Holocene to modern deepwater sources in the eastern Fram Strait investigated by Neodymium isotope tracers - First results and open questions

• Main Authors: Werner, Kirstin, Teschner, Claudia, Zieringer, Moritz, Spielhagen, Robert F., Frank, Martin
• Other Authors: Immonen, Ninna, Jakobsson, Martin, Lunkka, Juhann Pekka, Strand, Kari
• Format: Conference Object
• Language: unknown
• Published: University of Oulu and Thule Institute 2012
• Subjects: Arctic; Arctic Ocean; Fram Strait; north atlantic current; North Atlantic; Sea ice; Spitsbergen
• Online Access: https://oceanrep.geomar.de/id/eprint/14816/; http://thule.oulu.fi/englanti/documents/APEXVI_abstracts.pdf

Seawater-derived neodymium (Nd) isotope ratios of sediment coatings have increasingly been used in paleoceanographic reconstructions to derive information on the past variability of deepwater sources and mixing. Dissolved Nd in seawater originates from weathering processes of the continental crust. It is delivered to the oceans either through boundary exchange processes or in dissolved or particulate form through riverine input (Frank, 2002). The use of radiogenic Nd isotopes as oceanic tracers is enabled by the average ocean residence time of Nd, which is similar to the global mixing time of oceans (ca 400 – 2,000 years) and by their independence of stable isotope fractionation by biological or physical processes (van de Flierdt et al., 2006). In this study, we investigate Nd isotope ratios of both core-top and Holocene sediment samples (leachates and detritus) and compare them to modern seawater Nd isotope signatures in the eastern Fram Strait, as well as to a multitude of proxy indicators for the climatic and oceanographic variability in the eastern Fram Strait during the past 8,500 years. The West Spitsbergen Current (WSC) represents the major means of northward heat transport to the Arctic Ocean via eastern Fram Strait. While the upper layers of the WSC are fed by warm and saline Atlantic Water derived from the North Atlantic Current, deepwater inflow through eastern Fram Strait is still subject of debate. Our study is primarily intended to reconstruct Holocene variability of bottom water sources in the Arctic Gateway. However, relatively radiogenic Nd isotope ratios of the leached fraction since the late Holocene suggest a contribution of fine lithic grains transported by sediment-laden sea ice from the East Siberian shelves to the Fram Strait (Dethleff and Kuhlmann, 2009). This is in contrast to the less radiogenic Nd isotope ratios of present-day intermediate and deep water in the area documenting an Atlantic source. We therefore suggest an alternative explanation, which is input and transport of ...