VARIATIONS IN DEEP-WATER CIRCULATION ON EIRIK DRIFT FROM THE LAST GLACIAL MAXIMUM TO EARLY HOLOCENE

Various proxy records (e.g., benthic foraminiferal d¹³C, Cd/Ca, sediment accumulation patterns) show that the deep-water circulation system in the North Atlantic alternated between modes with a deeply penetrating form of North Atlantic Deep Water (NADW) during warming periods and a shallow variety during colder intervals (e.g., Curry et al., 1988). These patterns hold on the orbital time-scales (Oppo et al., 1995) as well as on the millennial-scales (Piotrowski et al., 2005). Eirik Drift, located off the southern tip of Greenland, forms as south-flowing North Atlantic Deep Water (NADW) slows and deposits suspended sediment. Sediment cores were collected from the shallow and deep depo-centers during KN166-14 cruise. Here, we report results from core 15JPC, which was collected in 2200 m water depth on the lee side of the Eirik ridge crest. 3.5 kHz records indicate that this region on Eirik drift was near the depo-center during the Last Glacial Maximum (LGM). Twelve AMS ¹⁴C dates were converted to calendar years and constrain the chronology for the upper 200 cm as being deposited between 20.6 and 7.9 ka, yielding an average sedimentation rate of ~15.5 cm/kyr. From 20.5 to 17 ka, sedimentation rates increase from ~40 to > 150 cm/kyr. Throughout this interval, benthic foraminiferal d¹³C values were high (~ 1 ‰), while coarse fraction values remained low (< 10 %), indicating current controlled deposition, which was sourced in the North Atlantic. All three proxies suggest that during the LGM, the axis of NADW was proximal to this to this location. Beginning at 16 ka, a marked decrease in sedimentation rates (< 30 cm/kyr) and benthic foraminiferal d¹³C values (< 0 ‰) indicate that NADW circulation decreased abruptly. The timing of this change corresponds to the H1 event, when it has been suggested that a massive flux of fresh water reduced NADW production. Following the H1 event, sedimentation rates and benthic foraminiferal d¹³C values increased indicating a resumption of NADW flow. This high flux of NADW persisted into the early Holocene until approximately 9 ka. At this time, sedimentation rates decreased and coarse fraction values increased dramatically, suggesting that the deep current was actively winnowing the sediments at this site. Core top ages indicate that NADW switched to the strong, deep penetrating interglacial flow regime in the early Holocene approximately 7.7 ka.