Eolian dust dispersal patterns since the last glacial period in eastern Central Asia: insights from a loess-paleosol sequence in the Ili Basin

Abstract

Abstract. The extensive loess deposits of the Eurasian midlatitudes provide important terrestrial archives of Quaternary climatic change. As yet, however, loess records in Central Asia are poorly understood. Here we investigate the grain size and magnetic characteristics of loess from the Nilka (NLK) section in the Ili Basin of eastern Central Asia. Weak pedogenesis suggested by frequency-dependent magnetic susceptibility (χ fd %) and magnetic susceptibility (MS) peaks in primary loess suggest that MS is more strongly influenced by allogenetic magnetic minerals than pedogenesis, and may therefore be used to indicate wind strength. This is supported by the close correlation between variations in MS and proportions of the sand-sized fraction. To further explore the temporal variability in dust transport patterns, we identified three grain size end-members (EM1, mode size 47.5 µm; EM2, 33.6 µm; EM3, 18.9 µm) which represent distinct aerodynamic environments. EM1 and EM2 are inferred to represent grain size fractions transported from proximal sources in short-term, near-surface suspension during dust outbreaks. EM3 appears to represent a continuous background dust fraction under non-dust storm conditions. Of the three end-members, EM1 is most likely the most sensitive recorder of wind strength. We compare our EM1 proportions with mean grain size from the Jingyuan section in the Chinese loess plateau, and assess these in the context of modern and Holocene climate data. Our research suggests that the Siberian High pressure system is the dominant influence on wind dynamics, resulting in loess deposition in the eastern Ili Basin. Six millennial-scale cooling (Heinrich) events can be identified in the NLK loess records. Our grain size data support the hypothesis that the Siberian High acts as teleconnection between the climatic systems of the North Atlantic and East Asia in the high northern latitudes, but not for the mid-latitude westerlies.

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

“…The pronouncedly ameliorative environmental conditions shortened dust season, noticeably reducing dust storm frequency. However, background dust sedimentation under non‐dust storm conditions was continuous throughout time, which significantly led to higher proportions of background dust fraction (Li, Song, Fitzsimmons, Chang, et al, ). Against this background, the capacity of the land surface to efficiently capture dust was responsible for the higher early‐MIS3 MARs, as discussed above.…”

“…Interestingly, the relatively higher MARs recorded in the NLK and Jingyuan sections during early MIS3 lack the counterparts in Greenland and the North Pacific (Figure ). Grain sizes of particles in these two loess sections get minima in early MIS3 (Li, Song, Fitzsimmons, Chang, et al, ; Sun, Wang, et al, ), suggesting the weaker SH and the existence of persistent background dust contributions from relatively distant sources. The lifetime of atmospheric fine particles is primarily constrained by wet deposition (Lambert et al, ).…”

The relationship between environmental factors and magnetic susceptibility in the Ili loess, Tianshan Mountains, Central Asia

“…The relationships between the different grain size fractions and the MS in the Nilka (NLK) section which is located in the eastern Ili Basin, also indicated that the dominant contribution of coarse particles to the MS (Y. Li, Song, Fitzsimmons, et al, 2017). Thus, the grain size of magnetic properties is a research item in Xinjiang loess.…”

“…Recently, Zan et al () evaluated the relative contributions of pedogenic and detrital components in a loess‐paleosol sequence from the northern slope of the North Tianshan Mountains, Ili Valley, and the northern slope of the West Kunlun Mountains, and the results showed that the contribution of pedogenically produced superparamagnetic (SP) and stable single‐domain (SD) magnetic particles to the bulk magnetic properties is very limited. The relationships between the different grain size fractions and the MS in the Nilka (NLK) section which is located in the eastern Ili Basin, also indicated that the dominant contribution of coarse particles to the MS (Y. Li, Song, Fitzsimmons, et al, ). Thus, the grain size of magnetic properties is a research item in Xinjiang loess.…”

Central Asian Modulation of Northern Hemisphere Moisture Transfer Over the Late Cenozoic

“…This aeolian dust has been transported by air masses associated with the major climate subsystems of the region, chiefly the westerlies 17 , with additional contributions from northerly transport or local katabatic winds 12,18 . Despite the potential of its widespread aeolian deposits 19 to record palaeoclimatic information [20][21][22][23][24] , paleoclimate datasets generated for ACA thus far are either coarse in timescale 17 or focus on recent, short-term intervals insufficient to inform us about long-term feedbacks 13,25 .…”