| Summary: | Methane is a product of biogeochemical processes which respond to changes in climate. The history of atmospheric methane is recorded by ice cores providing insight into past changes in these biogeochemical processes. This dissertation is comprised of three studies which focus on centennial- and millenial-scale variability of methane from ice core records; first these variations are used as a tool to reconstruct the age of ice in an ice core, then, we assess the fidelity which ice cores record atmospheric methane, and finally we investigate how abrupt climate events affected different methane sources. Whether the recession of the West Antarctic Ice Sheet (WAIS) contributed to sea level rise during the deglaciation is an open question (Denton et al., 1989; Clark et al., 2002; Lambeck et al., 2014; Halberstadt et al., 2016). To better constrain the history of WAIS, the Roosevelt Island Climate Evolution (RICE) project drilledan ice core on Roosevelt Island in the East Ross Sea, West Antarctica. In Chapter 2, we establish an age scale for the RICE ice core and discuss initial observations from its climate records. The age scale is developed by matching gas records to the well-dated WAIS Divide ice core, initially by an automated matching routine developed here and then by visual matching for the bottom section of the core, and by modeling the ice age-gas age offset. A continuous age-depth relationship without a temporal hiatus and climate records comparable to other Antarctic ice cores implies that the ice dome persisted as an independent ice feature from WAIS. Additionally, the RICE methane record is the highest resolution record for the Holocene (0-11.7 ka) and clearly captures centennial-scale variability throughout this period; a mode of variability previously used as evidence of human influence on climate in the late Holocene (Ferretti et al., 2005; Houweling et al., 2008; Mitchell et al., 2013). Methane records have been measured from a number of ice cores, with recent records greatly improving precision and ...
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