Tesis sobre el tema "Changements climatiques – Arctique"
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Doiron, Madeleine. "Impacts des changements climatiques sur les relations plantes-herbivores dans l'Arctique". Doctoral thesis, Université Laval, 2014. http://hdl.handle.net/20.500.11794/25487.
Texto completoWhen species at different trophic levels respond to climate change at different rates, this may lead to a trophic mismatch between the phenology of consumers and that of their resources. As polar regions are warming more rapidly than the rest of the planet, migratory birds breeding in the Arctic are expected to be among the species most affected by trophic mismatch in the wake of rapid climate change. This study examines the impact of climate warming on the interactions between an arctic herbivore, the greater snow goose (Chen caerulescens atlantica), and its food plants on Bylot Island, Nunavut, Canada. Using small greenhouses, we examined the impact of increased temperatures on plant biomass and a proxy of nutritive quality, nitrogen concentration, of graminoid plants used by geese during the brood-rearing period. This experiment showed that annual warming significantly increased biomass of graminoids but also led to an acceleration of the seasonal decline in plant nutritive quality and resulted in a decrease in the nitrogen concentration of plants by up to 14% during the period of gosling growth. We also showed that satellite-derived Normalized Difference Vegetation Index (NDVI) can be used as a proxy to determine date of peak nitrogen concentration in some tundra plants, and can thus be a reliable measure of the early changes in the timing of the availability of high quality food for herbivores. Using NDVI, we were then able to estimate the date of peak nitrogen in years when we had no empirical data on plant phenology. Finally, we analysed long-term data on climate, plant phenology and the reproduction of geese in order to examine the potential impact of mismatched reproduction on the growth of young. We found that geese are only partially able to adjust their breeding phenology to compensate for annual changes in the timing of high quality food plants, and that gosling body mass and structural size at fledging was reduced when trophic mismatch was high. Our results support the hypothesis that trophic mismatch can negatively affect the fitness of arctic herbivores, and that it is likely to be exacerbated by rising global temperatures.
Veillette, Julie. "Stucture et dynamique d'écosystèmes aquatiques côtiers du haut Arctique comme sentinelles de changements environnementaux". Thesis, Université Laval, 2010. http://www.theses.ulaval.ca/2010/27290/27290.pdf.
Texto completoDegeorges, Damien. "Le rôle du Groënland dans les enjeux de l'Arctique". Paris 5, 2011. http://www.theses.fr/2011PA05D014.
Texto completoThe strengthened interest for the Arctic region, due to the consequences of climate change, coincides with the emergence of Greenland on the Arctic and international scenes. At the intersection of American and European interests in the region, Greenland, a self-ruled territory four times the size of France and inhabited by about 57,000 persons, forms part of a specific debate which is of an evolutionary nature and goes beyond the regional context. Stronger autonomy within the Kingdom of Denmark is bringing Greenland closer to possible independence, generating growing interest amongst the international community. Greenland, due to its huge icecap, its natural resources, particularly an enormous potential in Rare Earth Elements, and a location at the centre of the Arctic, new frontier of international relations, assumes a strategic dimension. The territory appears as a key issue for developments in the Arctic region and for global challenges such as adaptation to climate change and energy security in the context of an economy expected to become lowcarbon. Greenland’s state-building, between the desire for independence soon and a pragmatic approach, appears as a central issue to define the role of Greenland in the Arctic. Particularly given the territory’s strategic resources, Greenland’s state-building process may become a major security issue if it goes too fast. In case of economic difficulties, assistance to a Greenlandic state from a state willing to position or strengthen its presence in the region may have consequences for developments in the Arctic and global energy security
Potier, Hugo. "Major and trace elements in the changing Arctic environment : interactions between C-N-Mo-V biogeochemical cycles". Electronic Thesis or Diss., Sorbonne université, 2024. https://accesdistant.sorbonne-universite.fr/login?url=https://theses-intra.sorbonne-universite.fr/2024SORUS094.pdf.
