Decadal-scale Evolution of the Subtropical Climate and Hydrography During High-frequency Climate Oscillations of the Last 70.000 Years

Frank Sirocko (GeoForschungsZentrum Potsdam, 14473 Potsdam, Germany; ph. +49 30 1332; fax. +49 30 1302; email. sirocko@gfz-; Michael Staubwasser (GeoForschungsZentrum Potsdam, 14473 Potsdam, Germany; ph. +49 30 1347; fax. +49 30 1302; email.; Dirk Leuschner (GeoForschungsZentrum 14473 Potsdam, Germany; ph. +49 30 1347; fax. +49 30 1302; email.

Atmospheric temperature variations during oxygen isotope stage 3 in the Greenland ice cores reveal flickering oscillations with periods of about 1450- and 3000 years, the Dansgaard-Oeschger cycles. These cycles also occurred in the intermediate water ventilation of the equatorial Pacific. We now find the entire suite of Dansgaard- Oeschger cycles also in the bidecadal-resolution dust and upwelling record from deep-sea sediments of the Arabian Sea, northern Indian Ocean. Apparently, the hydrography and climate of the North Atlantic, Indian Ocean and Pacific followed a very similar general structure over the entire last 70,000 years. Unfortunately, possible minor phase differences cannot be resolved with the precision of available dating methods.

To further aproach the question of synchroneity and cause-and- effect relationships (possible leads and lags) between climate events in the three oceans we study laminated sediments of the early Holocene from the northern Indian Ocean, equatorial Pacific and northern Europe. In particular, the main Asian monsoon intensification at about10,000 cal-yrBP is also documented in the Santa Barbara Basin as a short aridity pulse in the vegetation of southern California, coinciding with the Preboreal to Boreal transition in the vegetation of Northern Europe.

Within the precision of dating the temperature over Europe, the strength of the Indian Ocean monsoon and ventilation of the Pacific intermediate water masses followed coeval patterns, and thus forcing. The laminated lake and ocean records from Europe, Indian Ocean and equatorial Pacific reveal cyclicities with 6-, 11-, 210-year oscillations at the high-frequency end of the spectrum, indicating forcing by either El-Nino anomalies, solar variability, or the north Atlantic oscillation.