GSA Annual Meeting in Seattle, Washington, USA - 2017

Paper No. 341-11
Presentation Time: 4:35 PM


CHELLMAN, Nathan J.1, MCCONNELL, Joseph R.2, ARIENZO, Monica M.2, PEDERSON, Greg3, AARONS, S.M.4, CSANK, Adam5 and PATTYN, Frank6, (1)Graduate Program of Hydrologic Sciences, University of Reno, Nevada, Reno, NV 89557; Division of Hydrologic Sciences, Desert Research Institute, 2215 Raggio Parkway, Reno, NV 89512, (2)Division of Hydrologic Sciences, Desert Research Institute, 2215 Raggio Parkway, Reno, NV 89512, (3)Northern Rocky Mountain Science Center, USGS, 2327 University Way, Suite 2, Bozeman, MT 59715, (4)Department of Earth System Science, University of California, Irvine, Irvine, CA, (5)Department of Geography, University of Nevada, Reno, Reno, NV, (6)Laboratoire de Glaciologie, Department of Geosciences, Environment and Society, Université libre de Bruxelles, Brussels,

The Upper Fremont Glacier (UFG), located in the Wind River Range of Wyoming, has been studied extensively to examine interior continental pollution and climate over the past 250 years. Here we present a new chronology for two ice cores recovered from UFG in the 1990s. The new depth-age scale is consistent with the few unambiguous age control points from the original UFG chronologies, but refinement by synchronizing the ice core water isotopes to a nearby tree-ring width index suggests changes of up to 80 years from the original chronology. The significant changes in the dating of these ice cores fundamentally alters previous interpretations of climate and pollution records preserved in the cores. On the new chronology, industrial pollutants parallel trends observed in Arctic ice cores, and mercury increases previously attributed to the mid-19th century Gold Rush are now shifted into the early-20th century, consistent with records from other North American ice and lake sediment cores. Preliminary ice flow modeling indicates glacier and basin geometry are the main controls on the depth-age scale at UFG and that accumulation at UFG has been relatively constant over the past 250 years. Comparisons of the UFG ice core water isotopes to new measurements of cellulose oxygen isotopes from nearby trees will provide a multi-proxy understanding of climate in this region.