No description available.

No description available.

Surge-type glaciers experience cyclical variations between long periods of slow flow, followed by shorter periods of rapid flow. These glaciers have been thoroughly analysed in many regions, but detailed studies of surging in the Canadian Arctic are lacking. This thesis provides the first comprehensive reconstruction of the dynamics of Iceberg and Airdrop glaciers, located on western Axel Heiberg Island, and reveals detailed observations of a surge for the first time in the Canadian Arctic. A variety of remotely sensed data, including historical aerial photographs, declassified intelligence satellite photographs, optical satellite imagery (e.g., ASTER, Landsat), and synthetic aperture radar data (e.g., ERS-1, ERS-2) were used to quantify changes in terminus position, ice velocity, and ice thickness since the 1950s. A surge initiated at the terminus of Iceberg Glacier in 1981 and terminated in 2003, suggesting an active phase length of 22 years. High surface velocities, peaking at ~2300 m a⁻¹ at the terminus in summer 1991, were accompanied by a terminus advance of >7 km over the period 1981-1997 and a large transfer of mass down-glacier, causing significant median surface elevation changes reaching >3 ± 1 m a⁻¹ across the entire trunk width. The ensuing quiescent period has seen a continual decrease in flow rates to an average centreline velocity of 11.5 m a⁻¹ in 2020-2021, a gradual steepening of the glacier surface, and a terminus retreat of >2.5 km. Observations on Airdrop Glacier show a continuous advance totalling ~6 km since 1950 and notably less variability in its surface velocities in comparison to Iceberg Glacier. This advance can be attributed to consistently high flow rates of Airdrop’s entire surface, resulting in significant thickening near its terminus since at least 1977. However, velocities have more than halved within the last 15 years, but without any clear evidence of previous fast flow events, we cannot confirm whether Airdrop’s behaviour is cyclic in nature and therefore characteristic of a surge. Instead, Airdrop Glacier could be experiencing a delayed response to positive mass balance conditions of the Little Ice Age, and its recent slowdown could be indicative of a gradual adjustment to recent climatic conditions.

The Arctic cryosphere is experiencing a higher rate of warming compared to the rest of the world due to Arctic amplification. As glacier elevation change provide reliable evidence of climate change it is routinely measured by satellite altimeters. Satellite altimetry, while a valuable tool for monitoring elevation change over time, is subject to inherent uncertainties caused by, among other factors, the small scale surface roughness of the target surfaces. Previous studies have identified surface roughness as a key source of uncertainty when measuring sea ice freeboard and studies suggest the surface roughness strongly influences the Synthetic Aperture Radar (SAR) signatures of sea ice. Similar studies over snow- and glacier surfaces, are rare. In this context, we attempt to conduct a small scale calibration and validation (cal/val) campaign over glacier surfaces, using the ideal location and infrastructure of the University Centre in Svalbard. We demonstrate the process, from planning through field data collection and data analysis. By doing so, we identify good as well as bad practices. Using high resolution in-situ LiDAR data, collected under two ICESat-2 (IS2) overpasses in Svalbard we generated Digital Elevation Models (DEM) and calculated surface roughness estimates across glacier- and snow surfaces. The surface roughness was quantified by calculating the Root Mean Square (RMS) of deviations from the overall topography of the surfaces. The DEMs were used for direct comparison with the satellite elevation retrievals and the observed elevation differences were tested for correlation with surface roughness at different length scales. We then investigated the effect of surface roughness on the photon cloud of the lower level ATL03 ICESat-2 data products, by quantifying the precision in the data. We found little to no correlation between RMS roughness and the observed elevation differences between in-situ and satellite data sets, possibly explained by errors in georeferencing the DEMs. We show moderate to strong correlation between photon cloud precision and along- and across-track absolute surface slopes, with correlation coefficients of 0.6–0.8. Correlation between photon cloud precision and RMS roughness was found, with a maximum correlation coefficient of 0.9 for a roughness length scale of 1m. The results suggest IS2 is sensitive to surface roughness at similar length scales but we identify a need for more data, covering a wider range of surfaces and potential roughness scenarios, to draw strong conclusions. We demonstrate how a small team can carry out a cal/val campaign in the high arctic and collect coincident data under satellite overpasses, data which is typically rare for the remote high Arctic regions.

No description available.

No description available.