Texto completoClimate change is deeply affecting the functioning of Arctic ecosystems through increases in temperature and precipitation in these environments. In particular, the increase in primary productivity resulting from the lifting of thermal and hydric constraints on plant growth, coupled with changes in the nature of the plant cover and the thawing of permafrost, is likely to induce significant constraints on the biogeochemical cycles of elements composing organic matter, especially carbon (C) and nitrogen (N). An important lever to reduce nitrogen limitation of plant growth could be to increase the flux of biological nitrogen fixation (BNF), a microbial process that requires, among other elements, molybdenum (Mo) or vanadium (V). The abundance of these two trace elements may thus limit the availability of nitrogen and, therefore, the plant growth in those ecosystems. The aim of this research work is to improve our understanding of the interactions between the biogeochemical cycles of major (C, N) and trace (Mo, V) elements in these environments. It explores the potential of using stoichiometric data collected in subarctic habitats with contrasting plant and soil characteristics of the Abisko region (northern Sweden). The quantification of elemental stocks in aboveground biomass and soils highlighted the importance of variations in plant community composition for the distribution of these stocks in biomass compartments with different dynamics, as well as the relatively weak links in elemental stocks between aboveground biomass and soils. Considering several processes potentially involved in soil surface enrichment of Mo and V, both elements have distinct behaviours in light of the respective contribution of lithogenic and biological influences and the role of physicochemical conditions for their mobility. A modelling approach highlighted the strong links between N, Mo and V in soil stoichiometry and suggested that organic soils have a relatively important nitrogen-fixing activity. The results of this thesis highlight the strong interaction between major and trace elements, their expected modifications as induced by changes in vegetation in the Arctic, and the potential limitation of BNF by the availability of Mo and V. These results call for a more detailed characterisation of the bioavailability of these trace elements to microbial communities combined with measurements focusing on the BNF process in order to further explore these limitations. Finally, this work points out the need to continue exploring the interaction of biogeochemical cycles of major and trace elements for the future of Arctic ecosystems
Morrissette-Boileau, Clara. "Dynamique de deux espèces arbustives de la toundra arctique en réponse aux changements climatiques et au broutement du caribou migrateur". Master's thesis, Université Laval, 2017. http://hdl.handle.net/20.500.11794/27785.
Texto completoGeneralized shrub expansion has been observed over the circumpolar Arctic in response to climate change. This phenomenon is causing major alterations to the biotic and abiotic environments, a consequence of the increased shrub growth in height. We characterised tundra shrub species dynamics in response to climate change and migratory caribou browsing. To do so, we evaluated dominant erect shrub species dynamics and tested experimentally how shrub responds to these disturbances, using Betula glandulosa as model species. Our results show that shrub cover in Deception Bay is mainly driven by B. glandulosa, a species with increasing recruitment since early 2000s. However, it seems that this species’ vertical structure remains low which might not modify the biotic and abiotic environment normally associated with shrub expansion. We also showed experimentally that increase in shrub growth is a result of enhanced soil nitrogen fertility, a proxy of increase microbiological activity in response to global warming. Moreover, we demonstrated that caribou browsing has a negative cumulative effect on B. glandulosa growth. Thus, we showed in this study that shrub expansion is rather limited in Deception Bay and might be slowed down by the combined effects of harsh climatic conditions and herbivores. Moreover, our study stressed that herbivores must be taken into account when predicting vegetation change in the tundra.
Racine, Calypso. "Écologie des foraminifères benthiques en domaine arctique dans un contexte de changements climatiques : cas des mers de Chukchi, Barents et Baffin". Thesis, Bordeaux, 2019. http://www.theses.fr/2019BORD0008/document.
Texto completoBenthic foraminifera are widely used in oceanography as paleoclimate and paleoenvironmental bio-indicators due to their presence in all marine environments, their sensitivity to environmental changes and their great capacity to fossilize. However, the use of benthic foraminifera as paleoenvironmental proxies requires a good knowledge of the ecological conditions and the parameters controlling species distribution. Although knowledges about the ecology of benthic foraminifera are improving, they remain sporadic in Arctic area, a complex ecosystem characterized by multiple interactions between the atmosphere, the ocean and the cryosphere and particularly sensitive to change and vulnerable to global warming. Temperatures in the Arctic have risen twice as fast as the global average over the past decades, a phenomenon that has been dubbed the “polar amplification of global warming”. In this context, this thesis aims at better understanding the ecology of living benthic foraminifera in Arctic regions and at defining the importance of environmental controls on fauna such as water mass properties, primary productivity, organic matter flux as well as sea-ice dynamics. Living benthic foraminifera were identified in the first centimetres of 21 surface sediment cores collected in three Arctic areas during summer in 2014 and 2015: Baffin Bay and the Barents and Chukchi Seas. These three regions present specific characteristics in terms of sea-ice cover, water mass circulation or primary productivity. Our results suggest that these factors influence the distribution of benthic foraminifera. The flux of organic matter resulting from primary productivity intensified during spring and summer periods near hydrographic polar fronts, sea-ice edges (marginal ice zones) and in the north water polynya (Baffin Bay) increases the fauna’s densities and diversity and favours the development of specific species. Nonionellina labradorica in cold Arctic waters and Cassidulina neoteretis associated with Atlantic waters respond to fresh supply of organic matter while Melonis barleeanus is found in environment rich in degraded organic matter. In deeper oligotrophic environments, Oridorsalis tenerus is a ubiquitous species associated with Cibicidoides wuellerstorfi on the west continental margin of Barents Sea and Ioanella tumidula in the deeper basin in the north of the Chukchi Sea. Physical and chemical water mass properties also affect the distribution of living benthic foraminifera. In the Baffin Bay and the continental shelf of the Chukchi Sea, corrosive waters lead to carbonate dissolution, favouring the dominance of agglutinated species. This thesis hence contributes to calibrate the benthic foraminifera to their environment and to improve their application as paleoclimate and paleoenvironmental proxies in the Arctic. Finally, a preliminary study about fossil benthic foraminifera in three cores of Barents Sea allowed to show variations of environmental conditions during the last two centuries
Ouellet, Félix. "Spatialisation du modèle de couvert nival SNOWPACK dans le Nord canadien pour l’étude de l’accès à la nourriture du caribou de Peary". Mémoire, Université de Sherbrooke, 2016. http://hdl.handle.net/11143/8899.
