oa: Perturbation of the seawater carbonate system

Description

Describes the various approaches that can be used to alter the seawater carbonate system. Its main purpose is to assist the design of ocean acidification perturbation experiments.

Usage

oa(flag, var1, var2, pCO2f, pCO2s=1e6, S=35, T=25, P=0, 
	Pt=0, Sit=0, k1k2='l', kf='pf', pHscale="T", plot=FALSE)

Arguments

flag

select the couple of variables available to describe the initial seawater. The flags which can be used are: flag = 1 pH and CO2 given flag = 2 CO2 and HCO3 given flag = 3 CO2 and CO3 given flag = 4 CO2 and ALK given fla

var1

Value of the first variable available to describe the initial seawater, in mol/kg except for pH and for pCO2 in uatm

var2

Value of the second variable available to describe the initial seawater, in mol/kg except for pH

pCO2f

pCO2 target value, in uatm

pCO2s

pCO2s is the pCO2, in uatm, of the high-CO2 seawater that will be mixed with normal seawater. The default value is 10^6 uatm, that is seawater bubbled with pure CO2 gas and saturated with CO2.

Salinity, default is 35

Temperature in degrees Celsius, default is 25

Hydrostatic pressure in bar (surface = 0), default is 0

Concentration of total phosphate in mol/kg, default is 0

Sit

Concentration of total silicate in mol/kg, default is 0

k1k2

"l" for using K1 and K2 from Lueker et al. (2000) and "r" for using K1 and K2 from Roy et al. (1993), default is "l"

"pf" for using Kf from Perez and Fraga (1987) and "dg" for using Kf from Dickson and Goyet (1979), default is "pf"

pHscale

"T" for the total scale, "F" for the free scale and "SWS" for using the seawater scale, default is "T" (total scale)

plot

A plot of the different perturbation methods can be plotted in a DIC vs ALK field with pCO2 isoclines are drawn in the back. Default is false.

Value

The function returns a list built as follows:
descriptionA table describing in plain English the various ways to reach the target pCO2. Note that if a vector is given in argument only the first value is used.
perturbationTable providing key parameters for the following methods: CO2 bubbling: high-CO2 air is bubbled in seawater. The first parameter is the value of the pCO2 in the air required to bubble the seawater (in uatm). SW mixing: mixing of normal and high-CO2 seawater. The fist parameter, Weight fraction high-CO2 SW or wf, is the weight fraction of the high-CO2 seawater per kg seawater. Addition of acid: strong acid is added to seawater. Note that this method is not recommended because it does not closely mimic natural ocean acidification (Gattuso and Lavigne, 2009). The first parameter, H+ (mol/kg), is the amount of H+ that must be added (mol/kg). Addition of HCO3 and acid: bicarbonate (HCO3) and a strong acid are added. The first parameter, HCO3, is the amount of HCO3 that must be added (mol/kg). The second parameter, H+, is the quantity of H+ that must be added (mol/kg). Addition of CO3 and acid: carbonate, CO3, and a strong acid are added. The first parameter, HCO3, is the quantity of CO3 that must be added (mol/kg). The second parameter, H+, is the quantity of H+ that must be added (mol/kg).
summaryTable summarizing the carbonate chemistry before and after applying each perturbation: pCO2 bubbling, mixing with high-CO2 seawater, addition of strong acid, and addition of bicarbonate/carbonate and strong acid.

encoding

latin1

Warnings

It is recommended to use concentrated solutions of acid or base in order to add small volumes.
The addition of strong acid does not simulate well natural ocean acidification (higher concentration of dissolved inorganic carbon at constant total alkalinity) since it generates a decrease in total alkalinity while dissolved inorganic carbon is kept constant.
Other important advice is provided in Gattuso and Lavigne (2009), Schulz et al. (2009) and in theGuide for Best Practices on Ocean Acidification Research and Data Reporting(http://www.epoca-project.eu/index.php/Home/Guide-to-OA-Research/)

Details

The arguments can be given as a unique number or as vectors. If the lengths of the vectors are different, the longer vector is retained and only the first value of the other vectors is used. It is recommended to use either vectors with the same dimension or one vector for one argument and numbers for the other arguments. Pressure corrections and pH scale

For K1, K2, pK1, pK2, pK3, Kw, Kb, Khs and Ksi, the pressure correction was applied on the seawater scale. Hence, values were first transformed from the total scale to the seawater scale, the pressure correction applied as described by Millero (1995), and the value was transformed back to the required scale (T, F or SWS).
For Kf, the pressure correction was applied on the free scale. The formulation of Dickson and Goyet (1979) provides Kf on the free scale but that of Perez and Fraga (1987) provides it on the total scale. Hence, in that case, Kf was first transformed from the total scale to the free scale. With both formulations, the pressure correction was applied as described by Millero (1995), and the value was transformed back to the required scale (T, F or SWS).
For Ks, the pressure correction was applied on the free scale. The pressure correction was applied as described by Millero (1995), and the value was transformed back to the required scale (T, F or SWS).
For Kn, The pressure correction was applied on the seawater scale. The pressure correction was applied as described by Millero (1995), and the value was transformed back to the required scale (T, F or SWS).

References

Dickson A. G., Sabine C. L. and Christian J. R., 2007. Guide to best practices for ocean CO2 measurements. PICES Special Publication 3, 1-191. Gattuso J.-P. and Lavigne H., 2009; Technical note: approaches and software tools to investigate the impact of ocean acidification. Biogeosciences 21, 6:2121-2133. Lueker, T. J. Dickson, A. G. and Keeling, C. D. 2000. Ocean pCO2 calculated from dissolved inorganic carbon, alkalinity, and equations for K1 and K2: validation based on laboratory measurements of CO2 in gas and seawater at equilibrium. Marine Chemistry 70 105-119. Perez, F. F. and Fraga, F. 1987. Association constant of fluoride and hydrogen ions in seawater. Marine Chemistry 21, 161-168. Roy, R. N. Roy, L. N. Vogel, K. M. Porter-Moore, C. Pearson, T. Good C. E., Millero F. J. and Campbell D. M., 1993. The dissociation constants of carbonic acid in seawater at salinities 5 to 45 and temperatures 0 to 45oC. Marine Chemistry 44, 249-267. Schulz K. G., Barcelos e Ramos J., Zeebe R. E. and Riebesell U., 2009. CO2 perturbation experiments: similarities and differences between dissolved inorganic carbon and total alkalinity manipulations. Biogeosciences 6, 2145-2153. Zeebe, R. E. and Wolf-Gladrow, D. A., 2001. CO2 in seawater: equilibrium, kinetics, isotopes. Amsterdam: Elsevier, 346 pp.

Examples

Run this code

oa(flag=24, var1=384, var2=2325e-6, pCO2s=1e6, pCO2f=793, S=34.3, T=16, 
	P=0, pHscale="T", kf="pf", k1k2="l", plot=TRUE)

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