Fig. 3.

Compilation of LGM ventilation data from subtropical western North Atlantic core sites (16, 34) with the new data presented here (Dataset S3). (A) Stable isotope profiles of Cibicidoides δ¹³C (filled red circles) and δ¹⁸O (open black circles) on Carolina Slope, Bahama Outer Ridge (BOR), Blake Ridge, and BR. Cibicidoides are very rare during the LGM along the western margin, so, in most cases, the δ¹³C are single measurements where a few individuals were found. Otherwise, error bars are a nominal ±1σ. Multiple analyses were possible on BR, but the large scatter in Cibicidoides δ¹³C may represent greater influence of bioturbation and/or the presence of low δ¹³C in fluff layers where diatoms are preserved. Because the samples for stable isotope data were not dated, the curves represent average conditions for the LGM (18−21 ka). (B) Profile of the difference between benthic and planktonic (B-P) conventional ¹⁴C ages from NW Atlantic sediment cores during the LGM. Note similar trends in the two C isotope data sets. It is argued here that the reversal in the trends of δ¹³C and ¹⁴C_B-P below 4.2 km is evidence for a young source of North Atlantic bottom water during the LGM. Figs. S4−S7 put the new ¹⁴C_B-P data in a stratigraphic framework.