Texto completoNicolle, Marie. "Variabilités hydro-climatiques multi-décennales à pluri-séculaires en Arctique-subarctique depuis 2000 ans". Thesis, Normandie, 2018. http://www.theses.fr/2018NORMR129/document.
Texto completoThe temperature increase during the 1850-2012 period is not uniform globally and the Arctic is warming twice as much as the average. However, the short time coverage of instrumental data makes it difficult to distinguish natural climate variability and anthropogenic forcing. The study of climatic variability "free" of human influence requires the use of proxies data measured in continental and marine palaeoclimatic archives. In the Arctic-subarctic region, high resolution records have been centralized in the Arctic 2k PAGES database. The objectives of this work are to improve the characterization and interpretation of climatic variability over the last 2000 years, going beyond the millennial trend and the major climatic periods, but also by focusing on the role and spatial expression of the internal variability of the climate system. This thesis is based on the Arctic 2k PAGES database, which allows the study of temperature variations in the Arctic-subarctic region, as well as a new database to reconstruct hydroclimatic variations (precipitation and humidity) in the region and created during this study. The use of climate signal analysis methods on regional records calculated from these two databases has highlighted climate variability in the Arctic-subarctic region from the multi-decadal to millennial scales.In particular, multi-decadal variability is related to the internal variability of the climate system. The hydroclimatic and temperature variations expressed at multi-decadal scales in the region are characterized by frequencies specific to regional climate oscillations (North Atlantic oscillation and decadal Pacific oscillation), particularly over the last 200 years. The work done on the temperature database and the reflection on the creation and exploitation of the hydroclimatic database have also led to the definition of a working methodology with a palaeoclimatic database, from its construction to the definition of its limits, in particular in terms of the spatial representability of the series contained in the database and the assimilation of data with different seasonings
Bélanger, Simon. "Impacts des changements climatiques sur les flux de carbone stimulés par la lumière dans l'Océan Arctique : quantification et suivi de la photo-oxydation de la matière organique dissoute dans la Mer de Beaufort par télédection spatiale". Paris 6, 2006. http://www.theses.fr/2006PA066520.
Texto completoPhotochemical oxidation of colored dissolved organic matter (CDOM), and the resulting production of CO2, is now known to be a significant process in the cycling of carbon in the ocean-atmosphere system. One environment where that process may play a major role in the context of climate change is the Arctic ocean because of: 1) the increasing amount of terrestrial CDOM released by the melting permafrost and brought to coastal ocean by rivers, 2) the decreasing summer ice cover that allows more solar radiation to penetrate the water column, and 3) the continuing increase in UV radiation over that region. A coupled optical-photochemical model was used to assess the role of photooxidation in the carbon cycle of the Arctic Ocean. To calculate the photoproduction of CO2 (PDIC), the incoming spectral irradiance, including UV, was modeled with a radiative transfer model that uses satellite observations of sea ice, ozone, aerosols and cloud cover covering the 1979 to 2004 period. In situ determinations of the apparent quantum yield for the photoproduction of CO2 made in the Beaufort Sea were used for the calculations. A key parameter in the model was the contribution of CDOM to the total absorption coefficient. It was either obtained from in situ measurements or derived from Ocean Color imagery using a new empirical algorithm. Unlike most semi-analytical approaches found in the literature, the proposed empirical algorithm provides a mean to separate CDOM absorption coefficient from nonalgal particles absorption coefficient at the regional scale. The use of Ocean Color remote sensing at high latitude is, however, compromised by the presence of sea ice that contaminates the data. This problem was addressed in the present study, and a method was proposed to detect and eliminate contaminated pixels. Finally, it was shown that the level of PDIC is similar to the level of sequestered rates of organic carbon in the ocean sediments, which was produced through marine photosynthesis; and that the increase in UV and decrease in summer sea ice over the last 26 years have led to an increased in PDIC by about 15%. These results indicate that the predicted trend of ongoing contraction of sea ice cover will greatly accelerate the photomineralization of CDOM in Arctic surface waters
Gagnon, Samuel. "Changements climatiques et interactions écologiques affectant le pergélisol et l'activité des coins de glace dans la vallée de la rivière Narsajuaq, Nunavik (Canada)". Doctoral thesis, Université Laval, 2020. http://hdl.handle.net/20.500.11794/66305.
