Results

The cruise track of the R/V Hespérides is shown in Fig. 1. A summary of the 33 TCO₂ stations that were sampled during the cruise is given in Table 4. Based upon the CRM calibrations at sea, the accuracy of the measured parameters is estimated to be ±7 µmol/kg for TALK and TCO₂ and ±0.02 for pH. The thermodynamic consistency of the measurements can be shown by comparing the calculated values of pH (7.944), TALK (2334 µmol/kg), and TCO₂ (1984 µmol/kg) using the constants of Roy et al. (1993) with the measured values (Table 3). The agreement is quite good. The values of TALK, TCO₂, and pH as a function of depth for all of the samples are shown in Fig. 3, Fig. 4, and Fig. 5. Plots of the surface properties of the waters sampled are shown in Fig. 6, Fig. 7, and Fig. 8.

The temperature increases from 22°C near the Spanish coast to 27°C off the coast of Florida. The salinities go through a maximum (37.5) between stations 20 to 50 (30° to 45° W). The surface values of TALK (Fig. 7) follow this trend. The TCO₂ is fairly constant from stations 1 to 60 (2108 ± 10 µmol/kg) and decreases off the coast of Florida to 2020 µmol/kg. The pH at 25°C increases from 8.05 off the coast of Spain to about 8.12 off the coast of Florida (average pH = 8.05 ± 0.03). The values of TALK and TCO₂ normalized to S = 35 are shown in Fig. 8. The average normalized TALK is 2293 ± 4 µmol/kg for the surface waters, whereas the average normalized TCO₂ is 1970 ± 20 µmol/kg. The in situ fugacities of CO₂ (fCO₂) calculated from the measured values of TALK and TCO₂ are shown in Fig. 8. From these calculations, the surface waters (fCO₂ = 402 ± 15 µatm) are supersaturated with CO₂ (ΔfCO₂ = 42 ± 15 µatm ) for all the surface waters.

Table 4. Summary of carbonate system stations occupied during the cruise