Water is a primary driver of the physical, geochemical and biological evolution of the Earth. The near-surface hydrosphere (exosphere) includes the atmosphere, cryosphere (glacial and polar ice), the biosphere, surface water, groundwater, and the oceans. The amounts of water in these various reservoirs of the hydrologic cycle have likely varied significantly over the past 700 Ma, with the cryosphere and continental biosphere reservoirs likely showing the most dramatic variations relative to the modern. For example, 700 Ma, during snowball-Earth conditions, the planet may have been almost entirely enveloped in ice, whereas throughout much of the Phanerozoic, greenhouse conditions predominately prevailed and the Earth had a much smaller cryosphere. Similarly, before about 444 Ma and the proliferation of land plants, the continental biosphere reservoir would have effectively non-existent. However, today, plants play a critical role in storage and transfer of water within the hydrologic cycle. Because the amount of water in the exosphere is thought to have remained relatively constant during the past 700 Ma, variations in the amounts of water held by the in the various exogenic reservoirs exert concomitant effects on other reservoirs in the exosphere. We present a conceptual and numerical model that examines variations in the amount of water in the various reservoirs of the near-surface hydrologic cycle (exosphere) during the past 700 Ma and quantify variations in the rates of exchange of water between these reservoirs in deep time. Variations in the sizes of major reservoirs are primarily controlled by changes in global average temperature, and the movement of water between the atmosphere, surface water, and ocean reservoirs varies in concert with the waxing and waning of the cryosphere. We find that variations in the sizes of major reservoirs are primarily controlled by changes in global average temperature, and the flux of water between the atmosphere, surface water, and ocean reservoirs varies in concert with the waxing and waning of the cryosphere, with some fluxes decreasing to 0.0 kg/yr during snowball-Earth conditions. We find that the amount of water precipitated from the atmosphere to the cryosphere increases from greenhouse conditions to -10.5°C and decreases from -10.5°C to snowball-earth conditions, highlighting "tipping-point" behavior due to changes in temperature and cryosphere surface area. The amount of surface runoff to the oceans varies in proportion to the amount of water removed from the surface water reservoir and transferred into the continental biosphere. Variations in the movement of water between near-surface reservoirs that are driven by the waxing and waning of the cryosphere and emergence and growth of plant life thus have significant implications for the transfer of weathering products to the oceans and could contribute to short-term (<1 Ma) variations in seawater composition and isotopic signatures. / Ph. D. / Water drives the evolution of the planet, and the distribution of water throughout Earth’s atmosphere and surface has varied during the geologic past. The amounts of water in the atmosphere, polar ice, the biosphere, surface water, groundwater, and the oceans have changed during the past 700 million years, and the polar ice and biosphere reservoirs have undergone the most significant changes during that time. For example, at extremely cold conditions the planet may have been covered in ice, and during warmer conditions the planet may have been covered in little to no ice. Similarly, before 444 million years ago, the biosphere on Earth’s continental surface was almost non-existent. The evolution of land plants after 444 Ma resulted in an increase in the amount of water in the biosphere. Changes in the amounts of water in one reservoir of water over time will have effects on the other reservoirs of water in the water cycle. We produce a numerical model that examines changes in the sizes of water cycle reservoirs and the movement of water between those reservoirs during the past 700 million years. Variations in reservoir sizes are primarily controlled by changes in global average temperature, and the movement of water between the atmosphere, surface water, and ocean reservoirs varies with changes in the amount of polar ice on Earth. We find that total annual precipitation to polar ice increases from greenhouse temperatures to - 10.5°C and decreases from -10.5°C to cold snowball-earth temperatures due to changes in both temperature and the surface area of polar ice. The amount of surface runoff to the oceans varies in proportion to the amount of water removed from the surface water reservoir and transferred into the continental biosphere. Variations in the movement of water between reservoirs that are driven by the waxing and waning of polar ice and the growth of plant life have significant implications for the movement of dissolved material to the oceans and could contribute to short-term (<1 Ma) variations in seawater chemistry.

