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Author Jean Lilensten, Mathieu Barthélemy, Gérard Besson, Hervé Lamy, Magnar G. Johnsen, Jøran Moen doi  openurl
  Title The thermospheric auroral red line Angle of Linear Polarization Type Journal
  Year 2016 Publication Journal of Geophysical Research: Space Physics Abbreviated Journal  
  Volume 121 Issue 7 Pages 7125-7134  
  Keywords (down) ionosphere polarization  
  Abstract The auroral red line at 630 nm is linearly polarized. Up to now, only its Degree of Linear Polarization had been studied. In this article, we examine for the first time the Angle of Linear Polarization (AoLP) and we compare the measurements to the apparent angle of the magnetic field at the location of the red line emission. We show that the AoLP is a tracer of the magnetic field configuration. This opens new perspectives, both in the frame of space weather and in the field of planetology.  
  Programme 1026  
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  Corporate Author Thesis  
  Publisher Place of Publication Editor  
  Language Summary Language Original Title  
  Series Editor Series Title Abbreviated Series Title  
  Series Volume Series Issue Edition  
  ISSN 2169-9402 ISBN Medium  
  Area Expedition Conference  
  Notes Approved yes  
  Call Number Serial 7644  
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Author Labat J.P., Mayzaud P. & Sabini S. doi  openurl
  Title Population dynamics of Themisto gaudichaudii in Kerguelen Islands waters, Southern Indian Ocean. Type Journal Article
  Year 2005 Publication Polar biology Abbreviated Journal Polar Biol.  
  Volume 28 Issue 10 Pages 776-783  
  Keywords (down) Invertebrata ; Arthropoda ; Crustacea ; Aquatic environment ; Climatic zone ; Antarctic Islands ; Kerguelen Islands ; Amphipoda ; Marine environment ; Polar region ; Indian Ocean ; Southern Ocean ; Kerguelen Islands ; Population dynamics  
  Abstract Fieldwork was carried out at Kerguelen Islands. Two groups of stations in a coastal area, the Morbihan gulf, were surveyed. At both stations, macroplankton biomass ranged from 2.3 mg dry weight m-3 to 89 mg dry weight m-3and consisted mostly of Themisto gaudichaudii with values ranging from 1.9 mg dry weight m-3 to 50.6 mg dry weight m-3. Biomass was high for sub-Antarctic waters with marked seasonal and inter-zone differences. Biomass minima were observed at the end of the winter, from September to November, while maxima were recorded in summer and in early fall at the beginning of the year between January and April. T. gaudichaudii showed a recruitment of new size classes, mainly from November to January, followed by a rapid growth phase in summer. which slowed down during the southern winter period. Individuals breed after 1 year. Large individuals, older than 1 year, were not a significant presence in the gulf of Morbihan. The main pattern of the population dynamics were characterised by an univoltine life cycle with a very high biomass marked by a strong seasonal signal linked with the hydrological and trophic parameters of the Gulf.  
