Aeolian dust transport, cycle and influences in high-elevation cryosphere of the Tibetan Plateau region: New evidences from alpine snow and ice

Abstract

Aeolian dust has a great influence on mountain hydrology, climate, and biogeochemical cycles. Dust deposited on glaciers and snowpack of the high alpine mountains in Tibetan Plateau (TP) and its surrounding regions can provide a unique method of determining the high-elevation transport and deposition of Asian dust in the middle and upper troposphere. Long-range-transported (LRT) Asian dust is often transmitted through the high troposphere, thus studies on dust deposition in the high-elevation cryosphere can reflect the LRT information of aeolian dust, and provide an unparalleled record to understand the regional climate and environment change in the “Third Pole” region. This paper comprehensively reviews the current status of the major factors that determine aeolian dust transport, settling, and cycling, and the key components of this dust cycles in high-elevation cryosphere regions, revealed by glacial snowpack and ice-core dust geochemistry recorded in the mountain glacier areas of TP and western China. Research on glacial dust concentrations indicated that much higher amounts of aeolian dust were found to transport and cycle in the high-elevation troposphere over TP and surroundings, compared to other locations of the globe. Dust concentrations and fluxes in high elevation regions of the TP were closely related to the transport distance of the nearby dust sources (e.g. large deserts and Gobi in western China, and arid deserts on the plateau surface). Isotopes tracers (e.g. 87Sr/86Sr, and εHf, εNd) and dust size distributions revealed that aeolian dust transported over TP mainly originated from the arid and semi-arid deserts and surface crust soils on TP; Aeolian dust from the large deserts of central Asia (e.g. the Taklimakan Desert with small ratio) have not been easily transported to the hinterland of TP under the current climatic conditions. An End-Member Mixing Analysis model was also used to calculate the relative contributions of northern hemisphere dust sources to the TP glacier dust sinks. The marked spatial differences in LRT dust sources of TP glaciers were caused by the large-scale atmospheric circulation strength and interactions in the Asian region. In addition, Asian dust has a large influence on the radiative forcing of glacier and snow melt in which the iron oxide composition constitute an important driving factor. Biogeochemical cycles in cryospheric regions were significantly affected by aeolian dust cycles, influencing glacial ecosystems, meltwater geochemistry (e.g. dFe release) and nutrients supply for downstream aquatic ecosystems. Ice core records for the past hundred years revealed a general decreasing trend of dust storm frequency and atmospheric concentration over the TP region. This work provides new insights and perspectives on aeolian dust transport and cycling in high regions of the troposphere and cryosphere of the TP, identifying critical uncertainties and priorities for future research.