Benthic foraminiferal Cd/Ca from a Florida Current sediment core documents the history of the northward penetration of southern source waters within the surface return flow of the Atlantic meridional overturning circulation (AMOC). Cd seawater estimates (CdW) indicate that intermediate-depth southern source waters crossed the equator and contributed to the Florida Current during the Bølling-Allerød warm period of the last deglaciation, consistent with evidence of only a modest AMOC reduction compared to today. The CdW estimates also provide the first paleoceanographic evidence of a reduction in the influence of intermediate-depth southern source waters within the Florida Current during the Younger Dryas, a deglacial cold event characterized by a weak North Atlantic AMOC. Our results reveal a close correspondence between the northward penetration of intermediate-depth southern source waters and the influence of North Atlantic Deep Water, suggesting a possible link between intermediate-depth southern source waters and the strength of the Atlantic AMOC.

Accelerator mass spectrometer (AMS) radiocarbon dates were converted to calendar age using the online calibration program Calib 5.02 (Stuiver and Reimer, 1993), the Marine04 calibration data set (Hughen et al., 2004), and a reservoir correction of 400 years.

Supplement to: Came, Rosemarie E; Oppo, Delia W; Curry, William B; Lynch-Stieglitz, Jean (2008): Deglacial variability in the surface return flow of the Atlantic meridional overturning circulation. Paleoceanography, 23(1), PA1217