Permafrost and Thermokarst Lake Dynamics in the Old Crow Flats, Northern Yukon, Canada

Roy-Léveillée, Pascale

doi:10.22215/etd/2015-10757

Cited by 4 publications

(13 citation statements)

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“…This is 4–5 times greater that the annual rate from 1951 to 1972 (Figure ). Thermokarst processes have also been shown to drive shoreline recession in some parts of Old Crow Flats [ Roy‐Léveillée and Burn , ], but it is likely that our approach was too coarse to detect increases in surface area, resulting from shoreline recession rates between 0.1 and 2 m/yr [ Roy‐Léveillée , ].…”

Section: Resultssupporting

confidence: 82%

Changes in lake area in response to thermokarst processes and climate in Old Crow Flats, Yukon

2015

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Growing evidence indicates that lake-dominated ecosystems at high latitudes are undergoing significant hydrological changes. Research examining these changes is complicated because both thermokarst and climatic processes likely influence lake dynamics. To examine the relative impacts of these processes in permafrost landscapes, we investigated the dynamics of lake area and number in Old Crow Flats (OCF), Yukon using historical air photos and satellite imagery. Between 1951 and 2007, OCF experienced a decline of~6000 ha in total lake area but gained 232 lakes. Close to half (49%) of the difference in lake area was driven by the rapid and persistent drainage of 38 large lakes. These catastrophic drainages were associated with new or enlarged outlet channels, resulted in the formation of numerous residual ponds, and were likely driven by thermokarst processes. Our analysis shows that catastrophic lake drainages have become more than 5 times more frequent in recent decades. These changes are likely related to the impacts of increased temperature and precipitation on thermokarst processes. Fifty-nine of the 170 intensively studied lakes showed either large bidirectional fluctuations or gradual cumulative declines. These changes affected a much smaller portion of OCF and were likely driven by interactions between increased precipitation and temperature and individual catchment characteristics. To anticipate landscape-scale changes in these systems, and assess their impact on hydrology, wildlife habitat, and carbon storage, field research is required to better characterize the mechanisms responsible for changes.

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Section: Resultssupporting

confidence: 82%

Changes in lake area in response to thermokarst processes and climate in Old Crow Flats, Yukon

2015

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“…Amongst the locations where data were successfully collected, annual mean temperature at the permafrost surface ( T ps ) varied between −2.6 and −4.5° C in basin centres and between −0.7 and −4.2° C at the margins (Table ). These T ps are consistent with the range of ground temperatures previously reported from OCF (Roy‐Leveillee et al , ). Thaw depth, measured in basin 1, was thinnest in the wet basin margins and thickest in the drier centre (Figure a).…”

Section: Resultsmentioning

confidence: 99%

“…The early development of ice wedges in the margins of drained basins on the Arctic Coastal Plain may be due to the reactivation of ice wedges preserved beneath shallow water, as observed by Billings and Peterson () near Point Barrow and by Mackay and Burn () at Illisarvik. In OCF, the lakes lack littoral terraces and talik development begins close to shore (Roy‐Leveillee, ). Depending on the extent of thaw penetration, some wedge ice may be preserved near shore in the lake bottom (Mackay, ).…”

Section: Discussionmentioning

confidence: 99%

“…Near the southeast shore of basin 2 the detrital basal layer, characterized by sandy sediment and occasional large peat debris, was <2 m thick. An abrupt transition separated this sandy layer from the underlying silt loam (Figure ), which was of a texture similar to that of sediment around the lakes (Roy‐Leveillee, ). We interpret the silt loam to have been deposited prior to lake expansion over the area.…”

Section: Discussionmentioning

confidence: 99%

“…Surface conditions in the lake basin sediments have evolved from marshes through fens, to sphagnum bogs (Ovenden, ). Today OCF is located within the forest–tundra ecotone of northern Yukon, with subarctic boreal forest dominating to the south and tundra to the north (Roy‐Leveillee, ).…”

