1,721,007 research outputs found
Twenty years of Mean Annual Ground Temperature (MAGT) across latitudinal and elevational gradients in the Yukon Territory (NW Canada)
No full textThis published dataset are time series of Mean Annual Ground Temperature (MAGT) close to the surface across latitudinal and elevational gradients covering a multitude of permafrost landscapes and land surface types in the Yukon Territory, NW Canada. The station network was specifically set up by Prof. A. Lewkowicz (University of Ottawa, Canada) and his colleagues and collaborators from April 2001 to assess the current thermal state of permafrost across wide climate and elevational gradients, as the operational Environment and Climate Change Canada climate stations in the Yukon area (NW Canada) are primarily located in valley bottom sites. However, much of the Yukon Territory is composed of mountainous terrain, therefore the degree of climate change and thermal state of permafrost for these vast areas is difficult to predict in part because present-day conditions are not known.
The monitoring sites for air temperature and ground surface temperature were set up in logistically accessible elevations across as wide a range of elevations as possible and in a variety of positions relative to topography (ridge crests, valley bottoms, long slopes, etc.) in order to assess the impact of localized air temperature inversions. The wide range of elevations being monitored (330 m asl to 2077 m asl) as well as their geographical coverage (from 60°N to 65°N and 129°W to 141°W) covering a multitude of permafrost landscapes and land surface types make these records unique, providing an important snapshot across this complex landscape.
The 111 monitoring sites (air temperature and upper ground temperature) are located in eight regions:
1. Wolf Creek and vicinity, near Whitehorse (60.54N, 135.15W): 27 sites
2. Dawson and vicinity (64.12°N, 139.68°W): 15 sites
3. Keno region (63.92°N 135.33°W): 13 sites
4. Johnson's Crossing region (60.57°N, 133.15°W): 13 sites
5. Sa Dena Hes mine site and vicinity (60.42°N, 128.59°W): 13 sites
6. Faro region (62.22°N, 133.13°W): 13 sites
7. Alaska Highway Corridor (from the Alaska border to 300 km east of Whitehorse): 12 sites
8. Dempster and Klondike Highway Corridors (from 61° to 65°N): 5 sites
Until 2008 the network grew to more than 100 stations. Some stations were removed from 2009 onwards, and more taken down in 2015, while a small number of new sites were installed during this period. The COVID pandemic prevented planned downloads in 2020 so the last downloads of the 47 stations still in operation were undertaken variously in 2017, 2018 or 2019.
Level 0 to Level 2 data: Field work, station installation and data read-out has been conducted by A.G. Lewkowicz (University Ottawa, Canada) and colleagues. Primary data treatment and processing up to daily temperature time series has been conducted by A.G. Lewkowicz.
Level 3 data (this published dataset): Mean Annual Ground Temperature (MAGT) time series were created from the daily temperature datasets (Level 2 data, by A.G. Lewkowicz) by Mareike Wieczorek (Alfred-Wegener-Institut Helmholtz-Zentrum fuer Polar- und Meeresforschung, Germany) within the framework of the European Space Agency (ESA) Climate Change Initiative (CCI) Permafrost programme as reference data set for the ESA CCI Permafrost time series product on Ground Temperature (https://climate.esa.int/en/projects/permafrost/)
High-resolution Permafrost Distribution Modelling for the Central and Southern Yukon, and Northwestern British Columbia, Canada
No full textBasal Temperature of Snow (BTS) measurements were used as the primary inputs to a high resolution (30 x 30 m grid cells) empirical-statistical regional permafrost probability model for the southern and central Yukon, and northernmost British Columbia (59° - 65°N). Data from seven individual study areas distributed across the region were combined using a blended distance decay technique, with an eighth area used for validation. The model predictions are reasonably consistent with previous permafrost maps for the area with some notable differences and a much higher level of detail. The modelling gives an overall permafrost probability of 52%. North of 62°N, permafrost becomes more extensive in the lowland areas whereas farther south permafrost is typically common only above treeline.
Significant differences exist between the mountain environments of the Yukon and the Swiss Alps where the BTS method originated and as a result different modelling approaches had to be developed. This work therefore: (1) develops additional explanatory variables for permafrost probability modelling, the most notable of which is equivalent elevation, (2) confirms the use of ground truthing as a requirement for empirical-statistical modelling in the Yukon and (3) uses a combination of models for the region in order to spatially predict between study areas.