Texto completoTo determine the direct impact of climate change on ice-wedge dynamics and the permafrost thermal regime, 16 study sites in the Narsajuaq river valley (Nunavik, Canada) that were extensively studied for ice wedge between 1989 and 1991 were revisited between 2016 and 2018. Observations and measurements show that over the last 25 years, the ice wedges of the Narsajuaq river valley have experienced an unprecedented degradation of their upgrowth forms, resulting in a generalized deepening of their main stages due to the active layer reaching depths 1.2 to 3.4 times greater than in 1991. The thermal regime of the four main soil types identified (thin sandy peat, thick sandy peat, thick peat, fluvial sands) in the valley was modelled to reproduce permafrost temperature changes since 1990 and predict active layer thickness until 2100. In recent decades, ice wedges of all soil types have been active, cracking almost every year except in 2010, the warmest year on record. For the rest of the 21st century, simulations predict a complete cessation of soil cracking between 2020 and 2095 depending on the soil type, soil cracking threshold and the selected climate scenarios. However, based on the interannual variability of the climate in the region, it is very likely that ice wedges will stop cracking over the next 20-30 years. The active layer reached a record depth in 2010, then moved up with recent cooling. It is expected that the active layer will deepen sufficiently in the next few decades to cause widespread ice-wedge degradation, leaving only fossil ice-wedge roots deep in permafrost by the end of the century. This thesis also suggests a new approach to improve estimates of carbon stocks in Arctic permafrost based on image analysis of surface geology and landforms, as well as on the reconstitution of the geological history of Arctic permafrost landscapes. There is a strong connection between landscape features and surficial geology on the one hand, and carbon stocks as organic matter in soils on the other.
Ben, Mustapha Sélima. "Étude de la variabilité spatio-temporelle des processus physiques et biologiques dans la mer de Beaufort par télédétection et dans un contexte de changements climatiques dans l'océan Arctique". Thèse, Université de Sherbrooke, 2014. http://savoirs.usherbrooke.ca/handle/11143/5364.
Texto completoSoriot, Clément. "Caractérisation de la banquise Arctique à partir d'observations micro-ondes multi-satellites". Electronic Thesis or Diss., Sorbonne université, 2022. http://www.theses.fr/2022SORUS451.
Texto completoSea ice plays a major role in ocean circulation as well as in the climate and weather system. In the context of global warming, the extent of the Arctic sea ice has been decreasing steadily over the last 40 years and monitoring of the Arctic is essential. Microwave instruments on board satellites allow the study of this region of the Earth under all weather conditions, and regardless of the day/night cycle. Particularly suited over polar regions with high cloud cover and a six-month polar night, microwave satellite provide key observations for estimating geophysical parameters of the sea ice. Nevertheless, the understanding of the physics underlying the observed microwave signatures is still partial. This thesis aims at improving our understanding of the microwave signals of the sea ice and is part of the preparation of two upcoming Earth observation missions led by the European Space Agency: the Copernicus Imager Microwave Radiometer (CIMR) and the Copernicus Polar Ice and Snow Topography ALtimeter (CRISTAL). In a first part, the covariabilities of passive microwave signals, highlighted by an unsupervised classification technique, will be analyzed and interpreted jointly with active microwave signals, using a microwave radiative transfer model. The results showed that it is possible to identify specific behaviors of sea ice concentration and thickness, and snow structure. The importance of metamorphism within the snowpack for the interpretation of passive microwave signals was highlighted. In a second part, an algorithm for estimating sea ice thickness from passive microwave observations was developed using an artificial intelligence technique. The results were compared to in situ sea ice thickness measurements and also showed good performance compared to other satellite-based sea ice thickness products. By applying the algorithm to a long collection of intercalibrated satellite data, a time series of Arctic sea ice thickness was constructed between 1992 and 2020, making it the longest to date. A final section deals with microwave altimetry techniques for measuring geophysical parameters of the sea ice. The sensitivity of microwave altimetry waveforms to the thickness of the snow cover of the Arctic sea ice is analyzed
Mercier, Denis. "La géomorphologie paraglaciaire. Analyse de crises érosives d'origine climatique dans les environnements englacés et sur leurs marges". Habilitation à diriger des recherches, Université Blaise Pascal - Clermont-Ferrand II, 2010. http://tel.archives-ouvertes.fr/tel-00613729.
Texto completoLebrun, Anaïs. "Réponses des communautés benthiques arctiques peu profondes au changement climatique". Electronic Thesis or Diss., Sorbonne université, 2023. http://www.theses.fr/2023SORUS479.
