Glacial water mass geometry and the distribution of δ13C of ΣCO2 in the western Atlantic Ocean
This table contains the new isotopic data for the KNR159 cores completed by the date of publication of Curry and Oppo (2005). (40.90Kb)
Three sections from the western Atlantic Ocean: 1) a section based on the modern δ13C values measured in the water column (Kroopnick, 1985); 2) a section based on the Holocene Cibicidoides spp. δ13C values presented in Tables 1 and 2 of Curry and Oppo (2005); and 3) a section based on the glacial Cibicidoides spp. δ13C values presented in Tables 1 and 2 of Curry and Oppo (2005). (699.9Kb)
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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 δ13C transect of Duplessy et al. (1988). The distribution of δ13C of ΣCO2 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 δ13C value of about 0.3–0.5‰ VPDB, a middepth (∼1500 m), northern source water mass with an end-member value of about 1.5‰, and a deep (>2000 m), southern source water with an end-member value of less than −0.2‰, and perhaps as low as the −0.9‰ values observed in the South Atlantic sector of the Southern Ocean (Ninnemann and Charles, 2002). The origins of the water masses are supported by the meridional gradients in benthic foraminiferal δ18O. A revised glacial section of deep water δ13C documents the positions and gradients among these end-member intermediate and deep water masses. The large property gradients in the presence of strong vertical mixing can only be maintained by a vigorous overturning circulation.
Author Posting. © American Geophysical Union, 2005. This article is posted here by permission of American Geophysical Union for personal use, not for redistribution. The definitive version was published in Paleoceanography 20 (2005): PA1017, doi:10.1029/2004PA001021.
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