Littérature scientifique sur le sujet « Changements climatiques – Kerguelen, Îles (Terres australes et antarctiques françaises) »
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Articles de revues sur le sujet "Changements climatiques – Kerguelen, Îles (Terres australes et antarctiques françaises)":
Jeanblanc-Risler, Florence. « Les Terres australes et antarctiques françaises : des territoires-frontières au cœur des enjeux de la planète ». Administration N° 279, no 3 (4 octobre 2023) : 54–56. http://dx.doi.org/10.3917/admi.279.0054.
Thèses sur le sujet "Changements climatiques – Kerguelen, Îles (Terres australes et antarctiques françaises)":
Herlédan, Maïwenn. « Biodiversité des amibes à thèque et environnements de l'archipel de Kerguelen : caractérisation actuelle et évolution récente sous contrainte climatique ». Electronic Thesis or Diss., Université de Lille (2022-....), 2023. http://www.theses.fr/2023ULILR002.
The objective of this PhD is to describe the current diversity of testate amoebae on the Kerguelen archipelago depending on climate and environmental context and to understand the recent evolution of the last 260 years by a paleoenvironmental approach combining microscopic observations, sedimentology and geochemistry. Located at the polar front in the sub-Antarctic zone, the Kerguelen archipelago is subject to extreme wind and precipitation conditions while being preserved from direct anthropic impacts. This makes it an ideal natural environment to study the impact of global climate change on the environment.Two scientific campaigns on the Kerguelen archipelago in 2019 and 2021 have allowed us to collect samples of current plants (mainly bryophytes and azorelles), underlying soils and soil cores. The samples studied were selected to reflect the geographical and geological diversity of the archipelago, in terms of rainfall (west-east contrast), sedimentary nature (organic soil, alluvial sediments, etc.. ) and petrographic context (basalts - phonolites). Optical observations of the testate amoebae communities growing in the plant samples (101 samples) have allowed us to build a new database of testate amoebae in the archipelago. Sedimentological and geochemical analyses (water content, elemental and isotopic analyses, mineralogy) were carried out in parallel on 485 soil samples in order to characterize the environmental parameters.This work has allowed to update and complete the 1981 database of 50 species with the description of 107 species of testate amoebae. Sedimentological analyses of soils revealed significant differences in terms of weathering between the western and eastern parts of the archipelago, reflecting contrasting rainfall patterns. This trend is also reflected in the testate amoebae assemblages whose diversity, variable according to the type of environment, is much greater in the west. The coupling of these different observations has made it possible to highlight the ecological affinities of certain species with specific environments, which depend mainly on the water content of the sediment, the type of environment and the vegetation, thus allowing the definition of indicator species. The use of this approach to reconstruct recent paleoenvironments from the different soil cores has allowed us to highlight local changes in the environment, which could be attributable to recent climate change. This study demonstrates the relevance of testate amoebae not only as an environmental indicator but also for tracing the recent evolution of paleoenvironmental conditions under climatic constraints
Labarrere, Bastien. « Comment les plantes répondent et s'adaptent aux changements climatiques : étude aux marges froides (subantarctique) ». Thesis, Rennes 1, 2017. http://www.theses.fr/2017REN1B002/document.
