Population growth in the Pacific Northwest has led to increased demand for water resources. Current understanding of the natural cycle of moisture availability is limited, however, by the short duration for which instrumental climate data are available. Here, a detailed paleoenvironmental study from Castor Lake in north-central Washington State is presented to examine the frequency, duration, and magnitude of droughts, lake system dynamics, and other climate events during the past ~16,000 years. The combined use of stable isotope measurements of endogenic carbonate and organic sediment with trace element analysis and standard sedimentological methodologies provides a more coherent basis for understanding environmental change through this period than would be possible through the application of a single technique. Results show that the region was significantly affected by the Younger Dryas cold reversal between approximately 12,500 cal yr BP and 11,500 cal yr BP. The period from approximately 8,200 cal yr BP to 5,900 cal yr BP contains evidence for prolonged aridity, as lake-levels declined and water column stratification broke down. The period spanning the last ~6,000 years is characterized by relative climate stability, but the highly resolved sediment proxy data for this interval reveal several drought events larger than anything experienced in the historic record, with some episodes persisting well over a century. Furthermore, the past fifty-years appear to be anomalously wet in the context of the long-term record obtained from Castor Lake. Preparation for large drought events may therefore be inadequate because water resource allocation laws were written during this interval. Future large-scale drought events are inevitable, however, given the frequency with which they are observed to occur in the past, and the increasing influence of anthropogenic warming.
| Identifer | oai:union.ndltd.org:PITT/oai:PITTETD:etd-12102004-063021 |
| Date | 02 February 2005 |
| Creators | Nelson, Daniel B |
| Contributors | Mark Abbott, Michael Rosenmeier, Brian Stewart |
| 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-12102004-063021/ |
| Rights | unrestricted, 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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