DATA DESCRIPTION FOR FILE <TTO_1981_recalc_DIC_ALK.csv>



CONTRIBUTORS
Toste Tanhua
Leibniz Institute of Marine Sciences at Kiel University
Marine Biogeochemistry 
Duesternbrooker Weg 20 
D-24105 Kiel, 
Germany 
Email: ttanhua@ifm-geomar.de

Douglas W.R. Wallace 
Leibniz Institute of Marine Sciences at Kiel University
Marine Biogeochemistry 
Duesternbrooker Weg 20 
D-24105 Kiel, 
Germany 
Email: dwallace@ifm-geomar.de

SCOPE
The dissolved inorganic carbon (DIC) and total alkalinity measurements made during the 
Transient Tracer in the Ocean, North Atlantic Study (TTO-NAS) in 1981 are re-calibrated 
based on comparisons with modern results obtained on a cruise in 2004.
The background and procedures of the correction is described in detail by Tanhua and 
Wallace (2005).

DATA DESCRIPTION
The TTO-NAS data were downloaded from the Carbon Dioxide Information and 
Analysis Centre (CDIAC; http://cdiac.esd.ornl.gov/oceans/ndp_004/ndp004.html).
These data are the 'revised data' described by Brewer et al. (1986) and consist of total 
dissolved inorganic carbon (DIC) and alkalinity data, both measured by potentiometric 
titration and discrete pCO2 data, as well as calculated DIC from pCO2 and total alkalinity.

This dataset is extended with corrected alkalinity and DIC as described below.

TOTAL ALKALINITY
The total alkalinity is corrected by subtracting 3.6 umol/kg from the original data.

DISSOLVED INORGANIC CARBON (DIC)
The DIC is calculated from the corrected values of total alkalinity and pCO2 (as 
measured at 20°C) using the CO2SYS program (Lewis and Wallace, 1998). 
The following set of constants was applied: 
CO2 solubility: (Weiss, 1974), 
dissociation constants: (Mehrbach et al., 1973) as refitted by (Dickson and Millero, 1987), 
borate dissociation constant: (Dickson, 1990) 
phosphoric acid and silicic acid from (Millero, 1995).

To the DIC values obtained this way, a constant off-set of 2.4 umol/kg was added.

DATA FORMAT
The data are supplied in comma separated format (.csv).

The header records the; 
TTO Leg#, Station#, Lat (°N), Lon (°E), Year, Month, Day, Bottom depth (m), Bottle#, 
Pressure, Depth, Temperature, Potential Temperature, Salinity, Sigma-0, Sigma-2, Sigma-4, 
Oxygen (umol/kg), SiO4 (umol/kg), PO4 (umol/kg), NO3 (umol/kg), 
Total Alkalinity (umol/kg), DIC (umol/kg), pCO2 at 20°C, DIC-calc (umol/kg), 
Total Alkalinity corrected as described above, DIC corrected as described above.

Missing data are denoted with -999.9, the units for the revised data are identical with the 
original data. 


REFERENCES
Brewer, P.G., T. Takahashi, and R.T. Williams (1986b), Transient tracers in the Ocean 
(TTO)- Hydrographic data and carbon dioxide systems with revised carbon chemistry data,
CDIC Numeric Data Collection, NDP-004/R. 

Dickson, A.G., and F.J. Millero (1987), A comparison of the equilibrium constants for the 
dissociation of carbonic acid in seawater media, Deep-Sea Res., 34A (10), 1733-1743. 

Dickson, G.D. (1990), Thermodynamics of the dissociation of boric acid in synthetic seawater 
from 273.15 to 318.15 K, Deep-Sea Res., 37 (5), 755-766.

Lewis, E., and D.W.R. Wallace (1998), CO2SYS- Program developed for the CO2 system 
calculations, Carbon Dioxide Inf. Anal. Center; Report ORNL/CDIAC-105.

Mehrbach, C., C.H. Culberson, J.E. Hawley, and R.M. Pytkowitcz (1973), Measurements of 
the apparent dissociation constants of carbonic acid in seawater at atmospheric pressure, 
Limn. Oceanogr., 18, 6, 897-907.

Millero, F.J. (1995), Thermodynamics of the carbon-dioxide system in the oceans., Geochem. 
Cosmochem. Acta, 59 (4), 661-677.

Tanhua, T., and D.W.R. Wallace (2005), Consistency of TTO-NAS Inorganic Carbon Data 
with modern measurements, Geophys. Res. Lett., 32, L14618, doi:10.1029/2005GL032348.

Weiss, R.F. (1974), Carbon dioxide in water and seawater: the solubility of a non-ideal gas, 
Mar. Chem., 2, 203-215.