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Semester: SS 2023 

Ocean Gateways TP B1: Denmark's Strait Paleo-Intensity of Overflow

Projektleitung:Prof. Dr. phil. Johann Michael Sarnthein-Lotichius, (pens.), Prof. Dr. Pieter M. Grootes, Priv.-Doz. Dr. rer. nat. Mara Weinelt
Beteiligte:Dr. rer. nat. C.-Dieter Garbe-Schönberg, Dipl.-Biogeoch. Gretta Bartoli
Förderer:DFG
Mitwirkende
Institutionen:
Leibniz-Labor für Altersbestimmung und Isotopenforschung
Stichwörter:paleoceanography; climate; trace elements
Laufzeit:1.7.2002 - 30.6.2006
Inhalt und Ziele:The Denmark Strait and Iceland-Scotland Ridge serve as gateways for giant currents of intermediate water flowing from the European Nordic Seas into the North Atlantic. This Overflow‘ forms a main deepwater source for the global ocean. At the same time it leads to the advection of warm and highly saline surface water from the Atlantic into the Nordic Seas and thus, to todays fairly warm, but highly variable climate in Europe. It is the objective of this study to trace the variability of the thermohaline circulation system in the Denmark Strait at multidecadal resolution over geological times, specifically for the last 80,000 years and for some of the major warm interglacial stages in the Pleistocene and Late Pliocene. This especially implies the reconstruction of the paleosalinity and density gradients in the surface layer and of the differential quality and paleo-14C ages of the Overflow water in the deep ocean.
In particular, we aim to analyse the sedimentology, trace metal chemistry, stable isotopes, radiometric ages, and the faunal composition in a series of long sediment cores, many of them already retrieved, to trace the impact of the following environmental factors: (1) The influence of surging Greenland outlet glaciers on salinity variations in the East Greenland Current, which change deepwater convection and possibly induce the millennial-scale Dansgaard-Oeschger (D-O) cycles, and (2) the effect of eustatic and (glacio-) isostatic sea-level changes on the aperture of the Denmark Strait and thereby, on the intensity of the Overflow and Irminger Current, moreover, on the south-north exchange of planktic and benthic foraminiferal species. Here potential new insights are expected from molecular genetics. These objectives imply a close cooperation with geodynamics (Prof. D. Wolf, Potsdam) and ocean modeling (Theme A), especially with regard to the global impact of changes found in the Denmark Strait gateway. Viceversa, Theme B1 will provide crucial quantitative data for model validation. Global teleconnections of centennial-to-millennial-scale climate change between high and low-latitude sites will be reconstructed together with Themes B and C, using a joint ultrahigh-resolution time scale based on D-O and Milankovitch cycles.

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