As well, this new Intertropical Overlap Region (ITCZ) can be found with its northward updates

Yet not, most of the uncertainties surrounding the connection ranging from salinity therefore the secure isotopic constitution from seawater are due to the lack of seawater isotope data (Conroy ainsi que al

As explained in the Oceanographic Settings, the bifurcation zone of the south and central branches of the SEC is located in the region between 5-14°S in the Winter. Thus, it can be considered that during the present sampling period, there is no mesoscale process acting in the region and this consequently controls the physical isotopic fractionation. To verify the influence of the continental discharge on the isotopic content, the isotopic distribution was also analyzed in regard to the distance of the coast, and no pattern was clearly detected (Supplementary Material, Figure S1). This means that no evidence was found for the existence of a cross shelf fractionation pattern of the ? 18 O_sw and ?D_sw in this region, probably due to a low contribution of river discharge.

Because ? 18 O_sw and Salinity are strongly correlated and basically controlled by the same processes, a similar latitudinal behavior for these variables was expected, as suggested by Craig and Gordon GORDON AL and PIOLA AR. 1983. Atlantic Upper Layer Salinity Budget. J Phys Oceanogr 13: 1293-1300. (1965). However, the latitudinal distribution of the surface ? 18 O_sw and salinity for the Southwestern Tropical Atlantic ( Fig. 4) showed that the salinity has a well-defined distribution with a maximum center near 15°S, corroborating the salinity budget proposed by Gordon and Piola (1983), whereas the ? 18 O_sw data revealed its highest levels near 25°S (Pierre et al. 1991).

The outcome associated with analysis (93 this new matched procedures), when compared to the relationships acquired lo que es be2 by the Pierre and Ostlund, show variations in regards to the winter (this research) and you can June (Pierre and you can Ostlund) range, strengthening new argument out-of Schmidt (1999), due to the relatively deeper level of trials from this studies

Previous studies of Pierre and Ostlund contributed to regional analysis of latitudinal fractionation, although hampered by the lack of regular spatial distribution. Nevertheless, combining the results of this work with these historical observations made it possible to validate the latitudinal separation of the Salinity and ? 18 O_sw relationship. As pointed out by Gordon and Piola (1983), northward the salinity maximum zone, the salinity and ? 18 O_sw have a similar decreasing tendency, which is most likely controlled by the high precipitation rates near the equator. However, south of 15°S, salinity has a strong increasing trend whereas the ? 18 O_sw levels are nearly stable (increase of 0.007‰ for each latitudinal degree). Fig. 5 shows the means and standard deviations of values ? 18 O_sw and Salinity for each water mass and considering only the samples with 60% or higher of a specific water mass. The seasonal fluctuation signal as a result of a ? 18 O_sw enrichment coupled to a freshwater input in the Southwestern Tropical Atlantic Ocean can be identified by the wide error bar in the TW salinity.

Significant differences in salinity between ocean basins are apparent, especially the relatively higher salinities of the Atlantic Ocean. In part, this difference is due to the continental distribution in the ocean basins. The narrowing of the Atlantic contributes to higher evaporation rates, and consequently higher salinity values, since a large fraction of its surface area is influenced by continental dry air (Gordon et al. 2015). The ?D:? 18 O_sw relationship can be used as an indicator of the local E/P ratio, and ? 18 O_sw and salinity are also used for this purpose. Schmidt (1999) demonstrated that smaller slope in mixing lines are characteristic of evaporative areas (in opposite, regions with a high rainfall rate have steeper lines). 2014). The weaker correlation in the surface, as shown in Fig. 2, can be an indicator that the hydrologic cycle (precipitation and evaporation) is not the only control in the ? 18 O_sw:?D_sw relationship for this region and other forcing (i.e., advection and lateral mixing) may have importance, as also found by Hasson HASSON AE, DELCROIX T and DUSSIN R. 2013. An assessment of the mixed layer salinity budget in the tropical Pacific Ocean. Observations and modelling (1990–2009). Ocean Dynamics 63(2-3): 179-194. et al. (2013) working in similar areas in the Pacific Ocean. Due to the different vapor pressure kinetic enrichment (fractionation factors) between ? 18 O_sw and ?D_sw, evaporative regions have a smaller slope than the MWL (Craig and Gordon 1965, Gat 1996). Thus, the steepening can be used as an indicator of the local E/P ratio and the slope of 7.62 found here suggests that this region has a small evaporative tendency. Rohling (2007) analyzed 244 samples collected worldwide and proposed a similar equation (?D_sw= 7.37* ? 18 O_sw – 0.72). In both studies, the “deuterium excess” is slightly negative, which was already expected because it is relative to the average ocean water composition, referred to as the VSMOW (Rohling 2007, Kendall KENDALL C and CALDWELL EA. 1998. Fundamentals of Isotope Geochemistry. In: Kendall C and McDonnel JJ (Eds), Isotope Tracers in Catchment Hydrology. Elsevier Science B.V., Amsterdam, p. 51-86. and Caldwell 1998).