Abstract

Glaciers are intrinsically linked to climate, and given the sensitivity of small alpine glaciers to climate change, accurate and precise chronologies of their fluctuations are important in elucidating both the temporal and spatial structure of climate variability. Despite nearly a century of research, the timing of latest Pleistocene and Holocene alpine glaciation in much of western North America remains poorly constrained. I will present _{125 10Be ages from} 20 cirque moraines in 10 mountain ranges across western North America that were previously interpreted as mid- to late Holocene in age. Our new 10Be glacial chronology indicates that these moraines were deposited during the latest Pleistocene to earliest Holocene, requiring a refined interpretation of Holocene glacial activity in western North America and the associated climate forcing. Although alpine glaciers may have continued to fluctuate during the Holocene, they never advanced beyond their Little Ice Age maximum limit. Instead, cirque glacier activity in western North America has followed in near step with late Pleistocene high and mid latitude climate with alpine glaciers retreating to high altitude cirques early during the last deglaciation.