A thermal model is developed to find the distribution of stable near-surface ground ice on Mars that is in diffusive contact with the atmosphere for past and present epochs. Variations in the orbit of Mars are able to drive climate changes that affect both surface temperatures and atmospheric water content so the distribution of ground ice will vary significantly in past epochs. A technique is developed to correct the average water vapor density above the surface for depletion due to diurnal frost formation. Also presented is a simple model to estimate the atmospheric water content, based on the water vapor carrying capacity of the atmosphere over water ice on the martian surface.Maps of the distribution of ground ice are generated for the present epoch of Mars with varying amounts of water vapor in the atmosphere. The water vapor depletion scheme restricts the extent of stable ground ice as more water is put into the atmosphere so that ice never becomes stable at low latitudes. As the position of the perihelion varies, the extent of ground ice changes several degrees in the latitudinal extent, primarily in the northern hemisphere. The extent of ground ice is sensitive to the obliquity of Mars, however high obliquities are still not able to make ground ice stable at low latitudes. Finding ice is never stable at low latitudes is consistent with the lack of terrain softening at low latitudes and models that indicate Mars had high obliquities for much of its history.Also presented is the first L-band spectrum of an irregular satellite from the outer Solar System. Spectra of Himalia were obtained with the Visual and Infrared Mapping Spectrometer onboard the Cassini spacecraft. The Himalia spectrum is essentially featureless, showing a slight red slope and a suggestion of an absorption feature at 3 microns that would indicate the presence of water. Better measurements of the spectrum of Himalia, particularly in the region of the apparent 3-micron band, could help determine whether water is present, and if so, in what form.

This dissertation examines several questions in Martian surface processes relating to water or ice using a combination of geomorphology and modeling. I first examine sublimation of ice from new small mid-latitude craters with freshly exposed ice imaged by the High Resolution Imaging Science Experiment (HiRISE) camera. I discuss the theory of sublimation by free convection and describe a model that improves on the standard version used in the Mars literature. This model shows some differences from experimental data, but this appears to be because experimental conditions do not accurately capture the sublimation regime appropriate to the Martian surface. I use this sublimation model in concert with a thermal model and calculate sublimation rates at the sites of freshly exposed ice. Calculated sublimated thicknesses of one or more millimeters during the period when HiRISE images show ice imply that this ice is relatively pure, not pore-filling. The ice table thus revealed appears consistent with a model of the Martian subsurface in which relatively clean ice overlies pore-filling ice.Pingos are hills with cores of ice formed by freezing of liquid water under pressure. Possible pingos on Mars have been much discussed because they would have significant implications for Martian hydrological processes. I surveyed HiRISE images across a broad portion of the Martian surface searching for fractured mounds. Such features are candidate pingos, since pingos often develop surface fractures as they grow. A small number of Martian landforms, not previously identified, are morphologically consistent with pingos; however, landforms that appear related to these do show morphological differences from pingos. Other origins are possible, particularly since it is difficult to produce the requisite hydrologic conditions for pingo formation. Previously proposed pingos on Mars lack surface fracturing and are unlikely to be pingos.

Ice formed by water vapour deposition has been identified in different terrestrial environments: 1) in the atmosphere; 2) at the ground’s surface; 3) in caves; 4) in seasonally frozen ground; and 5) in perennially frozen ground (permafrost). Thus far, ground ice formed by diffusion and deposition of vapour in soils (types 4 and 5) has rarely been studied in a natural setting and remains one of the most poorly described ice types on Earth. This thesis focuses on the dynamics of deposition and sublimation of atmospheric water vapour into permafrost and the isotopic signature (D/H and 18O/16O) of the emplaced ground ice under different experimental conditions. Ground ice was produced in sediments with different thermo-physical characteristics (glass beads, JSC Mars-1 simulant). After a two-month growth period, the higher porosity sediments (JSC) had more than 7x the gravimetric water content than the lower porosity soil. Ground ice profiles had a distinct concave downwards shape due to the decrease in saturation vapour pressure with depth. Results also indicate that vapour deposited ground ice has a distinct δD-δ18O composition that plots near regression slope value of 8. Pore water isotopes plot below the global meteoric water line (GMWL) when the source of moisture is directly on top of the sediments. If an air gap is introduced between the source of moisture and the sediments, the pore water isotopes shift above the GMWL due to re-sublimation at the ground surface. Overall, this thesis addressed some fundamental knowledge gaps required to better understand the growth and isotopic evolution of ground ice emplaced by vapour deposition.

