Geochemical and isotopic tracers of Arctic sea ice sources and export with special attention to the Younger Dryas interval

Abstract

Radiogenic isotopes (Sr, Nd) in Ice Rafted Debris (IRD) sediments from the Lomonosov Ridge and Fram Strait Arctic areas are used to document changes in Arctic sea-ice sources and trajectories since the Last Glacial Maximum (LGM). The two records provide evidence for enhanced sea-ice production in the Beaufort Sea and its subsequent export through Fram Strait during the Younger Dryas (YD) interval. This pattern, exclusive to the YD, followed an LGM–Bølling–Allerød interval, when multiyear and/or reduced sea-ice mobility resulted in sedimentary hiatuses in the Central Arctic. Meanwhile, IRD from Svalbard–Barents ice-sheet margin source were still deposited in the Fram Strait area. The “isotopic excursion” of the YD points to enhanced sea-ice production in the Beaufort Sea, which we link to the Lake Agassiz (?)/Laurentide ice sheet drainage event through the Mackenzie route. Following this event, the Holocene depicts a 5-fold reduction in IRD rates with a shift towards prominent sea-ice production along Russian shelves. From a methodological viewpoint, we demonstrate that radiogenic isotopes must be used in a multi-proxy approach to better constrain IRD and sea-ice sources and routes. From a paleoceanographic perspective, we conclude that an Arctic freshwater/sea-ice export route should now be seen as the most likely mechanism for an AMOC reduction during the YD in accordance with more recent improved model experiment.