Dr. Ed Brook of Oregon State University will give a talk at Speakers Club entitled "Greenhouse gas dynamics at the end of the last ice age:  new views from the WAIS Divide ice core and Taylor Glacier, Antarctica."

Abstract

The repeated transitions from cold glacial to warm interglacial states during the late Quaternary is in part due to positive feedbacks on biogeochemical cycles that cause changes in levels of greenhouse gases in the earth’s atmosphere.  Multiple mechanisms control these changes and understanding them is a major goal of paleoclimatology.  This talk discusses recent work from our laboratory and collaborators on constructing highly detailed records of methane, carbon dioxide, and nitrous oxide concentrations and isotopic compositions across the last glacial termination and in the last glacial period, using novel and traditional methods.   Findings of interest include:

1. Extremely well constrained, tight coupling between Antarctic temperature and CO₂ during the last deglaciation. 
2. Abrupt changes in carbon dioxide during the last deglaciation that appear to be related to various flavors of abrupt change elsewhere in the world and seem to require multiple mechanisms for abrupt CO₂ changes.
3. Small but significant shifts in methane concentrations during cold stadial periods of the last ice age which we propose are signatures of the impact of large ice rafting events on the tropical hydrologic cycle, but also precisely correspond to times of abrupt changes in CO₂, perhaps indicating a link to southern ocean carbon cycle.
4. Isotopic tracing of changes in nitrous oxide across the last glacial-interglacial transition which indicates that both the ocean and terrestrial nitrogen cycle must be involved in the glacial-interglacial increase.