Abrupt warming and alpine glacial retreat through the last deglaciation in Alaska interrupted by modest Northern Hemisphere cooling.

Alpine glacier-based temperature reconstructions spanning the last deglaciation provide critical constraints on local-to-regional climate change and have been reported from several formerly glaciated regions around the world yet remain sparse from high northern latitude regions. Using newly and previously 10Be-dated moraines, we report paleo-glacier equilibrium line altitudes (ELA) for 15 time slices spanning the Last Glacial Maximum (LGM) to the Little Ice Age (LIA) for a valley in the western Alaska Range. We translate our ELA reconstructions into a proxy for summer temperature by applying a dry adiabatic lapse rate at each reconstructed ELA relative to the outermost LIA moraine. We observe ~4°C warming through the last deglaciation at our site that took place in two steps following initial gradual warming: ~1.5°C abrupt warming at 16 ka, ~2 kyr after global CO2 rise, and ~2° C warming at ~15 ka, near the start of the Bølling. Moraine deposition and modest summer cooling during Heinrich Stadial 1 and the early Younger Dryas (YD) suggest that despite these events expressing more strongly in wintertime, the classic blueprint of North Atlantic climate variability extends to the western Arctic region. [ABSTRACT FROM AUTHOR]