Leaf wax hydrogen isotope data, and modern precipitation isotope data, Lake E5, Alaska, 2014-2018

The Late-Quaternary climate of Beringia remains unresolved despite the region’s role in modulating glacial-interglacial climate and as the conduit for human dispersal into the Americas. We investigate Beringian temperature change using an ~32,000-year record of leaf wax hydrogen isotope ratios (δDwax) archived in lake sediments in Arctic Alaska. Temperatures were 2.9 °C colder during the Last Glacial Maximum (LGM; 21-25 thousand years before present, ka) than the pre-industrial era (PI; 2-0.1 ka). LGM temperatures were substantially warmer than in other parts of the Arctic, reflecting the greater continentality and altered atmospheric circulation which together contributed to weaker, rather than amplified, glacial cooling in the region. The transition to Holocene warmth was punctuated by abrupt events that are largely synchronous with events seen in Greenland ice cores but which also arise from local processes. Warming of 1.7 °C over the anthropogenic era has reversed a 5.5 °C decline through the Holocene, such that that recent warming in Arctic Alaska has not surpassed peak Holocene warmth. Our reconstruction, together with climate modeling experiments, indicates that Eastern Beringia responds more strongly to global climate forcings under modern-day, open-Bering Strait conditions.