Fig. 1. Vertical distribution of δ¹³C ∑CO₂ in the world’s oceans (after Charles and Fairbanks, 1992). NADW with high δ¹³C values originates in the North Atlantic and penetrates into the circumpolar region, inserting itself into the Antarctic Circumpolar Current. Site 1090 is located at the lower boundary of NADW and the upper boundary of lower CPDW.

Fig. 2. Positions of core locations (see also Table 1) are shown in potential temperature versus salinity space relative to the major deep water masses in the world’s oceans (after Oppo and Fairbanks, 1987). Holocene δ¹³C value at each site is noted in parentheses. MOW, Mediterranean Overflow Water; NCW, Northern Component Water; LSW, Labrador Sea Water; CPDW, Circumpolar Deep Water; POW, Pacific Outflow Water. Data for water mass properties are from Oppo and Fairbanks (1987) and Broecker and Peng (1982), summarized in Table 2.

Fig. 3. Age versus depth plot of isotopic and paleomagnetic control points. Note the change in sedimentation rates at 35 mcd (1.1 Myr). Sedimentation rates average 3 cm/1000 years above 35 mcd (1.1 Myr) and 1.2 cm/1000 years below 35 mcd (1.1 Myr).

Fig. 4. Oxygen isotopic records of benthic foraminifers (Cibicidoides wuellerstorfi) from piston core TTN057-6-PC4 (dashed line; Hodell et al., 2000), Site 1090 (bold solid line; this study) and Site 607 (gray solid line; Ruddiman and Raymo) versus age with magnetic stratigraphy and selected isotopic stages labeled. Hiatuses in the record from Site 1090 are noted by vertical dashed lines ( Table 4).

Fig. 5. (Left) Oxygen isotopic records of benthic foraminifera (Cibicidoides wuellerstorfi) from Site 982 and Site 607 versus age. Plots have been offset for clarity by adding 1‰ to the Site 607 data. (Right) Carbon isotopic record of benthic foraminifera (C. wuellerstorfi) from Site 982 versus age.

Fig. 6. Oxygen isotopic (A) and carbon isotopic (B) records for the planktonic foraminifer Globigerina bulloides in Site 1090. Oxygen isotopic (C) and carbon isotopic (D) records of Cibicidoides in Site 1090. The horizontal lines denote MIS 52 and MIS 22 in all records.

Fig. 7. Calculated benthic carbon isotopic gradients between the Southern Ocean (Site 1090) and the Pacific (Site 849) and among a latitudinal and depth transect of the Atlantic including Sites 982, 607, 925, 929, and 1090.

Fig. 8. Comparison of the Southern Ocean benthic δ¹³C record from Site 1090 (red) with similar records from cores located within other deep water end member locations: Site 982 (mid-depth North Atlantic; blue), Site 607 (deep North Atlantic; green), and Site 849 (deep Pacific; black). Refer to Table 1 for core locations and references.

Fig. 9. Comparison of the Southern Ocean benthic δ¹³C record from Site 1090 (heavy dark line) with similar records from Site 929 (deep equatorial North Atlantic; dashed line) and Site 607 (deep North Atlantic; thin dark line). Refer to Table 1 for core locations and references.

Fig. 10. Oxygen (left) and carbon (right) isotopic records of benthic foraminifera from Site 1090 (black; this study), Site 704 (green; Hodell and Venz, 1992), and piston core RC13-229 (red; Oppo et al., 1990). Note the similarity of δ¹³C values in the interval of overlap between Sites 1090 and 704 from 2.9 to 1.1 Myr and the overlap between Site 1090 and piston core RC13-229 from 0.8 to 0 Myr.

Fig. 11. Calculation of %NCW at Site 607 (top) and Site 929 (middle) using Eq. 1 with Site 982 as the NCW end member and Site 1090 as the SCW end member (solid line). The line drawn through the plot is a curve calculated using the weighted least squared error method with a smoothing factor that considers 3% of the data when smoothing. Variation in the long-term mean %NCW at Site 607 and 929 represented by the weighted curves in the top and middle panels is shown without large glacial/interglacial variation in the bottom panel.

Fig. 12. Schematic representation of glacial-to-interglacial changes in deep water mass boundaries in the North Atlantic inferred from benthic δ¹³C records and Δ¹³C gradients from Sites 982, 607, 925, 929, and 1090.

Fig. 13. Calculation of %NCW at Site 607 using Eq. 1 with Site 982 as the NCW end member and Site 1090 as the SCW end member (left). The calculation was repeated using Pacific Site 849 as the SCW end member in place of the record from Site 1090 (middle). The benthic δ¹⁸O record from Site 1090 is also shown (right). Gaps in the %NCW proxy represent gaps or hiatuses in the Site 1090 and Site 929 records.

Table 1. Core locations

Table 2. Water mass properties

Potential temperatures are from Broecker and Peng (1982) and Broecker et al. (1985) (after Oppo and Fairbanks, 1987).

Table 3. Age/depth points for Sites 1090 and 982

Table 4. Hiatuses present in Site 1090