Internal consistency of marine carbonate system measurements and assessments of aragonite saturation state: Insights from two U.S. coastal cruises

Patsavas, Mark C.; Byrne, Robert H.; Wanninkhof, Rik; Feely, Richard A.; Cai, Wei‐Jun

doi:10.1016/j.marchem.2015.06.022

Cited by 55 publications

(36 citation statements)

References 49 publications

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“…Also, although the spectrophotometric pH method has been used since the early 1990s, Yao et al (2007) revealed that impurities in the indicator dye used can significantly bias spectrophotometric pH measurements, and Liu et al (2011) subsequently published calibration equations that allow seawater pH measurements to be made using purified m-cresol purple dye. Others (Carter et al 2013;Patsavas et al 2015;Williams et al 2017) have since shown that measurements with purified dyes appear to have an (unexplained) broadly consistent-but-pHdependent discrepancy from the pH calculated from combinations of A T , C T , and pCO 2 whether calculated at in situ or laboratory conditions (Fig. 2c).…”

Section: Data Products Used To Train and Test Lirsmentioning

confidence: 83%

Updated methods for global locally interpolated estimation of alkalinity, pH, and nitrate

Carter

Feely

Williams

et al. 2017

Limnology & Ocean Methods

149

200

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Section: Data Products Used To Train and Test Lirsmentioning

confidence: 83%

Updated methods for global locally interpolated estimation of alkalinity, pH, and nitrate

Carter

Feely

Williams

et al. 2017

Limnology & Ocean Methods

149

200

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“…Several sets of equilibrium constants are available for use in carbonate system calculations, and the choice of constants may introduce a bias in pCO 2sw (pH, TA) [Wanninkhof et al, 1999]. Here we use the equilibrium constants of Lueker et al [2000] as recommended by A. Dickson [Wanninkhof et al, 2016a] because, given the choice of pH on the total scale, they provide the most consistent intercomparison for the four measurable carbonate system parameters [Patsavas et al, 2015]. The estimated uncertainty in K 0 from Dickson and Riley [1978] (based on Weiss [1974]) and estimates of the uncertainties in K 1 and K 2 are used to estimate their contributions to uncertainty in pCO 2sw (pH, TA).…”

Section: Carbonate System Equilibrium Constants and Nutrient Concentrmentioning

confidence: 99%

Calculating surface ocean pCO₂ from biogeochemical Argo floats equipped with pH: An uncertainty analysis

Williams

Juranek

Feely

et al. 2017

Global Biogeochemical Cycles

139

171

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More than 74 biogeochemical profiling floats that measure water column pH, oxygen, nitrate, fluorescence, and backscattering at 10 day intervals have been deployed throughout the Southern Ocean. Calculating the surface ocean partial pressure of carbon dioxide (pCO 2sw ) from float pH has uncertainty contributions from the pH sensor, the alkalinity estimate, and carbonate system equilibrium constants, resulting in a relative standard uncertainty in pCO 2sw of 2.7% (or 11 μatm at pCO 2sw of 400 μatm). The calculated pCO 2sw from several floats spanning a range of oceanographic regimes are compared to existing climatologies. In some locations, such as the subantarctic zone, the float data closely match the climatologies, but in the polar Antarctic zone significantly higher pCO 2sw are calculated in the wintertime implying a greater air-sea CO 2 efflux estimate. Our results based on four representative floats suggest that despite their uncertainty relative to direct measurements, the float data can be used to improve estimates for air-sea carbon flux, as well as to increase knowledge of spatial, seasonal, and interannual variability in this flux.

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“…Impurities in m‐cresol purple dye from common manufacturers are known to create a pH‐dependent bias (Liu et al, ). However, there seems to be an additional source for this bias, as a pCO 2 ‐dependent bias in pCO 2 (disc) and pCO 2 (pH, DIC) was observed even when purified m‐cresol purple was used (Patsavas et al, ). Studies have demonstrated that no such bias exists between directly measured pCO 2 and pCO 2 (TA, DIC) (Chen et al, ; Patsavas et al, ; Wang et al, ), indicating that pCO 2 , TA, and DIC are internally consistent.…”

Section: Discussionmentioning

confidence: 99%

“…However, there seems to be an additional source for this bias, as a pCO 2 ‐dependent bias in pCO 2 (disc) and pCO 2 (pH, DIC) was observed even when purified m‐cresol purple was used (Patsavas et al, ). Studies have demonstrated that no such bias exists between directly measured pCO 2 and pCO 2 (TA, DIC) (Chen et al, ; Patsavas et al, ; Wang et al, ), indicating that pCO 2 , TA, and DIC are internally consistent. Furthermore, an analysis of historical hydrography data revealed that this pH‐dependent bias (between pH(spec) and pH(DIC, TA)) only manifested after the use of purified m‐cresol purple (Carter et al, ).…”

Section: Discussionmentioning

confidence: 99%

Assessment of Autonomous pH Measurements for Determining Surface Seawater Partial Pressure of CO₂

et al. 2018

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The Southern Ocean Carbon and Climate Observations and Modeling (SOCCOM) program currently operates >80 profiling floats equipped with pH sensors in the Southern Ocean. Theoretically, these floats have the potential to provide unique year‐around estimates of pCO2 derived from pH measurements. Here, we evaluate this approach in the field by comparing pCO2 estimates from pH sensors to directly measured pCO2. We first discuss data from a ship's underway system which covered a large range in temperature (2–30°C) and salinity (33.6–36.5) over 43 days. This pH sensor utilizes the same sensing technology but with different packaging than those on SOCCOM floats. The mean residual varied between −4.6 ± 4.1 and 8.6 ± 4.0 (1σ) μatm, depending on how the sensor was calibrated. However, the standard deviation of the residual, interpreted as the ability to track spatiotemporal variability, was consistently < 5 μatm and was independent of the calibration method. Second, we assessed the temporal stability of this approach by comparing pCO2 estimated from four floats over 3 years to the Hawaii Ocean Time‐series. Good agreement of −2.1 ± 10.4 (1σ) µatm was observed, with coherent seasonal cycles. These results demonstrate that pCO2 estimates derived from profiling float pH measurements appear capable of reproducing spatiotemporal variations in surface pCO2 measurements and should provide a powerful observational tool to complement current efforts to understand the seasonal to interannual variability of surface pCO2 in underobserved regions of the open ocean.

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Internal consistency of marine carbonate system measurements and assessments of aragonite saturation state: Insights from two U.S. coastal cruises

Cited by 55 publications

References 49 publications

Updated methods for global locally interpolated estimation of alkalinity, pH, and nitrate

Updated methods for global locally interpolated estimation of alkalinity, pH, and nitrate

Calculating surface ocean pCO₂ from biogeochemical Argo floats equipped with pH: An uncertainty analysis

Assessment of Autonomous pH Measurements for Determining Surface Seawater Partial Pressure of CO₂

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Internal consistency of marine carbonate system measurements and assessments of aragonite saturation state: Insights from two U.S. coastal cruises

Cited by 55 publications

References 49 publications

Updated methods for global locally interpolated estimation of alkalinity, pH, and nitrate

Updated methods for global locally interpolated estimation of alkalinity, pH, and nitrate

Calculating surface ocean pCO2 from biogeochemical Argo floats equipped with pH: An uncertainty analysis

Assessment of Autonomous pH Measurements for Determining Surface Seawater Partial Pressure of CO2

Contact Info

Product

Resources

About

Calculating surface ocean pCO₂ from biogeochemical Argo floats equipped with pH: An uncertainty analysis

Assessment of Autonomous pH Measurements for Determining Surface Seawater Partial Pressure of CO₂