Water resources in the American west are under mounting stress due to increasing demand, receding glaciers, and diminishing winter snowpack amounts. By understanding past aridity patterns, we can improve the ability of global climate models to predict regional hydroclimatic conditions in the coming decades and centuries. Such forecasting is critical to the development of sound water allocation policies. To produce accurate forecasts, global climate models rely on paleo-proxy evidence to constrain climate parameters that govern, for example, important potential changes in the El Niño Southern Oscillation and its associated impacts on extratropical precipitation and drought patterns in response to future anthropogenic climate forcing. Lake sediment oxygen isotope records are one such form of paleo-proxy evidence, providing valuable information about past climatic conditions on time scales ranging from years to millennia. Here a numerical lake-catchment model defined by a system of twelve ordinary differential equations is developed and used to describe the physical processes controlling lake-catchment hydrology and oxygen isotope dynamics. This model is applied to Castor Lake and Scanlon Lake, central Washington, and used to conduct simulations designed to characterize lake hydrologic and isotopic responses to mean state and stochastic hydroclimatic variability. Ultimately, the Castor Lake sediment oxygen isotope record is interpreted using an ensemble of Monte Carlo lake model simulations to produce a probabilistic, quantitative reconstruction of precipitation amounts over the past 1500 years. This reconstruction indicates that the Medieval Climate Anomaly (MCA) (9501250 BP) was a relatively wet period and that the Little Ice Age (LIA) (14501850 BP) was relatively dry, suggesting that the MCA was characterized by a La Niña like state of the tropical Pacific and the LIA was characterized by El Niño like conditions. These results are the first quantitative, probabilistic estimate of paleo-precipitation using lake sediment oxygen isotope records from the interior Pacific Northwest, and will provide a resource for the parameterization of climate models designed to investigate future Pacific Ocean responses to anthropogenic forcing and the associated influence on aridity patterns in the American west.
| Identifer | oai:union.ndltd.org:PITT/oai:PITTETD:etd-04212011-202522 |
| Date | 30 June 2011 |
| Creators | Steinman, Byron Anthony |
| Contributors | Michael F. Rosenmeier, Mark B. Abbott, Daniel J. Bain, William Harbert, Stacey Levine |
| Publisher | University of Pittsburgh |
| Source Sets | University of Pittsburgh |
| Language | English |
| Detected Language | English |
| Type | text |
| Format | application/pdf |
| Source | http://etd.library.pitt.edu/ETD/available/etd-04212011-202522/ |
| Rights | restricted, I hereby certify that, if appropriate, I have obtained and attached hereto a written permission statement from the owner(s) of each third party copyrighted matter to be included in my thesis, dissertation, or project report, allowing distribution as specified below. I certify that the version I submitted is the same as that approved by my advisory committee. I hereby grant to University of Pittsburgh or its agents the non-exclusive license to archive and make accessible, under the conditions specified below, my thesis, dissertation, or project report in whole or in part in all forms of media, now or hereafter known. I retain all other ownership rights to the copyright of the thesis, dissertation or project report. I also retain the right to use in future works (such as articles or books) all or part of this thesis, dissertation, or project report. |
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