MODERN EOLIAN DUST DEPOSITION IN CENTRAL-ASIA

Glaciers around the globe provide a unique medium for investigating the temporal and spatial variation of dust deposition. Here we investigate the spatial and seasonal distribution of eolian dust deposition in central Asia through the analysis of concentrations and size distributions of insoluble particles (over the size range 1-22 mum diameter) in snow and ice samples collected from eight glaciers in the mountains of central Asia. The sample locations cover a wide geographic area and fall within 4 distinct landscape/climate zones: the southern slopes of the eastern Himalaya; the Karakoram; south eastern Tibetan Plateau; northern/western Tibetan Plateau. Snow samples from each of the 4 landscape/climatic zone displays distinct dust deposition characteristics which are dependent upon the physiographic location of the sampling site with respect to source regions of dust and atmospheric transport pathways. The southern slopes of the eastern Himalaya show very low particle concentrations and low annual dust deposition. This region is relatively free from the influence of Asian dust. The Karakoram appears to be a major sink for particles less than 2 mum in diameter which have been transported long distances with the westerly jet stream. Glaciers in the south eastern Tibetan Plateau record the influx of dust generated in the arid and semi-arid regions to the west. Glaciers on the northern and western margin of the Tibetan Plateau lie adjacent to vast arid and semi-arid regions of western China and provide dust depostion records mainly of local significance. Our results suggest that high elevation glaciers in the eastern Himalaya, Karakoram and the south eastern Tibetan Plateau are those most likely to provide longer term dust deposition records which reflect regional to hemispheric signals.