Este trabalho investiga a dinâmica de retração frontal de duas geleiras de maré, Drummond (66°40'S, 65°43'O) e Widdowson (66°43'S, 65°46'O), na costa ocidental da Península Antártica. O estudo usou fotografias aéreas e imagens satelitais LANDSAT (a partir de 1986) para determinar a variação de área dessas geleiras no período 1957–2015 e analisar a sensibilidade às recentes mudanças ambientais na Península Antártica. O modelo digital de elevação AsterGDEM2 foi usado para caracterizar a morfologia e morfometria da bacia de drenagem dessas massas de gelo. A análise estatística dos dados de temperatura média anual da Estação Vernadsky (65°14’ S, 64°15’ O) mostra tendência ao aquecimento atmosférico no período 1950–2015 (0,047°C ano-1) nesta parte da Península Antártica ocidental. As frentes das duas geleiras retraíram ao longo dos últimos 68 anos, no entanto a geleira Widdowson apresentou uma perda maior (36,03 km2, ou 16,81% da área original) e uma linha de neve mais elevada (200 m a.n.m. em 2016) do que a geleira Drummond (18,84 km2, ou 4,26% da área original; linha de neve a 100 m a.n.m. em 2016) no período. Essa diferença na retração da duas geleiras, lado a lado e com a mesma orientação de fluxo do gelo, são atribuídas as diferentes declividades da superfície e proporção da área de acumulação sobre a área total. A geleira de menor área, Widdowson, somente atingiu um ponto de estabilização (apoiada ao embasamento rochoso lateral) em 2001, enquanto a frente da Drummond estabilizou-se em 1974. Além disso, a geleira Widdowson é mais íngreme no setor frontal, o que pode ter influenciado na taxa de desprendimento de icebergs e gerado um deslizamento basal mais eficiente, aumentando a velocidade de fluxo do gelo e, por consequência, aumentando as taxas de retração. Esses resultados condizem com estudos para outras geleiras de descarga com frentes flutuantes na Península Antártica, as quais são mais sensíveis às mudanças climáticas. A dinâmica dessas geleiras também é influenciada por mudanças nas forçantes oceânicas, taxas de precipitação, derretimento superficial e morfologias diferentes do embasamento rochoso; esses pontos devem ser tratados em trabalhos futuros. Como subproduto desta investigação, foi gerado um banco de dados em SIG para a continuidade do monitoramento das duas geleiras. / This work investigates the ice front retreat dynamics of two tidewater glaciers, Drummond (66°40'S, 65°43'W) and Widdowson (66°43'S, 65°46'W), on the western coast of the Antarctic Peninsula, associated with environmental changes in the last six decades. The study uses aerial photographs and LANDSAT satellite images (from 1986 onwards) to determine these glaciers area variations in the period 1957–2015 and to analyze their sensitivity to recent environmental changes in the Antarctic Peninsula. The digital elevation model ASTERDEM2 was edited by a routine to characterize the morphology and the morphometry of the drainage basins of these ice masses. The statistical analysis of the updated mean annual temperature data from the Faraday/Vernadsky station (65°14’ S, 64°15’ W) shows a trend towards regional atmospheric warming in the period 1950–2015 (0.047°C year-1) in this part of the West Antarctic Peninsula. The ice fronts of these two glaciers have retreated for the last 68 years, however, the Widdowson Glacier had a more significant loss (36.03 km² or 16.81% of the original area) and a higher snow line elevation (200 m a.s.l. in 2016) than the Drummond Glacier (18.84 km2, or 4.26% of the original area; snow line at 90 m a.s.l. in 2016) in the period. This retreat difference of the two glaciers, side by side and with the same ice flow orientation is attributed to different surface slopes and accumulation area proportion over the total area. The smaller area glacier, Widdowson, has shown to be more sensitive to environmental changes and only reached a stabilization point (supported to the lateral bedrock) in 2001, while the Drummond front stabilized in 1974. In addition, the Widdowson glacier is steeper in the frontal sector, which may have influenced on the calving rate and generate a more efficient basal slip, increasing the ice flow rate and, consequently, increasing the retraction rate. These results are consistent with studies for other floating outlet glaciers with calving in the Antarctic Peninsula, which are more sensitive to climate change. The dynamics of these glaciers is also influenced by changes in ocean forcing, precipitation rates, surface melting and bedrock morphology; these points should be investigated in future works. As a by-product of this research, a GIS database wasgenerated for a continuous monitoring of the two glaciers.