Section: Old Crow Flatsmentioning

confidence: 99%

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A modified landform development model for the topography of drained thermokarst lake basins in fine‐grained sediments

Roy-Léveillée

Burn

2016

Earth Surf Processes Landf

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Permafrost degradation associated with the expansion of thermokarst lakes is commonly interrupted by catastrophic drainage. Subsequently, in tundra areas, permafrost aggradation in drained basins leads to uneven topography characterized by raised centres and wet, depressed margins. The genesis of such topography has been investigated in Old Crow Flats (OCF), a glaciolacustrine plain in the continuous permafrost of northern Yukon. The thermokarst lakes of OCF have a mean depth of only 1.5 m because excess ice is dominantly found only in the uppermost 10 m of the ground. Surface conditions were measured in three drained thermokarst lake basins, including relief, snow conditions, ground temperatures, near‐surface ground ice, and sediment stratigraphy. Four nearby lakes provided information on wave base, shore recession patterns, and bathymetry before drainage: the bottoms of these lakes were not raised in the centre. An elevation difference of up to 2 m was recorded between drained basin margins and centres but was not associated with variations in ice‐wedge density or segregated ice content. Hence basin topography was not controlled by differences in volumetric ground‐ice content between margins and centres. We propose that transport of fine sediment away from eroding lake margins during lake development is the primary mechanism for the genesis of depressed margins and raised centres in drained basins of OCF. Over time, the transport results in the deposition of more and finer sediment in the central parts of lakes, where the lake bottom has subsided below wave base, than at the shallow margins, where resuspension by wave action occurs frequently. This difference in sediment volume is revealed in the topography after drainage, when permafrost aggrades in the lake‐bottom sediment and underlying talik. Copyright © 2016 John Wiley & Sons, Ltd.

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Ecosystem responses of shallow thermokarst lakes to climate-driven hydrological change: Insights from long-term monitoring of periphytic diatom community composition at Old Crow Flats (Yukon, Canada)

et al. 2023

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Shallow waterbodies are abundant in Arctic and subarctic landscapes where they provide productive wildlife habitat and hold cultural and socioeconomic importance for Indigenous communities. Their vulnerability to climate-driven hydrological and limnological changes enhances a need for long-term monitoring data capable of tracking aquatic ecosystem responses. Here, we evaluate biological and inferred physicochemical responses associated with a rise in rainfall-generated runoff and increasingly positive lake water balances in Old Crow Flats (OCF), a 5600 km2 thermokarst landscape in northern Yukon. This is achieved by analyzing periphytic diatom community composition in biofilms accrued on artificial-substrate samplers at 14 lakes collected mostly annually during 2008–2019 CE. Results reveal that diatom communities at 10 of the 14 lakes converged toward a composition typical of lakes with rainfall-dominated input waters. These include six of nine lakes that were not initially dominated by rainfall input. The shifts in diatom community composition infer rise of lake-water pH and ionic content, and they reveal that northern shallow lake ecosystems are responsive to climate-driven increases in rainfall. Based on data generated during the 12 -year-long monitoring period, we conclude that lakes located centrally within OCF are most vulnerable to rapid climate-driven hydroecological change due to flat terrain, larger lake surface area, and sparse terrestrial vegetation, which provide less resistance to lake expansion, shoreline erosion, and sudden drainage. This information assists the local Indigenous community and natural resource stewardship agencies to anticipate changes to traditional food sources and inform adaptation options.

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Permafrost and Thermokarst Lake Dynamics in the Old Crow Flats, Northern Yukon, Canada

Cited by 4 publications

References 173 publications

Changes in lake area in response to thermokarst processes and climate in Old Crow Flats, Yukon

Changes in lake area in response to thermokarst processes and climate in Old Crow Flats, Yukon

A modified landform development model for the topography of drained thermokarst lake basins in fine‐grained sediments

Ecosystem responses of shallow thermokarst lakes to climate-driven hydrological change: Insights from long-term monitoring of periphytic diatom community composition at Old Crow Flats (Yukon, Canada)

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