Cosmogenic 10Be exposure ages from moraines in the Wallowa Mountains, Oregon, identify two maximal late Pleistocene glaciations at 21.1 ± 0.4 ka and 17.0 ± 0.3 ka and a minor glacial event at 10.2 ± 0.6 ka. Our new high-resolution chronology, integrated with other well-dated glacial records from the western United States, demonstrates substantial differences in the synoptic responses of western U.S. glaciers to climate forcing associated with the global Last Glacial Maximum and subsequent millennial-scale events originating in the North Atlantic region. These variable synoptic glacier responses identify large changes in the relative contributions of regional to global controls on the climate of the western United States that accompanied the deglaciation.

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