The ongoing climate warming is expected to increase thermokarst activity and their impacts by inducing permafrost degradation and active layer deepening. A retrogressive thaw slump, which represents the most dynamic thermokarst landform, was investigated in the Richardson Mountains-Peel Plateau region. The exposed material at the thaw slump represents an opportunity to characterize the cryostratigraphy of the uppermost 5 m of permafrost. Analyses of the stratigraphy, sedimentology, isotope geochemistry and radiocarbon dating is presented. Six sites were also identified on an elevation-vegetation gradient to provide complementary data on thaw layer thickness. Summer air temperatures, vegetation cover type, mesoscale conditions modifying the snowpack, timing of the snow accumulation and winter air temperature inversions are identified as the main drivers of thaw layer thickness in the region. The physical and chemical parameters of the massive ground ice exposed at the thaw slump are characteristic of buried glacier ice that experienced water infiltration and partial refreezing. The layer between the massive ground ice units and the thaw layer in the thaw slump is identified as a relict thaw layer and represents the period of maximum active layer deepening. It dates to the Holocene thermal maximum, which represents a period of important thermokarst activity that resulted in widespread paleo-thaw unconformities across northwestern Canada. Association of the region’s thaw slump activity with paleoclimatic parameters provide indication that the combination of formerly glaciated continuous permafrost, hummocky rolling moraine terrain, stream-incised relief, and massive ground ice, coupled with major rainfall events, represents a set of condition that is favourable to thaw slump activity.

Polygonal terrain underlain by ice wedges (IWs) are a widespread feature in continuous permafrost and make up 20-35%vol of the ground ice in the upper few meters of permafrost. Despite the numerous contemporary studies examining factors that control ice wedge cracking, development and degradation, relatively few have explored ice wedge activity in relation with past climate and vegetation conditions. In the Eureka Sound region, ice wedge polygons dominate the permafrost terrain. Their degradation has started to occur, leading to growth of thaw slumps. The objective of this study is twofold, the principal objective is to investigate the timing of ice wedge activity in the Eureka Sound region using the ¹⁴CDOC dates. The second objective is to evaluate the use of ice wedges as paleotemperature proxies. In July 2018, four ice wedges were sampled at 3-4 depths with each core sample being ~1m in length. In the following summer, eight ice wedges were sampled from the surface, 3-5 core samples were extracted per wedge. Active layer and snow samples were also recovered. Laboratory analyses on the ice wedge samples includes dissolved organic carbon content (DOC) and δ¹³CDOC, radiocarbon dating of DOC, geochemical concentration, and stable water isotopes. The DOC and geochemical results show that snowmelt is the main moisture source for ice wedges in the Eureka Sound region with a minor contribution of leached surface organics. The age (¹⁴CDOC) and size of the studied ice wedges were compared against a cracking occurrence model developed by Mackay (1974), these ice wedges align well with this model and suggest that ice wedge growth is non-linear. Ice wedges in the Eureka Sound region were active during the early to late Holocene (9-2.5 ka). The majority of the activity occurred in the later stage of the early Holocene following regional deglaciation and marine regression. ¹⁴CDOC, high resolution δ¹⁸O and D-excess suggests the occurrence of peripheral cracking in both large and small ice wedges. Rayleigh-type isotopic fractionation was found to occur with depth. As well, post depositional isotopic modification of snow and snowmelt accounts for up to a 4‰ difference of δ18O in surface ice wedge samples. δ¹³CDOC of surface ice wedge samples suggest a habitat transition during the late Holocene from dry meadows to polygonal terrain and the geochemical composition of ice wedges closely reflects that of glacial ice core records.

