Date of Award

Spring 5-2016

Level of Access Assigned by Author

Open-Access Dissertation

Language

English

Degree Name

Doctor of Philosophy (PhD)

Department

Earth Sciences

Advisor

Paul A. Mayewski

Second Committee Member

Karl Kreutz

Third Committee Member

Kirk Maasch

Additional Committee Members

Vladimir Aizen

Shichang Kang

Abstract

Recent climate change has impacted natural and human systems across the Earth, emphasizing the need for greater understanding of both the existing and changing natural and anthropogenic forcing mechanisms and subsequent responses of the Earth’s climate system. High-resolution, multi-parameter ice core records retrieved and analyzed from two Asian Ice Core Array (AICA) sites, Geladaindong (central Tibetan Plateau) and Inilchek (central Tien Shan) were utilized to reconstruct atmospheric chemical concentrations and composition over the past ~100-500 years, improving the understanding of late Holocene climate and environmental variability in Asia. Both ice cores were analyzed for major and trace elements, major soluble ions, stable water isotopes and radionuclides.

The 147 m Geladaindong record (1477-1982) provides a Ca proxy for atmospheric dust concentrations and westerly wind strength over the Tibetan Plateau. Corresponding declines in zonal wind velocities, and subsequent declines in dust transport, are likely the result of increasing temperatures lowering meridional pressure gradients (i.e. weakening the Siberian High) over large portions of northern Asia. Late twentieth century concentrations suggest the lowest atmospheric dust concentration and the weakest westerly wind strength in the past ~500 years.

The 160 m Inilchek record (1908–1995) established the natural baseline and subsequent anthropogenic increases of Pb, Cd and Cu concentrations during the twentieth century. Element concentrations and enrichment factor trends suggest Soviet industrial and agricultural sources between the 1950s-1980s and dominant Chinese sources during the late 1980s-1990s. Increases in regional mining activities during the 1950s-1970s potentially resulted in enriched mineral dust compositions (e.g. Al, Ti, Mn), suggesting commonly assumed crustal reference species may be biased and potentially underestimate non-crustal contributions at Inilchek. A major soluble ion record from Inilchek revealed dominant dust proxy species (Ca2+) had the highest concentrations during the 1950s-1970s, with subsequent declining decadal trends to the 1990s, likely reflecting regional dust storm activity in central Asia post-1950, that has been associated with coupled atmospheric circulation variability and anthropogenic activities. Excess concentration trends of NO3-, K+, SO42- and Cl- suggest discernable anthropogenic inputs beginning in the 1950s-1970s and peaking until the mid-late 1980s, followed by declines, coinciding with Soviet industrial and agricultural emission records.

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