Research: Radiogenic isotope geochemistry and paleoceanography

Particle-reactive trace metals such as neodymium, hafnium and lead have a heterogeneous isotopic distribution in the global oceans because their residence times are short (on the order of hundreds of years) compared to ocean mixing times (on the order of one thousand years). Deep water masses are tagged with characteristic isotopic signatures by the continental weathering inputs in their source regions, providing a tracer (or dye) for mixing between water masses. By reconstructing changes in this isotopic distribution through time, we are addressing questions on the variability of past ocean currents, the weathering of the continents and the relation of these and other processes to global and regional climatic changes.

Nd isotopes may be particularly valuable for reconstructing past changes in deep ocean circulation and structure because they are insensitive to biological processes and other low temperature fractionation effects. This is in contrast to nutrient-based proxies (e.g. benthic foraminiferal δ13C and Cd/Ca ratios) which are affected by changes in export productivity and preformed nutrient contents of a water mass, in addition to circulation. In this respect, heavy radiogenic isotopes potentially provide a more unambiguous record of circulation changes. This allows us to address the potential role of ocean circulation as a forcing and/or feedback process affecting earth's climate during the glacial-interglacial cycles of the Quaternary.

 


Publications: 2006-Present

Last updated on 20-Nov-12 16:10