Hydrogen and Oxygen Isotopes as Mass Proxies Along the South Atlantic Ocean

It was determined the values of δ(D) and δ(¹⁸O) on 432 seawater samples from 18 depth profiles collected during the Geotraces West Atlantic cruise leg 3; JC057 on RRS James Cook, 03/2011-04/2011. The first sampling station was located north of Falkland Island and the last one near the Equator line. The samples were collected using a 24 bottles rosette and storage on 2 mL glass vials, kept at 3-4 ^oC until the measurement. The measurements were carried out applying a PICARRO water analyzer, using IAEA VSMOW2, SLAP2 and GISP reference materials as standards, each batch consisted of the three standards and six samples, with seven injections each and the sample result represent the mean value of the three last injections.

The delta values ranged from -0.91 (station 9, 1250 m) to 1.46 (station 7, 250 m) for δ(¹⁸O) and -4.5 (station 5, 5150 m) to 8.2 (station 13, 10 m).

The δ(¹⁸O)-salinity relationship varies with the depth range with a slope of 0.37 (R=0.845) for (10- 100 m), 0.39 (R=0.747) for (100-250 m), 0.53 (R=0.813) for (250-1000 m) but poor correlated (R = 0.506) for deeper samples (>1000 m). Similar figure was observed for the δ(D)-salinity relationship with a slope of 3.04 (R=0.938) for (10- 100 m), 3.02 (R=0.879) for (100-250 m), 4.21 (R=0.898) for (250-1000 m) and poor correlated (R = 0.610) for deeper samples (>1000 m).

The δ(¹⁸O)-temperature presented a similar figure as observed for the salinity although constant for the depths higher than 1000 m changing for deeper samples. The δ(¹⁸O)-temperature relationship had a slope of 0.053 (R=0.820) for (10- 100 m), 0.054 (R=0.739) for (100-250 m), 0.048 (R=0.716) for (250-1000 m) but poor correlated (R = 0.582) for deeper samples (>1000 m). The δ(D)-temperature relationship has also quite constant until 1000 m with a slope of 0.45 (R=0.933) for (10- 100 m), 0.43 (R=0.886) for (100-250 m) and 0.41 (R=0.850) for (250-1000 m) changing the slope to 0.82 (R=0.710) for deeper samples (>1000 m).