Late Quaternary variations of sea surface salinity and temperature in the western tropical Atlantic: Evidence from δ18O of Globigerinoides sacculifer

In order to reconstruct hydrographic changes during glacial‐interglacial cycles for a transequatorial transect we analyzed oxygen isotopes of Globigerinoides sacculifer (without sac‐like chamber) and abundances of Globorotalia truncatulinoides (dextral) from FS Meteor cores GeoB 2204‐2 (Brazilian continental slope) and GeoB 1523‐1 (Ceara Rise). Δδ18O values of G. sacculifer between the two cores were calculated. Modern Δδ18O (G. sacculifer) is ∼0.2‰ between the two core positions, reflecting differences in sea surface salinity (SSS). Higher SSS at GeoB 1523‐1 (Ceara Rise) is the result of increased precipitation in the region of the Intertropical Convergence Zone. During glacials the δ18O records from the two cores converge to the same absolute value, resulting in Δδ18O values of around 0‰. Maximum abundances of G. truncatulinoides (dex) correlate with minimum Δδ18O, suggesting a possible increase of SSS at GeoB 1523‐1 during stages 2, 3, 4, and 6, which is related to a glacial weakening of the tropical Hadley Cell [Gates, 1976]. Variations in tropical sea surface temperatures are assumed to be low [Climate: Long‐Range Investigation, Mapping, and Prediction (CLIMAP), 1981].