The adaptive potential of a species can be defined as its capacity to cope with environmental change. Adaptive potential increases with phenotypic variation, from the intra-individual to the inter-population level, but factors controlling and explaining this variation still remain poorly understood.We studied four plant species from Iles Kerguelen in the sub-Antarctic region which is currently facing one of the strongest climate changes worldwide. Plant species from Iles Kerguelen are known to show high phenotypic integration (i.e. strong correlation among traits), a phenomenon that has been suggested to constrain trait variation. For these species we studied what constrains phenotypic variation, considering the external environment, the internal phenotypic integration and the associated performance costs. We found that intra-individual variation, i.e. plasticity, may be constrained by complex environmental change and the performance costs it triggers. In contrast, plasticity may be favored by high degree of phenotypic integration (Chapter 3). We found that inter-individual variation within populations may not be constrained by environmental factors, but may be favored by high phenotypic integration (Chapter 1). We found inter-population variation within regions may be constrained by restricted environmental variation (Chapter 1). Finally, we studied secondary metabolites (amines and flavonols) that connect environmental variation to phenotypic variation. We found that compositions and functions of these metabolites vary among regions, probably reflecting evolutionary differentiation among regions (Chapter 2). Patterns of variation betweenregions suggest that within species metabolites may be functionally redundant or versatile, for which to our knowledge our results are the first hint. Overall, we suggest that climate change in Kerguelen will impact plant species performance, and that the persistence of suitable wet habitats will be determinant in species capacities to cope with such changes. Furthermore, this project identified so far underestimated factors which may favor the adaptive potential of species. Particularly, we emphasize that the adaptive potential of species may increase due to (i) phenotypic integration, (contrary to common suggestion) and (ii) metabolite redundancy or versatility (only poorly studied so far). Moreover, we evidenced, partly for the first time, multiple costs and limits of plasticity and suggest that plasticity does not guarantee plant success in the new environment
Verfaillie, Deborah. « Suivi et modélisation du bilan de masse de la calotte Cook aux iles Kerguelen. Lien avec le changement climatique ». Thesis, Grenoble, 2014. http://www.theses.fr/2014GRENU035/document.
Glaciers of the southern hemisphere sub-polar regions between 45 and 60°S have declined dramatically over the last century. The islands of Kerguelen archipelago (49°S, 69°E) represent a unique location in regions where few data are available to understand glacier retreat. Situated at low altitudes and close to the ocean, their glaciers have shown particular sensitivity to atmospheric and oceanic variations. Thus, since the 1960s, the Cook Ice Cap (~400km2) has retreated spectacularly, losing 20% of its area in 40 years. The aim of my thesis was to assess the present and future state of the ice cap, and to understand the causes of this decline while putting them in a global context. To do so, a meteorological and glaciological network was set up in 2010 on Kerguelen archipelago and field campaigns have been carried out annually since then. Analysis of these measurements confirms the negative mass balance of Cook Ice Cap. In parallel, the study of the albedo over the whole ice cap from MODIS satellite images (MODerate resolution Imaging Spectroradiometer) gives us access to the evolution of the snow line since 2000, highlighting an important reduction of Cook Ice Cap accumulation area over the last decade. Mass balance modelling of the Cook Ice Cap using a degree-day model coupled to a simple ice motion routine further reveals that its retreat is mainly due to a strong decrease in precipitation over the Kerguelen Islands since the 1960s. In order to put the decline of the cryosphere on Kerguelen in a global context, climatic trends over the whole sub-polar regions are studied, revealing that the sub-Antarctic area is currently the one where glacier retreat is the strongest. To understand these variations, we analyse a complete set of field and satellite observations and modelling results : reanalyses, models from the CMIP5 (Coupled Model Intercomparison Project phase 5) experiment, atmospheric and oceanic temperature and precipitation observations, etc. The latter show warming and quasigeneralised drying of the whole 40-60°S area, linked to the southward shift of storm tracks in response to the more frequent positive phases of the Southern Annual Mode (SAM). Recent glacier retreat on Kerguelen archipelago, and for other glaciers and ice caps located at similar latitudes, is thus mainly due to a deficit of accumulation caused by the SAM, and amplified by atmospheric warming. The future evolution of Cook Ice Cap mass balance is evaluated using the MAR (Modèle Atmosphérique Régional) model, forced at its boundaries by CMIP5 models. Recent mass balance simulations are first carried out using ERA-Interim and NCEP1 reanalyses, and compared to in situ observations. In parallel, one-year simulations are produced with the precipitation desagregation scheme SMHiL (Surface Mass balance High resolution downscaLing) on MAR outputs, at various scales, in order to evaluate the impact of downscaling on precipitation. An evaluation of CMIP5 models over the recent period against ERA-Interim is then carried out, considering certain key climatic variables. The model closest to ERA-Interim as well as the two most extreme models are then used to force the MAR model over the next century, and surface mass balance outputs are critically analysed. The analysis of the decline of the Kerguelen ice cap using different tools and techniques brought new insights on the link between glaciers and climate, highlighting the major role of the SAM, but also raised new questions
Massardier-Galatà, Lauriane. « Succès de la reproduction de prédateurs en contexte de changements climatiques et de la dynamique océanique – Application aux « central place foragers » des zones australes, approche par la modélisation individu centrée ». Thesis, Université Côte d'Azur (ComUE), 2017. http://www.theses.fr/2017AZUR4050/document.