  Programme 353  
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  Corporate Author Thesis  
  Publisher Place of Publication Editor  
  Language Summary Language Original Title  
  Series Editor Series Title Abbreviated Series Title  
  Series Volume Series Issue Edition  
  ISSN 0722-4060 ISBN Medium  
  Area Expedition Conference  
  Notes Approved yes  
  Call Number Serial 3093  
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Author Leki V, Romanowicz B, doi  openurl
  Title Inferring upper-mantle structure by full waveform tomography with the spectral element method Type Journal Article
  Year 2011 Publication Geophysical Journal International Abbreviated Journal 0956-540X  
  Volume 185 Issue 2 Pages 799-831  
  Keywords (down) Inverse theory, Surface waves and free oscillations, Seismic anisotropy, Seismic tomography, Computational seismology, Wave propagation,  
  Abstract Mapping the elastic and anelastic structure of the Earth's mantle is crucial for understanding the temperature, composition and dynamics of our planet. In the past quarter century, global tomography based on ray theory and first-order perturbation methods has imaged long-wavelength elastic velocity heterogeneities of the Earth's mantle. However, the approximate techniques upon which global tomographers have traditionally relied become inadequate when dealing with crustal structure, as well as short-wavelength or large amplitude mantle heterogeneity. The spectral element method, on the other hand, permits accurate calculation of wave propagation through highly heterogeneous structures, and is computationally economical when coupled with a normal mode solution and applied to a restricted region of the Earth such as the upper mantle (SEM). Importantly, SEM allows a dramatic improvement in accounting for the effects of crustal structure. Here, we develop and apply a new hybrid method of tomography, which allows us to leverage the accuracy of SEM to model fundamental and higher-mode long period (>60 s) waveforms. We then present the first global model of upper-mantle velocity and radial anisotropy developed using SEM. Our model, SEMum, confirms that the long-wavelength mantle structure imaged using approximate semi-analytic techniques is robust and representative of the Earth's true structure. Furthermore, it reveals structures in the upper mantle that were not clearly seen in previous global tomographic models. We show that SEMum favourably compares to and rivals the resolving power of continental-scale studies. This new hybrid approach to tomography can be applied to a larger and higher-frequency data set in order to gain new insights into the structure of the lower mantle and more robustly map seismic structure at the regional and smaller scales.
 
  Programme 133  
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  Address  
  Corporate Author Thesis  
  Publisher Blackwell Publishing Ltd Place of Publication Editor  
  Language Summary Language Original Title  
  Series Editor Series Title Abbreviated Series Title  
  Series Volume Series Issue Edition  
  ISSN 1365-246X ISBN Medium  
  Area Expedition Conference  
  Notes Approved yes  
  Call Number Serial 3794  
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Author Visser K, Trampert J, Kennett B L N, doi  openurl
  Title Global anisotropic phase velocity maps for higher mode Love and Rayleigh waves Type Journal Article
  Year 2008 Publication Geophysical Journal International Abbreviated Journal  
  Volume 172 Issue 3 Pages 1016-1032  
  Keywords (down) Inverse theory, Surface waves and free oscillations, Seismic anisotropy, Seismic tomography,  
  Abstract It is well established that the Earth's uppermost mantle is anisotropic, but there are no clear observations of anisotropy in the deeper parts of the mantle. Surface waves are well suited to observe anisotropy since they carry information about both radial and azimuthal anisotropy. Fundamental mode surface waves, for commonly used periods up to 200 s, are sensitive to structure in the first few hundred kilometres, and therefore, do not provide information on anisotropy below. Higher mode surface waves have sensitivities that extend to and beyond the transition zone, and should thus give insight about azimuthal anisotropy at greater depths. We have measured higher mode Love and Rayleigh phase velocities using a model space search approach, which provides us with consistent relative uncertainties from measurement to measurement and from mode to mode. From these phase velocity measurements, we constructed global anisotropic phase velocity maps. Prior to inversion, we determine the optimum relative weighting for anisotropy. We present global azimuthal phase velocity maps for higher mode Rayleigh waves (up to the sixth higher mode) and Love waves (up to the fifth higher mode) with corresponding average model uncertainties. The anisotropy we derive is robust within the uncertainties for all modes. Given the ray theoretical sensitivity kernels of Rayleigh and Love wave modes, the source of anisotropy is complex, but mainly located in the asthenosphere and deeper. Our models show a good correspondence with other studies for the fundamental mode, but we have been able to achieve higher resolution.