Texto completoSince the beginning of the 20th century, the average surface air temperature in the Arctic has risen by around 2 to 3°C. This rapid rise in temperature is leading to a year-on-year reduction in the extent of the Arctic cryosphere. Melting ice leads to increased turbidity and reduced salinity in coastal waters, resulting in changes of natural habitats. In addition, with ongoing warming, the shallow coastal Arctic is experiencing an increase in the frequency, intensity and duration of marine heat waves. All these changes can have profound repercussions on the Arctic marine ecosystem, affecting the distribution and behavior of the organisms that live there. The main aim of this thesis is to analyze the effects of climate change on benthic communities in the shallow Arctic, in particular kelp forests, which are home to a high level of biodiversity. By modifying light, sedimentation, physical abrasion and bottom currents, kelp forests provide a habitat, food source and breeding ground for fish and invertebrates. In the short term, the increase in water turbidity induced by melting snow and land ice will trigger a local remodeling of communities, limiting the expansion of some species but giving others a competitive advantage, such as Alaria esculenta in low-light areas. In the longer term, the melting of glaciers and sea ice will expand the potential habitat range of kelp which, as this thesis suggests, should be able to withstand rising temperatures, marine heat waves, and decreasing salinity and underwater light. However, the disappearance of ice, particularly glaciers, which serve as habitats for top predators, could lead to the decline of these crucial species regulating ecosystem diversity and induce, as in Tromsø but also in other Norwegian fjords or in south-west Alaska, a significant reduction in kelp populations due to an overabundance of herbivores, particularly sea urchins. Further research into the responses of Arctic coastal communities is needed to refine our predictions and provide sound scientific recommendations for ecosystem management. To study the long-term effects of climate change, ex situ experiments spanning several months and in situ monitoring programs in several Arctic locations appear essential
Vargel, Céline. "Caractérisation du manteau neigeux arctique, suivi climatique et télédétection micro-onde". Thesis, Université Grenoble Alpes, 2020. http://www.theses.fr/2020GRALU029.
Texto completoNorthern high-latitude regions are warming more intensely than the rest of the world. This phenomenon, called Arctic amplification, is due in part to the decrease in sea ice extent and snow cover. Snow, which is present 9 months of the year, could have a significant effect on the increase in land surface temperatures by changing its reflective and insulating properties. Thawing of permafrost which could release important amount of soil carbone into the atmosphere could have a significant positive feedback on the future climate of the Arctic. The objective of this research project is to improve the monitoring of Arctic snow cover and ground temperatures. Detailed models of snow cover evolution such as the Crocus multi-layered model are unable to reproduce the particular physics of Arctic snow, which leads to significant uncertainties in the modeling of ground temperatures. New physical parameterizations have been implemented within the Crocus model to improve the vertical stratification of the snowpack by introducing vegetation effects (less dense snow at the bottom) and wind effects (denser snow at the surface), as well as to modify the thermal conductivity of snow. These new parameterizations allow a better representation of ground temperatures under the snowpack, validated with a large dataset in Alaska, Canadian Arctic and Siberia. The simulations thus carried out using the modified Crocus model, driven by the ERA-Interim meteorological reanalysis over the last 39 years (1979-2018), at the pan-Arctic scale, show a significant increase in snow density in spring as well as in snow moisture, mainly in spring and fall, accompanied by a significant decrease in the duration of the snow cover. These effects, combined with the increase in air temperature, lead to an increase in ground temperature of up to +0.89 K per decade for the month of June. In order to improve monitoring the spatial and temporal evolution of the snow cover, the use of microwave satellite observation data is proposed. Based on the analysis of a unique dataset of surface radiometric measurements, associated with the in-situ characterization of the snowpit (119 snowpits with simultaneous observations) in the Arctic and sub-Arctic zones, an optimal parameterization of the SMRT model has been defined. The results show that using a fitted exponential correlation length as a snow microstructure parameter in the Improved Born Approximation (IBA) electromagnetic model gives the best results compared to the other model configurations tested, with a mean error (RMSE) of less than 30% of the observations for subarctic snow and 24% for Arctic snow. Coupled with Crocus, the simulated brightness temperatures over the entire Arctic are significantly better with modified Crocus than with standard Crocus (38 K improvement in mean bias). These results pave the way for using the assimilation of satellite microwave observations into the Crocus model to improve simulations of Arctic snow density, a key snowpack parameter influencing the evolution of ground temperatures under the snow
Jiang, Weimin. "Centennial AMOC variability : mechanism and impacts". Electronic Thesis or Diss., Sorbonne université, 2022. https://accesdistant.sorbonne-universite.fr/login?url=https://theses-intra.sorbonne-universite.fr/2022SORUS193.pdf.
