Atmospheric dust loadings and their relationship to rapid oscillations of the Asian winter monsoon climate: two 250-kyr loess records

摘要

Similar to records extracted from marine sediments (Paleoceanography 6 (1991) 349; Rev. Geophys. 32 (1994) 159) and ice cores (Nature 399 (1999) 429), estimates of dust inputs to the Chinese Loess Plateau indicate that the dust fluxes during periods of extensive glaciation were higher than those in interglacial times (Catena 18 (1991) 125; Quat. Res. 41 (1994) 35). Prior studies (Nature 375 (1995) 305; Quat. Sci. Rev. 18 (1999) 811) indicating that millennial-scale oscillations of Asian dust occurred during glacial times have raised questions about the conditions that govern the generation and transport of dust, particularly those operating during the winter monsoon. We present here atmospheric dust loadings reconstructed from two central Loess Plateau sections; these extended our present-day observations to cover the last two glacial cycles and thus provided a unique perspective on the relationships between Asian dust and climate. The reconstructed loadings indicate that higher and more variable dust concentrations occurred during glacials compared with interglacials, and the high dust loadings frequently preceded decreases in winter sea surface temperature of the North Pacific Ocean during glacials. A mechanism was proposed to explain how the thermal contrasts between the Eurasian continent and the surrounding oceans induced by the high dust loadings could either trigger or modulate millennial-scale variations in the winter monsoon climate and thus rapid transitions of glacial dust loadings.