28 Sep 2023
 | 28 Sep 2023
Status: this preprint is currently under review for the journal CP.

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

Joseph P. Tulenko, Jason P. Briner, Nicolas E. Young, and Joerg M. Schaefer

Abstract. 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.

Joseph P. Tulenko 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-2023-75', Anonymous Referee #1, 13 Oct 2023
  • RC2: 'Comment on cp-2023-75', Anonymous Referee #2, 26 Oct 2023

Joseph P. Tulenko et al.

Joseph P. Tulenko et al.


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Short summary
We take advantage of a site in Alaska – where climate records are limited – where a former alpine glacier deposited a dense sequence of moraines spanning the full deglaciation to construct a proxy summer temperature record. Building on age constraints for moraines in the valley, we reconstruct paleo-glacier surfaces and estimate the summer temperatures (relative to the Little Ice Age) for each moraine. The record suggests the influence of North Atlantic climate forcing extended to Alaska.