Predicated on Schmidt (1999) SCHMIDT GA, BIGG GR and you can ROHLING EJ
In oceanic regions with a positive E-P (Evaporation-Precipitation) balance, there is enrichment in the superficial ocean layer due to preferential evaporation of the lighter species ( Meredith MEREDITH MP, GROSE KE, MCDONAGH EL, HEYWOOD KJ, FREW RD and DENNIS PF. 1999. J Geophys Res Oceans (1978–2012) 104(C9): 20949-20962. et al. 1999). On the other hand, river discharges, high precipitation and ice melting are related to regions with depleted values of ? 18 Osw ( Redfield REDFIELD AC and FRIEDMAN I. 1965. Factors affecting the distribution of deuterium in the ocean. In Symposium on Marine Geochemistry. Rhode Island University Narragansett Marine Laboratory Occasional Publication, Vol. 3, p. 149-168. and Friedman 1965). On a geologic time scale, the glacial boundary conditions influence the isotopic composition of the oceans due to the storage of lighter ? 18 O and ?D isotopes in the ice sheets, which is known as global ice volume effect. However, during interglacial periods, this effect was reversed (Holloway et al. 2015).
Because salinity and ? 18 Osw are controlled by the same processes, they show a quasi-linear relationship, and the slope is dependent on the kinetic processes acting in the water mass formation area. 2015. Differences among subtropical surface salinity patterns. Oceanogr 28(1): 32-39. 1965). 1999. Global Seawater Oxygen-18 Database – v1.21. , the global mixing line between ? 18 Osw and salinity can be used as an approximation only in mid to high latitudes, since the scatter for the tropical samples could be up to 0.13‰. Therefore, regional mixing lines become essential pieces in paleoclimatic studies in the equatorial and tropical regions. Holloway et al. (2015) suggested that regions with marked variability in the evaporation-precipitation budget and strong oceanographic dynamics need additional constraints to establish good salinity and ? 18 Osw relationships on spatial and temporal scales. On the other hand, South Atlantic, Indian and Tropical Pacific Oceans have more reliable paleosalinity reconstructions without the need of additional constraints.
Despite the importance of the Southwest Atlantic Ocean for thermohaline circulation and the global climate through in the South Atlantic Meridional Overturning Circulation (SAMOC), only a few studies have been carried out in this area using stable isotopes. For example, GEOSECS was conducted in the South Atlantic focusing on open waters (Kroopnick 1980, Ostlund OSTLUND HG, CRAIG H, BROECKER WS and SPENCER D. 1987. GEOSECS Atlantic, Pacific and Indian ocean expeditions, shorebased data and graphics, Vol. 7. Technical report, I.D.O.E. National Science Foundation, p. 200. et al. 1987) and an independent work of Pierre et al. (1991) focused on a small offshore area of the southwestern Atlantic. None of these papers were focused on paleoclimatic applications. The aim of the present study was to investigate the distribution of the stable isotopes (? 18 Osw and ?Dsw) at the Western Tropical South Atlantic border, from the continental shelf to slope, in order to better understand the main fractionation processes of these isotopes and establish a regional salinity and ? 18 Osw relationship to improve paleoceanographic knowledge in the study region.
Up coming, following the liquid mass basins, the connection stays steady on the liquids bulk life (Craig and you can Gordon GORDON AL, GIULIVI CF, BUSECKE J and you may BINGHAM FM
The newest east Brazilian continental margin is common because of its reduced depth and you may low deepness in comparison with other areas of Southwestern Atlantic margin, due to reduced continental erosion rates in addition to quick area of marine sedimentation. Likewise, the ceaseless presence of your Brazil Newest moving towards southwest parallel with the shelf while the North Brazil Most recent moving equatorward transporting loving and you may saline Exotic Water offers the area a fundamentally oligotrophic profile, hence diminishes the new genesis out-of biogenic topic that define very of sedimentary bottoms on southeastern Brazilian continental shelf ( Knoppers KNOPPERS B, EKAU W and you will FIGUEIREDO AG. 1999. New coast and you may shelf away from east and you may northeast Brazil and you can topic transport. Geo-Marine Lett 19: 171. ainsi que al. 1999). This new bifurcation of the South Equatorial Latest (SEC) takes place around 10°–14°S near the body therefore the continental bookshelf thickness differs from 42 kilometer of Maceio to eight kilometer out-of Salvador, with an average of 31 km ( Fig. 1).