Texto completoThe Atlantic Meridional Overturning Circulation (AMOC) consists of a warm northward current on the surface and a cold southward branch in the deep. It brings tremendous heat into the mid-latitudes in the Northern Hemisphere and thus plays an important role in governing the climate of the North Atlantic region and beyond. This thesis investigates the driving mechanism and climate impacts of a centennial to multi-centennial variability of the AMOC. The AMOC intensity is modulated by the delayed freshwater exchanges through the Fram Strait between the Arctic Ocean and the North Atlantic. The thesis also investigates the climate impacts of this low-frequency AMOC variability and associated energy transport changes. The impacts of a strong AMOC mainly include a wide warming in the Northern Hemisphere, a northward displacement of the intertropical convergence zone and more precipitations in the Northern mid-latitudes. The enhanced northward oceanic energy transport induced by intensified AMOC is compensated by the anomalous southward energy transport in the atmosphere, which leads to climate variations. This response in the atmosphere is damped by the Indo-Pacific Ocean
Alraddawi, Dunya. "Rôle de la vapeur d'eau dans le cycle hydrologique en Arctique". Thesis, Université Paris-Saclay (ComUE), 2017. http://www.theses.fr/2017SACLV094/document.
Texto completoAtmospheric water vapour plays a key role in the Arctic radiation budget, hydrological cycle and hence climate, but its measurement with high accuracy remains an important challenge. Arctic water vapor is characterized by a spatial and temporal variability which is not completely understood yet. Its mass integrated in the atmospheric column (TCWV) is studied in this thesis. TCWV seasonal cycle at 18 polar stations is examined following the effect of latitude, longitude in addition to the continental effect. The measurements used in this thesis were validated at three polar stations, the satellites measurements of TCWV in the NIR/VIS/IR bands by MODIS/ SCIAMACHY/ AIRS sensors are compared to those obtained from ground based GPS signals delay. Their uncertainties and limitations are evaluated in season and month scales especially their sensitivities to the clouds presence. In NIR and VIS, the measurements undergo increased sensitivity to the presence of clouds at high latitudes in summer. In addition, albedo estimation is still a challenge to their TCWV inversion models, especially where canopies are snow-covered. Following the validation results, the distribution and seasonal trends of the TCWV over the entire Arctic was assessed via MODIS. Trends and anomalies are discussed mainly in response to changes in the Arctic vegetation, snow cover, and sea ice during 2001-2015. Increased trends in TCWV may be related to local increase of vegetated areas coincidently to snow cover decrease during transient seasons. Increased trends in TCWV were observed by MODIS, forced by local summer warming from many warm waves. A dramatic decline in sea ice near the Siberian and Beaufort coasts led to an observed local increase in TCWV in early fall. A warm-up phase in the Svalbard archipelago, persisting in all seasons except summer, also resulted in additional quantities of TCWV. The detection and justification of trends is a task still far from being accomplished. Arctic TCWV measurements are in question, TCWV measurements over green areas in winter, or through cloudy skies in summer are the major challenges
De, Cesare Silvia. "Les bivalves filtreurs Astarte moerchi : modèle biologique pour l'étude des écosystème marins arctiques". Thesis, Paris, Muséum national d'histoire naturelle, 2016. http://www.theses.fr/2016MNHN0010/document.
Texto completoIn the context of climate change, Arctic marine ecosystems are affected by rapid environmental modifications, whose effects on biotic communities are still debated. The sea-ice decline and the increase in freshwater inputs and turbidity are likely to impact Arctic primary producers, with cascade effects on a key-process in those ecosystems: the trophic relationship between primary producers and benthic consumers (generally referred as “pelagic-benthic coupling”). The direct study of such complex interaction is not straightforward in the Arctic. The biological model of filter-feeding bivalves offers the possibility to get around these problems, allowing to study those ecological processes indirectly. Among the advantages of this model, there is first of all the fact that these organisms record in their shell, in the carbonate layers, some dynamics of their environments. The information recorded in such “bioarchives” are interpreted through the methods of sclerochronology and sclerochemistry and relate to a time window corresponding to the organism lifespan (from some years to more than 500 years). Given that these organisms are primary consumers, another advantage of this biological model is that the study of their diet can provide information about the trophic relationship with primary producers. With the methods of trophic ecology, especially fatty acids and stable isotopes, the study of the tissues allows the investigation of sources assimilated at a timescale of weeks/months.The main objective of this thesis is to test the potential of bivalves Astarte moerchi (borealis complex) as a biological model for the study of marine Arctic ecosystems. A coupled approach is used to combine shell analysis by the methods of sclerochronology and sclerochemistry (elemental ratios) and tissue analysis by the methods of trophic ecology (fatty acids, carbon and nitrogen stable isotopes, compound-specific carbon stable isotopes on individual fatty acids). Two living A. moerchi populations have been studied in two fjords presenting contrasted environmental conditions: Young Sound in North-East Greenland (considered as “Arctic” site) and Kongsfjorden in the West coast of the Svalbard Archipelago (considered as a “sub-Arctic” site). The study of the tissues of A. moerchi allowed to show the trophic plasticity of this species, with differences in food sources of the two populations linked to local primary production dynamics. The analysis of the shell of A. moerchi allowed to: a) corroborate the hypothesis of annual growth lines formation, thus confirming the longevity of this species that can attain 150 years; b) show the potential interest of the analysis of elemental ratios and particularly the ratio between Barium and Calcium (Ba/Ca), which could be relied to phytoplanktonic blooms and c) show that contrasted environmental conditions in the Arctic and sub-Arctic sites result in different shell growth patterns. Some perspectives for the further use of this model study in ecology are discussed. To conclude, an epistemological reflection is sketched about the specificity of the biological model study of filter-feeding bivalves. In contrast to the classical notion of “model organism” used in experimental biology, we suggest that filter-feeding bivalves (as well as other “bioarchives” like trees, corals and coralline algae) belong to a category of biological models that could be named “in situ” and seems specific to the ecological discipline
Bernard, Eric. "Les dynamiques spatio-temporelles d'un petit hydrosystème arctique : approche nivo-glaciologique dans un contexte de changement climatique contemporain (bassin du glacier Austre Lovén, Spitsberg, 79°N)". Phd thesis, Université de Franche-Comté, 2011. http://tel.archives-ouvertes.fr/tel-00910122.