 
  Programme 133  
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  Corporate Author Thesis  
  Publisher Blackwell Publishing Ltd Place of Publication Editor  
  Language Summary Language Original Title  
  Series Editor Series Title Abbreviated Series Title  
  Series Volume Series Issue Edition  
  ISSN 1365-246X ISBN Medium  
  Area Expedition Conference  
  Notes Approved yes  
  Call Number Serial 2813  
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Author Lebedev Sergei, Van Der Hilst Rob D, doi  openurl
  Title Global upper-mantle tomography with the automated multimode inversion of surface and S-wave forms Type Journal Article
  Year 2008 Publication Geophysical Journal International Abbreviated Journal  
  Volume 173 Issue 2 Pages 505-518  
  Keywords (down) Inverse theory, Numerical approximations and analysis, Mantle processes, Seismic tomography, Cratons, Dynamics of lithosphere and mantle,  
  Abstract We apply the Automated Multimode Inversion of surface and S-wave forms to a large global data set, verify the accuracy of the method and assumptions behind it, and compute an Sv-velocity model of the upper mantle (crust660 km). The model is constrained with 51 000 seismograms recorded at 368 permanent and temporary broadband seismic stations. Structure of the mantle and crust is constrained by waveform information both from the fundamental-mode Rayleigh waves (periods from 20 to 400 s) and from S and multiple S waves (higher modes). In order to enhance the validity of the path-average approximation, we implement the automated inversion of surface- and S-wave forms with a three-dimensional (3-D) reference model. Linear equations obtained from the processing of all the seismograms of the data set are inverted for seismic velocity variations also relative to a 3-D reference, in this study composed of a 3-D model of the crust and a one-dimensional (1-D), global-average depth profile in the mantle below. Waveform information is related to shear- and compressional-velocity structure within approximate waveform sensitivity areas. We use two global triangular grids of knots with approximately equal interknot spacing within each: a finely spaced grid for integration over sensitivity areas and a rougher-spaced one for the model parametrization. For the tomographic inversion we use LSQR with horizontal and vertical smoothing and norm damping. We invert for isotropic variations in S- and P-wave velocities but also allow for S-wave azimuthal anisotropyin order to minimize errors due to possible mapping of anisotropy into isotropic heterogeneity. The lateral resolution of the resulting isotropic upper-mantle images is a few hundred kilometres, varying with data sampling. We validate the imaging technique with a spectral-element resolution test: inverting a published global synthetic data set computed with the spectral-element method using a laterally heterogeneous mantle model we are able to reconstruct the synthetic model accurately. This test confirms both the accuracy of the implementation of the method and the validity of the JWKB and path-average approximations as applied in it. Reviewing the tomographic model, we observe that low-Sv-velocity anomalies beneath mid-ocean ridges and backarc basins extend down to 100 km depth only, shallower than according to some previous tomographic models; this presents a close match to published estimates of primary melt production depth ranges there. In the seismic lithosphere beneath cratons, unambiguous high velocity anomalies extend to 200 km. Pronounced low-velocity zones beneath cratonic lithosphere are rare; where present (South America; Tanzania) they are neighboured by volcanic areas near cratonic boundaries. The images of these low-velocity zones may indicate hot materialpossibly of mantle-plume origintrapped or spreading beneath the thick cratonic lithosphere.
 
  Programme 133  
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  Corporate Author Thesis  
  Publisher Blackwell Publishing Ltd Place of Publication Editor  
  Language Summary Language Original Title  
  Series Editor Series Title Abbreviated Series Title  
  Series Volume Series Issue Edition  
  ISSN 1365-246X ISBN Medium  
  Area Expedition Conference  
  Notes Approved yes  
  Call Number Serial 2811  
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Author Vallée M, Charléty J, Ferreira A M G, Delouis B, Vergoz J, doi  openurl
  Title SCARDEC: a new technique for the rapid determination of seismic moment magnitude, focal mechanism and source time functions for large earthquakes using body-wave deconvolution Type Journal Article
  Year 2011 Publication Geophysical Journal International Abbreviated Journal 0956-540X  
  Volume 184 Issue 1 Pages 338-358  
  Keywords (down) Inverse theory, Earthquake source observations, Body waves, Surface waves and free oscillations, Wave propagation, Subduction zone processes,  
