Atmospheric Dust Variations in the Ili Basin, Northwest China, During the Last Glacial Period as Revealed by a High Mountain Loess‐Paleosol Sequence

Abstract

Atmospheric dust emission is closely related to conditions in the source area. Typically, loess deposits represent the accumulation of locally derived dust, providing the opportunity to reconstruct past variations in dust emission and hence insights into dust-climate linkages and the underlying mechanisms of dust mobilization, transport, and deposition. As yet, however, information on patterns of dust emission in Central Asia is sparse. Here we present the last glacial sedimentological data of a loess section from the Ili Basin, northwest China. Our results show that the variations in sand-sized fraction can indicate frequencies of occurring strong winds, which was likely driven by the Eurasian ice sheets during Marine Isotope Stage Stage 2 (MIS2) and MIS4 and by the boreal summer insolation during MIS3. The mass accumulation rate (MAR) reflects an integration of sediment availability in the provenance, vegetation cover in the deposition area, and wind regime. The differences of driving factors potentially explain the observed mismatches between variations in grain size and MAR. Comparison of dust fluxes observed in Greenland ice core and the North Pacific deep-sea sediment with the Central/East Asian MAR records supports the idea that the high flux of long-distance export of Asian dust is closely associated with the Siberian High and also influenced by changes in the atmospheric transport efficiency and likely by the source strength.

Formation and evolution of mountainous aeolian sediments in the northern Tibet Plateau and their links to the Asian winter monsoon and westerlies since the Last Glacial Maximum

“…The spatial relation of grain size to latitude implies that there is a thinning trend from north to south in the Qilian Mountains (Figure 2(d), (f), (h), (j)). When a typical sandstorm occurs, the sand component gradually increases with the strengthening wind power, while fine particles gradually decrease (Li et al, 2019), which has been confirmed in wind tunnel experiments (Wang et al, 2018). In arid and semi-arid areas of northwest China, the degree of soil development is low, and magnetic minerals are mainly from dust deposition.…”

Evolution of Near‐Surface Wind Strength in Northeastern Arid Central Asia During the Holocene

“…Moreover, there is no corresponding change in grain size with vegetation change at ∼33.5 ka in the NLK section (Y. Li et al, 2019). This suggests that the variation trend of the grain size of the quartz component is relatively unaffected by humidity changes in the source area.…”

“…A study of the NLK section in the Ili Valley suggested that humid conditions developed during the middle of Marine Isotope Stage (MIS) 3 and that the abundance of sand-sized particles consistently increased at the same time (Y. Li et al, 2019). Moreover, there is no corresponding change in grain size with vegetation change at ∼33.5 ka in the NLK section (Y.…”

“…The Siberian high-pressure system significantly influences the near-surface wind strength in northeastern central Asia (Y. Li et al, 2019;F. Wang, Lang, et al, 2018;F.…”

“…A strong Siberian high-pressure system would result in strong near-surface wind strength in the study area (Y. Li et al, 2019), and thus lead to high value of mean grain size of the quartz component. Therefore, the high value of mean grain size of the quartz component indicates that stronger Siberian high-pressure system and near-surface wind occurred during the early to middle Holocene and that subsequently the Siberian high-pressure system and near-surface wind strength weakened gradually.…”