Atmospheric Dynamics Patterns in Southern Central Asia Since 800 ka Revealed by Loess‐Paleosol Sequences in Tajikistan

Abstract

The atmospheric mechanisms responsible for the loess grain‐size variations in central Asia are less clear, and an increasing number of studies have found that the coarse‐grained component is likely supplied by the surface circulation rather than by the westerlies (westerlies circulation). In this study, we attempt to determine the atmospheric dynamics patterns in the Afghan‐Tajik Basin during the past 800 kyr, based on the coarse grain‐size fraction of loess, combined with a study of modern dust transport processes. We suggest that the coarse grain‐size fraction can be used to indicate the intensity of near‐surface winds, while on glacial‐interglacial time scales, the variations of loess grain size in Tajikistan are dominated by Northern Hemisphere ice volume via its effect on the strength of the Siberian High. In addition, we suggest that atmospheric greenhouse gases concentration affected the loess grain size during interglacials via their influence on the temperature of southern high latitudes.

Insolation and CO2 Impacts on the Spatial Differences of the MIS‐9 and MIS‐11 Climate Between Monsoonal China and Central Asia

“…MIS-11 is relatively dry. The most humid environment during MIS-9 is also verified by other soil weathering proxies (e.g., lightness and other magnetic parameters; Jia et al, 2018;Lu et al, 2020).…”

“…The climate of the region is characterized by hot‐dry summers and cool‐humid winters. The uppermost 125 m of this section, which includes nine soil complexes and eight loess units, has been investigated in our previous studies (Jia et al., 2018; Lu et al., 2020). The westerlies circulation is the most important factor transporting moisture to this region, and is prevalent in winter and spring; in summer, it is replaced by the Subtropical High reduces water vapor transport from the Mediterranean, Black Sea, and Caspian Sea to southern central Asia (Dai et al., 2006; Karger et al., 2017; Sun et al., 2008).…”

Local mineral dust transported by varying wind intensities forms the main substrate for loess in Kashmir

“…The thick deposits of loess from the last glacial cycle in Kashmir (e.g. > 8, ∼ 10, ∼ 18 m for the last glacialinterglacial cycle; Dar and Zeeden, 2020;Meenakshi et al, 2018;Shah et al, 2021; and references in these) support this interpretation, as it appears unlikely that such substantial sediment masses were transported over the > 2000 m high mountain ranges surrounding Kashmir.…”

“…Due to similarities of the stratigraphies of the records under study with parts of a 17 m thick LPSs at Shankerpora, Kashmir (Fig. 1a), temporally placed into the last glacial cycle (Meenakshi et al, 2018), we start from the premise that both studied sections formed during the late last glacial cycle in the interval between oxygen isotope stages (OISs) 4 to 2.…”

Drivers for Asynchronous Patterns of Dust Accumulation in Central and Eastern Asia and in Greenland During the Last Glacial Maximum

“…The proposed CasHKI index captures the pressure gradient between the Caspian Sea High and the Hindu Kush Low, and has been shown to be the main factor affecting dust activity over southwest CA (Li, Song, Kaskaoutis, et al., 2019). Although the mechanisms that control dust activity differ between the northern and southwestern CA, there is a significant correlation between the SH index and CasHKI, which suggests that the SH may have a strong influence on summer dust activity in southwestern CA (Lu et al., 2020). The influence of the SH on dust storm over Central Asia has also been supported by a positive correlation between the interannual variation of dust event frequency in CA with Arctic Oscillation (AO) index, which is usually related to the SH index (Gong et al., 2006; Zhang et al., 2020).…”