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

2014 ◽  
Vol 11 (2) ◽  
pp. 2793-2822 ◽  
Author(s):  
M. Ribas-Ribas ◽  
V. M. C. Rérolle ◽  
D. C. E. Bakker ◽  
V. Kitidis ◽  
G. A. Lee ◽  
...  
Keyword(s):  
Degrees Of Freedom ◽  
Dissolved Inorganic Carbon ◽  
Maximum Amplitude ◽  
Total Alkalinity ◽  
Carbonate Chemistry ◽  
Carbonate System ◽  
European Shelf ◽  
Shelf Seas ◽  
The Difference ◽  
System Variables

Abstract. Four carbonate system variables were measured in surface waters during a cruise traversing northwestern European shelf seas in the summer of 2011. High resolution surface water data were collected for partial pressure of carbon dioxide (pCO2; using two independent instruments) and pHT, 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. Calculations of carbonate system variables from other measurements generally compared well (Pearson's correlation coefficient always ≥ 0.94; mean residuals similar to the respective uncertainties of the calculations) with direct observations of the same variables. We therefore conclude that the four independent datasets of carbonate chemistry variables were all of high quality, and as a result that this dataset is suitable to be used for the evaluation of ocean acidification impacts and for carbon cycle studies. A diurnal cycle with maximum amplitude of 41 μatm was observed in the difference between the pCO2; values obtained by the two independent analytical pCO2; 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 research cruises.

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

2014 ◽  
Vol 11 (16) ◽  
pp. 4339-4355 ◽  
Author(s):  
M. Ribas-Ribas ◽  
V. M. C. Rérolle ◽  
D. C. E. Bakker ◽  
V. Kitidis ◽  
G. A. Lee ◽  
...  
Keyword(s):  
Degrees Of Freedom ◽  
Dissolved Inorganic Carbon ◽  
Maximum Amplitude ◽  
Total Alkalinity ◽  
Future Research ◽  
Carbonate Chemistry ◽  
Carbonate System ◽  
European Shelf ◽  
Shelf Seas ◽  
System Variables

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 (pCO2; using two independent instruments) and pH using the total pH scale (pHT), 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 pCO2 values obtained by the two independent analytical pCO2 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.

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

Ocean Science ◽  
2020 ◽  
Vol 16 (4) ◽  
pp. 847-862 ◽  
Author(s):  
Olivier Sulpis ◽  
Siv K. Lauvset ◽  
Mathilde Hagens
Keyword(s):  
Surface Water ◽  
Ocean Acidification ◽  
Carbonic Acid ◽  
Dissolved Inorganic Carbon ◽  
Dissociation Constants ◽  
Total Alkalinity ◽  
Global Ocean ◽  
Polar Regions ◽  
Carbonate System ◽  
System Variables

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 data products 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 temperatures below about 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.

scholarly journals CO<sub>2</sub> perturbation experiments: similarities and differences between dissolved inorganic carbon and total alkalinity manipulations

2009 ◽  
Vol 6 (10) ◽  
pp. 2145-2153 ◽  
Author(s):  
K. G. Schulz ◽  
J. Barcelos e Ramos ◽  
R. E. Zeebe ◽  
U. Riebesell
Keyword(s):  
Ocean Acidification ◽  
Inorganic Carbon ◽  
Dissolved Inorganic Carbon ◽  
Total Alkalinity ◽  
Calcium Carbonate Precipitation ◽  
Carbonate Chemistry ◽  
Carbonate System ◽  
Experimental Conditions ◽  
Saturation State ◽  
Basic Approaches