Permafrost is vulnerable to climate changes and the associated landscape changes that are enhanced by amplification processes and feedbacks unique to the Arctic. Permafrost degradation leads to important changes in terrestrial and aquatic ecosystems, and determining regions that are sensitive to permafrost degradation therefore represents an urgent issue. The Tombstone Territorial Park (TTP) and its surroundings (Ogilvie Mountains, central Yukon) represent one of those sensitive permafrost environment that should be monitored. The central Yukon is an enigmatic permafrost environment that reflects both Pleistocene and Holocene permafrost and climate conditions. The area is particularly intriguing because of the extensive presence of permafrost landforms that are more typical of areas much further north, especially ice-wedge (IW) polygons. It also represents a major transportation corridor linking multiple northern communities (Dempster Highway). Despite access along the road, and signs of permafrost degradation, there have been a limited number of studies addressing permafrost and ground ice conditions throughout the landscape. Consequently, this PhD thesis aims to characterize IW polygons, define the type and magnitude of landscape changes, and model permafrost distribution, conditions and sensitivity to climate changes in the study area. Characterization of IW polygons reveals that they occupy 2.6% of the TTP and preferentially develop in woody sedge peat, glaciofluvial and alluvial deposits along the lower reaches of the Blackstone and East Blackstone rivers on hillslopes of ≤1°. Vegetation type, surface wetness, and polygon spatial pattern are influenced by the development stage of ice-wedge polygons, while the size and angles of polygons seem independent of the development stage. A Landsat-based landscape change analysis of the TTP and surrounding region covering the 1986-2021 period shows that statistically significant spectral changes occurred in 24% of the study area, and most of these changes are associated with vegetation succession and hydrological processes (i.e., erosion and deposition). Other landscape changes included wildfires, slumps, changes to riverbanks and lake shores, earlier melting of icings in the summer, degradation on the peripheries of some ice wedge polygonal terrain, and potential insect damage to forests. The analysis reveals that the extent and magnitude of landscape changes in the study area are influenced by the geomorphic setting, ecological succession and glacial history of the region. Modeling current and future permafrost conditions in the study area using the Northern Ecosystem Soil Temperature (NEST) model indicate that permafrost has persisted through the 20th century and beginning of the 21st century and is currently present throughout the area. Modeled mean permafrost depth (113.8 ± 49.6 m), active layer thickness (2.45 ± 7 m), surface, near-surface, and deep ground temperatures (−1 ± 1.2°C, −1.6 ± 1.2°C, −2.4 ± 1.3°C, respectively) are in the range of other local and regional measurements. Predicted ALTs and permafrost depth show areas of permafrost loss by 2100 (22% of study area under RCP4.5, and 29% under RCP8.5). Permafrost degradation in the study area could greatly impact slope stability and conditions of aquatic systems, and shrubification could contribute to increased degradation.

