Geology and Geophysics
Understanding the causes and impacts of past climate changes is critical to predicting the present and future response of the climate system to global warming. As such, my research investigates the interactions of ice sheets, oceans and the climate system on orbital to centennial time scales. Broadly speaking, my areas of expertise are glacial geology and paleoclimatology. Addressing these research areas, however, has necessitated my development as a geochemist and an oceanographer. My dissertation research at Oregon State University used multiple geochemical proxies and cosmogenic dating techniques to determine the impacts of the deglaciation of the Laurentide Ice Sheet on climate. More specifically, I was able to confirm that continental routing forced the Younger Dyras (13 to 11.5 ka) and 8.2 ka (8.2 to 8.0 ka) cold events due to the retreat of the Laurentide Ice Sheet. Also, I dated the previously unknown final disappearance of the Laurentide Ice Sheet and demonstrated that this ice retreat was extremely rapid. This project established the role of the Laurentide Ice Sheet in delaying the Holocene Thermal Maximum in eastern Canada and in initiating the formation of Labrador deep seawater, as well as its contribution to an abrupt rise in sea level that may have accelerated retreat of the West Antarctic Ice Sheet. I was also involved in a collaborative project addressing the role of subglacial sediment and basal drainage systems in ice sheet motion.
At Woods Hole Oceanographic Institution, I am working with my Postdoctoral Scholar sponsors Delia Oppo (Geology & Geophysics Dept.) and Jeff Donnelly (Geology & Geophysics Dept.) on several projects. 1) I am constructing sea surface salinity time series spanning the last deglaciation (25 to 0 ka) from multiple sites across the North Atlantic to see if there is a relationship between surface water density and variability in Atlantic meridional overturning circulation. 2) I am developing possible geochemical proxies preserved in ocean sediments surrounding the Greenland Ice Sheet to determine the aerial extent (and thus sea level contribution) of this ice sheet during the Holocene (the current interglacial) and earlier interglacials (i.e. MIS 5e and MIS 11). 3) Collaborating with Oppo and Gavin Schmidt at NASA GISS, we are using the state-of-the-art NASA GISS Atmospheric-Oceanic General Circulation Model, ModelE, which tracks oxygen isotopes, to simulate Holocene climate change focusing on the climate effects of the remnant Laurentide Ice Sheet, the forcing behind the 8.2 ka cold event, and the effects of insolation changes on climate through the Holocene.
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