Interpreting temporal patterns in the late Quaternary dust flux from Asia to the North Pacific
详细信息 查看全文
文摘
A comparative study of the literature on the late Quaternary accumulation of aeolian dust in China, Japan and the Pacific Ocean shows three different temporal patterns of dust signals. The main dust sources in Asia, the deserts and desert margins, contain large amounts of wind-suspensible allochthonous material. Commonly, an increase in dust accumulation is taken as an indicator of increased aridity in the interior of Asia. Differences among the signals of Asian desert dust accumulation in different depositional areas indicate that this interpretation requires critical evaluation. The dust supply of the desert regions was maximal during the Pleistocene Glacial maxima. The widespread assumption that these stages were the most arid periods is not necessarily valid. Additional factors likely to lead to temporal and regional differences in dust accumulation are (1)eustatic sea level changes associated with changes in the amount of exposed shelf material and changes in the extent of sea ice affecting atmospheric changes; (2)the frequency of meteorological situations allowing long range dust transport; (3)the strength of the dust transporting winds; (4)changes in the wet deposition rate; and (5)the presence of a dust-trapping vegetation cover. Temporal variations in dustiness in different depositional areas are the result of specific combinations of these factors. Simplified assumptions concerning the reasons for dust variability may lead to incomplete or even erroneous palaeoecological conclusions.