Methane Isotope Variations Covering the Holocene from the WAIS Divide Core

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Sowers 0944584This award supports a project to better predict how natural CH4 emissions will respond to and force future climate change through a detailed study of the global biogeochemical cycles that control atmospheric CH4 over the past 11,000 years (11kyr), when the Earth's climate has remained relatively close to its current state. During that time, methane concentrations changed significantly. The project involves generating 13C/12C isotopic records of atmospheric CH4 using the core material from the WAIS Divide ice core. The ä13CH4 data from WAIS will be used to construct the first Antarctic atmospheric record covering the Holocene. This record will be compared to our recent Holocene record from the GISP2 ice core from Greenland. The new Antarctic record will provide an important verification of the GISP2 record as well as our first glimpse of the inter-hemispheric ä13CH4 gradient covering the Holocene. Together these records provide important boundary conditions for testing various emission scenarios (time, space and source) that should provide a quantitative basis for assessing the nature of CH4 emissions throughout the Holocene. The intellectual merit of this work relates to the fact that the earth's climate is directly influenced by levels of trace, "greenhouse" gases (carbon dioxide, methane, nitrous oxide, CFC's, and others), and the modern build up of these gases in the atmosphere is a fundamental concern for human society. In terms of broader impacts the proposed work will enhance our understanding of the patterns and causes of methane change throughout the Holocene. This is important for understanding the natural climate system, and in particular, feedbacks between climate and greenhouse gas biogeochemistry. The Holocene CH4 record suggests that the global methane cycle was profoundly influenced by various feedbacks that do not involve large temperature swings. This implies strong feedbacks to a relatively small (and presently unknown) forcing. The proposed work will lead to improved understanding of why methane levels changed throughout the Holocene, providing fundamental information to refine and test global models. It will also contribute to testing the controversial, but important, hypothesis, that humans impacted the atmosphere significantly starting about 5000 years ago. Undergraduate and graduate students will participate in all phases of the research and a special emphasis will be placed on recruiting under represented minority students thru our college based office of educational equity. All data will be archived on appropriate databases per OPP policies.