RUI: Using the Products of Volcano-Ice Interaction to Constrain Paleo-ice Conditions II: Documenting Fluctuations in Continental Ice-sheets

Dickinson College, Carlisle PA

Investigators

Abstract

"This award is funded under the American Recovery and Reinvestment Act of 2009 (Public Law 111-5)." One of the greatest challenges for modern science is trying to predict the future implications of global climate change. While significant progress is being made towards understanding present-day controls on climate, in order to predict the direction of future climate change we must understand the Earth's climate cycle during the recent geological past. Information collected from the Earth's oceans and ice samples from Greenland and Antarctic ice help to understand changes in local and global temperature. However, much less information is available about how past temperature changes have affected snowfall and the formation of glaciers in North America. One of the most important records of continental climate in western North America is preserved within deposits formed by volcanic eruptions that occurred beneath snow and ice in northwestern British Columbia, Canada. This project will attempt to determine the eruption dates for several of those volcanoes in order to improve the on-land record of how continental climate, in northern latitudes, has responded to past changes in global temperature. Many of these volcanoes record the presence of ice during periods of the recent geological past when global temperatures were much cooler than today. Other volcanic deposits appear to have formed when no large ice masses were present; these deposits are also important as they document periods when continental climate may have been relatively warmer. Comparison of the continental record to the oceanic record will help scientists better make integrated global climate models. The goal of this project is to conduct a comprehensive field, geochemical and geochronological study of 34 basaltic glaciovolcanic and subaerial centers in the Tuya-Kawdy area in northern British Columbia, Canada, to determine if fluctuations in continental ice-sheet volumes affected the eruption frequencies and compositions of Pleistocene volcanism. The results of the proposed research will have important implications for two linked but separate scientific areas: (1) magma-ice dynamics and (2) Pleistocene paleoclimate. The proposed research will provide a detailed record of the presence, position and minimum thickness of the northern part of the Cordilleran ice sheet (CIS) throughout the Pleistocene. Glaciovolcanic deposits can survive erosion by multiple ice advances, and consequently are one of the few means of documenting the former presence of ice-bodies older than the Last Glacial Maximum (~30-20 ka); such deposits are crucial for investigating long-term responses of volcanism to ice fluctuations. Preliminary work in the Tuya-Kawdy area has already documented glaciovolcanic eruptions at ~700 ka and ~1.8 Ma. An expanded database will significantly improve our ability to understand how changes in Pleistocene climate, as recorded by marine proxies, correlate with the presence of continental ice sheets in northwestern North America. This study will be the most comprehensive to use glaciovolcanism to document the presence/absence of a major ice sheet in northwestern North America and attempt to correlate its fluctuations with the marine proxy ice-volume record. The results will give important constraints for understanding the terrestrial response to changes in ocean temperatures, ice sheet dynamics, biodiversity in deglaciated landscapes, and Pleistocene erosion rates.