Decoupling of Climatic Drying and Asian Dust Export During the Holocene

摘要

Both paleoclimatic records and models suggest that the dust accumulation in ice cores and marine sediments, which is often regarded as a direct record of changing atmospheric dust loading and used to estimate its climatic impact, is strongly coupled to the aridity of dust source regions. However, the underlying association of this couple has not been tested directly because of the lack of continuous and well-dated independent records of eolian activity in dust source regions. Here we present a high-resolution multiproxy record of the Holocene eolian activity and climate changes from Lake Xiarinur in north China, a major Asian dust source region. Our data, together with the records of Asian dust accumulation in downwind areas, including the North Pacific Ocean and Greenland, suggest a decoupling between long-distant Asian dust export and climatic drying in the Holocene. Although the climate was humid and the eolian activity was weak in the source region during the early Holocene, the dust accumulation in the North Pacific Ocean and Greenland was relatively high. Similarly, while climatic drying and strong eolian activity occurred in north China during the late Holocene, the rate of dust accumulation in the downwind areas was low. The long-distant export of Asian dust is closely correlated with the strength of the Siberian High rather than the westerlies as widely believed before. The rate of dust accumulation in the GISP2 Greenland ice core is comparable in patterns with the intensity of the Siberian High forced eolian activity on both millennial and centennial time scales. Plain Language Summary Scientific grounds: We bring new, uniquely indicative evidence to bear on the dynamics of long-distant Asian dust exports. By uniting the evidences of Holocene aeolain activity and climate changes in north China, dust accumulation in Northwest Pacific Ocean and Greenland ice, the atmospheric circulations dominated Asian dust export, we confirm a central role of the Siberian High in long-range Asian dust export, rather than climate drying and the westerlies as most previous studies suggested. These results have important implications for both accurately estimating aerosol climate forcing and predicting future impact of atmospheric dust concentration changes with climate changes. Popular appeal: Our work also provides important insight into the climatic and environmental impact of anthropogenic aerosols, an important issue of international broad interest. The central role of the atmospheric circulations in long-range Asian dust export, combined with comparisons between the environment with heavy and that without or little human interference in the Holocene, indicate that the anthropogenic activity would contribute little to the long-range Asian dust export without strong atmospheric circulations. Therefore, modern Asian anthropogenic pollutant aerosols would be poorly dispersed from the source regions, otherwise transported across the whole global.