Deep-water circulation and detrital provenance in the South Pacific, from the present day until 240 000 years ago : evidence from Nd, Sr and Pb isotopes and Rare Earth Elements

• Main Author: Molina Kescher, Mario
• Other Authors: Frank, Martin, Pahnke, Katharina
• Format: Doctoral or Postdoctoral Thesis
• Language: English
• Published: 2014
• Subjects: thesis; ddc:550; Deep-water circulation; detrital provenance; South Pacific; Nd isotopes; Sr isotopes; Pb isotopes; Rare Earth Elements; Pacific; New Zealand; Sea ice
• Online Access: https://nbn-resolving.org/urn:nbn:de:gbv:8-diss-153843; https://macau.uni-kiel.de/receive/diss_mods_00015384; https://macau.uni-kiel.de/servlets/MCRFileNodeServlet/dissertation_derivate_00005628/Dissertation_Molina-Kescher_2014.pdf

Present and past climate of the Earth has strongly depended on oceanic circulation and marine biological productivity. The formation of deep and bottom waters in high latitudes as a consequence of density changes and their pathways through the global ocean, the so called thermohaline circulation (THC) have been of primary importance for the redistribution of heat, for the Earth’s albedo through control on the sea ice distribution, and it serves as a reservoir of greenhouse gases such as CO2. The understanding of the mechanisms that have driven the THC in the past is crucial to reliably predict future climatic variations. For example, large amounts of CO2 were stored in the deep ocean during glacial periods, which depended on the structure of the water column but also on the availability of nutrients for primary producers in the surface ocean. Besides macronutrients, phytoplankton depends also on dust input to the ocean, which releases iron, one of the most important micronutrients, in particular in High Nutrient Low Chlorophyll areas. These issues have been poorly studied in the South Pacific, despite its importance for these processes. It represents a key area for the interchange of deep waters from all ocean basin because it is the main entrance and exit of deep waters to the largest of all oceans, the Pacific, which is also one of the principal CO2 reservoirs on Earth. For the study of present and past deep-water circulation regimes and the provenance of the dust input in this region, Rare Earth Element (REE) distributions and radiogenic isotopes of neodymium (Nd), lead (Pb) and strontium (Sr) have been analyzed in water and sediment samples obtained from a meridional transect of the South Pacific, spanning all the way from South America to New Zealand. Radiogenic isotopes have been proved to be very reliable traces for studying different surface earth processes, such as, in the case of Nd and Pb, the advection of water masses. These are labeled with characteristic isotope compositions through weathering of ...