title: Reassessment of the Upper Fremont Glacier Ice-Core Chronologies by Synchronizing of Ice-Core-Water Isotopes to a Nearby Tree-Ring Chronology.
abstract: The Upper Fremont Glacier (UFG), Wyoming, is one of the few continental glaciers in the contiguous United States known to preserve environmental and climate records spanning recent centuries. A pair of ice cores taken from UFG have been studied extensively to document changes in climate and industrial pollution (most notably, mid-19th century increases in mercury pollution). Fundamental to these studies is the chronology used to map ice-core depth to age. Here, we present a revised chronology for the UFG ice cores based on new measurements and using a novel dating approach of synchronizing continuous water isotope measurements to a nearby tree-ring chronology. While consistent with the few unambiguous age controls underpinning the previous UFG chronologies, the new interpretation suggests a very different time scale for the UFG cores with changes of up to 80 years. Mercury increases previously associated with the mid-19th century Gold Rush now coincide with early-20th century industrial emissions, aligning the UFG record with other North American mercury records from ice and lake sediment cores. Additionally, new UFG records of industrial pollutants parallel changes documented in ice cores from southern Greenland, further validating the new UFG chronologies while documenting the extent of late 19th and early 20th century pollution in remote North America.
authors.affiliation: Desert Research Institute, Division of Hydrologic Sciences , Reno, Nevada 89512, United States.
authors.forename: Nathan
authors.identifier: 0000-0002-1117-1046
authors.initials: N
authors.lastname: Chellman
authors.affiliation: Desert Research Institute, Division of Hydrologic Sciences , Reno, Nevada 89512, United States.
authors.forename: Joseph R
authors.initials: JR
authors.lastname: McConnell
authors.affiliation: Desert Research Institute, Division of Hydrologic Sciences , Reno, Nevada 89512, United States.
authors.forename: Monica
authors.initials: M
authors.lastname: Arienzo
authors.affiliation: U.S. Geological Survey, Northern Rocky Mountain Science Center , Bozeman, Montana 59715, United States.
authors.forename: Gregory T
authors.identifier: 0000-0002-6014-1425
authors.initials: GT
authors.lastname: Pederson
authors.affiliation: Department of Earth System Science, University of California , Irvine, California 92697, United States.
authors.forename: Sarah M
authors.initials: SM
authors.lastname: Aarons
authors.forename: Adam
authors.initials: A
authors.lastname: Csank
mesh_terms: D046448:Ice Cover; D007554:Isotopes; D008628:Mercury; D014197:Trees; D014867:Water
chemical_list: D007554:Isotopes; D014867:Water; D008628:Mercury