Benthien, A. FB Geowissenschaften, Universitaet Bremen, benthien@allgeo.uni-bremen.de
Andersen, N. Geologisches Institut, ETH-Zentrum, andersen@erdw.ethz.ch
Mueller, P. J.. FB Geowissenschaften, Universitaet Bremen, pmueller@allgeo.uni-bremen.de
Schneider, R. R.. FB Geowissenschaften, Universitaet Bremen, rschneid@allgeo.uni-bremen.de
Wefer, G. FB Geowissenschaften, Universitaet Bremen, gwefer@allgeo.uni-bremen.de

 
ALKENONE DELTA C-13 DERIVED PCO2 LEVELS IN SURFACE WATERS OF THE SOUTH ATLANTIC: HOLOCENE VS. LAST GLACIAL MAXIMUM
 
The carbon isotopic composition of a marine biomarker (C37:2 alkenone) was used to reconstruct ancient PCO2 levels in the surface waters of the eastern South Atlantic Ocean. Since recent studies suggest that estimations of ancient concentrations of dissolved molecular carbon dioxide [CO2(aq)] in oceanic surface waters will also require knowledge of growth rate dependent intracellular carbon demand (expressed by b-value) we used bulk sediment delta N-15 as a proxy parameter to calculate ancient b-values. This approach is based on the findings that estimated b-values are related to the delta N-15 signal in surface sediments in the South Atlantic. Two time slices, the Last Glacial Maximum (LGM) and the latest Holocene (core-tops) were examined. The estimated PCO2 values decrease towards higher latitudes, but are not significantly different for both time slices. The reconstructed PCO2 levels of the Holocene time slice (240-340 ľatm) correspond well to pre-industrial PCO2 values which were obtained by substracting 70 ľatm from direct surface water measurements (Weiss et al., 1992). Due to the much lower glacial atmospheric pCO2 (about 200 ľatm), the estimated LGM values (240-360 ľatm) indicate a more pronounced oceanic CO2 source compared to the latest Holocene.
 
Day: Tuesday, Feb. 2
Time: Poster
Location: Sweeney Center
 
Code: SS32TU0752S