Abstract. Increasing atmospheric carbon dioxide (CO2) through human activities and invasion of anthropogenic CO2 into the surface ocean alters the seawater carbonate chemistry, increasing CO2 and bicarbonate (HCO3−) at the expense of carbonate ion (CO32−) concentrations. This redistribution in the dissolved inorganic carbon (DIC) pool decreases pH and carbonate saturation state (Ω). Several components of the carbonate system are considered potential key variables influencing for instance calcium carbonate precipitation in marine calcifiers such as coccolithophores, foraminifera, corals, mollusks and echinoderms. Unravelling the sensitivities of marine organisms and ecosystems to CO2 induced ocean acidification (OA) requires well-controlled experimental setups and accurate carbonate system manipulations. Here we describe and analyse the chemical changes involved in the two basic approaches for carbonate chemistry manipulation, i.e. changing DIC at constant total alkalinity (TA) and changing TA at constant DIC. Furthermore, we briefly introduce several methods to experimentally manipulate DIC and TA. Finally, we examine responses obtained with both approaches using published results for the coccolithophore Emiliania huxleyi. We conclude that under most experimental conditions in the context of ocean acidification DIC and TA manipulations yield similar changes in all parameters of the carbonate system, which implies direct comparability of data obtained with the two basic approaches for CO2 perturbation.

scholarly journals 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

2020 ◽  
Author(s):  
Olivier Sulpis ◽  
Siv K. Lauvset ◽  
Mathilde Hagens
Keyword(s):  
Surface Water ◽  
Ocean Acidification ◽  
Carbonic Acid ◽  
Dissolved Inorganic Carbon ◽  
Dissociation Constants ◽  
Total Alkalinity ◽  
Global Ocean ◽  
Polar Regions ◽  
Carbonate System ◽  
System Variables

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.

scholarly journals Improved routines to model the ocean carbonate system: mocsy 2.0

2015 ◽  
Vol 8 (3) ◽  
pp. 485-499 ◽  
Author(s):  
J. C. Orr ◽  
J.-M. Epitalon
Keyword(s):  
Best Practices ◽  
Best Practice ◽  
Inorganic Carbon ◽  
Dissolved Inorganic Carbon ◽  
Equilibrium Constants ◽  
Potential Temperature ◽  
Total Alkalinity ◽  
Carbonate System ◽  
Carbon Cycle Model ◽  
System Variables

Abstract. Modelers compute ocean carbonate chemistry often based on code from the Ocean Carbon Cycle Model Intercomparison Project (OCMIP), last revised in 2005. Here we offer improved publicly available Fortran 95 routines to model the ocean carbonate system (mocsy 2.0). Both codes take as input dissolved inorganic carbon CT and total alkalinity AT, tracers that are conservative with respect to mixing and changes in temperature and salinity. Both use the same thermodynamic equilibria to compute surface-ocean pCO2 and simulate air–sea CO2 fluxes, but mocsy 2.0 uses a faster and safer algorithm (SolveSAPHE) to solve the alkalinity-pH equation, applicable even under extreme conditions. The OCMIP code computes only surface pCO2, while mocsy computes all other carbonate system variables throughout the water column. It also avoids three common model approximations: that density is constant, that modeled potential temperature is equal to in situ temperature, and that depth is equal to pressure. Errors from these approximations grow with depth, e.g., reaching 3% or more for pCO2, H+, and ΩA at 5000 m. The mocsy package uses the equilibrium constants recommended for best practices. It also offers two new options: (1) a recently reassessed total boron concentration BT that is 4% larger and (2) new K1 and K2 formulations designed to include low-salinity waters. Although these options enhance surface pCO2 by up to 7 μatm, individually, they should be avoided until (1) best-practice equations for K1 and K2 are reevaluated with the new BT and (2) formulations of K1 and K2 for low salinities are adjusted to be consistent among pH scales. The common modeling practice of neglecting alkalinity contributions from inorganic P and Si leads to substantial biases that could easily be avoided. With standard options for best practices, mocsy agrees with results from the CO2SYS package within 0.005% for the three inorganic carbon species (concentrations differ by less than 0.01 μmol kg−1). Yet by default, mocsy's deep-water fCO2 and pCO2 are many times larger than those from older packages, because they include pressure corrections for K0 and the fugacity coefficient.

