50,000 years of paleoenvironmental change recorded in meteoric waters and coeval paleoecological and cryostratigraphic indicators from the Klondike goldfields, Yukon, Canada

Porter, Trevor J.; Mahony, Matthew E.; Pumple, Joel; Calmels, Fabrice; Froese, Duane G.

doi:10.7939/r34t6ff58

Cited by 3 publications

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“…Precise δ 18 O measurements are commonly obtained from ice-cores , and syngenetic permafrost archives for reconstructing paleoclimatic and paleoenvironmental conditions. , In our study region, the active layer begins to thaw in spring and reaches a maximum depth by late summer/autumn. As thawing proceeds, meteoric water gets transported vertically downward through the active layer.…”

Section: Resultsmentioning

confidence: 97%

Postdepositional Mercury Mobility in a Permafrost Peatland from Central Yukon, Canada

Bandara

Froese

Louis

et al. 2019

ACS Earth Space Chem.

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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.

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Section: Resultsmentioning

confidence: 97%

Postdepositional Mercury Mobility in a Permafrost Peatland from Central Yukon, Canada

Bandara

Froese

Louis

et al. 2019

ACS Earth Space Chem.

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Collapse of the mammoth-steppe in central Yukon as revealed by ancient environmental DNA

et al. 2021

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The temporal and spatial coarseness of megafaunal fossil records complicates attempts to to disentangle the relative impacts of climate change, ecosystem restructuring, and human activities associated with the Late Quaternary extinctions. Advances in the extraction and identification of ancient DNA that was shed into the environment and preserved for millennia in sediment now provides a way to augment discontinuous palaeontological assemblages. Here, we present a 30,000-year sedimentary ancient DNA (sedaDNA) record derived from loessal permafrost silts in the Klondike region of Yukon, Canada. We observe a substantial turnover in ecosystem composition between 13,500 and 10,000 calendar years ago with the rise of woody shrubs and the disappearance of the mammoth-steppe (steppe-tundra) ecosystem. We also identify a lingering signal of Equus sp. (North American horse) and Mammuthus primigenius (woolly mammoth) at multiple sites persisting thousands of years after their supposed extinction from the fossil record.

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Permafrost-derived dissolved organic matter composition varies across permafrost end-members in the western Canadian Arctic

MacDonald

Tank

Kokelj

et al. 2021

Environ. Res. Lett.

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Organic matter, upon dissolution into the aqueous state as dissolved organic matter (DOM), can undergo mineralization by microbes. There has been increasing effort to characterize DOM released from thawing permafrost because it may perpetuate a permafrost carbon feedback. Permafrost-derived DOM often has a composition that can be highly susceptible to mineralization by microbes, but most studies to date that characterize permafrost-derived DOM have been limited to select regions, and tend to focus on a single type of permafrost (sometimes unspecified) that reflects a particular deposit type. Importantly, diversity in the nature of the deposit, formation of permafrost, and thaw modification processes leads to spatial and stratigraphic variability in its properties, but our understanding of variation in the composition of DOM derived from differing permafrost types (end-members) is poor. Here, we used ultrahigh-resolution mass spectrometry to characterize DOM composition derived from a series of permafrost end-member types that are commonly found within the thaw-vulnerable western Canadian Arctic, including: tills (glacially deposited), diamicton (thawed and remobilized material of mixed origin), lacustrine (lake basin sediments into which permafrost has aggraded), peat (partially decomposed organic material), and Yedoma (syngenetic silty loess) deposits. We identified marked variation in DOM composition among permafrost end-member types. Tills were compositionally dissimilar to all other permafrost end-members. Compounds unique to Yedoma were predominantly aliphatic, while compounds unique to peat, lacustrine, and diamicton spanned saturation and oxygenation gradients. All permafrost leachates were generally higher in aliphatics, lower in aromatics, and less oxygenated than active layer leachates. Compositional differences appear to reflect variation in permafrost parent materials, and particularly strong effects from past modification processes while in the unfrozen or thawed state. Constraining DOM composition and assessing its stratigraphic variability will become more pressing as the spatial and stratigraphic extent of thaw increases with future warming.

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50,000 years of paleoenvironmental change recorded in meteoric waters and coeval paleoecological and cryostratigraphic indicators from the Klondike goldfields, Yukon, Canada

Cited by 3 publications

References 0 publications

Postdepositional Mercury Mobility in a Permafrost Peatland from Central Yukon, Canada

Postdepositional Mercury Mobility in a Permafrost Peatland from Central Yukon, Canada

Collapse of the mammoth-steppe in central Yukon as revealed by ancient environmental DNA

Permafrost-derived dissolved organic matter composition varies across permafrost end-members in the western Canadian Arctic

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