On the Origin of the 200-yrs Cycle in an Early Holocene Monsoon Record of Climate Variability

M Staubwasser (GeoForschungsZentrum, Albert-Einstein-Strasse, Haus G, D-14473 Potsdam; ph. +49-331-288-1347; fax +49-331-288-134; e-mail: staub@gfz-potsdam.de); F Sirocko (GeoForschungsZentrum, Albert-Einstein-Strasse, Haus G, D-14473 Potsdam; ph. +49-288-1332; fax +49-331-288-134; e-mail: staub@gfz-potsdam.de)

Annually Laminated sediments from the upper continental slope off Pakistan are used for a reconstruction of the monsoon climate system with decadal time resolution. 30 planktonic AMS ages (G. sacculifer) provide a high resolution age control allowing the location of 14C plateaus, their correlation to 14C plateaus of tree ring records, and reveal the main intensification of the summer monsoon at 9000 14C (10000 cal), i.e. during the Preboreal-Boreal transition.

The early Holocence records of both d18O (G.ruber) and U/Al ratios from 5300 14C yrBP to 10000 14C yrBP show a clear cyclic progression in surface water and sediment redox conditions with a period of about 200 yrs. This cyclicity has been observed previously in tree ring radiocarbon content, d18O of ice cores, and in warve thickness of European and American lakes, and is often discussed in the context of primary variations in the intensity of solar insolation. Its presence in a paleo-monsoon record indicates either a direct influence of the sun on the strength of the monsoons during the Holocene, or calls for a re-evaluation of the origin of this cycle.