Calcium carbonate dissolution triggered by high productivity during the last glacial-interglacial interval at the deep western South Atlantic

Studies reconstructing surface paleoproductivity and benthic conditions allow us to measure the effectiveness of the biological pump, an important mechanism in the global climate system. In order to assess surface productivity changes and their effect on the seafloor, we studied the core SAT-048A, recovered from the continental slope of the southernmost Brazilian continental margin, in the western South Atlantic. We assessed the sea surface productivity, the organic matter flux to the seafloor and the dissolution effects, based on micropaleontological (benthic and planktonic foraminifers, ostracods), geochemical (benthic and planktonic δ13C isotopes) and sedimentological data (carbonate and bulk sand content). Superimposed on the climate-induced changes related to the last glacial-interglacial transition, the reconstruction indicates paleoproductivity changes synchronized with the precessional cycle. From the reconstructed data, it was possible to identify high (low) surface productivity, high (low) organic matter flux to the seafloor, and high (low) dissolution rates of planktonic Foraminifera tests during the glacial (postglacial). Furthermore, within the glacial, enhanced productivity was associated with higher insolation values, explained by increased NE summer winds that promoted meandering and upwelling of the nutrient-rich South Atlantic Central Water. Changes in the Atlantic Meridional Overturning Circulation and the reorganization of bottom water masses could also have changed the CO3 2saturation levels and have influenced the carbonate preservation. However, changes in the Uvigerina spp. δ13C values are very likely linked to the organic matter flux and not to the sea bottom dissolved inorganic matter δ13C values.

2 Regional setting 69 The studied core was recovered off Santa Marta Cape, at the Pelotas Basin slope, 70 western South Atlantic (Figure 1a,b). The proximal portion of the continental shelf of 71 the Pelotas Basin represents a submerged coastal plain (Martins, 1984) that was exposed 72 during the last Pleistocene regression (Marine Isotope Stage 2) and dissected by drainage 73 networks from fluvial systems (Weschenfelder et al., 2014), contributing with larger in-74 puts of nutrients from continental outflows compared to the Holocene. 75 Surface circulation in the shelf portion of the study area is dominated by the north-  The water masses that circulate in the subsurface (Figure 1c Antarctic Bottom Water (AABW) (Reid et al., 1976;Campos et al., 1995;Hogg et al., 96 1996; Stramma & England, 1999). The NADW represents slightly warmer and saltier 97 water bodies when compared to AAIW, UCDW and AABW. In addition, the NADW 98 also promotes the preservation of carbonate, due to the oversaturation of the carbon-         can be interpreted as a closer BMC (Boltovskoy et al., 1996), due to the enhanced SW 221 winds during the late last glacial. The second mechanism involves the NE winds blow-222 ing along the shore, pushing surface waters offshore due to the Ekman transport, allow- would also be depleted in silicic acid) to the photic zone (as shown by warmer SST 100m , 310 low G.bull:G.rub ratio, and low relative abundance of G. glutinata). Furthermore, the 311 onshore displacement of the BC, along with higher relative sea level, and rivers outflow-312 ing farther away, inhibited the terrigenous input, leading to oligotrophic conditions. Thus,

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-12-manuscript submitted to Paleoceanography and Paleoclimatology  ference between the present-day δ 13 C of dissolved inorganic carbon values for the UCDW 373 and the NADW which is up to up to 0.4‰ (Fig 11a). Therefore, the observed pattern 374 is more likely linked to changing OM fluxes to the seafloor. Aditionally, after δ 13 C "cor-375 rections" (e.g., Schmiedl et al., 2004;-2‰) from benthic foraminifers tests and ambient 376 bottom water, SAT-048A δ 13 C Uvi still remains more negative from the supposed orig-

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inal values, which also points to the input of OM fluxes, richer in 12 C than 13 C.

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Based on Nd in benthic Foraminifera at mid-depths at the western South Atlantic,

Introduction
The present Supporting Information file presents data for: i) other analyzed cores (Table  S1), ii) the Sea Surface Temperature (SST) residuals ( Figure S1), iii) the age model construction ( Figure S1, Table S2 and Table S3), as well as iv) the appendix of planktonic Foraminifera species (Appendix S1).

Table S1
In the manuscript Figure 1 are shown the core SAT-048A location, as well as the location of the other analyzed cores. Names, coordinates, and depths below sea level of the mentioned cores are shown in Table S1. The SST estimates at 100 m waters below sea level, performed on the present study, are show in manuscript Figure 4. Residual of this reconstruction is showed in Figure S1. The 95% of the residuals are located between 2.5 and -2.5°C, while the 90% are between 1.8 and -1.8°C. Figure S1. Residuals vs. Annual mean SST estimates at 100 m waters below sea level for core SAT048A. Red lines encompass 95% of the residuals (between 2.5 and -2.5°C) and blue lines encompass 90% (between 1.8 and -1.8°C).