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Thermokarst lakes are thought to have been an important source of methane (CH4) during the last deglaciation when atmospheric CH4 concentrations increased rapidly. Here we demonstrate that meltwater from permafrost ice serves as an H source to CH4 production in thermokarst lakes, allowing for region-specific reconstructions of ?DCH4 emissions from Siberian and North American lakes. ?DCH4 reflects regionally varying ?D values of precipitation incorporated into ground ice at the time of its formation. Late Pleistocene-aged permafrost ground ice was the dominant H source to CH4 production in primary thermokarst lakes, whereas Holocene-aged permafrost ground ice contributed H to CH4 production in later generation lakes....
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Tephras are often used in paleolimnology and other stratigraphic applications as a chronostratigraphic marker. Where analytical errors in radiocarbon or other dating methods make precise comparison between sites difficult, tephras provide an absolute stratigraphic reference that can be used to assess the relative ages of events across a region. Applications of tephrochronology typically make the assumption that a tephra is deposited at what was the top of the stratigraphic sequence at the time of deposition, and that the contact between the tephra and underlying sediments is an isochron. This paper presents evidence from two lakes in western Canada which suggest that tephras may be very mobile within the sedimentary...
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Combining proxy methods in paleoecology studies has the potential to bring new insight into changes in vegetation over time. Keyhole Pond, a small lake in southwest Yukon Territory, is surrounded by small grasslands but located within the boreal forest. This lake was chosen to explore local grassland and forest changes over the Holocene, as well as the impact of fire on these communities. A 3-metre lake sediment core was retrieved from the deepest part of the lake using a modified Livingston piston-corer. The lake sediment core has a basal date of ∼11,000 before present (BP). Samples were extracted at 3-centimetre intervals (∼100 years between samples) and processed for both pollen and charcoal analysis. Only charcoal...
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Pollen grains from bodies of ancient people provide clues to their diet and domicile. To learn more about Kwäday Dän Ts'ìnchí (Long Ago Person Found), who died on a British Columbia glacier 550 years ago, we studied the Chenopodiaceae pollen found in his stomach and robe. Environmental scanning electron microscopy was used to distinguish pollen of the native chenopod genera Atriplex, Chenopodium, Eurotia, Suaeda, and Salicornia (here including Sarcocornia). All chenopod pollen grains in one stomach sample were from Salicornia (Tourn.) L. (glasswort), which grows only in saline soils and has been used for food and medicine. Elders from the Champagne and Aishihik, Tagish, Gwitch'in, and Tlingit First Nations report...
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The objective biomization method developed by Prentice et al. (1996) for Europe was extended using modern pollen samples from Beringia and then applied to fossil pollen data to reconstruct palaeovegetation patterns at 6000 and 18,000 14C yr bp. The predicted modern distribution of tundra, taiga and cool conifer forests in Alaska and north-western Canada generally corresponds well to actual vegetation patterns, although sites in regions characterized today by a mosaic of forest and tundra vegetation tend to be preferentially assigned to tundra. Siberian larch forests are delimited less well, probably due to the extreme under-representation of Larix in pollen spectra. The biome distribution across Beringia at 6000...
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Disturbances are mechanisms that mediate ecosystem changes in response to climate-driven vegetation changes. While many studies have looked at the effect of fire on ecosystem components, few have considered the response of fire to climate and vegetation change. The effects that past climate and vegetation shifts have on fire regimes and the potential consequences to ecosystem change are examined here. Charcoal and pollen analyses were used to determine geographic and temporal patterns of past fire regimes in the North American western boreal forest. Seventeen high-resolution records from north-central Canada (NWT and Manitoba), interior Alaska, and northwestern Ontario were analyzed for large charcoal particles...
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The Nenana River valley, located in the northern foothills of the Alaska Range, contains a group of sites that collectively spans 11,300 to 7000 B.P., and provides critical information on the settlement of Alaska during this interval. Major localities include Dry Creek, Walker Road, Panguingue Creek, and Moose Creek, all of which contain cultural remains buried in a deep aeolian sedimentary context. Three of these sites yielded assemblages comprising small bifacial points, endscrapers, scraper planes, and other tools dating to between ca. 11,300 and 11,100 B.P. (Nenana complex). Three sites contain assemblages of microblades, lanceolate points, burins, and other lithic artifacts that stratigraphically overlie the...
Chapter within the book Global Change in the Holocene
Categories: Publication; Types: Citation; Tags: Paleo and Holocene
Disturbances are mechanisms that mediate ecosystem changes in response to climate-driven vegetation changes. While many studies have looked at the effect of fire on ecosystem components, few have considered the response of fire to climate and vegetation change. The effects that past climate and vegetation shifts have on fire regimes and the potential consequences to ecosystem change are examined here. Charcoal and pollen analyses were used to determine geographic and temporal patterns of past fire regimes in the North American western boreal forest. Seventeen high-resolution records from north-central Canada (NWT and Manitoba), interior Alaska, and northwestern Ontario were analyzed for large charcoal particles...
map background search result map search result map Late Glacial and Holocene environmental change inferred from sedimentary archives of Kusawa Lake, Boundary Range Mountains, Yukon Territory, Canada A 14,000 yr paleoenvironmental record from Windmill Lake, central Alaska; lateglacial and Holocene vegetation in the Alaska Range Pollen-based biomes for Beringia 18,000, 6000 and 0 14C yr bp? Density-induced settling of tephra through organic lake sediments Identification of last interglacial deposits in eastern Beringia; a cautionary note from the Palisades, interior Alaska Vegetative and fire history of the area surrounding Keyhold Pond, Yukon Territory Late Pleistocene and Early Holocene Sites in the Nenana River Valley, Central Alaska Forensic palynology and ethnobotany of Salicornia species (Chenopodiaceae) in northwest Canada and Alaska Fire history of boreal forests: Implications for past climate change Responses of boreal fire regimes to climatic and land-cover changes: Perspectives from multiple spatiotemporal scales Density-induced settling of tephra through organic lake sediments Late Pleistocene and Early Holocene Sites in the Nenana River Valley, Central Alaska Vegetative and fire history of the area surrounding Keyhold Pond, Yukon Territory Late Glacial and Holocene environmental change inferred from sedimentary archives of Kusawa Lake, Boundary Range Mountains, Yukon Territory, Canada Responses of boreal fire regimes to climatic and land-cover changes: Perspectives from multiple spatiotemporal scales Identification of last interglacial deposits in eastern Beringia; a cautionary note from the Palisades, interior Alaska A 14,000 yr paleoenvironmental record from Windmill Lake, central Alaska; lateglacial and Holocene vegetation in the Alaska Range Fire history of boreal forests: Implications for past climate change Forensic palynology and ethnobotany of Salicornia species (Chenopodiaceae) in northwest Canada and Alaska Pollen-based biomes for Beringia 18,000, 6000 and 0 14C yr bp?