Texto completoRojo, Maxence. "Impacts des événements météorologiques extrêmes et du changement climatique sur les régions arctiques et subarctiques : Perspectives croisées en climatologie et en sciences humaines et sociales". Thesis, Université Paris-Saclay (ComUE), 2016. http://www.theses.fr/2016SACLV075.
Texto completoThe perception of the climate is culturally and socially constructed. For this reason, we have studied some weather events integrating the cultural, political and historical contexts in which they occur.In a first part, we analyzed the impact of Polar Lows, intense mesocyclones that develop over ice-free Arctic seas during winter time, on coastal regions of Norway. The passage of PL can provoke dangerous sea conditions with strong waves, sudden snowfall and blizzard. This phenomenon may represent a risk to maritime and coastal activities in the region, particularly for shipping, fishing and oil and gas offshore platforms.In a second part we studied the impacts of climate change and severe weather events in the Republic of Tuva. Tuva is a very southern subarctic region. Its climate is extremely continental and precipitation tend to be low due to the low moisture content in the cold air. During the twentieth century, the region has experienced major socio-economic changes, sometimes brutal, including the transition from a communist and planned economy to a market economy in the early 1990. Despite these recent changes, pastoralists in western Tuva (horses, cows, yaks, sheep, camels) and reindeer herders in eastern Tuva, still live in close contact with the natural environment. Indigenous peoples of Tuva are facing global changes caused by certain contemporary regional and national policies, including the expansion of the mining industry and the development of mega projects. They offer different points of view, describing environmental changes and their impact on their daily activities
Lecouffe, Audrey. "Évolution et persistance des vortex stratosphériques polaires Arctique et Antarctique sur la période 1979 - 2021". Electronic Thesis or Diss., Sorbonne université, 2021. https://accesdistant.sorbonne-universite.fr/login?url=https://theses-intra.sorbonne-universite.fr/2021SORUS293.pdf.
Texto completoThis PhD study focuses on the study of the evolution of the stratospheric polar vortices over the last forty years. The intensity and position of the Southern and Northern stratospheric polar vortex edge are evaluated as a function of equivalent latitude over the 1979 - 2021 period on 3 isentropic levels in the lower and middle stratosphere (675 K, 550 K and 475 K) from ECMWF ERA-Interim reanalysis. An analysis of the onset and breakup dates of the polar vortices is included. The solar cycle and to a lower extent the quasi-biennal oscillation, El Niño Southern Oscillation and the Arctic Oscillation modulate the interannual evolution of the strength of the vortex edge and the vortex breakup dates. In the SH, long-term increase of the vortex edge intensity and breakup dates is observed over the 1979 - 1999 period, linked to the increase of the Antarctic ozone hole. After early break-ups between 1981 and 1987, more persistent vortex occured in the NH during the 1990s. For both hemispheres stronger vortex edge and longer vortex duration is observed in solar minimum (minSC) years. For the SH, the vortex edge is stronger and lasts longer for maxSC/wQBO years than for maxSC/eQBO years, and is somewhat stronger during cold ENSO phase (cENSO). For the NH, the stronger vortex edge is more pronounced than in SH during the wQBO phase, and it is stronger during minSC/wQBO years
Jacquot, Mathilde. "L'action multidimensionnelle de l'Union Européenne en Arctique : une contribution à l'action extérieure de l'Union européenne". Thesis, Brest, 2019. http://www.theses.fr/2019BRES0106.
