Doctoral Dissertation Research in Geography and Regional Science

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Paleolakes in closed basins are sensitive indicators of past climatic variations. The chronology of the fluctuations in the level of a particular lake can provide evidence of changes in local climate, while basin-wide variations reveals past changes in the large-scale circulation of the atmosphere. One hypothesis resulting from lake studies states that latitudinal shifts in the jet stream and associated surface weather systems, resulting from decay of the continental ice sheet, affected the timing of high stands of closed basin lakes during the late Pleistocene. This project will develop lake-level chronologies during a critical interval of the late Quaternary period for three basins in eastern Oregon. These chronologies will be used to test hypotheses concerning atmospheric circulation controls of regional climatic change. Chronologies will be determined from radiocarbon dates on samples collected from shoreline sediments. A physically based evaporation model and a water balance model will be used to estimate the range of climatic conditions consistent with a specific lake level. The resulting climate scenarios will be employed in a test of the hypothesis that high lake stands were governed by the mean seasonal positions of the jet stream over the western United States. This research will contribute to the regional geomorphology of a region in need of additional study, and it will further our understanding of the mechanisms that control regional climate changes, and thus the responses of hydrological systems.