To validate the results obtained in our study, we compared the current Salinity: ? 18 Osw ratio found by this study along with the primary data of Pierre and Ostlund, and the equation used by Toledo et al. (2007), which estimates the sea surface salinity based on the oxygen isotope composition of Globigerinoides ruber (white) adultspace. All of these works are based on data from the upper Southwest Atlantic Ocean (<250 m). Toledo et al. (2007) used an equation obtained from previous data available from NASA/GISS (also using data from Pierre et al. (1991) and Ostlund et al. (1987), among others), converted from PBD (Pee Dee Belemnite) to V-SMOW using the -0.27 factor ( Hut HUT G. 1987. Consultants Group Meeting on Stable Isotopes Reference Samples for geochemical and hydrological investigations. Report to Director General. International Atomic Energy Agency, Vienna, 42 p. 1987):
So it fusion line keeps a slope really close to the Meteoric Water line (MWL:?=8) (Craig 1961), and this signifies an average relationship between hydrogen and you may oxygen isotope rates in pure oceans
In order to compare our ? 18 Osw and T-S data in the regional context with literature, ? 18 Osw data available in the NASA/GISS Global Seawater Oxygen-18 Database (Schmidt et al. 1999) from the South Atlantic Ocean (Pierre et al. 1991, Ostlund et al. 1987) were used. As explained in the introduction, the study by Pierre et al. (1991) was conducted in a narrow area between 21.9°S and 26.5°S latitude during the austral Summer, from pling from surface to
2000) close 21°S while the leftover analysis off surface products merely over the GEOSECS point (Fig. 1). Afterwards, such functions might be called due to the fact Pierre and Ostlund, correspondingly.
Although recent isotopic data on the southeast Brazilian coast have been published by Venancio et al. (2014), this dataset is not comparable because it refers to a coastal upwelling area under the influence of different continental and internal processes. All ? 18 Osw, ?Dsw and salinity data presented here will be submitted to NASA/GISS to improve the coverage of isotopic data for the South Atlantic Ocean.
Steady ISOTOPES Delivery And you may FRACTIONATION Activities
Hydrographic studies and you will isotopic values each take to was sumples was split up by water mass depending on the big sum gotten immediately following the brand new fusion triangle analyses. So it dataset is an excellent symbol of your own isotopic vertical shipments to 2000 m depth, and was well-distributed within liquids public (a total of 34 TW samples, 21 SACW trials, 18 AAIW samples and you will 20 NADW products, except for the 5 CW samples).
Following the well-established ?Dsw and ? 18 Osw linear relationship (Merlivat and Jouzel 1979), we found at the surface layer a moderate correlation (R?= 0.55, n=27), and at the intermediate and deeper layer, a stronger correlation (R?=0.94 and 0.81; n= 33 and 38, respectively). The ? 18 Osw:?Dsw relationship for the whole dataset is presented in Figure 2 with a strong linear correlation (R 2 =0.94, n=98), which indicates that all of the future considerations regarding the ? 18 Osw can be extrapolated to ?Dsw including the Salinity and ? 18 Osw relationship.
Because the slopes and intersection points for each of the layers were very similar (?=7.05, 7.02 and 6.91; b= -0.49, -0.67 and -1.4, respectively), we propose a mixing line gathering together the entire dataset (?Dsw= 7.62* ? 18 Osw – 1.18) ( Fig. 2).
Following the Salinity and ? 18 Osw relationship, the vertical ? 18 Osw profile has a similar pattern to salinity ( Fig. 3). The upper layer, corresponding to TW, is characterized by a maximum with values up to 1.34‰ and controlled mainly by the E-P balance (Craig and Gordon 1965). Along the SACW layer, there is a consistent depletion of this isotope from 1.13‰ at 180 m to 0.19‰ at 700 m. This behavior follows the temperature and salinity profile tendency in the thermocline. The ? 18 Osw minimum is associated with the positioning of AAIW, which is characterized by minimum salinity derived from the sea melt and high precipitation rates in the Antarctic Divergence region (Tomczak and Godfrey 2003), which reduces the levels of ? 18 Osw (up to -0.33‰). Below 1000 m depth, a slight increase of the ? 18 Osw and salinity levels associated with the NADW layer can be observed.