Susan Kaspari

Date of Award

2007

Level of Access Assigned by Author

Campus-Only Dissertation

Degree Name

Doctor of Philosophy (PhD)

Department

Earth Sciences

Advisor

Paul A. Mayewski

Second Committee Member

Kirk Maasch

Third Committee Member

Karl Kreutz

Abstract

Recent and projected climate change emphasizes the need to understand how the climate system varies naturally. Understanding Asian climate is of particular interest because variations in Asian climate can have large-scale effects on global climate. A 108-m Mt. Everest ice core record is used to investigate late Holocene Asian climate and environmental variability. The ice core was analyzed for trace and major elements, major ions and stable isotopes. A decrease in marine and increase in continental air masses is related to a reduction in northward incursions of the summer South Asian monsoon since ~1400. Other proxy records from lower sites south of the Himalayas indicate strengthening of the monsoon since this time. These regional differences reflect a southward shift in the mean summer position of the monsoon trough since ~1400, synchronous with a reduction in solar irradiance and the onset of the Little Ice Age. The Everest snow accumulation rate decreased from the 1500s to the mid 1800s, increased to 1970, and subsequently decreased to present. Comparison with six other records from the Himalayas and the Tibetan Plateau shows that the changes in accumulation at Mt. Everest are broadly consistent with a regional pattern, suggesting that there may be an overarching mechanism controlling precipitation and mass balance over this area. The trace element record spanning the period 1650-2002 indicates that Bi, U and Cs concentrations and enrichment factors (EF) have increased since the ~ 1950s, and S and Ca concentrations and EFs have increased since the late 1980s. Likely sources for the recent enrichment of these elements include mining, refinement and end uses for Bi, mining and refinement for U and Cs, and land use and environmental change for S and Ca. The Everest trace element dust record provides a proxy of regional variations in atmospheric dust loading. The dominant sources of dust are the Arabian Peninsula, Thar Desert, and northern Sahara. Atmospheric dust loading is linked to soil moisture, temperature, and wind strength. There are periods of high dust concentrations throughout the 350-year Mt. Everest dust record, however there are more frequent periods of high dust concentrations since the early 1800s.

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