Climate change has certain impact on the marine ecosystems. A southward shift in productive frontal systems serving as the main foraging sites for many top predator species is likely to occur in the Subantarctic areas. Central place foragers, as seabirds and pinnipeds, are thus likely to cope with an increase in the distance between foraging locations and their land-based breeding colonies. We studied the impact of climate change on the breeding success and population dynamics of Antarctic fur seals (Arctocephalus gazella) at Kerguelen Islands by means of an individual based model we developped, MarCPFS (Marine Central Place Foragers Simulator) which showed that the survival of the female-pup pair is particularly sensitive to the distribution of preys (abundance and structure), to the memorization abilities of the best resource sites found by the female during the rearing period, to the female size and to the foraging distance which it is necessary to cover at each trip. The results suggest that during the next three decades a southward shift greater than 2 km year-1 could compromise the survival and the sustainability of the populations. A coupling with a model of simulation of the oceanic dynamics and the resource (SEAPODYM) allowed projections till the end of this century based on scenarios RCP8.5 of the IPCC (2014), confirming the trends previously obtained. Globally, these works lead us to conclude with pessimistic perspectives about the sustainability of populations even when considering an evolution through time towards individuals of greater sizes
Baudena, Alberto. « How do marine mid trophic levels respond to fine scale processes ? » Electronic Thesis or Diss., Sorbonne université, 2018. http://www.theses.fr/2018SORUS136.
The comprehension of the coupling between physical and biological dynamics is a pivotal step to assess the health of the oceans, in order to protect the ecosystems therein from the effects of global change, human exploitation and pollution as well as for understanding the role of the ocean in the climate system. Indeed, in the oceans, physical phenomena and biological processes are intimately linked, since marine organisms live in a fluid environment, continuously under the effect of the currents. Thus, contrary to what happens on land, where the landscape topography changes over evolutionary timescales (periods in the order of hundreds to millions of year) in the ocean the landscape ("seascape") evolves on the same timescales of ecological processes. In the present thesis I analyse in particular the role of the fine scales, which present a peak in the ocean energy spectrum, and whose time scales (of days to weeks) overlap important marine ecological processes like the development of planktonic blooms and the duration of foraging trips for top predators. The fine scale features have been already shown to play a central role into conditioning primary production, lower trophic levels abundance and composition, and apex predators behaviors. However, less is known on their influence on intermediate trophic levels, i.e. swimming organisms (such as fish), which however constitute an essential part of the trophic chain, and which are under unprecedented pressure by human activities. This is mainly due to the scarce availability of data on them at large scales, and to problems of ship-based measurements. Two knowledge gaps are addressed in this thesis. The first is the fact that intermediate trophic levels distributions cannot be detected by remote sensing, and thus require the development of novel, ad hoc sampling strategies. The second open challenge addressed by this thesis is how the swimming ability of the nekton can interact with the fine scale physical dynamics. In order to address the aforementioned questions, in this work I adopt a Lagrangian approach, therefore focusing on water parcel trajectories, and I integrate it with novel methodologies applied to acoustic data, complex system analysis and network theory. I focus on the Kerguelen region, because of its ecological importance and the large availability of informations, which permitted to characterize its relatively simple ecological dynamics, mainly based on iron limitation which is furnished by the plateau. I consider the myctophids as reference fish of the present study, for their worldwide abundance and for their importance for the ecology of the area, and because they may constitute a future target by commercial fishing. (...)