The results of this thesis will be of use to linear infrastructure route-planning, geohazard assessment and climate change adaptation strategies. Future work employing the model will allow the effects of scenario-based climate warming to be examined
The effect of detachment sliding on surface wash erosion in the continuous permafrost zone, Hot Weather Creek, Fosheim Peninsula, Ellesmere Island, Northwest Territories.
No full textAn experimental design was developed to evaluate the effect of active-layer detachment sliding on surface wash erosion. Specifically, the aim was to examine to what extent the disturbance of vegetation cover, changes in hydrological conditions due to topographic modification by detachment sliding and the formation of a fresh active layer affect rates of surface wash erosion. Detachment slides generally accumulated more snow than adjacent slopes and yielded greater amounts of surface runoff than vegetated slopes with similar snow covers. Surface drainage was inhibited on well-vegetated hummocky slopes where lags between radiation inputs and discharge responses were greater than at the rilled detachment slide plots. During rainfall events following snowmelt, plot response was affected by antecedent moisture conditions and the vegetation cover: surface flow was generated only in detachment slide scars and at the mixed plots but not on vegetated undisturbed slopes or on the bare undisturbed slope. Suspended sediment concentrations at the fresh detachment slide scars are two orders of magnitude greater than on vegetated slopes. Greater amounts of surface runoff production at fresh scars and the removal of vegetation result in high rates of surface erosion and high sediment yields (1560 g/m\sp2) at fresh detachment slide scars. (Abstract shortened by UMI.
Towards a TTOP-Model of Permafrost Distribution for Three Areas in Yukon and Northern British Columbia
No full textAir, ground surface and top of permafrost temperatures (TTOP) were measured at 58 sites in three areas of Yukon and northern British Columbia in order to: (1) explore relationships between climate-permafrost transfer functions and environmental variables, (2) assess and validate the TTOP-model, and (3) attempt the first implementation of the TTOP-model (Smith and Riseborough, 1996, 2002) for these regions with complex terrain. The strongest factors controlling climate-permafrost transfer functions are elevation and land cover, though slope, aspect, topographic position and surficial geology were also investigated. In 1000 iterations of the model using random equally possible scenarios, 64% of the TTOP-model predictions were within ±1°C of measured values, a result that is 6% better than applying a simple 3°C “total offset” to the mean annual air temperature. A sensitivity analysis confirmed that the TTOP-model is most sensitive to changes in snow, thermal conductivity of the ground and summer air temperatures. A land cover driven TTOP-model was then developed and implemented. The model correctly predicts high likelihoods of permafrost (> 0.8) for sites with permafrost present and low likelihoods (< 0.4) for non-permafrost sites
Morphometry and biophysical characteristics of turf-banked lobes and terraces, Kluane Lake, Yukon Territory.
No full textThe distribution, morphometry and biophysical characteristics of turf-banked lobes and terraces are described from a small subarctic alpine plateau (1300--1900 m a.s.l.) overlooking Kluane Lake in the southwest Yukon Territory, Canada. Observations on the distribution of lobes and terraces at this site indicate that the main controlling factors are the complexity of the topography and the properties of snow cover. Morphometric analysis of 85 lobes subdivided into five different slope orientations indicates a morphogenetic underpinning in which lobe form remains consistent (length-to-width ratio below unity) at different scales and between aspects, however, morpho-biophysical correlations could not provide an explanation for this. Nonparametric and multivariate parametric statistical tests indicate significant inter-aspect differences in the dimensions and biophysical characteristics of the lobes. These appear to be related to differences in site-specific factors. Measurements made along certain transects reveal a definitive downslope trend in the size of lobes. This organization is developed as a result of downslope gradients of various biophysical factors, primarily soil moisture and frost-susceptible soil (silt and clay), which are created by slopewash processes
Development of solifluction lobes, Kluane Range, Yukon Territory
