Salinity and stable oxygen isotope relationship in the Southwestern Atlantic: constraints to paleoclimate reconstructions

Abstract

Stable isotopes have been widely used in the literature both to discuss current ocean circulation processes, as well as to reconstitute paleoceanographic parameters. the distribution of oxygen and deuterium stable isotopes in seawater (δ 18 O sw and δD sw) at the Western tropical South Atlantic border was investigated to better understand the main fractionation processes of these isotopes and establish a regional salinity and δ 18 O sw relation to improve the paleoceanographic knowledge in the region. this study was conducted during a quasi-synoptic oceanographic cruise in which 98 discrete seawater samples were collected in the core of the main water masses for stable isotope analysis. A strong correlation between δ 18 O sw and δD was found, which made it possible to extrapolate the results for δ 18 O sw to δD. Although it was not possible to distinguish the water masses based only on their isotopic signatures, the water masses had a strong salinity and δ 18 O sw relation, and compared with previous studies, a seasonal pattern was observed. Paleosalinity differences of up to 0.2 psu between Summer and Winter are reported. Considering the limitations of the current techniques to seasonally separate the samples for the paleoceanographic studies, an intermediate Mixing Line for the Tropical South Atlantic (SSS = 1.942* δ 18 O sw + 34.56) was proposed to reduce the estimated errors associated with these seasonal variations.

Characterization of water masses around the southern Ryukyu Islands based on isotopic compositions

“…Our δD data are snapshot values rather than long-term data, such as the JODC salinity and temperature data, so they may not necessarily represent average δD values of water masses. However, as the same is true for most of the δD data in previous studies (Benetti et al 2017;Belem et al 2019), it is appropriate to use our δD data here in delineating water masses around the RIA. Therefore, the argument based here on δD data is less rigorous than that based on Nd and δ 18 O data.…”

Niche Partitioning Among Marine Mammals Inhabiting a Large Estuary as Revealed by Stable Isotopes of C, N, S, and O

“…4; Guerrero et al 1997;Acha et al 2004;Botto et al 2011). Here, the main source of δ 18 O variation between the marine mammal groups is the salinity of the water where they feed, as demonstrated by the strong positive correlation between these two factors (Conroy et al 2014;Belem et al 2019). Indeed, although data for the Río de la Plata estuary are limited, a general increase in δ 18 O values is observed from inshore (δ 18 O = ~−1‰ PDB; ~29.8‰ SMOW) to offshore (δ 18 O = ~+2‰ PDB; ~32.9‰ SMOW) marine environments in the nearby Atlantic Ocean (LeGrande and Schmidt 2006;McMahon et al 2013).…”

“…On the contrary, the O stable isotope ratio ( 18 O/ 16 O; δ 18 O) has been rarely used in ecological studies on marine mammals, despite being relatively common in other research areas such as paleontology (Seyboth et al 2018;Newsome et al 2010). The δ 18 O values in the marine environment are positively and linearly correlated with the salinity of the water (Gat 1996;Conroy et al 2014), and therefore, it can be a useful habitat tracer in areas where an abundant freshwater input creates marked horizontal and vertical salinity gradients (Guerrero et al 1997;Conroy et al 2014;Belem et al 2019). The δ 18 O values in animal tissues often reflect with great precision those of the body of water where they feed (Yoshida and Miyazaki 1991;Ben-David and Flaherty 2012), allowing to discriminate between species with estuarine, coastal, and marine habits (Clementz and Koch 2001;Rubenstein and Hobson 2004;Newsome et al 2010;Matthews et al 2016;Drago et al 2020).…”

Contrasting late-glacial paleoceanographic evolution between the upper and lower continental slope of the western South Atlantic

“…5c). A glaciolacustrine varved record (FCMC17) that reports the dynamics of ice-margin retreat of the Patagonian Ice Sheet indicates that the varve thickness decreases in two steps after the LGM, denouncing a prominent regional warming between 18 and 17.4 ka (Bendle et al, 2019). According to these authors, this glacial retreat highlights the potential synchronicity in atmospheric warming trends over the Southern Hemisphere mid-to high latitudes with the onset of the last deglaciation.…”

“…According to these authors, this glacial retreat highlights the potential synchronicity in atmospheric warming trends over the Southern Hemisphere mid-to high latitudes with the onset of the last deglaciation. Part of the warming responsible for the Patagonian Ice Sheet melting recorded from 18 ka would be the result of unbalanced oceanic heat distribution due to the bipolar seesaw resulting in increasing temperatures in the South Atlantic, the South Pacific, and Antarctica, with subsequent upwelling-driven CO 2 release from the Southern Ocean (EPICA community members, 2004;Lamy et al, 2007;Lüthi et al, 2008;Bendle et al, 2019) (Fig. 5a-e).…”