scholarly journals Controls on pH in surface waters of northwestern European shelf seas

2014 ◽  
Vol 11 (1) ◽  
pp. 943-974 ◽  
Author(s):  
V. M. C. Rérolle ◽  
M. Ribas-Ribas ◽  
V. Kitidis ◽  
I. Brown ◽  
D. C. E. Bakker ◽  
...  
Keyword(s):  
Biological Activity ◽  
Surface Water ◽  
Irish Sea ◽  
Carbonate Chemistry ◽  
Ph Distribution ◽  
European Shelf ◽  
Shelf Seas ◽  
Water Ph ◽  
The Impact ◽  
Chemistry Dynamics

Abstract. We present here a high resolution surface water pH dataset obtained in the Northwest European shelf seas in summer 2011. This is the first time that pH has been measured at such a high spatial resolution (10 measurements h–1) in this region. The aim of our paper is to investigate the carbonate chemistry dynamics of the surface water using pH and ancillary data. The main processes controlling the pH distribution along the ship's transect, and their relative importance, were determined using a statistical approach. The study highlights the impact of biological activity, temperature and riverine inputs on the carbonate chemistry dynamics of the shelf seas surface water. For this summer cruise, the biological activity formed the main control of the pH distribution along the cruise transect. Variations in chlorophyll and nutrients explained 29% of the pH variance along the full transect and as much as 68% in the northern part of the transect. In contrast, the temperature distribution explained ca. 50% of the pH variation in the Skagerrak region. Riverine inputs were evidenced by high dissolved organic carbon (DOC) levels in the Strait of Moyle (northern Irish Sea) and the southern North Sea with consequent remineralisation processes and a reduction in pH. The DOC distribution described 15% of the pH variance along the full transect. This study highlights the high spatial variability of the surface water pH in shelf seawaters where a range of processes simultaneously impacts the carbonate chemistry.

Organic and inorganic whole system metabolism in two acidified coastal systems in Ireland

2020 ◽  
Author(s):  
Maria Teresa Guerra ◽  
Carlos Rocha
Keyword(s):  
Ocean Acidification ◽  
Dissolved Inorganic Carbon ◽  
Total Alkalinity ◽  
Carbonate System ◽  
Net Community Production ◽  
Coastal Acidification ◽  
Autumn And Winter ◽  
System Metabolism ◽  
Internal Buffer ◽  
Community Production

&lt;p&gt;Organic and inorganic whole system metabolism for two Irish coastal areas were compared to evaluate carbonate system resilience to acidification. The two systems are characterized by contrasting watershed input types and composition. Kinvara Bay is fed by Submarine Groundwater Discharge (SGD) derived from a karstic catchment while Killary Harbour is fed by river discharge draining a siliciclastic catchment. Freshwater sources to sea have distinct Total Alkalinity (TA) and Dissolved Inorganic Carbon (DIC) concentrations, higher and lower than the open ocean, respectively, but both evidence seasonally variable low pH, ranging from 6.20 to 7.50. Retention of TA and DIC was calculated for the two areas using LOICZ methodology. In Kinvara bay, annually averaged retention of DIC was greater than for TA (5 &amp;#215; 10&lt;sup&gt;4&lt;/sup&gt; and 1.5 &amp;#215; 10&lt;sup&gt;5&lt;/sup&gt; mol d&lt;sup&gt;-1&lt;/sup&gt;), suggesting the system is acidifying further. Conversely, Killary Harbour shows negative TA and DIC retention, with DIC:TA &lt;1, suggesting an internal buffer against ocean acidification is operating.&lt;/p&gt;&lt;p&gt;Net Community Production (NCP) was calculated for both systems using Dissolved Oxygen data. Subsequently, we estimated Net Community Calcification (NCC) from the ratio between TA and DIC. NCP was always positive in Killary Harbour with an average of 318 mmol O&lt;sub&gt;2&lt;/sub&gt; m&lt;sup&gt;-2 &lt;/sup&gt;d&lt;sup&gt;-1&lt;/sup&gt; (equivalent to 89 mol C m&lt;sup&gt;-2&lt;/sup&gt; y&lt;sup&gt;-1&lt;/sup&gt;). However, Kinvara Bay shows relatively lower positive NCP in spring and summer (average of 46 mmol O&lt;sub&gt;2&lt;/sub&gt; m&lt;sup&gt;-2&lt;/sup&gt; d&lt;sup&gt;-1&lt;/sup&gt;), but negative NCP in autumn and winter. Therefore, Kinvara Bay&amp;#8217;s Total Organic Carbon (TOC) production was low, at ~21 g m&lt;sup&gt;-2&lt;/sup&gt; y&lt;sup&gt;-1&lt;/sup&gt; and not enough to overcome acidification driven by the SGD source composition. These results emphasize the complexity of interactions between the drivers of coastal acidification rate, affecting our ability to accurately assess the resilience of the carbonate system in these areas to ocean acidification pressure in the future.&lt;/p&gt;

