Date of Award

Spring 1993

Project Type

Dissertation

Program or Major

Earth Sciences

Degree Name

Doctor of Philosophy

First Advisor

Paul Mayewski

Abstract

Central Asia represents one of the largest voids with respect to our understanding of geochemical cycles in the continental troposphere and hydrosphere. Fortunately, the vast extent of glaciers in central Asia provide several high elevation ($>$5000 m) locations from which to recover glaciochemical records, and thereby furnish a unique window through which to study biogeochemical cycles in the mid- to upper-troposphere.

Snow and ice samples collected from nine glacier basins spread throughout the mountains of central Asia were analyzed for their major ion and particle content. Aerosol samples collected from four sites in central Asia were analyzed for their water soluble major ion chemistry. The data are used to characterize the spatial distribution of major ion, particle and snow accumulation in central Asia.

Tropospheric aerosols from the southeastern Tibetan Plateau show chemical compositions and concentrations that are comparable to previously reported measurements in the remote troposphere. The general composition and spatial pattern in summer snow chemistry is similar to that for aerosols.

The spatial distribution of major ion and particle content of central Asian snow is controlled primarily by the influx of dust derived from the arid and semi-arid regions of Asia. Glaciers in the northern and western regions of the Tibetan Plateau, which are surrounded by large source regions for mineral aerosol, show elevated levels of major ions and particles. Glaciers in the south-eastern Tibetan Plateau show lower levels of major ions and particles due to longer transport distances from mineral aerosol source regions in western China. Glaciers in the Karakoram and western Himalaya show high annual fluxes of major ions and particles derived from sources to the west and south. Snow from the southern slopes of the eastern Himalaya snows very low concentrations and annual fluxes of major ions and particles.

High elevation mountain sites in the Himalaya, Karakoram and south-eastern Tibetan Plateau preserve glaciochemical records of regional to hemispheric significance and provide isolated platforms above the planetary boundary layer from which to investigate the composition of the remote continental troposphere. Glaciers in these regions are the ones most likely to contain longer-term glaciochemical records which detail annual to century scale variation in the strength of the Asian monsoon and long-range transport of Asian dust.

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