<p> The thaw rates of the active layer above the permafrost zone from a series of sites along the Hudson Bay coastline at lat. 56° have been examined with respect to temperature and moisture gradients, the characteristics of the surface layer and the bulk thermal properties for each profile. The thermal properties have been examined using firstly a Fourier approach with the parameter of degree days and using secondly a graphical approach employing thermal relationships obtained in the laboratory analyses by Kersten (1949).</p> <p> It was found that thaw rates are controlled by the interaction of a number of environmental factors of which vegetation appears to be the most important.</p> <p> The two approaches to the derivation of thermal properties give quite different results, such that the graphical approach is deemed to be unsuitable to field application.</p> / Thesis / Bachelor of Science (BSc)

This study aims to quantify ground ice content and describe the cryostructures and sediment in 15 ice-bearing permafrost cores collected from nine sand-wedge polygons in University Valley. The objectives were reached through laboratory measurements and computed tomodensitometric (CT) scanned image analysis of the permafrost cores. The soils in the valley were predominantly medium-sand. Four types of cryostructures were present in the cores: structureless, suspended, crustal and porphyritic. Excess ice content ranged from 0 to 93%, gravimetric water content ranged from 13 to 1881% and volumetric ice content varied from 28 to 93%. Median excess ice, volumetric ice and gravimetric water contents significantly increased in the top 20 cm of the cores taken from the polygon shoulders with increasing distance from University Glacier. Ground ice was preferentially stored in the centre of the investigated polygons where the ground surface remains cryotic throughout the year. Conversely, higher ground ice contents were measured in the shoulders of the investigated polygon where the ground surface is seasonally non-cryotic. CT-scanned images were shown to reasonably assess the distribution and presence of excess ice in permafrost cores taken from a cold and hyper-arid environment. The results of this thesis provide the first cryostratigraphic study in the McMurdo Dry Valleys of Antarctica.

In Canada’s western Arctic, perennial discharge from permafrost watersheds is the surface manifestation of active groundwater flow systems, yet understanding the mechanisms of groundwater recharge and flow in periglacial environments remains enigmatic. This thesis addresses questions on how and where groundwater recharge occurs. Watersheds were selected in Yukon (Fishing Branch River at Bear Cave Mountain) and the Northwest Territories at latitudes spanning from continuous to discontinuous permafrost (five tributary rivers to the Mackenzie River from Wrigley to Aklavik). All are characterized by perennial flow with open water in the winter, and discharge from sedimentary formations of karstic carbonates and evaporate rocks. Determinations of groundwater contributions to discharge, mixing, recharge conditions and circulation times were made on the basis of a suite of analytical approaches involving measurements of major dissolved ions, δ18O, δD, δ13CDIC, 3H, noble gases and flow gauging was conducted at some sites. The application of these tracers show that hydrogeological conditions and flow paths in permafrost terrains are surprisingly similar to those of temperate regions. Groundwater recharge was determined to be a mix of annual precipitation with contributions from snowmelt and precipitation. All systems investigated show that groundwaters have recharged through organic soils with elevated PCO2, which suggests that recharge occurs largely during summer when biological activity is high. Noble gas concentrations show that the recharge temperature was between 0 and 6 °C, which, when considered in the context of discharge temperatures, suggests that there is no significant imbalance of energy flux into the subsurface. Groundwater ages were found using the 3H-3He method and were dependent on flow path. By characterizing groundwater and surface water chemistry, the proportion of groundwater was found in numerous water courses. The possible impact of ground ice formation and melting on noble gas concentrations in groundwater was considered. To assess this link, a new method to measure the noble gas composition of ground ice bodies was developed. The method can be used to determine the origin of ice, based on changes in noble gas ratios between ice originating from compaction of snow (e.g. glacier ice) vs. ice originating from freezing of water. No significant fractionation of noble gases during groundwater freezing and ground ice formation was identified. Applied to determination of the origin of ground ice bodies, the method was shown to be both diagnostic of ice origin and un-encumbered by reactivity in the subsurface, which compromises the use of the dominant atmospheric gases (O2 and N2).   