Variation of atmospheric dust over the past 100 years recorded by visible dusty layers of the Kuokuosele ice core, western Tibetan Plateau

Abstract

Atmospheric dust plays a significant role on regional and global climate change through modifying the radiative balance via changing solar radion, altering the microphysical precipitation process and so on. However, many uncertainties of their climatic effects exist due to obvious regional distribution and short transportation system. The large desert and semi-desert area of Asia, makes this region as one of most severe global dust sources and effecting globally. Glaciers distributed in the Tibetan Plateau contain substantial dust deposition which privide an opportunity to reconstruct past continental aridity and atmospheric circulation. As microparticles, visible dust layers also show excellent potential on environmental exploration. Additionaly, their visible external appearances benefit researchers acquiring both dating and environmental coding as soon as they get the cores. The Kuokuosele ice core was retrieved in 2012 from the Muztagh Ata Mts. in the eastern Pamir Plateau circumfused by Asian arid regions and deserts. Due to its proximity to the dust sources, the ice core contained clear visible dust layers clearly observed under natural light and floodlight in the cold room by three independent researchers before any sampling process. Two indicators including level ( L VDL) and thickness ratio ( R VDL) of visible dust layers were examined and calculated. Meanwhile, concentrations of Ca2+ and SO42 - were analyzed in order to evaluate the accuracy of observations by naked eyes. The top 52 m ice core was dating to the period of 1900–2012 with ±1 uncertainty via identifying stratigraphic markers of beta activity and counting seasonal cycles of d 18O and dust layers. The current ice core contains 181 visible dust layers and can be classified to five different levels. Moreover, five-year average R VDL spaned the whole era showed a decreasing trend, and illustrated vivid low values in 1900–1915, 1920–1930, 1990–2010 and high values in 1915–1920. The visible dust layers were then compared with Ca2+ and SO42 - records. To begin with, simultaneous veriation was found between L VDL and two ions. Moreover, R VDL in recent decades was positively correlated with observed records of arid areas of central Asia and northern Tibetan Plateau, suggesting that both sources continuously distributing the for dust deposition in this ice core. Therefore, visible dust layers of the Kuokuosele ice core could be seen as credible excellent medium for study of atmospheric dust deposition, and thus provided an unique opportunity to acquire the enviromental information. In Summary, the entire record of thickness ratio of visible dusty layers in the Kuokuosle ice core revealed a decreasing trend of atmospheric dust over the past 100 year, accompanied by an increasing trend of tempreture expressed by ice-core d 18O and a varied precipitation pattern. Increasing precipitation in the possible source area and the local region caused by the strength of Westerlies might be related to this trend, in addition to this, decreasing wind speeds in the past cannot be ignored.