Deep-sea corals evidence periodic reduced ventilation in the North Atlantic during the LGM/Holocene transition

Nine new intermediate water ages estimated with coupled uranium-series and radiocarbon measurements on deep-sea corals from the northeastern Atlantic are presented. Together with six intermediate and deep-water ages from the western North Atlantic [Adkins et al., Science 280 (1998) 725–728] and one from the equatorial Atlantic [Mangini et al., Nature 392 (1998) 347–348] they span the time period from 15 400 to 560 yr ago and show abrupt variations of intermediate and deep-water ages from 270 up to 2320 yr. Both major pulses of meltwater discharge MWP 1A, following Heinrich Event 1 and MWP 1B after the Younger Dryas cold event are followed by enhanced supply of southern source water at intermediate depths in the North Atlantic, together with reduced formation of well-ventilated glacial North Atlantic intermediate water (1000–2000 m). This result gives strong support to numerical models, predicting fast and sharp increase of bottom water age in the Atlantic triggered by pulses of freshwater discharge into the North Atlantic [Rahmstorf, Nature 372 (1994) 82–85; Stocker and Wright, Radiocarbon 40 (1998) 359–366].