The westerlies-dominated area of arid Central Asia is the furthest dust source from the oceans. Located between the European loess sequences to the west and the extensive Chinese Loess Plateau to the east, Central Asia is one of the most significant loess landscapes on earth.
This enables researchers to carry out interregional paleoclimatic investigations along a west-east transect across the entire Eurasian loess belt of the Northern Hemisphere. However, Central Asian loess is still far from intensively investigated, there are few reports of climatic change during the last glacial period in Central Asia, dust formation and climatic forcing mechanisms are yet not systematically understood.
Recently, SONG Yougui from the Institute of Earth Environment (IEE) of the Chinese Academy of Sciences and his collaborators investigated magnetism and sedimentology proxies of loess sections in the Ili Basin, eastern Central Asia, and elucidated environmental dynamics for dust accumulation and paleoclimate change. Their findings were published in Climate of the Past.
The researchers found that magnetic susceptibility (MS) was more strongly influenced by allogenetic magnetic minerals than pedogenesis and might be used to indicate wind strength. To further explore the temporal variability in dust transport patterns, they separated loess grain size distributions based on the hierarchical Bayesian model for end-member modeling analysis.
Three grain size end-members (EM1, mode size 47.5 μm; EM2, 33.6 μm; EM3, 18.9 μm) were generated. These EMs 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.
They selected EM1 as the most sensitive proxy of wind strength. Considering modern and Holocene climate data, they argued that the Siberian High (SH) pressure system was the dominant influence on wind dynamics.
These data supported the transmitting mechanisms hypothesis that the SH acted as teleconnection between the climatic systems of the North Atlantic and East Asia. It provides new evidences for climatic teleconnection between high latitudes in the northern Hemisphere and Chinese Loess Plateau.
This study is of significance for understanding the climatic implications of loess proxies, source tracing of Central Asian dust. Furthermore, six millennial-scale cooling (Heinrich) events were identified from the loess grain size records.
Comparison between EM1 grain size variability and the timing of glacial advances in the Tian Shan; stable oxygen isotope variations from the Greenland ice cores; mean grain size (MGS) record of the Jingyuan loess section from the CLP and U-ratio (15.6–63.4 μm/ 5.61–15.6 μm) of the SE Kazakhstan loess. A five-point running average was performed for the intervals with higher sedimentary rate on EM1 curve (red line). (Image by IEE)
52 Sanlihe Rd., Xicheng District,
Beijing, China (100864)