Millennial-scale Holocene climate variability in the NW China drylands and links to the tropical Pacific and the North Atlantic

A loess-paleosol sequence and a lake sediment record from the central Hexi Corridor in the drylands of NW China show patterns of persistent millennial- to centennial-scale climate variability during the Holocene epoch, which can be well correlated with abrupt climatic events reported from the North Atlantic and the Asian monsoon-dominated regimes. Our results show that the drylands in NW China might have been regulated both by the westerlies and by the East Asian summer monsoon (EASM) in a roughly synchronous manner. It seems that cold-dry intervals in the central Hexi Corridor may generally correspond to cooling phases in high latitudes of the Northern Hemisphere, and that cold/warm-wet intervals largely correlate with relatively warm phases in northern high latitudes. A candidate mechanism involving NAO/AO and ENSO dynamics is tentatively proposed to account for this synchroneity. Climatic patterns may be spatially different in the NW China drylands in response to the changing predominant control of either the westerlies or the EASM, depending on the contrast of their relative strengths. Glacier meltwater discharges associated with alpine warming may be partly responsible, at least for the two records discussed in this paper, for such spatial heterogeneity of climatic changes during the Holocene. More work is needed to evaluate the individual roles and combined impacts of the EASM, the westerlies and alpine glacier meltwater regulation on the NW China dryland dynamics. (c) 2005 Elsevier B.V. All rights reserved.