scholarly journals The Sensitivity of the Marine Carbonate System to Regional Ocean Alkalinity Enhancement

2021 ◽  
Vol 3 ◽  
Author(s):  
Daniel J. Burt ◽  
Friederike Fröb ◽  
Tatiana Ilyina
Keyword(s):  
Southern Ocean ◽  
Dissolved Inorganic Carbon ◽  
Ocean Model ◽  
Total Alkalinity ◽  
Surface Pattern ◽  
Carbon Uptake ◽  
Max Planck ◽  
Carbonate System ◽  
Carbon Cycle Model ◽  
Marine Carbonate

Ocean Alkalinity Enhancement (OAE) simultaneously mitigates atmospheric concentrations of CO2 and ocean acidification; however, no previous studies have investigated the response of the non-linear marine carbonate system sensitivity to alkalinity enhancement on regional scales. We hypothesise that regional implementations of OAE can sequester more atmospheric CO2 than a global implementation. To address this, we investigate physical regimes and alkalinity sensitivity as drivers of the carbon-uptake potential response to global and different regional simulations of OAE. In this idealised ocean-only set-up, total alkalinity is enhanced at a rate of 0.25 Pmol a-1 in 75-year simulations using the Max Planck Institute Ocean Model coupled to the HAMburg Ocean Carbon Cycle model with pre-industrial atmospheric forcing. Alkalinity is enhanced globally and in eight regions: the Subpolar and Subtropical Atlantic and Pacific gyres, the Indian Ocean and the Southern Ocean. This study reveals that regional alkalinity enhancement has the capacity to exceed carbon uptake by global OAE. We find that 82–175 Pg more carbon is sequestered into the ocean when alkalinity is enhanced regionally and 156 PgC when enhanced globally, compared with the background-state. The Southern Ocean application is most efficient, sequestering 12% more carbon than the Global experiment despite OAE being applied across a surface area 40 times smaller. For the first time, we find that different carbon-uptake potentials are driven by the surface pattern of total alkalinity redistributed by physical regimes across areas of different carbon-uptake efficiencies. We also show that, while the marine carbonate system becomes less sensitive to alkalinity enhancement in all experiments globally, regional responses to enhanced alkalinity vary depending upon the background concentrations of dissolved inorganic carbon and total alkalinity. Furthermore, the Subpolar North Atlantic displays a previously unexpected alkalinity sensitivity increase in response to high total alkalinity concentrations.

scholarly journals Anomalies in the Carbonate System of Red Sea Coastal Habitats

2019 ◽  
Author(s):  
Kimberlee Baldry ◽  
Vincent Saderne ◽  
Daniel C. McCorkle ◽  
James H. Churchill ◽  
Susana Agusti ◽  
...  
Keyword(s):  
Red Sea ◽  
Dissolved Inorganic Carbon ◽  
Total Alkalinity ◽  
Carbonate Precipitation ◽  
Mangrove Forests ◽  
Sedimentary Processes ◽  
Carbonate System ◽  
Seagrass Meadows ◽  
Basin Scale ◽  
The Impact

