ALBERT

Description: Millennial-scale oscillations are known to be important in the climatic evolution of the Atlantic basin, but which internal processes originates these oscillations are still uncertain. In this study, we investigated how the Greenland and Antarctic climates affect the SW Atlantic through basin-wide oceanographic features (such as the NADW formation and the Agulhas leakage). We reconstructed sea surface and subsurface temperatures (SST and subT) using three lipid-based biomarker proxies (UK’37, TEX86 and LDI indexes) from a sediment core (NAP 63-1) retrieved from the SW Atlantic slope (24.8°S, 44.3°W). This location allowed us to evaluate the temperature oscillations of the Brazil Current without any terrigenous or upwelling-derived biases. Both TEX86-based and LDI-based estimates represent the mean annual SST, while the UK’37-based estimates represent the subT (around 30m water depth). The periods with the most well-mixed water column were observed during intervals of cooling orbital trends due to the time required to transfer the surface cooling to the subsurface. The temperature reconstructions showed a general colder MIS 3 when compared to the MIS 4. They also showed evidence of a late response to deglaciation, with its onset in the SW Atlantic occurring in the middle of the Last Glacial Maximum. Based on these reconstructions, the NAP 63-1 SST orbital-scale trend seems to be linked to the Antarctic climate, influenced by local insolation changes. These temperature records also presented a clear millennial periodicity around 8 kyr. On this timescale, the millennial oscillations in the SW Atlantic's SST are likely linked to the NADW formation

Description: Mg/Ca ratios (mmol/mol) derived from the chemical analysis of the planktonic foraminifera Globigerinoides ruber (pink) tests (250-300 μm size fraction) from a marine sediment core 7616 retrieved from the SW Atlantic shelf (lat. -25.08333, long. -45.63333, 100 m water depth) in December 2004 during Oceanographic cruise Paleoprod, onboard the R/V Prof Wladimir Besnard.

Description: We present sortable silt mean grain size (a proxy for near-bottom current speed) from a sediment core retrieved at the modern core of Intermediate Water Brazil Current (IWBC), that carries Antarctic Intermediate Water (AAIW) to the north spanning the last 80 kyr. The sortable silt was measured using a Malvern Mastersizer 2000 Laser Analyzer and the data presented is the average of three different measurements per sample.

Description: Mg/Ca composition (mmol/mol) derived from the chemical analysis of the planktonic foraminifera Globigerinoides ruber (pink) tests (250 - 300 μm size fraction) from a marine sediment core 7610 retrieved from the SW Atlantic shelf (lat. -25.50000, long. -46.60000, 89.0 m water depth) in December 2004 during Oceanographic cruise Paleoprod, onboard the R/V Prof Wladimir Besnard.

Description: The dataset compiles morphological measurements of coccoliths (Gephyrocapsa spp.) from one sample from the Western Equatorial Pacific. The morphological measurements were applied to evaluate coccolithophore preservation aspects under different dissolution intensities in a laboratory experiment. For the dissolution experiment, we added different amounts of Calgon solution (0, 0.4, 0.8, 2, 4, and 6 ml) in subsamples prepared from one sediment sample (ODP 807A-2H2W57-59 cm). The length, volume, area, and mass were obtained using the C-Calcita software from images taken under a cross-polarized microscope (Zeiss AX10). Thickness and the shape factor ks were calculated. The columns include the sample name, how much Calgon was added into sediment suspension, the number of coccoliths measured per sample, length, mean ks shape factor and standard deviation of mean ks/mean ks.

Description: We present the Grain-size end-member modeling results from a record retrieved at the modern core of Intermediate Water Brazil Current (IWBC), which carries Antarctic Intermediate Water (AAIW) to the north spanning the last 80 kyr. The end-member model was performed with the BASIC-EM (BasEMMA) using grain-size data measured with a Malvern Mastersizer 2000 Laser Analyzer. The number of end-members considered was determined by analyzing the inflection curve of the progressive coefficients of determination.

Description: We present the Grain-size end-member contribution variations along core NAP63-1 retrieved at the modern core of Intermediate Water Brazil Current (IWBC), that carries Antarctic Intermediate Water (AAIW) to the north spanning the last 80 kyr. The end-member model was performed with the BASIC-EM (BasEMMA) using grain-size data measured with a Malvern Mastersizer 2000 Laser Analyzer. The number of end-members considered was determined by analyzing the inflection curve of the progressive coefficients of determination.

Description: Here we present planktonic foraminifera species relative abundance obtained in marine sediment core NAP63-1 (24.8384°S, 44.3187°W, 842 m water depth, 224 cm sediment recovery) retrieved with the aid of a piston corer from the SW Atlantic upper slope. The data presented here was applied to infer SW Atlantic sea-surface conditions (temperature and productivity) over the last 50 kyr. Our results highlight that since MIS3 changes in the SW Atlantic surface conditions have been associated with changes in Brazil Current strength, as a response to Atlantic Meridional Overturning Circulation strength changes.

Description: Here we present planktonic foraminifera Globigerinoides ruber (white) s.s. Mg/Ca ratios (mmol/mol) obtained in marine sediment core NAP63-1 (24.8384°S, 44.3187°W, 842 m water depth, 224 cm sediment recovery) retrieved with the aid of a piston corer from the SW Atlantic upper slope. For Mg/Ca analyses, between 30-50 shells of G. ruber (white) s.s. tests were picked from the 250–300 µm size fraction and analyzed with a Thermo Scientific iCap Q quadrupole ICP-MS. Mg/Ca ratios were applied to obtain SW Atlantic sea-surface temperature estimates over the last 50 kyr. Our results highlight the relationship between the SW Atlantic sea-surface conditions and Atlantic Meridional Overturning Circulation strength.

Description: Millennial-scale oscillations are known to be important in the climatic evolution of the Atlantic basin, but which internal processes originates these oscillations are still uncertain. In this study, we investigated how the Greenland and Antarctic climates affect the SW Atlantic through basin-wide oceanographic features (such as the NADW formation and the Agulhas leakage). We reconstructed sea surface and subsurface temperatures (SST and subT) using three lipid-based biomarker proxies (UK'37, TEX86 and LDI indexes) from a sediment core (NAP 63-1) retrieved from the SW Atlantic slope (24.8°S, 44.3°W). This location permitted to evaluate the temperature oscillations of the Brazil Current without any terrigenous or upwelling-derived biases. Both TEX86-based and LDI-based estimates represent the mean annual SST, while the UK'37-based estimates represent the subT (around 30 m water depth). The periods with the most well-mixed water column were observed during intervals of cooling orbital trends due to the time required to transfer the surface cooling to the subsurface. The temperature reconstructions showed a general colder MIS 3 when compared to the MIS 4. They also showed evidence of a late response to the deglaciation, with its onset in the SW Atlantic occurring in the middle of the Last Glacial Maximum. Based on these reconstructions, the NAP 63-1 SST orbital-scale trend seems to be linked to the Antarctic climate, influenced by local insolation changes. These temperature records also presented a clear millennial periodicity around 8 kyr. On this timescale, the millennial oscillations in the SW Atlantic's SST are likely linked to the NADW formation.