Regional patterns of climate and environmental response in southwestern North America during the pivotal millennia of the end of the Pleistocene epoch, and the relations of that regional pattern to global climate change continue to be nationally and internationally important research topics. The Sierra Nevadas of eastern California are a major climatic and vegetational boundary today, but at the end of the last ice age Great Basin-like vegetation coverered lower slopes on both sides of the southern Sierra Nevada. In this project, the investigator will collect, date, and examine lake-core chronologies from four lakes west of the Sierra crest in eastern Calfornia in order to evaluate two competing hypotheses that explain why the western Sierra was drier and the eastern Sierra was wetter at the end of the last glacial period. The first hypothesis argues that enhanced monsoonal activity was due to greater summer insolation and an enhanced land-sea thermal contrast. The second alternative explains the northern aridity and the southern moistness by a southward displacement of the winter jet stream. The study will illuminate our understanding of the late Quaternary vegetation history of arid North America and the climatic patterns that have influenced it. This knowledge will increase our understanding of processes of climatic and vegetation change and the ways the regional changes relate to global changes.
