Application of Sr-Nd-Pb isotopes to the late quaternary paleoceanography of the Atlantic Ocean

• Main Author: Wei, Ran
• Format: Doctoral or Postdoctoral Thesis
• Language: English
• Published: Johannes Gutenberg-Universität Mainz 2016
• Subjects: ddc:550; NADW; North Atlantic Deep Water; North Atlantic
• Online Access: https://openscience.ub.uni-mainz.de/handle/20.500.12030/4576; https://hdl.handle.net/20.500.12030/4576; https://doi.org/10.25358/openscience-4574

The Atlantic Meridional Overturning Circulation (AMOC) plays a crucial role in distributing heat around the globe and impacts strongly on Earth’s climate. The long-lived radiogenic systems Sm-Nd, Rb-Sr and Th-U-Pb have been developed and used extensively in oceanography as robust tracers of water mass provenance and water mass mixing, in particular, in relation to variability in the AMOC and its correlation with climate change and glacial-interglacial cycles. These applications of the Sr-Nd-Pb radiogenic isotope systems to paleoceanography are explored here by analyzing hydrogenetic components and terrigenous phases from Atlantic deep-sea sediment cores. The reconstruction of paleocurrents has long been a subject of paleoceanographic research. Many of these studies have focused on documenting variations in North Atlantic Deep Water (NADW) intensity on millennial and glacial-interglacial timescales. Changes in AMOC strength and formation of NADW during the Last Glacial Maximum (LGM) still remain very uncertain despite being discussed and argued about in many studies. Here, we present Sr and Nd radiogenic isotope records of Fe-Mn oxide leachates of bulk sediment - which reflect the composition of deep water - from cores located in the South Atlantic, to reconstruct past variability in NADW circulation over the last glacial cycle. The Fe-Mn leachate ƐNd records show a coherent decreasing trend from glacial radiogenic values towards less radiogenic values during the Holocene. Our results, along with published multi-proxy records, suggest that (a) a shallower Southern Component Water penetration northwards during the LGM, (b) there was continuous production and export of Northern Component Water over the last 24 kyr, and (c) the AMOC was reinvigorated progressively to its full strength today over the Holocene period. A second study presented here uses the radiogenic isotopic compositions of Sr, Nd and Pb hosted in detrital minerals extracted from ocean sedimentary cores to infer the provenance of air-borne dust ...