Modellierung der räumlichen und zeitlichen Variabilität mariner Radiokohlenstoff-Reservoiralter im Spätquartär
Final Report Abstract
The basis for alt simulations was the University of Victoria Earth System-Climate Model (UVic ESCM, Weaver et al., 2001) in version 2 7, update level 3 In the ocean part of the model, radiocarbon was included as a passive tracer To test the model for consistency with observations, two experiments were carried out • a control run, using constant pre-industrial/present-day boundary conditions, • a bomb radiocarbon experiment subject to a time-varying radiocarbon production due to the testing of nuclear weapons dunng the second half of the 20th century As outlined in the proposal, one approach to model manne radiocarbon reservoir ages variations IS to analyze the changes in ocean 14C content to prescnbed changes in the atmospheric 14C production rate ("production-rate forcing") The effect of the atmosphenc 14C forcing was studied for the pre-industrial/present-day (PD) ocean circulation state obtained from the control run and a Last Glacial Maximum (LGM) ocean state obtained under LGM-like boundary conditions. The work deviated from the original plan in that 14C was not treated as a concentration (Fiadeiro, 1982) Instead, an abiotic carbon cycle with both isotopes 14C and 14C was included, following the more complete protocol of the Ocean Carbon Modeling Intercompansion Project (OCMIP-2, Orr et al., 2000). Furthermore, an alternative approach to model manne radiocarbon reservoir ages variations was pursued by directly imposing changes in reconstructed atmospheric ?14C ("?14Catm forcing") Finally, the project strongly benefitted from a collaboration with Prof Dr Adkins (Caltech, USA) and an additional assessement of the so-called "projection age method"
Publications
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Modeling variations of marine reservoir ages during the last 45 000 years. Climate of the Past, 4,125-136, 2008
Franke, J., Paul, A., and Schulz, M.
