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The Late-Quaternary climate of Beringia remains unresolved despite the region's role in modulating glacial-interglacial climate and as the likely conduit for human dispersal into the Americas. Here, we investigate Beringian temperature change using an ∼32,000-year lacustrine record of leaf wax hydrogen isotope ratios (δ2H wax) from Arctic Alaska. Based on Monte Carlo iterations accounting for multiple sources of uncertainty, the reconstructed summertime temperatures were ∼3 °C colder (range: −8 to +3 °C) during the Last Glacial Maximum (LGM; 21-25 ka) than the pre-industrial era (PI; 2–0.1 ka). This ice-age summer cooling is substantially smaller than in other parts of the Arctic, reflecting altered atmospheric circulation and increased continentality which weakened glacial cooling in the region. Deglacial warming was punctuated by abrupt events that are largely synchronous with events seen in Greenland ice cores that originate in the North Atlantic but which are also controlled locally, such as by the opening of the Bering Strait between 13.4 and 11 ka. Our reconstruction, together with climate modeling experiments, indicates that Beringia responds more strongly to North Atlantic freshwater forcing under modern-day, open-Bering Strait conditions than under glacial conditions. Furthermore, a 2 °C increase (Monte Carlo range: −1 to +5 °C) over the anthropogenic era reverses a 6 °C decline (Monte Carlo range: −10 to 0 °C) through the Holocene, indicating that recent warming in Arctic Alaska has not surpassed peak Holocene summer warmth. • Alaska's climate history is evaluated using leaf wax hydrogen isotope ratios in a 32,000 year-long lacustrine record. • The record reveals mild ice-age cooling, abrupt deglacial climate events, strong Holocene cooling, and recent warming. • Proxy-model comparison highlights the importance of the Bering Strait opening as a control of Beringian climate. [ABSTRACT FROM AUTHOR]

Human paleodemographic changes were related to environmental fluctuations for the North American Arctic and boreal region, including Greenland. Using the frequency of archaeological radiocarbon dates as a proxy for population size, past changes in population were estimated and quantitatively examined in relation to reconstructions of temperature and sea ice conditions. This analysis was conducted across three spatial scales in order to better identify potential climate impacts on population size: the entire area, four major cultural-environmental regions and sixteen sub-regions. The timing of initial settlement differed by region, and population size fluctuated through time, but there was nevertheless an overall, accelerating increase in most areas. There was a high correspondence between millennial and centennial-scale climate variability and paleodemographic changes across the region, with population size generally increasing during warmer periods and decreasing during cooling episodes. Late Holocene cooling (neoglaciation) triggered a nearly-synchronous population decline across the entire region at 3.9 ka, a time when significant societal disruptions have been identified around the world, and are here shown in the Arctic. Decreasing temperatures and increased sea ice coverage also influenced large-scale migration patterns of Paleo-Inuit peoples as well as their cultural evolution. The growth of Paleo-Inuit populations after 3 ka during continued climate cooling is consistent with archaeological evidence suggesting Paleo-Inuit technological change enabled adaptations to increased sea ice. • Multi-scale analysis of human-environment interactions discerns local and regional population dynamics. • Climate changes caused increases and decreases in population in the Arctic and Subarctic. • Neoglaciation triggered continental-scale population decline across the north. • Population density underwent long-term growth despite climate-induced regional decreases. [ABSTRACT FROM AUTHOR]