climatology. To separate the effects of atmospheric CO2 exchange and mixing from phytoplankton uptake, the ratios of changes in DIC to nitrate of surface waters (ΔDIC/ΔNO3) were computed in the Biogeochemical Southern Ocean State Estimate (B‐SOSE) model. Phytoplankton uptake of DIC and nitrate are fixed in B‐SOSE at the Redfield Ratio (RR; 6.6 mol C/mol N). Deviations in the B‐SOSE ΔDIC/ΔNO3 must be due to non‐biological effects of CO2 gas exchange and mixing. ΔDIC/ΔNO3 values observed by floats and in the Takahashi climatology were corrected for the non‐biological effects using B‐SOSE. The corrected, in situ biological uptake ratio (C:N) occurs at values similar to the RR, with two major exceptions. North of 40°S biological DIC uptake is observed with little or no change in nitrate giving high C:N. In the latitude band at 55°S, the Takahashi data give a low C:N value, while floats are high. This may be due to a change in CO2 air‐sea exchange in this region from uptake during the Takahashi reference year of 2005 to outgassing of CO2 during the years sampled by floats.

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“…In addition, the water vapor pressure as a function of the temperature is calculated by equation 5 [51],…”

Section: Temperature Compensationmentioning

confidence: 99%

Photonic-Based Time-Resolved Multipulse Oxygen Sensor

2022

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Oxygen is one of Earth's vital elements, and its accurate measurement is crucial in numerous scientific and medical applications. Photonic-based sensors have recently become the subject of great attention for oxygen measurements due to their highly promising characteristics. These include the lack of requirement for repetitive calibrations and replacement of parts, being contactless, their accuracy, and fast response, and the potential to fabricate such sensors in small sizes. Here, we develop a dissolved-oxygen sensor by integrating time-resolved photoluminescence spectroscopy employing an FPGA-controlled multi-pulse LED source and amplified fast photodetector mounted on a PCB, light-emitting platinum porphine complex embedded polystyrene molecular oxygen-sensing probe, and a two-site Stern-Volmer function for the sensing and calibration. The PCB excites the molecular probe with multiple 50 ns blue light pulses, and the emission lifetime is extracted using an exponential function based on the Levenberg-Marquardt nonlinear fitting. Complete characterization of the sensor, including its sensitivity, repeatability, stability, and response time, in addition to the temperature and altitude compensation, is implemented to achieve excellent dissolved-oxygen sensing functionality.

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Delayed-Mode Quality Control of Oxygen, Nitrate, and pH Data on SOCCOM Biogeochemical Profiling Floats

Cited by 34 publications

References 56 publications

GOBAI-O₂: temporally and spatially resolved fields of ocean interior dissolved oxygen over nearly two decades

GOBAI-O₂: temporally and spatially resolved fields of ocean interior dissolved oxygen over nearly two decades

Carbon to Nitrogen Uptake Ratios Observed Across the Southern Ocean by the SOCCOM Profiling Float Array

Photonic-Based Time-Resolved Multipulse Oxygen Sensor

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Delayed-Mode Quality Control of Oxygen, Nitrate, and pH Data on SOCCOM Biogeochemical Profiling Floats

Cited by 34 publications

References 56 publications

GOBAI-O2: temporally and spatially resolved fields of ocean interior dissolved oxygen over nearly two decades

GOBAI-O2: temporally and spatially resolved fields of ocean interior dissolved oxygen over nearly two decades

Carbon to Nitrogen Uptake Ratios Observed Across the Southern Ocean by the SOCCOM Profiling Float Array

Photonic-Based Time-Resolved Multipulse Oxygen Sensor

Contact Info

Product

Resources

About

GOBAI-O₂: temporally and spatially resolved fields of ocean interior dissolved oxygen over nearly two decades

GOBAI-O₂: temporally and spatially resolved fields of ocean interior dissolved oxygen over nearly two decades