Middle to late Wisconsinan climate and ecological changes in northern Alaska: Evidences from the Itkillik River Yedoma

• Published in: Palaeogeography, palaeoclimatology, palaeoecology palaeoclimatology, palaeoecology, 2017-11, Vol.485, p.906-916
• Main Authors: Lapointe E., Lyna, Talbot, Julie, Fortier, Daniel, Fréchette, Bianca, Strauss, Jens, Kanevskiy, Mikhail, Shur, Yuri
• Format: Article
• Language: English
• Subjects: Arctic; Beringia; Paleoclimate; Paleoecology; Syngenetic permafrost; Wisconsinan glaciation
• ISSN: 0031-0182; 1872-616X
• DOI: 10.1016/j.palaeo.2017.08.006

Continuous paleoenvironmental records covering the period prior to the Last Glacial Maximum in northeastern Beringia are sparse. This study presents a multi-proxy analysis of a 35-m-high yedoma exposure located on the right bank of the Itkillik River in Alaska. The exposure accumulated over 39thousand years (kyr) during the Middle Wisconsinan Interstadial and the Late Wisconsinan glacial advance. We identified five stratigraphic units based on pollen, carbon and ice content, and isotopic composition (δ18O) of the sediments. Middle Wisconsinan climate in northern Alaska promoted peat accumulation prior to 33.6calkyrBP (calibrated kyr before present). Reconstructed July air temperatures were 1–2°C lower than current at 34.8calkyrBP, consistent with the timing of the interstadial climatic optimum in interior Alaska and Yukon. Colder (by up to 4°C) and drier conditions characterize the transition from interstadial to glacial conditions between 33.6 and 29.8calkyrBP. Late Wisconsinan (29.8–17.9calkyrBP) July air temperatures were 2–3°C lower than today, with grassland vegetation dominated by Poaceae, Artemisia and forbs, in contrast to the modern Cyperaceae dominance. Moister and warmer environmental conditions after 17.9cal kyr BP correspond to the Late Glacial to Early Holocene interval. •The yedoma-based reconstruction provides insights into the northern Alaska climate over 35ka.•The reconstructed climate fluctuations are consistent with other Beringian records.•Shifts between Cyperaceae and Poaceae pollen mostly drive the reconstruction.