High-resolution water isotope records from West Antarctic ice cores: Interpretations of climatic, glaciological, and diffusional processes
PhD: University of Colorado Boulder, 2015.
The polar ice sheets contain a vast archive of geochemical information that can be used to understand Earth’s past climate. One of the primary methods for studying past climate in polar regions is the extraction of ice cores. Depending on the region, some ice cores can be more than 10,000 feet long—prompting the popular nickname “Two-Mile Time Machines”—and can date to over 700,000 years ago. Ice cores are particularly useful for high-resolution laboratory measurements related to past temperature, atmospheric circulation, greenhouse gases, dust distribution, and many other physical processes.
In this dissertation, we present an ultra-high resolution record of water isotopes (a proxy for local temperature and regional atmospheric circulation) from the West Antarctic Ice Sheet (WAIS) ice core. The record was analyzed using laser absorption spectroscopy, consists of over 24 million data points, and extends to 68,000 years before present. It is the highest-resolution and longest continuous ice core climate record ever recovered from Antarctica. A number of analyses are performed, including
- Quantification of diffusional processes.
- Reconstruction of high-frequency decadal and sub-decadal oscillations.
- Analysis of low-frequency millennial-scale oscillations.
The results of the study hold important insight into Antarctic glaciology, the expression of 2-15 year climate variability that often originates as part of the El Niño Southern Oscillation (ENSO), and long-term variability that appears to be partially driven by solar activity. Due to the resolution of the record, we can assess climate change on the order of a presidential term (4 years) or less over most of the last glacial-interglacial cycle—a time period of human evolution and the rise of civilization. More importantly, the results provide context for current and future anthropogenic climate changes by defining natural variability in the past.