Coulometric total carbon dioxide analysis for marine studies: measurement and internal consistency of underway TCO2 concentrations

Johnson, Kenneth M.; Körtzinger, Arne; Mintrop, L.; Duinker, Jan C.; Wallace, Douglas W.R.

doi:10.1016/s0304-4203(99)00055-9

Cited by 34 publications

(16 citation statements)

References 27 publications

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“…For instance, Johnson et al (1999) compared C T , f CO 2 and A T measurements during the same intercomparison exercise as reported for f CO 2 by Körtzinger et al (2000). These scientists found a systematic f CO 2 overestimation of 9 µatm when calculated from C T and A T measurements relative to observed f CO 2 .…”

Section: Introductionmentioning

confidence: 86%

Intercomparison of carbonate chemistry measurements on a cruise in northwestern European shelf seas

et al. 2014

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Abstract. Four carbonate system variables were measured in surface waters during a cruise aimed at investigating ocean acidification impacts traversing northwestern European shelf seas in the summer of 2011. High-resolution surface water data were collected for partial pressure of carbon dioxide (pCO 2 ; using two independent instruments) and pH using the total pH scale (pH T ), in addition to discrete measurements of total alkalinity and dissolved inorganic carbon. We thus overdetermined the carbonate system (four measured variables, two degrees of freedom), which allowed us to evaluate the level of agreement between the variables on a cruise whose main aim was not intercomparison, and thus where conditions were more representative of normal working conditions. Calculations of carbonate system variables from other measurements generally compared well with direct observations of the same variables (Pearson's correlation coefficient always greater than or equal to 0.94; mean residuals were similar to the respective accuracies of the measurements). We therefore conclude that four of the independent data sets of carbonate chemistry variables were of high quality. A diurnal cycle with a maximum amplitude of 41 µatm was observed in the difference between the pCO 2 values obtained by the two independent analytical pCO 2 systems, and this was partly attributed to irregular seawater flows to the equilibrator and partly to biological activity inside the seawater supply and one of the equilibrators. We discuss how these issues can be addressed to improve carbonate chemistry data quality on future research cruises.

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Section: Introductionmentioning

confidence: 86%

Intercomparison of carbonate chemistry measurements on a cruise in northwestern European shelf seas

et al. 2014

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“…Chlorophyll a concentration was determined by fluorometry (Parsons et al, 1984). DIC was determined by coulometry (Johnson et al, 1999) using a coulometer (CM5012, UIC, Inc., Binghamton, NY, USA). The precision of DIC analysis from duplicate determinations is within ±0.1 % (Wakita et al, 2003).…”

Section: Methodsmentioning

confidence: 99%

Winter-to-summer evolution of pCO2 in surface water and air–sea CO2 flux in the seasonal ice zone of the Southern Ocean

et al. 2014

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Abstract. Partial pressure of CO 2 (pCO 2 ) in surface water and vertical profiles of the carbonate system parameters were measured during austral summer in the Indian sector of the Southern Ocean (64-67 • S, 32-58 • E) in January 2006 to understand the CO 2 dynamics of seawater in the seasonal ice zone. Surface-water pCO 2 ranged from 275 to 400 µatm, and longitudinal variations reflected the dominant influence of water temperature and dilution by sea ice meltwater between 32 and 40 • E and biological productivity between 40 and 58 • E. Using carbonate system data from the temperature minimum layer (−1.9 • C < T < −1.5 • C, 34.2 < S < 34.5), we examined the winter-to-summer evolution of surface-water pCO 2 and the factors affecting it. Our results indicate that pCO 2 increased by as much as 32 µatm, resulting mainly from the increase in water temperature. At the same time as changes in sea ice concentration and surface-water pCO 2 , the air-sea CO 2 flux, which consists of the exchange of CO 2 between sea ice and atmosphere, changed from −1.1 to +0.9 mmol C m −2 day −1 between winter and summer. These results suggest that, for the atmosphere, the seasonal ice zone acts as a CO 2 sink in winter and a temporary CO 2 source in summer immediately after the retreat of sea ice. Subsequent biological productivity likely decreases surface-water pCO 2 and the air-sea CO 2 flux becomes negative, such that in summer the study area is again a CO 2 sink with respect to the atmosphere.

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“…DIC and TA samples were preserved with 0.02% (by volume) saturated HgCl 2 solution onboard the vessel following DOE instructions. DIC was analyzed with the coulometric technique of Johnson et al [1999] using a SOMMA system. TA samples were analyzed by the potentiometric titration in an open cell as described by Mintrop et al [2000].…”

Section: Methodsmentioning

confidence: 99%

The pCO₂ variability in the midlatitude North Atlantic Ocean during a full annual cycle

Lüger

Wallace

Körtzinger

et al. 2004

Global Biogeochemical Cycles

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[1] The results of 1 year of automated pCO 2 measurements in 2002/2003 onboard the car carrier M/V Falstaff are presented and analyzed with regard to the driving forces that change the seawater pCO 2 in the midlatitude North Atlantic Ocean. The pCO 2 in surface seawater is controlled by thermodynamics, biology, air-sea gas exchange, and physical mixing. Here we estimate the effects on the annual cycle of pCO 2 and relate this property to parameters like SST, nitrate, and chlorophyll. On the basis of the amplitude in seawater pCO 2 for all 4°Â 5°grid boxes, this region can be separated into an eastern and western basin. The annual pCO 2 cycle in the eastern basin (10°W-35°W) is less variable, which can be related to the two counteracting effects of temperature and biology; air-sea gas exchange plays a minor role when using climatological MLD. In the western basin (36°W-70°W) the pCO 2 amplitude is more variable and strongly follows the thermodynamic forcing, since the biological forcing (as derived from nitrate concentrations) is decreased. Biology and air-sea exchange strongly depend on the MLD and therefore also include physical mixing effects. The pCO 2 data of the analyzed region between 34°N and 52°N compare well to the Takahashi et al. [2002] climatology except for regions north of 45°N during the wintertime where the bias is significant.

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Coulometric total carbon dioxide analysis for marine studies: measurement and internal consistency of underway TCO2 concentrations

Cited by 34 publications

References 27 publications

Intercomparison of carbonate chemistry measurements on a cruise in northwestern European shelf seas

Intercomparison of carbonate chemistry measurements on a cruise in northwestern European shelf seas

Winter-to-summer evolution of <i>p</i>CO<sub>2</sub> in surface water and air–sea CO<sub>2</sub> flux in the seasonal ice zone of the Southern Ocean

The pCO₂ variability in the midlatitude North Atlantic Ocean during a full annual cycle

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Coulometric total carbon dioxide analysis for marine studies: measurement and internal consistency of underway TCO2 concentrations

Cited by 34 publications

References 27 publications

Intercomparison of carbonate chemistry measurements on a cruise in northwestern European shelf seas

Intercomparison of carbonate chemistry measurements on a cruise in northwestern European shelf seas

Winter-to-summer evolution of &lt;i&gt;p&lt;/i&gt;CO&lt;sub&gt;2&lt;/sub&gt; in surface water and air–sea CO&lt;sub&gt;2&lt;/sub&gt; flux in the seasonal ice zone of the Southern Ocean

The pCO2 variability in the midlatitude North Atlantic Ocean during a full annual cycle

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Winter-to-summer evolution of <i>p</i>CO<sub>2</sub> in surface water and air–sea CO<sub>2</sub> flux in the seasonal ice zone of the Southern Ocean

The pCO₂ variability in the midlatitude North Atlantic Ocean during a full annual cycle