Active microwave sensors are known to provide valuable information regarding snow and ice surfaces in the polar regions, where darkness and cloud cover prevail. Here, data collected in the Arctic by a Ku-band microwave radar altimeter, designed and constructed in the UK, are analysed. The two main components of this study comprise data gathered in the East Greenland Sea marginal ice zone and over two Svalbard ice caps. A systematic treatment is made of the electromagnetic properties of snow and ice at 13.81 GHz, and the differences between various polar surface media are highlighted. Theoretical and empirical models are presented which enable calculation of the relevant dielectric and scattering properties of snow and ice layers. Parametric studies are undertaken to give insight into the range of scattering conditions likely to be encountered by a radar altimeter in the regions investigated. Examples of altimetric data and results of their analysis are presented, demonstrating the effects of different ice types and terrain upon incident altimeter pulses. Waveforms are characterised by their shape, and certain forms are linked with particular physical properties of the surface. To this a variety of supporting information is added in order to verify and validate interpretations of these results. Algorithms are proposed which enable geophysical information to be derived from altimetric data.

The growth of the Weddell Sea ice cover in 1980 is examined, using Nimbus-7 satellite Scanning Multi-channel Microwave Radiometer (SMMR) data in combination with data (positional, air temperature and atmospheric pressure) from 4 Nimbus-tracked drifting buoys. Ice concentrations are retrieved from the SMMR data by applying a cluster analysis algorithm developed by J. Comiso of NASA. Analyses of computed differential kinematic parameters (DKP)s of the buoy array offer insight into the complex mesoscale behaviour of the underlying Weddell Gyre. High frequency divergence, convergence and deformation events isolated in the DKP results, and driven largely by the regular passage of cyclones, are related to changes in ice concentration observed in the SMMR data. The profound role of the Antarctic Peninsula in influencing both atmospheric and oceanic circulation (and thus ice formation, drift and eventual decay) in the region is evaluated. Possible relationships between buoy drift in the inner pack and ice edge advance are examined, yielding information on the relative importance of ice growth in open water within the pack and that at the ice edge. After an introductory chapter, Chapter 2 describes the physical setting of the Weddell Sea. Comparisons are drawn both with other sectors of the Southern Ocean and the Arctic, emphasizing the uniqueness of the region not only in terms of its climate and oceanography but also its sea ice cover. Chapter 3 traces the evolution of passive microwave remote sensing from space as a tool for monitoring Antarctic sea ice extent and concentration; the relative merits and disadvantages of these techniques are evaluated. Chapter 4 concentrates on the use of SMMR data. Detailed comparisons are made of algorithms available for the extraction of ice concentrations from the raw brightness temperature data. The choice of algorithm used is justified. Chapter 5 is largely concerned with the analysis of the buoy data, and the kinematic behaviour of the array as a unit. These results are combined with the SMMR data in Chapter 6 to identify distinct dynamic zones and meridional advective sectors, and to compare the behaviour of the inner pack with that of the unconstrained ice edge. The evolution of a high concentration core within the unique perennial sea ice zone hugging the east coast of the Peninsula, which persists throughout the period of study is unusual enough to merit a separate sub-section. Conclusions are drawn in chapter 7.

been used to investigate the form and topography of the Antarctic ice sheet and to relate these to the physical processes of ice flow and basal conditions. Topographic roughness typically increases towards the thin ice of coastal reg ions as surface undulation wav el eng ths decrease and amplitudes increase. Temperature and velocity variations also have significant effects. The coastal zone is punctuated by embayments of severe topography immediately inland of outlet glaciers. This topographic variability has been summarized in a statistical model for the purposes of simulating satellite radar altimeter waveforms. Consideration of the relationship between bedrock and surface profiles has shown that ice temperature is a major influence on the response of the surface to bedrock irregularities. Regional subglacial water layers may al so have an important effect on surface topography. A re-analysis of models of longitudinal stress grad i ents suggests that er ystal fabrics favouring faster flow develop with distance from ice divides and that the relative depth of the zone of maximum shear fluctuates in response to topographic and glaciological constraints. Driving stress patterns have been associated with characteristic glaciological regimes and have suggested a qualitative difference between outlet glaciers and ice streams. The transition to high velocity flow in outlet glaciers has been shown to be triggered ab ruptly in response to subglac ial fjord heads. The dependence of fast flow on subglacial topography indicates a significant stabilizing effect on discharge from ice sheets and suggests that surge behaviour is unlikely within existing ice sheet outlets. The onset of basal sliding at the head of subglac ial fjords suggests a mechanism for the production of overdeepened fjords and steep headwalls through concentrated erosion. This may help in the reconstruction of the dynamics of former ice sheets. Some West Antarctic ice streams do not exhibit this rapid transition in behaviour.

Air, 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.

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.