Résumé Dans l’Ouest de l'Arctique canadien, la décharge pérenne dans certaines rivières en région de pergélisol est la manifestation en surface d’une circulation d’eau souterraine; cependant la compréhension des mécanismes d’écoulement et de recharge des eaux souterraines en région de pergélisol demeure énigmatique. Cette thèse s’intéresse à la question de savoir comment et où la recharge des eaux souterraines se produit. Des bassins versants ont été choisis au Yukon (Rivière Fishing Branch à Bear Cave Mountain) et dans les Territoire du Nord-Ouest à des latitudes s’étendant du pergélisol discontinu au pergélisol continu (cinq tributaires du Mackenzie entre Wrigley et Aklavik). Toutes ces rivières ont un écoulement d’eau pérenne avec des zones non gelées et une décharge dans des formations sédimentaires de roches carbonatées et d‘évaporites. L’identification des contributions des eaux à la décharge, les mélanges, les conditions de recharge, et les temps de circulation ont été faits à partir d’analyses qui ont inclus les concentrations en éléments majeurs, leur valeur isotopique (δ18O, δD, δ13C, 3H), ainsi que leur teneur en gaz rares. A certain des sites analysés des mesures d’écoulement ont été prises. L’application de ces traceurs montre que les conditions hydrauliques et le chemin des écoulements en région de pergélisol sont similaires à ceux des régions tempérées. La recharge en eau souterraine a été identifiée comme étant un mélange de précipitations annuelles, avec des contributions de neige et de pluies. Tous les systèmes étudiés montrent que les eaux souterraines se sont rechargées en traversant des sols organiques avec une PCO2 élevée, ce qui suggère que la recharge se produire largement durant l’été quand l’activité biologique est élevée. Cependant, les concentrations en gaz nobles montre que la température de recharge des eaux souterraines était entre 0 et 6 °C ce qui indique qu’il n’y a pas de déséquilibre de flux d’énergie à l’intérieur de la zone proche de la surface. L’âge des eaux a été déterminé par la méthode 3H-3He et cet âge est dépendant du chemin d'écoulement. En caractérisant les paramètres chimiques des eaux de surface et des eaux souterraines, il a été possible de trouver la contribution des eaux souterraines aux eaux surface. Le possible impact de la formation et de la fonte de la glace souterraine sur les concentrations des gaz nobles a été considéré. Pour déterminer s’il y a un lien entre ceux-ci, une nouvelle méthode pour mesurer la concentration en gaz nobles dans les glaces souterraines a été développée. La méthode peut être utilisée pour déterminer l’origine de la glace; elle est basée sur les changements dans les rapports des gaz nobles entre la glace issue de la compaction de la neige (c’est-à-dire la glace de glacier) par opposition à la glace issue du gel de l’eau. Aucun fractionnement significatif des gaz nobles durant l’engel des eaux souterraines et la formation de glaces souterraines n’a été identifié. Appliquée à l’identification de l’origine des masses de glace enfouies, on a montré que la méthode pouvait permettre d’identifier l’origine des glaces souterraines sans qu’elle soit affectée par des réactions biologiques de sub-surface, lesquelles rendent inutilisables les gaz atmosphériques (O2, and N2).

In Canada’s western Arctic, perennial discharge from permafrost watersheds is the surface manifestation of active groundwater flow systems, yet understanding the mechanisms of groundwater recharge and flow in periglacial environments remains enigmatic. This thesis addresses questions on how and where groundwater recharge occurs. Watersheds were selected in Yukon (Fishing Branch River at Bear Cave Mountain) and the Northwest Territories at latitudes spanning from continuous to discontinuous permafrost (five tributary rivers to the Mackenzie River from Wrigley to Aklavik). All are characterized by perennial flow with open water in the winter, and discharge from sedimentary formations of karstic carbonates and evaporate rocks. Determinations of groundwater contributions to discharge, mixing, recharge conditions and circulation times were made on the basis of a suite of analytical approaches involving measurements of major dissolved ions, δ18O, δD, δ13CDIC, 3H, noble gases and flow gauging was conducted at some sites. The application of these tracers show that hydrogeological conditions and flow paths in permafrost terrains are surprisingly similar to those of temperate regions. Groundwater recharge was determined to be a mix