No full textSolifluction lobe process and morphology were studied on an alpine slope (1800 m a.s.l) above Kluane Lake, south-western Yukon Territory. Contemporary rates of surface movements, measured by theodolite survey, were found to be greatest in the first two weeks of spring thaw, and movements were consistently faster on lobe treads than on lobe risers. Precise monitoring of thaw-consolidation parameters on a lobe indicated that most thaw-settlement occurred when the soil was saturated to the surface. At the slope scale, surface rates increased downslope in response to gradients in soil moisture, while long-term rates of lobe advance, inferred from 14C dating of buried organic horizons, were found to be similar among 12 dated lobes. The internal stratigraphy and age distribution of these lobes together suggest periodic advance of the fronts. Observations of lobe stratigraphy with the age distribution of buried humus points towards a conceptual model of lobe development involving the slow accumulation of soliflucted material behind a rigid riser, the progressive steepening of the riser and build-up of stress, and finally the rupture of the front and its extensive collapse on to the slope. The period for this developmental cycle was estimated to be about 600 years. This internal cycle of lobe development constitutes a serious buffer to climatic influence and must be taken into account when using solifluction lobes as paleoclimate sources
Development of solifluction lobes, Kluane Range, Yukon Territory
No full textSolifluction lobe process and morphology were studied on an alpine slope (1800 m a.s.l) above Kluane Lake, south-western Yukon Territory. Contemporary rates of surface movements, measured by theodolite survey, were found to be greatest in the first two weeks of spring thaw, and movements were consistently faster on lobe treads than on lobe risers. Precise monitoring of thaw-consolidation parameters on a lobe indicated that most thaw-settlement occurred when the soil was saturated to the surface. At the slope scale, surface rates increased downslope in response to gradients in soil moisture, while long-term rates of lobe advance, inferred from 14C dating of buried organic horizons, were found to be similar among 12 dated lobes. The internal stratigraphy and age distribution of these lobes together suggest periodic advance of the fronts. Observations of lobe stratigraphy with the age distribution of buried humus points towards a conceptual model of lobe development involving the slow accumulation of soliflucted material behind a rigid riser, the progressive steepening of the riser and build-up of stress, and finally the rupture of the front and its extensive collapse on to the slope. The period for this developmental cycle was estimated to be about 600 years. This internal cycle of lobe development constitutes a serious buffer to climatic influence and must be taken into account when using solifluction lobes as paleoclimate sources
Evaluation of the basal temperature of snow (BTS) method to map permafrost in complex mountainous terrain, Wolf Creek, Yukon Territory
No full textThis study is the first known attempt in North America to use the basal temperature of snow (BTS) method to predict the distribution of mountain permafrost. The study site, Wolf Creek Research Basin, Yukon Territory (60°30'N, 135°13'W), is a 195 km2 basin ranging in elevation from 650--2100 m with a mean annual air temperature of about -4°C at 1235 m a.s.l.
A modeled BTS surface, based on 394 measured BTS values and with elevation and potential incoming solar radiation as independent variables, was created within a GIS environment with an r2 value similar to European results. The distribution of permafrost within the basin was identified from pits and boreholes. A subsequent logistic regression was used to compare modeled BTS values to the actual permafrost distribution in order to produce a map of permafrost probability in the basin. A significantly higher likelihood of permafrost, observed in a confined valley bottom, was attributed to cold air drainage. This occurrence was not predicted by the BTS model and data from the affected area were removed from later analyses. (Abstract shortened by UMI.
An experimental study on the influence of climatic fluctuations on solifluction, Fosheim Peninsula, Ellesmere Island, Northwest Territories.
No full textA field experiment, involving direct manipulation of surface microclimate, was undertaken in the continuous permafrost zone to examine the influence of climatic fluctuations on solifluction rates and movements throughout the active layer. Movements and soil temperature were measured continuously from 1993-1997 using five electro-mechanical meters and thermocouple cables on an 8\sp\circ colluvial slope in Hot Weather Creek valley, Ellesmere Island. Natural variation of movement among the years and the meters was measured until summer of 1996 when surface climatic treatments (surface warming, wetting, a combination of these two, and cooling) were performed. The longer-term effects of the treatments were monitored until August 1997. Near-surface measurements alone do not provide an accurate picture of solifluction in areas with two-sided freezing ("cold" permafrost) because there can be substantial variation in movement rates at depth. In addition, multi-year average rates potentially hide a considerable range of annual variability and do not allow for the examination of a relationship between climatic fluctuations and annual movement. (Abstract shortened by UMI.
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