From dust to more dust: a paleoceanographic history of the East Asian Monsoon
Anderson, Chloe Hazel
MetadataShow full item record
At present, the East Asian Monsoon (EAM) influences water availability for nearly one third of the global population. The intensity and position of the EAM has varied considerably since its onset, but disagreement still exists related to the precise latitudinal and intensity shifts of the Westerly Jet and associated storm fronts, which mark the northern extent of the monsoon. Paleoclimate research can assist in improved assessment and prediction of EAM intensity, radiative forcing, and biogeochemical cycles in the Japan Sea and North Pacific, especially under the currently changing climate. My research primarily focuses on using major-, trace- and rare earth elements in sediments from International Ocean Drilling Program Expedition 346 in the Japan (Ulleung Basin) and East China Seas (Okinawa Trough) to track variability in the EAM on millennial time scales. Using geochemical and multivariate statistical techniques (Q-Mode Factor analysis and Constrained Least Squares multiple linear regressions), I differentiated compositionally similar terrigenous aluminosilicate materials (continental crust components, eolian dusts, volcanic ash) from these sediment archives. I successfully constructed a robust record of aluminosilicate provenance, which enables more precise determinations of EAM position and intensity than previously possible. Most of my research focused on the interpretation of aluminosilicate records over several different timescales from three sites from Expedition 346. In tandem with this research, I also refined values of the well-known, and widely used, Standard Reference Material (SRM) Hawaiian Volcano Observatory Basalt (BHVO-2). In the Okinawa trough (Sites U1428/U1429), I identified and tracked the increase in flux of five continental crust materials, loesses, and volcanic ashes during glacial cycles, continental shelf exposure, and the migration of paleo-rivers in the last 400 kyr. Additionally, I constructed a 12 Myr record, which identified and quantified the dust fluxes to Ulleung Basin (Site U1430), and emphasized the importance of the Taklimakan and Gobi Deserts as main sources of dust to the Japan Sea and Pacific through the Cenozoic. Collectively, these aluminosilicate flux reconstructions are first to identify multiple specific Asian source regions through the Cenozoic, and highlight the complexity of accurately reconstructing monsoons and other aspects of paleoclimate from sediment in dynamic environments.