Glacial water mass geometry and the distribution of δ 13 C of ΣCO 2 in the western Atlantic Ocean

Oxygen and carbon isotopic data were produced on the benthic foraminiferal taxa Cibicidoides and Planulina from 25 new piston cores, gravity cores, and multicores from the Brazil margin. The cores span water depths from about 400 to 3000 m and intersect the major water masses in this region. These new data fill a critical gap in the South Atlantic Ocean and provide the motivation for updating the classic glacial western Atlantic δ 13 C transect of Duplessy et al. (1988). The distribution of δ 13 C of ΣCO 2 requires the presence of three distinct water masses in the glacial Atlantic Ocean: a shallow (∼1000 m), southern source water mass with an end‐member δ 13 C value of about 0.3–0.5‰ VPDB, a middepth (∼1500…