HR: 09:45h
AN: PP41F-08    [Abstracts]
TI: Interpreting Si isotope records of diatomaceous opal
AU: * Reynolds, B C
EM: reynolds@erdw.ethz.ch
AF: IGMR, ETH Zurich, Clausistrasse 25, Zurich, CH8092, Switzerland
AB: In the polar oceans, sinking of diatom frustules can be the main export pathway of nutrient and diatoms can dominate the primary productivity over the annual cycle. As little of the exported organic matter is recorded in the high latitudes, we are left to try and reconstruct change in the polar surface oceans from the biogenic opal record. Whilst organic matter within the diatom frustules can provide carbon and nitrogen stable isotope records, the opal itself records the silicon isotope composition that is a proxy for silicic acid utilization. Carbon, nitrogen and silicon isotopes proxies for paleoproductivity actually record the degree of nutrient utilization (with no estimate of the total fluxes), and often give conflicting results. Here I will present a model for our present understanding of the links between upwelling, nutrient uptake by diatoms, and silicic acid utilization to interpret the Si isotope records of diatomaceous opal from polar regions. A strong interbasinal fractionation of silicic acid concentrations and Si isotope compositions is driven by southern ocean circulation, and further studies of Si isotopes should help us to understand changes in this circulation pattern, even if it does not provide a robust paleoproductivity proxy.
DE: 0424 Biosignatures and proxies
DE: 0454 Isotopic composition and chemistry (1041, 4870)
DE: 1605 Abrupt/rapid climate change (4901, 8408)
DE: 4835 Marine inorganic chemistry (1050)
DE: 4924 Geochemical tracers
SC: Paleoceanography and Paleoclimatology [PP]
MN: 2007 Fall Meeting