Date of Award

2003

Document Type

Dissertation

Degree Name

Doctor of Philosophy (PhD)

Department

Geology

First Advisor

Linsley, Braddock K.

Abstract

Oxygen and carbon isotopic measurements of the total inorganic carbon (TIC) fraction of sediments from Walker Lake (Nevada, USA) were completed at a decadal-scale resolution spanning the last ∼3000 years. On the basis of radiocarbon dating of the total organic fraction of cored sediments, the late Holocene isotope record recorded a relatively dry climate in Period LH-1 (1000 BC to AD 800), a relatively wet climate punctuated by a few severe droughts in Period LH-2 (AD 800 to 1900), and an anthropogenical perturbation era (L14-h: 1900–2000). Relative high accumulation rates in Period LH-2 (AD 800 to 1900) provided detailed information on climatic and hydrologic variability in this region. Coupled with the tree-ring-based Sacramento River flow record, the radiocarbon-based age model was refined for the interval of AD 800 through 1900. A high-resolution (3.5 year per sample) TIC δ18O record spanning the last 1200 years was generated to reflect fluctuations in winter snowfall of the Sierra Nevada. This TIC δ18O record shows two prolonged droughts that occurred during the Medieval Warm Epoch, which are chronologically well consistent with previous findings (STINF, 1994). Time series analyses on the TIC δ18O and the Sacramento River flow records reveal that interdecadal and centennial modes of climate variability persisted over the last millennium. PDO-like interdecadal oscillations that centered in the periods of 50–90 yr were almost in phase with thermal fluctuations in ocean climate of the California Current, suggesting that indedacadal climate oscillations in the Sierra Nevada were intimately linked with the Pacific dynamics. The underlying centennial to multicentennial variability corresponding to the Medieval Warm Epoch and the Little Ice Age comprise the major share of total variance. In addition, the TIC δ18O record of Walker Lake is visually well correlated with the polar ice-core-based cosmogenic nuclide production and the Rice Lake Mg/Ca records. This suggests that at least some centennial oscillations in winter precipitation of the Sierra Nevada were associated with solar activity over the last millennium.

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