<p> Long-term records of cyclic droughts are valuable for understanding future changes in hydrologic patterns and constraining climate models. A 3,300-year long record of δ<sup>18</sup>O and δ<sup>13</sup>C values from endogenic carbonate from Foy Lake, Montana is used to infer such droughts during the early Holocene. From 10.8 to 9.6 kyr BP, δ<sup>18</sup>O and δ<sup>13</sup>C values are low, indicating a period dominated by a cooler, less evaporative climate. Both records exhibit strong cyclicity in the ~200 yr range, which is inferred to be a solar cycle. A dramatic shift towards a warmer, drier climate occurs after 9.6 kyr BP in a step pattern, dramatic in the δ<sup>13</sup>C record. Warming occurs after the transition. Stochastic cyclicity dominates with weaker, but statistically significant, periodicities ranging from 40-70 yrs. These are believed to be an expression of the Atlantic Multidecadal Oscillation. This larger synoptic climate signal may be important to the overall Pacific Northwest climate. </p>
| Identifer | oai:union.ndltd.org:PROQUEST/oai:pqdtoai.proquest.com:1524897 |
| Date | 12 March 2014 |
| Creators | O'Neil, Deven M. |
| Publisher | California State University, Long Beach |
| Source Sets | ProQuest.com |
| Language | English |
| Detected Language | English |
| Type | thesis |
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