Texto completoThe Arctic is one of the regions most affected by climate change. These impacts include socio-economic changes in addition to the obvious environmental changes. Because of these multifaceted changes, the Arctic has simultaneously become an area in need of protection and an area full of promise. These challenges and opportunities have attracted outside intervention and the European Union and its Member States are no exception.Driven by the desire to play a central role in the region, the European Union has undertaken the task of developing policy specifically tailored for the unique situation in Arctic.This policy must serve as a framework for any of the European Union’s actions that impact the region.This dissertation seeks to both determine the role of the Union in the Arctic and determine the benefits that that this role is likely to bring. To this end, this study explores the way in which the Union attempts to reconcile the various dimensions of its action in the Arctic and defines the legal means through which the Union can achieve this goal
Martins, Varino Filipa Catarina. "Typologie des tempêtes du XXe siècle". Thesis, Toulouse 3, 2017. http://www.theses.fr/2017TOU30389/document.
Texto completoExtratropical cyclones (ETCs) variability is not only a subject that raises interest among the scientific community, but also extremely important in terms of social-economical impacts. Nevertheless, the study of both the extratropical cyclones variability and windstorms impacts is still scarce, particularly at time-scales that cover the twentieth century. This thesis aims to study, both storms track variability and associated losses from the beginning of the 20th century until 2010. In order to do so, the work was separated in two main parts, one witch focus on ETCs climatology during the last century using reanalysis data and another focused on loss indexes calculations and risk assessment of windstorms. The first part of this PhD concerns the study of ETCs variability after applying a tracking algorithm on the long-term ECMWF reanalysis ERA-20C. The number of ETCs per year shows three distinct periods for the moderate and deep cyclones. Two periods, one at the beginning and another at end of the century (1900-1935 and 1980-2010) for which no significant e trends are observed and a middle-century period between 1935-1980 which presents a significant positive trend. This last trend, however, a deeper analysis on this period should be done due to time-inhomogeneity of long-term reanalysis datasets. For this reason, a set of physical parameters are analysed and a physical interpretation made for each one of the periods. During the middle period, a general cooling of the atmosphere is observed, particularly at high-latitudes, which increases the meridional gradients of temperature and consequently baroclinicity and baroclinic conversion. Besides that, this increase is also observed more specifically in the Pacific (Atlantic) in the first (second) half of this period and linked with a Pacific Decadal Oscillation (Atlantic Multidecadal Oscillation) change in signs. On the opposite, the first and third periods are related with warmer polar temperatures that are more intense in the third period but never reach the upper levels of the troposphere. This creates differential changes in baroclinicity. On the one hand, baroclinicity decreases at lower levels and, on the other hand increases at upper levels. The second part of this thesis is focused on the analysis of the most damaging windstorms of the century. First, Loss and Meteorological indexes Pinto et al 2012 are computed for more than twenty countries. Then, a High-Loss Tracking Method is developed and the tracking algorithm trajectories are matched with the LI and MI information for each country. [...]
Vié, Marine. "Pour ne pas perdre le Nord : vers une protection efficace du milieu marin arctique". Thèse, 2015. http://hdl.handle.net/1866/19414.
Texto completoThe Arctic is currently facing significant environmental threats. Yet, because of its particular precariousness, those threats will possibly impact its ecosystem and local communities. As those problems are posing unique management challenges, some solutions have been put in place, but are not really effective. In order to protect the arctic marine environment, several hard law and soft law instruments have been set at the international, regional, subregional, bilateral and national scales, but they are all facing serious shortcomings. The question of arctic marine environmental governance has therefore become inevitable in addressing those issues. The needs to protect the arctic marine environment, its ecosystem and inhabitants and the economic imperatives of resources exploitation and economic growth have to be balanced. Thus, arctic marine environmental protection has to (1) put forth an instrument with more implementation and conformity mechanisms, with more flexibility, more precision and depth, and more transparence and accountability; (2) be thought in terms of continuum and synergies of the different levels of governance instead of approaching them separately; (3) put forward an international regimes complex; (4) include a plethora of actors in the governance system and (5) establish marine protected areas that recognize the concepts of ecosystem-based management and respect some environmental principles. In this way, equilibrium between environmental, social and economical needs and effectiveness in governance will be reached.
Chouinard, Christian. "Reconstitutions des températures de surface au Canada : des températures basales du glacier laurentidien aux changements récents du climat arctique". Thèse, 2008. http://www.archipel.uqam.ca/876/1/D1648.pdf.
Texto completoTarroux, Arnaud. "Utilisation de l'espace et des ressources chez un carnivore terrestre de l'Arctique : le renard polaire". Thèse, 2011. http://www.archipel.uqam.ca/4351/1/D2231.pdf.
Texto completoDehasse, Pascal. "Une comparaison des différentes configurations du modèle canadien GEM avec les données de réanalyse NCEP et ERA 40 dans l'Arctique pour la période 1978-2002". Mémoire, 2011. http://www.archipel.uqam.ca/4353/1/M12185.pdf.
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