Browsing by Author "Woywitka, Robin"
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ItemCatastrophic drainage from the northwestern outlet of glacial Lake Agassiz during the Younger Dryas(2021) Norris, S. L.; Garcia-Castellanos, D.; Jansen, J. D.; Carling, P. A.; Margold, M.; Woywitka, Robin; Froese, D. G.Catastrophic meltwater drainage from glacial Lake Agassiz has been hypothesised as a trigger for large-scale ocean circulation change initiating the Younger Dryas cold reversal. Here we quantify the flood discharge that formed the northwestern outlet of Lake Agassiz using a one-dimensional step-backwater model and a zero-dimension gradual-incision model. Applying these two independent models, we estimate a peak discharge range of 1.8-2.5 × 106 m3 s-1 and a flood volume of ~21,000 km. Such a discharge can only be derived from Lake Agassiz rather than one of the two smaller regional glacial lakes: Churchill or Meadow. When coupled with existing ice margin chronologies, these results demonstrate that the northwestern outlet of Lake Agassiz provides a viable link for catastrophic meltwater to drain to the Arctic Ocean over a 5-10 month period during the Younger Dryas, though it is unclear whether this was near its beginning. ItemIce, mountains, and people: applying a multi-proxy approach to reveal changes in Alberta’s alpine ecosystems through ice patch research(2023) Tirlea, Diana; Kristensen, Todd; Osicki, Aaron; Jensen, Britta; Williams, Krista; Caners, Richard; Lumley, Lisa; Woywitka, RobinGlacial archaeology has grown and progressed rapidly in recent decades with technological innovations and shifting socio-political issues. However, research on ice patches in the Canadian Rocky Mountains is in its infancy. While Holocene glacial ice retreat, advance, and morphology are well studied in Canada, ice patches in general tend to be understudied because of their limited geomorphological impact on landscapes. This oversight is concerning as their isolated nature, lower elevation, and small mass make ice patches even more susceptible to climate change than glaciers. The importance of documenting these features is heightened by a persisting but tenuous biological importance to a range of modern species. The lack of flow in ice patches also makes them excellent archives of palaeoenvironmental and organic-based cultural materials, as layers of ice and preserved contents are not as distorted as they may be by flow in glaciers. ItemLate Pleistocene aeolian deposition and human occupation on the eastern edge of the deglacial corridor, northeastern Alberta, Canada(2022) Woywitka, Robin; Froese, Duane; Lamothe, Michel; Wolfe, StephenThe lower Athabasca River basin in northeastern Alberta contains one of the highest known concentrations of prehistoric archaeological sites in the boreal forests of western Canada. This is due to the combination of readily available sources of lithic raw material stone near a major travel corridor, and extensive archaeological survey conducted in advance of oil sands mining. Typological studies have proposed immediate post-glacial occupations that were contemporaneous with, or immediately followed, the catastrophic glacial Lake Agassiz flood through the area at the end of the Pleistocene. Here, we complement the typology age estimates by using stratigraphic relations and infrared stimulated luminescence (IRSL) dating of aeolian material to determine the age of initial human occupation, and reconstruct the environment encountered by early inhabitants of the region. We find that the first occupations in our study area took place near the Pleistocene-Holocene boundary (ca. 11.3 ± 0.8 ka BP), shortly after catastrophic flooding from Lake Agassiz. The post-flood environment was dominated by cold climatic conditions that supported permafrost, presumably during the late Pleistocene, and underwent significant aeolian deposition. Our results indicate that this area represents a portion of the eastern edge of the deglacial corridor into which plants, animals, and humans dispersed following retreat of the Laurentide Ice Sheet. ItemPermafrost, geomorphic, and hydroclimatic controls on mercury, methylmercury, and lead concentrations and exports in Old Crow River, arctic western Canada(2022) Staniszewska, Kasia J.; Reyes, Alberto V.; Cooke, Colin A.; Miller, Brooklyn S.; Woywitka, RobinPermafrost degradation has been implicated as a dominant control on riverine mercury fluxes in arctic watersheds. However, the importance of permafrost thaw on fluxes of mercury, methylmercury, and trace metals such as lead—relative to other geomorphic and hydroclimatic controls—remains unclear. To investigate these controls, we conducted ~weekly water chemistry sampling at the mouth of the Old Crow River, a pristine, 13,900 km2 watershed in arctic Canada underlain entirely by continuous permafrost. Mercury, methylmercury, and lead concentrations were low on average (~ 2 ng/L, 0.04 ng/L, 0.8 μg/L, respectively), and peaked during the freshet (< 7 ng/L, 0.11 ng/L, 11 μg/L, respectively). The trace elements had strong positive association with suspended sediment, and were mobilized during periods of high discharge (freshet and rainfall). Summer time sampling of major tributaries and at thaw slumps revealed that trace element concentrations were not elevated downstream of thaw slumps or thermokarst lakes across the watershed. Ubiquitous thermokarst in the Old Crow basin did not result in anomalously high catchment-scale concentrations, fluxes, and yields of mercury, methylmercury, nor lead. Rather, warming-driven increases in precipitation and elevated discharge during freshet and rainfall promoted permafrost and talik river bank erosion. This erosion, which was controlled by landscape and geomorphic factors, supplied short-lived increases in particle-bound trace element flux. ItemA process-depositional model for the evaluation of archaeological potential and survey methods in a boreal forest setting, Northeastern Alberta, Canada(2020) Woywitka, Robin; Froese, DuaneMore than 1,000 archaeological sites occur within the Clearwater-Athabasca Spillway, a relict channel that routed catastrophic drainage from glacial Lake Agassiz during deglaciation of northeastern Alberta. This high site density is rare in the region, and artifact assemblages are large due to the presence of abundant sources of lithic raw material. Unfortunately, sites are rarely preserved in stratified or deeply buried deposits. As is often the case in subarctic areas, this lack of depositional context coupled with a paucity of datable organic materials has hindered the establishment of cultural chronologies for the region. To address this issue, we develop a process-depositional model and digital terrain analysis to identify where thicker sediments may have accumulated, and assess whether survey strategies have adequately tested these areas. We find current survey strategies are biased to testing upland ridges with thin deposits, and that inconsistent methods of recording sediment thickness make it difficult to assess whether vertical profiles are being sampled to sterile deposits. We recommend that future survey strategies in boreal forest settings focus on a broader suite of landforms and landform elements, including those that act as sediment traps.