Eastern Beringia is one of the few Western Arctic regions where full Holocene climate reconstructions are possible. However, most full Holocene reconstructions in Eastern Beringia are based either on pollen or midges, which show conflicting early Holocene summer temperature histories. This discrepancy precludes understanding the factors that drove past (and potentially future) climate change and calls for independent proxies to advance the debate. We present a ~13.6 ka summer temperature reconstruction in central Yukon, part of Eastern Beringia, using precipitation isotopes in syngenetic permafrost. The reconstruction shows that early Holocene summers were consistently warmer than the Holocene mean, as supported by midges, and a thermal maximum at ~7.6–6.6 ka BP. This maximum was followed by a ~6 ka cooling, and later abruptly reversed by industrial-era warming leading to a modern climate that is unprecedented in the Holocene context and exceeds the Holocene thermal maximum by +1.7 ± 0.7 °C.

No abstract

Ombrotrophic peat underlain by permafrost has been used to reconstruct past atmospheric mercury (Hg) deposition. Here, we analyze a core collected from a rapidly aggrading, raised peat bog near Dawson City, Yukon, Canada, to reconstruct natural and anthropogenic Hg deposition rates during the last 400 years. Our results differ from previous accounts of atmospheric Hg deposition based on natural archives in the northern hemisphere. We observe a correlative link between total Hg concentrations and pore-water/ice δ18O signatures from the same depths in our core. In light of this relation, we recognize that a portion of atmospherically deposited Hg may be subject to downward mobility through the annually thawed active layer until it becomes perched at the impermeable top of permafrost. An irregular 210Pb activity profile provides further evidence for postdepositional metal mobility which is partly facilitated by chemo-physical interactions between complexing and solubilizing agents in organic-rich pore-waters of the active layer. This empirical evidence for postdepositional Hg and Pb mobility implies the need for caution when interpreting ombrotrophic peat from permafrost regions as high-resolution archives of atmospheric metal deposition.

Thermokarst lakes form following the thaw of ice-rich permafrost and drain after a few decades to millennia. Drained thermokarst lake basins (DTLBs) become epicenters for peat accumulation and re-aggradation of ice-rich permafrost. This reaggradation of permafrost may be interrupted by subsequent thermokarst lake formation with sufficient disturbance. Thermokarst lakes and DTLBs are abundant near Old Crow, Yukon, Canada, but little is known about their evolution through the Holocene. In this study, we investigate the hydrology and drainage histories of seven DTLBs from the Old Crow Flats on the basis of cryostratigraphy, radiocarbon dating, and pore-ice δ 18 O and δ 2 H records. Cryostratigraphic evidence implies only one of the seven studied DTLBs underwent multiple thermokarst cycles. Radiocarbon agedepth models demonstrate a slowdown in the rate of post-drainage peat accumulation with time. Pore-ice isotope analyses reveal a spectrum of possible post-drainage isotopic histories resulting from spatial variability in permafrost, vegetation, and hydrology. Unlike lacustrine silt, post-drainage peat contains relatively constant poreice isotope trends. In light of our findings, we propose that syngenetic peat permafrost in DTLBs preserve a warm-season sampling of local meteoric waters. These pore-ice δ 18 O and δ 2 H records may aid millennial-scale paleoclimate investigations, as we demonstrate through our reconstruction of Holocene climate change in northern Yukon.

An examination of research in northern Canada and its ties to extractive, colonial practices has been highlighted in recent years, alongside heightened expectations for community-and Nation-engaged practises. Here, we explore the diverse ways that northern-focused early career researchers (ECRs), from a range of faculties, life experiences, and disciplines, engage with the communities and Indigenous Nations they work in and, more broadly, the knowledge they have gained from conducting research in the North. Scholars in the fi elds of education, anthropology, and renewable resources from the University of Alberta share their experiences to discuss 1) approaches to meaningfully and respectfully engaging with communities and Nations in the North; 2) knowledge translation and mutual capacity building; and 3) responsibilities and accountabilities for engaging with communities and Nations. We fi nd resonance with the Five R's of research-relevance, reciprocity, respect, responsibility, and relationship-that help ensure Western-derived knowledge benefi ts the communities and Nations that ECRs work alongside.