Preprints
https://doi.org/10.5194/cp-2021-106
https://doi.org/10.5194/cp-2021-106

  10 Sep 2021

10 Sep 2021

Review status: this preprint is currently under review for the journal CP.

Late Pleistocene glacial chronologies and paleoclimate in the northern Rocky Mountains

Brendon Quirk1, Elizabeth Huss2, Benjamin Laabs3, Eric Leonard4, Joseph Licciardi5, Mitchell Plummer6, and Marc Caffee7 Brendon Quirk et al.
  • 1Department of Geology and Geophysics, University of Utah, Salt Lake City, Utah 84112, USA
  • 2Department of Geosciences, State University of New York at Geneseo, Geneseo, NY 14454, USA
  • 3Department of Geosciences, North Dakota State University, Fargo, North Dakota 68102, USA
  • 4Department of Geology, Colorado College, Colorado Springs, Colorado 80903, USA
  • 5Department of Earth Sciences, University of New Hampshire, Durham, New Hampshire 03824, USA
  • 6Idaho National Engineering and Environmental Laboratory, Idaho Falls, Idaho 83415, USA
  • 7Department of Physics, PRIME Lab, Purdue University, West Lafayette, Indiana 47905, USA

Abstract. The geologic record of mountain glaciations is a robust indicator of terrestrial paleoclimate change. During the last glaciation, mountain ranges across the western U.S. hosted glaciers while the Cordilleran and Laurentide ice sheets flowed to the west and east of the continental divide, respectively. Records detailing the chronologies and paleoclimate significance of these ice advances have been developed for many sites across North America. However, relatively few glacial records have been developed for mountain glaciers in the northern Rocky Mountains near ice sheet margins. Here, we report cosmogenic beryllium-10 surface exposure ages and numerical glacier modeling results showing that mountain glaciers in the northern Rockies abandoned terminal moraines after the end of the Last Glacial Maximum around 17–18 ka and could have been sustained by −10 to −8.5 °C temperature depressions relative to modern assuming similar or drier than modern precipitation. Additionally, we present a deglacial chronology from the northern Rocky Mountains that indicates while there is considerable variability in initial moraine abandonment ages across the Rocky Mountains, the pace of subsequent ice retreat through the Lateglacial exhibits some regional coherence. Our results provide insight on potential regional mechanisms driving the initiation of and sustained deglaciation in the western U.S. including rising atmospheric CO2 and ice sheet collapse.

Brendon Quirk et al.

Status: final response (author comments only)

Comment types: AC – author | RC – referee | CC – community | EC – editor | CEC – chief editor | : Report abuse
  • RC1: 'Comment on cp-2021-106', Anonymous Referee #1, 27 Sep 2021
  • RC2: 'Comment on cp-2021-106', Anonymous Referee #2, 21 Oct 2021
  • EC1: 'Comment on cp-2021-106', Claudio Latorre, 08 Nov 2021

Brendon Quirk et al.

Brendon Quirk et al.

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Short summary
Glaciers in the northern Rocky Mountains began retreating 17 to 18 thousand years ago, after the end of the most recent global ice volume maxima. Climate in the region during this time was likely 10 to 8.5 degrees colder and drier or similar to present conditions. Glaciers across the Rockies began retreating at different times but eventually exhibited similar patterns of retreat, suggesting a common mechanism influencing deglaciation.