Evidence of abrupt climate change at 9.3 ka and 8.2 ka in the central Canadian Arctic: Connection to the North Atlantic and Atlantic Meridional Overturning Circulation

Abstract

This study presents the results of a multi-proxy analysis of a Holocene lacustrine sediment sequence recovered from a small tundra lake in the central Canadian Arctic and links climatic variations there to the North Atlantic. Chironomid and pollen-based reconstructions of mean July air temperature (MJAT) document notable deviations at 9.3 ka and 8.2 ka. Chironomid-inferred July air temperature is depressed by 1.4 °C at 9.3 ka and 1.7 °C at 8.2 ka relative to the long-term chironomid-inferred Holocene average of 9.4 °C. These cooling events also correspond to an increase in Gramineae (Poaceae) and a decrease in Betula pollen, reflecting a decrease in the density of dwarf birch cover. Concurrent, abrupt increases in several diatom taxa, including aerophilic epiphytes, and Sphagnum indicate an expansion of moss habitats as a result of wetter conditions. The expression and timing of the cooling evidenced at TK2 during the early Holocene is consistent with abrupt climate events identified in the North Atlantic and coincides with intervals of North Atlantic cooling and weakened Atlantic Meridional Overturning Circulation (AMOC). This research, which improves our understanding of the spatial extent and magnitude of the 9.3 ka and 8.2 ka events in the central Canadian Arctic, serves as a benchmark for coupled-ocean atmosphere climate models simulating the response of the climate system to abrupt climate events and provides insight in marine-atmosphere teleconnections in the circum-North Atlantic region.