Millennial-scale variability of deep-water temperature and delta O-18(dw) indicating deep-water source variations in the Northeast Atlantic, 0-34 cal. ka BP

• Published in: Geochemistry, Geophysics, Geosystems
• Main Authors: Skinner, Lc, Shackleton, Nj, Elderfield, H
• Format: Article in Journal/Newspaper
• Language: English
• Published: Amer Geophysical Union 2003
• Subjects: deep-water temperature; Mg/Ca; termination I; thermohaline circulation; paleoceanographycal and chemical : trace elements; oceanography : biological and chemical : trace elements; oceanography : biological and chemical : stable isotopes; Antarctic; Greenland; Antarc*; Greenland ice cores; NADW; North Atlantic Deep Water; North Atlantic; Northeast Atlantic
• Online Access: https://archimer.ifremer.fr/doc/00225/33654/32087.pdf; https://doi.org/10.1029/2003GC000585; https://archimer.ifremer.fr/doc/00225/33654/

Paired measurements of Mg/Ca and delta(18)O(cc) (calcite delta(18)O) in benthic foraminifera from a deep-sea core recovered on the Iberian Margin (MD99-2334K; 37degrees 48'N, 10degrees10'W; 3,146 m) have been performed in parallel with planktonic delta(18)O(cc) analyses and counts of ice-rafted debris (IRD). The synchrony of temperature changes recorded in the Greenland ice cores and in North Atlantic planktonic delta(18)O(cc) allows the proxy records from MD99-2334K to be placed confidently on the GISP2 time-scale. This correlation is further corroborated by AMS C-14-dates. Benthic Mg/Ca measurements in MD99-2334K permit the reconstruction of past deep-water temperature (T-dw) changes since -34 cal. ka BP (calendar kiloyears before present). Using these T-dw estimates and parallel benthic delta(18)O(cc) measurements, a record of deepwater delta(18)O (delta(18)O(dw)) has been calculated. Results indicate greatly reduced T-dw in the deep Northeast Atlantic during the last glaciation until -15 cal. ka BP, when T-dw warmed abruptly to near-modern values in parallel with the onset of the Bolling-Allerod interstadial. Subsequently, Tdw reverted to cold glacial values between -13.4 and -11.4 cal. ka BP, in parallel with the Younger Dryas cold reversal and the H0 ice-rafting event. Similar millennial-scale T-dw changes also occurred during the last glaciation. Indeed, throughout the last -34 cal. ka, millennial delta(18)O(dw) and T-dw changes have remained well coupled and are linked with IRD pulses coincident with Heinrich events 3, 2, 1, and the Younger Dryas, when transitions to lower T-dw and delta(18)O(dw) conditions occurred. In general, millennial T-dw and delta(18)O(dw) variations recorded in MD99-2334K describe an alternation between colder, low-delta(18)O(dw) and warmer, high delta(18)O(dw) conditions, which suggests the changing local dominance of northern-sourced North Atlantic Deep Water (NADW) versus southern-sourced Antarctic Bottom Water (AABW). The observed similarity of the T-dw and GISP2 delta(18)O(ice) records would therefore suggest a common component of variability resulting from the coupling of NADW formation and Greenland climate. A link between Greenland stadials and the incursion of cold, low-delta(18)O(dw) AABW in the deep Northeast Atlantic is thus implied, which contributes to the relationship between Greenland climate and the millennial benthic delta(18)O(cc) signal since -34 cal. ka BP.