Northwestern Arctic Canada is one of the most rapidly warming regions in the Arctic (Serreze et al., 2009). Retrogressive thaw slumps (RTS) are one of the most dramatic thermokarst features in permafrost terrain (Kokelj et al., 2013). Many studies have focused on describing the distribution of thermokarst landscapes (i.e., Olefeldt et al., 2016), as well as change in thermokarst terrain over the historical record (i.e., Kokelj and Jorgenson, 2013). However, improved high temporal and spatial resolution monitoring of thaw slump activity is required to enhance our understanding of factors governing their growth. Recent advances in aerial and ground-based Structure from Motion (SfM), a photogrammetry application, allow for temporal and spatial high-resolution characterization of landscape changes. This thesis explores two methods in SfM photogrammetry: 1) aerial imaging using an unmanned aerial vehicle (UAV) and 2) ground-based imaging using stationary multi-camera time-lapse installations, to derive high-resolution temporal and spatial data for change detection. A trend in mean elevation change was produced, and agrees with the RTS behaviour over the study period, which supports the viability of the proposed capture method. The lack of congruency in data range suggests need for further development in terms of analyses and differencing algorithms employed. The proposed method may be feasible for employment in other fields of science in which high temporal resolution change detection is desired. This proof of concept study was conducted at a small slump on the Peel Plateau, NWT, Canada, and aims to enhance understanding of the development and perpetuation of thaw slumps, to better anticipate landscape and ecosystem responses to future climate change.

Thesis advisor: Carling Hay / Modern day climate change is exacerbating sea level change both locally and globally. The magnitudes of these changes are dependent on numerous global and regional factors that make it difficult to accurately project local sea level into the future. In Alaska, there are many processes contributing to sea level changes along the coast. In particular, there is substantial vertical land movement, in the form of uplift and subsidence, due to the isostatic adjustment of the land once burdened by ice sheets. In Northern Alaska, there is an additional source of land motion that occurs because the flat, tundra landscape is underlain by ~100-300m of permafrost. This permafrost is currently melting and the area is experiencing land subsidence because of it. This study refines sea level projections along northern Alaska by accounting for this extra climate signal. The addition of permafrost-melt induced isotropic land subsidence in projections for the northern coast of Alaska results in sea level rise estimates at the end of the century that double previously published projections. These improved Alaska projections will be vital for the coastal communities, especially in coming decades, in order to minimize losses of coastal property and infrastructure. / Thesis (BS) — Boston College, 2018. / Submitted to: Boston College. College of Arts and Sciences. / Discipline: Arts and Sciences Honors Program. / Discipline: Earth and Environmental Sciences.

Rising temperature and precipitation are driving widespread changes in the area of surface water across the Arctic and sub-Arctic. Previous work suggests that broad-scale increases in surface water area are occurring in the zone of continuous permafrost, while decreases are occurring the zone of discontinuous permafrost. However, there are still uncertainties surrounding regional change and fine-scale terrain factors that may mediate the effects of temperature and precipitation. In my MSc research I examine terrain and climatic drivers of change in the area of lakes and ponds across the western Canadian Arctic and Sub-Arctic. In the first part of my thesis I use the Landsat satellite image archive to map change in lake area within the Lower Mackenzie Plain, NWT. I found that overall lake area has largely decreased since 1985, due to the drainage of large lakes. I also found that lakes located in fire scars were more likely to show persistent decreases in area, likely due to interactions with surrounding permafrost conditions. In the second part of my thesis, I used the Global Surface Water dataset developed by the GLAD research group to model changes in total permanent water across the Northwest Territories and the Yukon. I used a Random Forest model to analyze the effects of terrain and climate variables on the direction of change in permanent water. My observations show that surface water area has generally increased, and that the response of surface water to climate change largely depends on regional geology. Increases in permanent water were more likely to occur in wetter regions underlain by bedrock or fine-colluvium while decreases were more likely to occur in warmer regions and areas underlain till blanket. I also used methods developed in the first part of my thesis to compare regional changes in surface water across six distinct study areas. I observed increases in surface water across five of the six study areas and consistent decreases in lake area associated with wildfire. This research shows that changes in surface water are complex and depend on interactions between climate variables and fine-scale terrain factors. My research also demonstrates the importance of wildfire in driving permafrost and lake dynamics. / Graduate

Hur skapar man arkitektur för sociala och kulturella sammanhang på en plats som framstår som en ogästvänlig boplats för människor? Syftet med studien var att få bättre förståelse för relationen mellan natur, kultur, landskap, människa, teknik och miljö i ett av världens nordligaste samhälle, Longyearbyen på Svalbard, vars extrema klimat med rådande istid och långa mörkerperioder framstår som en skrämmande boplats för människor. Finns det plats för arkitektur som är något mer än bara ett konstruktivt skydd mot rovdjur, väder och vind? Målet var att skapa en plats för aktiva och oförpliktade möten; ett Campus Kultur som fungerar som knutpunkt dygnet runt. / How does one create an architectural design for a social and cultural context in a place that appears to be a hostile environment for people? The purpose of my studie was to to get a better understanding of the relation between nature, culture, landscape, people, technical application and environment at the world´s nothernmost town, Longyearbyen on Svalbard, whose extreme climate and months of darkness appear a frightening settlement for people. Is there room for architecture being more then a constructive shield against predators and the elements? My goal was to create a meetingplace for spontaneous activities without obligation; a Cultural campus and a hub around-the-clock.