Millennial‐scale variability of deep‐water temperature and δ 18 O dw indicating deep‐water source variations in the Northeast Atlantic, 0–34 cal. ka BP

Paired measurements of Mg/Ca and δ 18 O cc (calcite δ 18 O) in benthic foraminifera from a deep‐sea core recovered on the Iberian Margin (MD99‐2334K; 37°48′N, 10°10′W; 3,146 m) have been performed in parallel with planktonic δ 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 δ 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 14 C‐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 δ 18 O cc measurements, a record of deep‐water δ 18 O (δ 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 Bølling‐Allerød interstadial. Subsequently, T dw 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 δ 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 δ 18 O dw conditions occurred. In general, millennial T dw and δ 18 O dw variations recorded in MD99‐2334K describe an alternation between colder, low‐δ 18 O dw and warmer, high δ 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 δ 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‐δ 18 O dw AABW in the deep Northeast Atlantic is thus implied, which contributes to the relationship between Greenland climate and the millennial benthic δ 18 O cc signal since ∼34 cal. ka BP.