RECONSTRUCTION OF HOLOCENE MONSOON VARIABILITY FROM THE PEARL RIVER ESTUARY

The variability of East Asian Monsoon (EAM) is an important manifestation of global climate change, and is a regional system teleconnected to other systems such as North Atlantic Oscillations (NAO). The understanding of the variability of EAM is therefore globally significant. Furthermore, EAM is of tremendous socio-economic importance in East Asia where flood and drought hazards are common. The Pearl River estuary is well placed within the EAM region, and any variation in the intensity of EAM will result in a change in the freshwater flux into the estuary and inner shelf region of the South China Sea. The aim of this presentation is to show the potential of such estuarine environments for climate reconstructions over a Holocene timescale by linking together present day sedimentology, geochemistry and micropalaeontology of the estuarine system to fluctuations in freshwater flux associated with discharge from the Pearl River. The Pearl River is 2214 km in length with a drainage area of 425,000 km2 and an average annual discharge of 302 billion m3. Two small deltaic complexes lie within the drowned basin of the estuary itself. Sea level in this region since 7000 cal. Year BP has been stable with possible fluctuations of less than ±0.5m. We present diatom, foraminifera, carbonate stable isotope and bulk organic stable isotope data from a series of surface sediment samples from the eastern part of the Pearl River estuary and inner shelf that show a clear relationship with proximity to freshwater discharge. The identification of such a relationship makes it possible to examine the estuarine sedimentary archive to identify variations in freshwater discharge linked to changes in monsoon intensity. Preliminary, sedimentary, stable isotope and faunal data from a 10m sediment core from the eastern Pearl River estuary indicate changes in freshwater flux associated with EAM.