The internal consistency of the marine carbon dioxide system for high latitude shipboard and in situ monitoring

Raimondi, Lorenza; Matthews, J. B.; Atamanchuk, Dariia; Azetsu-Scott, Kumiko; Wallace, Douglas W.R.

doi:10.1016/j.marchem.2019.03.001

Cited by 33 publications

(35 citation statements)

References 70 publications

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“…As depicted in Fig. 6, in agreement with Raimondi et al (2019), we conclude that the DIC-pH pair offers the lowest overall relative uncertainty for computed pCO2 over the range of salinities and temperatures investigated. Using the DIC-pH pair also has the important benefit of not having to make any assumption regarding organic alkalinity or the boron to salinity ratio (Fong and Dickson, 2019).…”

Section: Uncertainties In Carbonate System Calculationssupporting

confidence: 86%

“…Bailey et al (2018) recently suggested that the same bias exists for the dissolution of CO2 in seawater and showed that previous expressions of Henry's Law constant for CO2 underestimate the CO2 solubility below 0 °C due to a lack of samples in cold waters. As explained by Raimondi et al (2019), because the only carbonate system variables currently measured by in situ sensor technologies are pH and the partial pressure of CO2 in seawater (pCO2), relating laboratory or on-board measurements that are usually performed at temperatures ~25 °C to these in situ measurements requires an accurate knowledge of the K1 * and K2 * temperature dependency. About 40% of the ocean volume is at an average temperature lower than 2 °C, outside of the temperature range for which the Mehrbach et al (1973) and derived constants are valid (from the data of .…”

Section: Introductionmentioning

confidence: 99%

“…in sea-ice brines (Brown et al, 2014) or in systems with substantial organic alkalinity (Koeve and Oschlies, 2012). We refer the reader to Raimondi et al (2019) for an overview of internal consistency studies, i.e., the agreement between measured and calculated variables. Disagreement between measured and computed values may arise from uncertainties in measurements and, more importantly, equilibrium constants (Orr et al, 2018), but can also result from the choice of relationship between total boron and salinity, as well as organic alkalinity (Fong and Dickson, 2019).…”

Section: Introductionmentioning

confidence: 99%

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Current estimates of K1 and K2 appear inconsistent with measured CO2 system parameters in cold oceanic regions

Sulpis¹,

Lauvset²,

Hagens³

2020

Preprint

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Abstract. Seawater absorption of anthropogenic atmospheric carbon dioxide (CO2) has led to a range of changes in carbonate chemistry, collectively referred to as ocean acidification. Stoichiometric dissociation constants used to convert measured carbonate system variables (pH, pCO2, dissolved inorganic carbon, total alkalinity) into globally comparable parameters are crucial for accurately quantifying these changes. The temperature and salinity coefficients of these constants have generally been experimentally derived under controlled laboratory conditions. Here, we use field measurements of carbonate system variables taken from the Global Ocean Data Analysis Project version 2 and the Surface Ocean CO2 Atlas databases to evaluate the temperature dependence of the carbonic acid stoichiometric dissociation constants. By applying a novel iterative procedure to a large dataset of 948 surface-water, quality-controlled samples where four carbonate system variables were independently measured, we show that the set of equations published by Lueker et al. (2000), currently preferred by the ocean acidification community, overestimates the stoichiometric dissociation constants at low temperatures, below ~ 8 °C. We apply these newly derived temperature coefficients to high-latitude Argo float and cruise data to quantify the effects on surface-water pCO2 and calcite saturation states. These findings highlight the critical implications of uncertainty in stoichiometric dissociation constants for future projections of ocean acidification in polar regions, and the need to improve knowledge of what causes the CO2 system inconsistencies in cold waters.

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Section: Uncertainties In Carbonate System Calculationssupporting

confidence: 86%

Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

See 1 more Smart Citation

Current estimates of K1 and K2 appear inconsistent with measured CO2 system parameters in cold oceanic regions

Sulpis¹,

Lauvset²,

Hagens³

2020

Preprint

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“…Climatologies of silicic acid and phosphate are repeated for each year, thus assuming no interannual variability. The dissociation constants by Dickson et al (1990) for K HSO4 and the total boron-salinity relationship by Uppström (1974) were used, as recommended by Orr et al (2015) and Raimondi et al (2019). For further details on the calculation and the full description of the marine carbonate system, see Dickson et al (2007).…”

Section: Computation Of Dic Ph and ωmentioning

confidence: 99%

“…An important consideration in these calculations is the internal consistency of the marine carbonate system, i.e., the error due to uncertainties in the equations and coefficients that describe the marine carbonate system. Raimondi et al (2019) pointed out that the pCO 2 -TA pair has the lowest error in the calculation of pH (0.003 ± 0.008 pH units) using the dissociation constants by Mehrbach et al (1973) as refitted by Dickson and Millero (1987). However, using the same pair and the same dissociation constants resulted in an estimate of Ω with respect to Aragonite that is very different from that computed using the DIC-TA pair.…”

Section: Computation Of Dic Ph and ωmentioning

confidence: 99%

OceanSODA-ETHZ: A global gridded data set of the surface ocean carbonate system for seasonal to decadal studies of ocean acidification

