This dissertation concentrates on the controlling factors on the instability of the Laurentide Ice Sheet (LIS) and their effects on abrupt climate change. Northern Hemisphere climate fluctuated abruptly during the last deglaciation possibly related to variability in Atlantic meridional overturning circulation (AMOC) and reduced aerial extent of the LIS. Reductions...
This thesis presents the results of an investigation into the interactions between the present-day South Cascade Glacier and the former Mauna Kea ice cap at short (annual to centennial) and long (millennial and multimillennial) time scales. To quantify the response of South Cascade Glacier to atmospheric conditions, a surface energy...
A stalagmite (sample OCNM8-02A) collected from Oregon Caves National Monument (OCNM) was sampled for stable isotope ratios in order to develop a record of Pacific Northwest climate history. Nine U-series dates indicate that the record spans the time period - 13.5 - 9.5 ka. The stalagmite growth rate varied from...
This dissertation focuses on the role of ice sheets in the transition during the middle Pleistocene (-1.2 Ma) from 41-kyr glacial cycles to 100-kyr glacial cycles. This research evaluates the hypothesis that the middle Pleistocene transition (MPT) was related to the glacial erosion of a regolith mantle and the subsequent...
This dissertation presents the results of three studies that assessed climate variability on short and long timescales in western United States. The growth of carbonate formations in caves (speleothems) is used to infer the timing and amplitude of past climate variability. We first assess the controls on speleothem growth for...
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PeterU. Clark
This dissertation presents the results of three studies that assessed
A change to a warmer, drier climate beginning as early as 1900 was responsible
for triggering a dramatic, rapid retreat of Collier Glacier, Oregon, between 1924 and
1940. Although there was a dramatic decrease in precipitation contemporaneous with this observed "step-function" response of mass loss, it is unclear if climate...
A sequence of glaciation based on relative dating parameters was established
in each of nine mountain ranges located along a northwest to southeast transect
through the northern Great Basin. Each sequence consists of two or three drift units.
Degree of weathering suggests that the younger drift unit in a two-fold...
This dissertation presents the results of statistical analyses of large climate datasets from two time intervals – the 20th century instrumental record and the proxy record of the last deglaciation – in order to understand the forcings and mechanisms of past climate variability.
A longstanding question in climate dynamics concerns...
This dissertation presents results from three studies that address major scientific questions in glacial geology and paleoclimatology for the late Pleistocene and Holocene using relatively new geochemical and statistical techniques. Each of the studies attempts to answer a longstanding question in the respective field using geochemical or statistical methods that...