Clim. Past Discuss., 8, 3791-3829, 2012
© Author(s) 2012. This work is distributed
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This discussion paper has been under review for the journal Climate of the Past (CP). Please refer to the corresponding final paper in CP.
Influence of orbital forcing and solar activity on water isotopes in precipitation during the mid and late Holocene
S. Dietrich1, M. Werner1, T. Spangehl2, and G. Lohmann1
1Alfred Wegener Institute for Polar and Marine Research, Bussestr. 24, 27570 Bremerhaven, Germany
2Deutscher Wetterdienst, Frankfurter Str. 135, 63067 Offenbach, Germany

Abstract. In this study we investigate the impact of mid and late Holocene orbital forcing and solar activity on variations of the oxygen isotopic composition in precipitation. Our study is based on a set of novel climate simulations performed with the atmosphere general circulation model ECHAM5-wiso enhanced by explicit water isotope diagnostics. From the performed model experiments we derive the following major results: (1) the response of both orbital and solar forcing lead to changes in surface temperatures and δ18O in precipitation with similar magnitudes during the mid and late Holocene. (2) Past δ18O anomalies correspond to changing temperatures in the orbital driven simulations. This does not hold true if an additional solar forcing is added. (3) Two orbital driven mid Holocene experiments, simulating the mean climate state approximately 5000 and 6000 yr ago, yield very similar results. However, if an identical additional solar activity-induced forcing is added, the simulated changes of surface temperatures as well as δ18O between both periods differ. From our findings we conclude that the Holocene variability of δ18O in precipitation, as stored in many paleoclimate archives, is rather complex to understand since the combined effect of different external forcings on δ18O in precipitation is non-linear.

Citation: Dietrich, S., Werner, M., Spangehl, T., and Lohmann, G.: Influence of orbital forcing and solar activity on water isotopes in precipitation during the mid and late Holocene, Clim. Past Discuss., 8, 3791-3829, doi:10.5194/cpd-8-3791-2012, 2012.
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