of annual precipitation with contributions from snowmelt and precipitation. All systems investigated show that groundwaters have recharged through organic soils with elevated PCO2, which suggests that recharge occurs largely during summer when biological activity is high. Noble gas concentrations show that the recharge temperature was between 0 and 6 °C, which, when considered in the context of discharge temperatures, suggests that there is no significant imbalance of energy flux into the subsurface. Groundwater ages were found using the 3H-3He method and were dependent on flow path. By characterizing groundwater and surface water chemistry, the proportion of groundwater was found in numerous water courses. The possible impact of ground ice formation and melting on noble gas concentrations in groundwater was considered. To assess this link, a new method to measure the noble gas composition of ground ice bodies was developed. The method can be used to determine the origin of ice, based on changes in noble gas ratios between ice originating from compaction of snow (e.g. glacier ice) vs. ice originating from freezing of water. No significant fractionation of noble gases during groundwater freezing and ground ice formation was identified. Applied to determination of the origin of ground ice bodies, the method was shown to be both diagnostic of ice origin and un-encumbered by reactivity in the subsurface, which compromises the use of the dominant atmospheric gases (O2 and N2).   Résumé Dans l’Ouest de l'Arctique canadien, la décharge pérenne dans certaines rivières en région de pergélisol est la manifestation en surface d’une circulation d’eau souterraine; cependant la compréhension des mécanismes d’écoulement et de recharge des eaux souterraines en région de pergélisol demeure énigmatique. Cette thèse s’intéresse à la question de savoir comment et où la recharge des eaux souterraines se produit. Des bassins versants ont été choisis au Yukon (Rivière Fishing Branch à Bear Cave Mountain) et dans les Territoire du Nord-Ouest à des latitudes s’étendant du pergélisol discontinu au pergélisol continu (cinq tributaires du Mackenzie entre Wrigley et Aklavik). Toutes ces rivières ont un écoulement d’eau pérenne avec des zones non gelées et une décharge dans des formations sédimentaires de roches carbonatées et d‘évaporites. L’identification des contributions des eaux à la décharge, les mélanges, les conditions de recharge, et les temps de circulation ont été faits à partir d’analyses qui ont inclus les concentrations en éléments majeurs, leur valeur isotopique (δ18O, δD, δ13C, 3H), ainsi que leur teneur en gaz rares. A certain des sites analysés des mesures d’écoulement ont été prises. L’application de ces traceurs montre que les conditions hydrauliques et le chemin des écoulements en région de pergélisol sont similaires à ceux des régions tempérées. La recharge en eau souterraine a été identifiée comme étant un mélange de précipitations annuelles, avec des contributions de neige et de pluies. Tous les systèmes étudiés montrent que les eaux souterraines se sont rechargées en traversant des sols organiques avec une PCO2 élevée, ce qui suggère que la recharge se produire largement durant l’été quand l’activité biologique est élevée. Cependant, les concentrations en gaz nobles montre que la température de recharge des eaux souterraines était entre 0 et 6 °C ce qui indique qu’il n’y a pas de déséquilibre de flux d’énergie à l’intérieur de la zone proche de la surface. L’âge des eaux a été déterminé par la méthode 3H-3He et cet âge est dépendant du chemin d'écoulement. En caractérisant les paramètres chimiques des eaux de surface et des eaux souterraines, il a été possible de trouver la contribution des eaux souterraines aux eaux surface. Le possible impact de la formation et de la fonte de la glace souterraine sur les concentrations des gaz nobles a été considéré. Pour déterminer s’il y a un lien entre ceux-ci, une nouvelle méthode pour mesurer la concentration en gaz nobles dans les glaces souterraines a été développée. La méthode peut être utilisée pour déterminer l’origine de la glace; elle est basée sur les changements dans les rapports des gaz nobles entre la glace issue de la compaction de la neige (c’est-à-dire la glace de glacier) par opposition à la glace issue du gel de l’eau. Aucun fractionnement significatif des gaz nobles durant l’engel des eaux souterraines et la formation de glaces souterraines n’a été identifié. Appliquée à l’identification de l’origine des masses de glace enfouies, on a montré que la méthode pouvait permettre d’identifier l’origine des glaces souterraines sans qu’elle soit affectée par des réactions biologiques de sub-surface, lesquelles rendent inutilisables les gaz atmosphériques (O2, and N2).