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Abstract

The formation of North Atlantic Deep Water (NADW) is a complex and important mechanism coupling the large oceanic reservoir of heat and carbon to the highly climate relevant atmospheric reservoir. In order to study the role of deep water formation during the last deglaciation, proxies archived in marine sediments are required. One proxy for the identification of local deep waters and their mixing is the isotope composition of seawater-derived Nd (Nd IC). An accurate interpretation of this proxy, however, requires good knowledge of the Nd ICs of water mass end members. In this thesis the distribution, reactivity, and mobility of Nd in deep sea sediments was assessed in detail. This investigation evidences a general immobility of Nd in sediments and results in a refinement of existing methods for the extraction of an authigenic Nd IC from bulk sediments of varying compositions. The subsequent reconstruction of deep water Nd ICs across the subpolar North Atlantic allows for the investigation of changes in the formation of NADW and the Nd IC it carries. The results show the first direct evidence that a prominent transient Nd IC change of deep NADW during the Holocene originated in its source waters, probably in the Nordic Seas.