Abstract. We use observations of dissolved inorganic carbon (DIC) and total alkalinity (TA) to assess the impact of ecosystem metabolic processes on coastal waters of the eastern Red Sea. A simple, single-end-member mixing model is used to account for the influence of mixing with offshore waters and evaporation/precipitation, and to model ecosystem-driven perturbations on the carbonate system chemistry of coral reefs, seagrass meadows and mangrove forests. We find that (1) along-shelf changes in TA and DIC exhibit strong linear trends that are consistent with basin-scale net calcium carbonate precipitation; (2) ecosystem-driven changes in TA and DIC are larger than offshore variations in > 85 % of sampled seagrass meadows and mangrove forests, changes which are influenced by a combination of longer water residence times and community metabolic rates; and (3) the sampled mangrove forests show strong and consistent contributions from both organic respiration and other sedimentary processes (carbonate dissolution and secondary redox processes), while seagrass meadows display more variability in the relative contributions of photosynthesis and other sedimentary processes (carbonate precipitation and oxidative processes).

scholarly journals PyCO2SYS v1.7: marine carbonate system calculations in Python

2021 ◽  
Author(s):  
Matthew P. Humphreys ◽  
Ernie R. Lewis ◽  
Jonathan D. Sharp ◽  
Denis Pierrot
Keyword(s):  
Automatic Differentiation ◽  
Dissolved Inorganic Carbon ◽  
Total Alkalinity ◽  
Carbonate System ◽  
Chemical Equilibria ◽  
Ph Response ◽  
Carbonate Ion ◽  
Seawater Ph ◽  
Marine Carbonate ◽  
Carbon Dioxide Co2

Abstract. Oceanic dissolved inorganic carbon (TC) is the largest pool of carbon that interacts considerably with the atmosphere on human timescales. Oceanic TC is increasing through uptake of anthropogenic carbon dioxide (CO2), and seawater pH is decreasing as a consequence. Both the exchange of CO2 between ocean and atmosphere and the pH response are governed by a set of parameters that interact through chemical equilibria, collectively known as the marine carbonate system. To investigate these processes, at least two of the marine carbonate system's parameters are typically measured – most commonly, two from TC, total alkalinity (AT), pH, and seawater CO2 fugacity (fCO2; or its partial pressure, pCO2, or its dry-air mole fraction, xCO2) – from which the remaining parameters can be calculated and the equilibrium state of seawater solved. Several software tools exist to carry out these calculations, but no fully functional and rigorously validated tool was previously available for Python, a popular scientific programming language. Here, we present PyCO2SYS, a Python package intended to fill this capability gap. We describe the elements of PyCO2SYS that have been inherited from the existing CO2SYS family of software and explain subsequent adjustments and improvements. For example, PyCO2SYS uses automatic differentiation to solve the marine carbonate system and calculate chemical buffer factors, ensuring that the effect of every solute and reaction is accurately included in all its results. We validate PyCO2SYS with internal consistency tests and comparisons against other software, showing that PyCO2SYS produces results that are either virtually identical or different for known reasons, with the differences negligible for all practical purposes. We discuss new insights that arose during the development process, for example that the marine carbonate system cannot be unambiguously solved from the total alkalinity and carbonate ion parameter pair. Finally, we consider potential future developments to PyCO2SYS and discuss the outlook for this and other software for solving the marine carbonate system. The code for PyCO2SYS is distributed via GitHub (https://github.com/mvdh7/PyCO2SYS) under the GNU General Public License v3, archived on Zenodo (Humphreys et al., 2021), and documented online (https://PyCO2SYS.readthedocs.io).

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