Decadal-centennial scale monsoon variations in the Arabian Sea during the Early Holocene

An essential prerequisite for the prediction of future climate change due to anthropogenic input is an understanding of the natural processes that control Earth's climate on timescales comparable to human-lifespan. The Early Holocene period was chosen to study the natural climate variability in a warm interval when solar insolation was at its maximum. The monsoonal system of the Tropics is highly sensitive to seasonal variations in solar insolation, and consequently marine sediments from the region are a potential monitor of past climate change. Here we show that during the Early Holocene period rapid δ18O-changes of the summer (upwelling) dwelling foraminifer G. bulloides of up to ∼0.6% in Core 905 from the Arabian Sea occurred on decadal-centennial timescales. This δ18O-change predominantly translates into summer temperature variations of roughly 2–3°C. Within the resolution of the AMS14C-dating, the isotope changes occur in phase with precipitation-induced δ18O-variations recorded in a stalagmite in the Hoti Cave in Oman [Neff et al., 2001]. From this relationship we conclude that solar insolation affecting the monsoonal system not only induced the precipitation changes as recorded in Oman (in the sense of Neff et al. [2001]) but also controlled temperature variations in the upwelled waters found off Somalia. The present study demonstrates that decadal-scale climate records can be obtained from nonlaminated ocean sediment records and that coherent rapid high-amplitude climate change is recorded in the Arabian Sea on a regional scale of >2000 km.