Les ressources en eau de l'Himalaya, vitales pour 800 millions de personnes, proviennent majoritairement de la mousson et de la fonte de la cryosphère. L'impact du changement climatique sur ces ressources, particulièrement important dans cette région selon le GIEC (2007), est un questionnement majeur à l'échelle de la chaîne himalayenne. Dans ce contexte, la quantification des composantes pluviales, nivales et glaciaires du bilan hydrologique est primordiale. A cet effet, un modèle hydrologique conceptuel distribué (HDSM) a été développé pour estimer la répartition de ces composantes dans les écoulements de la rivière Dudh Koshi de 2001 à 2005. Son bassin versant (3 700 km²), dont le point culminant est le Mont Everest, est situé à l'est du Népal. Les surfaces enneigées, calées à partir de données satellitaires, ainsi que les débits, sont correctement simulés par le modèle. Toutefois, le facteur de fonte glaciaire est surestimé, entrainant une composante glaciaire d'environ 60% des débits annuels, contre 5% selon la littérature. Cette surestimation compense une sous-estimation significative des précipitations, notamment solides. Après une correction des précipitations, les composantes pluviale, nivale et glaciaire expliquent respectivement, 63%, 9% et 29% des débits annuels de la Dudh Koshi sur la période 20012005. Pour compléter cette modélisation, les perceptions de la population sur les variations hydro-climatiques, obtenues à partir d'enquêtes dans les villages, ont été comparées aux données quantitatives utilisées et simulées par le modèle HDSM de 1977 à 2007. Cette comparaison la sous-estimation des précipitations solides. Les résultats mettent aussi en évidence une diminution significative des précipitations (totales, liquides et solides) en décembre, et une augmentation significative, non perçue par la population, des températures annuelles mesurées sur les 30 dernières années. Les deux approches, par modélisation et par enquêtes, soulignent les incertitudes importantes des données hydro-climatiques du bassin versant de la Dudh Koshi. Ces incertitudes limitent la compréhension des processus hydro-nivoglaciaires et l'estimation des impacts du changement climatique sur la ressource en eau de ce bassin. Les perceptions, bien qu'elles soient également associées à des incertitudes, apportent des informations complémentaires cruciales pour améliorer ces connaissances et la critique des données quantitatives de ce milieu de haute montagne himalayenne. / The Himalayan water resources, vital for 800 millions of people, come mainly from the monsoon and from the melting of the cryosphere. The impact of the climate change on these resources, especially significant in the area, is a major issue in the Himalayan range. In this context, the assessment of the rainfall, snowmelt and icemelt components of the water balance is crucial. Consequently, a distributed conceptual hydrological model (HDSM) was developed to estimate the contribution of each component to the Dudh Koshi River flows from 2001 to 2005. The Dudh Koshi River basin (3 700 km²), with the Mount Everest as highest peak, is located in Eastern Nepal. The snow cover areas, calibrated with satellite data, and as well as the runoff are correctly simulated by the model. Nevertheless, the ice degree-day factor is overestimated, leading to an icemelt contribution around 60% of annual discharge, against 5% in the literature. This overestimation offsets a significant underestimation of precipitation, especially solid precipitation. After a correction of the precipitation, the contributions of rainfall, snowmelt and icemelt represent respectively 63%, 9%, and 29% of the Dudh Koshi annual discharge from 2001 to 2005. To complete this modeling, perceptions of the population on the hydro-climatic variability, obtained by interviews in the villages, were compared to the quantitative data used and simulated by the model HDSM from 1977 to 2007. This comparison confirms the underestimation of precipitation, especially solid. These results also show a significant decrease of precipitation in December and a significant increase, not perceived by population, of the measured annual temperature on the last thirty years. Both approaches by modeling and interviews highlight large uncertainties on the hydro-climatic data of the Dudh Koshi River basin. These uncertainties limit the understanding of hydrological and cryospheric processes and the assessment of climate change impacts on the water resources of this basin. Although they are also uncertain, the perceptions bring crucial complementary information to improve this knowledge and the analysis of the quantitative data of this high mountain Himalayan area.

Climate change is predicted to be the most pronounced in high latitude ecosystems, however very little is known about their vulnerability to the projected warmer temperatures. In particular, natural organic matter (NOM) in the high latitude cryosphere which includes dissolved organic matter (DOM) and cryoconite organic matter (COM) from glaciers and soil organic matter (SOM) in permafrost, is highly susceptible to climate change which may lead to severe consequences on both local and global carbon biogeochemical cycles. Examination of DOM in glacier ice by a novel 1H nuclear magnetic resonance (NMR) water suppression pulse sequence at its natural abundance revealed and quantified the composition and the organic constituents in ice samples from Antarctica. 1H NMR spectra of samples from several glaciers were acquired and compared to the dominant fluorescent DOM fraction. This comprehensive approach showed that glacier ice DOM was mainly composed of small, labile biomolecules associated with microbes. Examination of the organic debris found on glacier surfaces (COM) from both Arctic and Antarctic glaciers were determined to be derived from microbes. Samples from Arctic glaciers were more chemically heterogeneous with small inputs of plant-derived material detected after targeted extractions. Therefore the COM carbon composition was determined to be dependent on the local glacier environment, suggesting a site specific contribution to the carbon cycle. Finally, the distribution of extracted branched glycerol dialkyl glycerol tetraether (GDGT)microbial membrane lipids and the deuterium incorporation of plant-wax n-alkane biomarkers extracted from dated permafrost SOM (paleosols) were independently applied for Canadian Arctic climate reconstruction during the last glacial maximum. Overall, the branched GDGT based temperature reconstructions from the Arctic paleosols reconstruct higher temperatures, likely when bacterial activity was optimal. The deuterium composition of the C29 n-alkane plant lipids appears to integrate an average annual signal. Further analysis by both non-selective NMR spectroscopic and targeted biomarker techniques on these paleosol samples revealed that the major vegetative sources from this paleoecosystem originated from woody and non-woody angiosperms. This thesis demonstrates several novel analytical characterization techniques, along with the major sources and composition of NOM in the cryosphere while demonstrating its use in paleoclimate applications.