Gregor¹,

Gruber²

2020

Preprint

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Abstract. Ocean acidification has altered the ocean's carbonate chemistry profoundly since preindustrial times, with potentially serious consequences for marine life. Yet, no long-term global observation-based data set exists that permits to study changes in ocean acidification for all carbonate system parameters over the last few decades. Here, we fill this gap and present a methodologically consistent global data set of all relevant surface ocean parameters, i.e., dissolved inorganic carbon (DIC), total alkalinity (TA), partial pressure of CO2 (pCO2), pH, and the saturation state with respect to mineral CaCO3 (Ω) at monthly resolution over the period 1985 through 2018 at a spatial resolution of 1 × 1°. This data set, named OceanSODA-ETHZ, was created by extrapolating in time and space the surface ocean observations of pCO2 (from the Surface Ocean CO2 ATlas (SOCAT)) and total alkalinity (TA, from the Global Ocean Data Analysis Project (GLODAP)) using the newly developed Geospatial Random Cluster Ensemble Regression (GRaCER) method. This method is based on a two-step (cluster-regression) approach, but extends it by considering an ensemble of such cluster-regressions, leading to higher robustness. Surface ocean DIC, pH, and Ω were then computed from the globally mapped pCO2 and TA using the thermodynamic equations of the carbonate system. For the open ocean, the cluster regression method estimates pCO2 and TA with global near-zero biases and root mean squared errors of 12 µatm and 13 µmol kg−1, respectively. Taking into account also the measurement and representation errors, the total error increases to 14 µatm and 21 µmol kg−1, respectively. We assess the fidelity of the computed parameters by comparing them to direct observations from GLODAP, finding surface ocean pH and DIC global biases of near zero, and root mean squared errors of 0.023 and 16 µmol kg−1, respectively. These errors are very comparable to those expected by propagating the total errors from pCO2 and TA through the thermodynamic computations, indicating a robust and conservative assessment of the errors. We illustrate the potential of this new dataset by analyzing the climatological mean seasonal cycles of the different parameters of the surface ocean carbonate system, highlighting their commonalities and differences. The OceanSODA-ETHZ data can be downloaded from https://doi.org/10.25921/m5wx-ja34 (Gregor and Gruber, 2020).

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Uncertainty sources for measurable ocean carbonate chemistry variables

Carter,

Sharp,

Dickson

et al. 2023

Limnology & Oceanography

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The ocean carbonate system is critical to monitor because it plays a major role in regulating Earth's climate and marine ecosystems. It is monitored using a variety of measurements, and it is commonly understood that all components of seawater carbonate chemistry can be calculated when at least two carbonate system variables are measured. However, several recent studies have highlighted systematic discrepancies between calculated and directly measured carbonate chemistry variables and these discrepancies have large implications for efforts to measure and quantify the changing ocean carbon cycle. Given this, the Ocean Carbonate System Intercomparison Forum (OCSIF) was formed as a working group through the Ocean Carbon and Biogeochemistry program to coordinate and recommend research to quantify and/or reduce uncertainties and disagreements in measurable seawater carbonate system measurements and calculations, identify unknown or overlooked sources of these uncertainties, and provide recommendations for making progress on community efforts despite these uncertainties. With this paper we aim to (1) summarize recent progress toward quantifying and reducing carbonate system uncertainties; (2) advocate for research to further reduce and better quantify carbonate system measurement uncertainties; (3) present a small amount of new data, metadata, and analysis related to uncertainties in carbonate system measurements; and (4) restate and explain the rationales behind several OCSIF recommendations. We focus on open ocean carbonate chemistry, and caution that the considerations we discuss become further complicated in coastal, estuarine, and sedimentary environments.

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The internal consistency of the marine carbon dioxide system for high latitude shipboard and in situ monitoring

Cited by 33 publications

References 70 publications

Current estimates of K<sub>1</sub><sup></sup> and K<sub>2</sub><sup></sup> appear inconsistent with measured CO<sub>2</sub> system parameters in cold oceanic regions

Current estimates of K<sub>1</sub><sup></sup> and K<sub>2</sub><sup></sup> appear inconsistent with measured CO<sub>2</sub> system parameters in cold oceanic regions

OceanSODA-ETHZ: A global gridded data set of the surface ocean carbonate system for seasonal to decadal studies of ocean acidification

Uncertainty sources for measurable ocean carbonate chemistry variables

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The internal consistency of the marine carbon dioxide system for high latitude shipboard and in situ monitoring

Cited by 33 publications

References 70 publications

Current estimates of K&lt;sub&gt;1&lt;/sub&gt;&lt;sup&gt;*&lt;/sup&gt; and K&lt;sub&gt;2&lt;/sub&gt;&lt;sup&gt;*&lt;/sup&gt; appear inconsistent with measured CO&lt;sub&gt;2&lt;/sub&gt; system parameters in cold oceanic regions

Current estimates of K&lt;sub&gt;1&lt;/sub&gt;&lt;sup&gt;*&lt;/sup&gt; and K&lt;sub&gt;2&lt;/sub&gt;&lt;sup&gt;*&lt;/sup&gt; appear inconsistent with measured CO&lt;sub&gt;2&lt;/sub&gt; system parameters in cold oceanic regions

OceanSODA-ETHZ: A global gridded data set of the surface ocean carbonate system for seasonal to decadal studies of ocean acidification

Uncertainty sources for measurable ocean carbonate chemistry variables

Contact Info

Product

Resources

About

Current estimates of K<sub>1</sub><sup></sup> and K<sub>2</sub><sup></sup> appear inconsistent with measured CO<sub>2</sub> system parameters in cold oceanic regions

Current estimates of K<sub>1</sub><sup></sup> and K<sub>2</sub><sup></sup> appear inconsistent with measured CO<sub>2</sub> system parameters in cold oceanic regions