Ice-sheet driven weathering input and water mass mixing in the Nordic Seas during the last 25,000 years

• Published in: Earth and Planetary Science Letters
• Main Authors: Struve, Torben, Roberts, Natalie L., Frank, Martin, Piotrowski, Alexander M., Spielhagen, Robert F., Gutjahr, Marcus, Teschner, Claudia, Bauch, Henning A.
• Format: Article in Journal/Newspaper
• Language: English
• Published: Elsevier 2019
• Subjects: Norwegian Sea; Svalbard; Ice Sheet; NADW; Nordic Seas; North Atlantic Deep Water; North Atlantic
• Online Access: https://oceanrep.geomar.de/id/eprint/46232/; https://oceanrep.geomar.de/id/eprint/46232/1/Struve%20et%20al%202019.pdf; https://oceanrep.geomar.de/id/eprint/46232/7/1-s2.0-S0012821X1930127X-mmc1.xlsx; https://oceanrep.geomar.de/id/eprint/46232/8/1-s2.0-S0012821X1930127X-mmc2.pdf; https://doi.org/10.1016/j.epsl.2019.02.030

Highlights • First deep water Nd and Pb isotope records from the glacial–deglacial Nordic Seas. • Deglacial changed by up to six units from unradiogenic LGM background. • Glacial–deglacial Nd and Pb isotope changes controlled by local weathering input. • Pb isotopes suggest synchronous postglacial weathering fluxes around the North Atlantic. • Holocene Nd isotope evolution dominated by re-invigorated water mass mixing. Abstract Neodymium (Nd) isotopes are a powerful proxy tool for reconstructing past changes in water mass mixing, but reliable application of this proxy requires constraints on past changes of source water compositions. A key region of the global deep water circulation system are the Nordic Seas, which provide dense waters fundamental for the formation of North Atlantic Deep Water (NADW). Yet, the Nd isotope evolution of past deep waters in the Nordic Seas is so far poorly constrained. Here we present the first reconstructions of seawater Nd isotope compositions extracted from marine sediments at two locations in the central and northern Nordic Seas covering the period from the last glacial to the present. Further insights into past changes in sediment provenance, weathering inputs and water mass mixing are provided by complementary seawater and detrital strontium (Sr) and lead (Pb) isotope compositions. Our new data reveal that changes in source and magnitude of weathering inputs from the Scandinavian and Svalbard–Barents Ice Sheets (SIS and SBIS, respectively) controlled the Nd and Pb isotope composition of the Nordic Seas' deep waters during the last glacial period. During the Last Glacial Maximum (LGM), deep waters showed distinctly unradiogenic Nd and radiogenic Pb isotope signatures most likely driven by weathering inputs of the SBIS. In contrast, the deglaciation was characterized by enhanced SBIS ice dynamics and/or meltwater release delivering sediments from the distal Eurasian shelves to the Norwegian Sea. Pulses of volcanogenic sediment supply changed the deep water Nd isotope ...