  Abstract Accurate and fast magnitude determination for large, shallow earthquakes is of key importance for post-seismic response and tsumami alert purposes. When no local real-time data are available, which is today the case for most subduction earthquakes, the first information comes from teleseismic body waves. Standard body-wave methods give accurate magnitudes for earthquakes up to Mw= 77.5. For larger earthquakes, the analysis is more complex, because of the non-validity of the point-source approximation and of the interaction between direct and surface-reflected phases. The latter effect acts as a strong high-pass filter, which complicates the magnitude determination. We here propose an automated deconvolutive approach, which does not impose any simplifying assumptions about the rupture process, thus being well adapted to large earthquakes. We first determine the source duration based on the length of the high frequency (13 Hz) signal content. The deconvolution of synthetic double-couple point source signalsdepending on the four earthquake parameters strike, dip, rake and depthfrom the windowed real data body-wave signals (including P, PcP, PP, SH and ScS waves) gives the apparent source time function (STF). We search the optimal combination of these four parameters that respects the physical features of any STF: causality, positivity and stability of the seismic moment at all stations. Once this combination is retrieved, the integration of the STFs gives directly the moment magnitude. We apply this new approach, referred as the SCARDEC method, to most of the major subduction earthquakes in the period 19902010. Magnitude differences between the Global Centroid Moment Tensor (CMT) and the SCARDEC method may reach 0.2, but values are found consistent if we take into account that the Global CMT solutions for large, shallow earthquakes suffer from a known trade-off between dip and seismic moment. We show by modelling long-period surface waves of these events that the source parameters retrieved using the SCARDEC method explain the observed surface waves as well as the Global CMT parameters, thus confirming the existing trade-off. For some well-instrumented earthquakes, our results are also supported by independent studies based on local geodetic or strong motion data. This study is mainly focused on moment determination. However, the SCARDEC method also informs us about the focal mechanism and source depth, and can be a starting point to study systematically the complexity of the STF.
 
  Programme 133  
  Campaign  
  Address  
  Corporate Author Thesis  
  Publisher Blackwell Publishing Ltd Place of Publication Editor  
  Language Summary Language Original Title  
  Series Editor Series Title Abbreviated Series Title  
  Series Volume Series Issue Edition  
  ISSN 1365-246X ISBN Medium  
  Area Expedition Conference  
  Notes Approved yes  
  Call Number Serial 3222  
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Author Tape Carl, Liu Qinya, Maggi Alessia, Tromp Jeroen, doi  openurl
  Title Seismic tomography of the southern California crust based on spectral-element and adjoint methods Type Journal Article
  Year 2010 Publication Geophysical Journal International Abbreviated Journal  
  Volume 180 Issue 1 Pages 433 -462  
  Keywords (down) Inverse theory, Body waves, Surface waves and free oscillations, Seismic tomography, Computational seismology, Crustal structure,  
  Abstract SUMMARY We iteratively improve a 3-D tomographic model of the southern California crust using numerical simulations of seismic wave propagation based on a spectral-element method (SEM) in combination with an adjoint method. The initial 3-D model is provided by the Southern California Earthquake Center. The data set comprises three-component seismic waveforms (i.e. both body and surface waves), filtered over the period range 230 s, from 143 local earthquakes recorded by a network of 203 stations. Time windows for measurements are automatically selected by the FLEXWIN algorithm. The misfit function in the tomographic inversion is based on frequency-dependent multitaper traveltime differences. The gradient of the misfit function and related finite-frequency sensitivity kernels for each earthquake are computed using an adjoint technique. The kernels are combined using a source subspace projection method to compute a model update at each iteration of a gradient-based minimization algorithm. The inversion involved 16 iterations, which required 6800 wavefield simulations. The new crustal model, m16, is described in terms of independent shear (VS) and bulk-sound (VB) wave speed variations. It exhibits strong heterogeneity, including local changes of ±30 per cent with respect to the initial 3-D model. The model reveals several features that relate to geological observations, such as sedimentary basins, exhumed batholiths, and contrasting lithologies across faults. The quality of the new model is validated by quantifying waveform misfits of full-length seismograms from 91 earthquakes that were not used in the tomographic inversion. The new model provides more accurate synthetic seismograms that will benefit seismic hazard assessment.
 
  Programme 133  
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  Corporate Author Thesis  
  Publisher Blackwell Publishing Ltd Place of Publication Editor  
  Language Summary Language Original Title  
  Series Editor Series Title Abbreviated Series Title  
  Series Volume Series Issue Edition  
  ISSN 1365-246X ISBN Medium  
  Area Expedition Conference  
  Notes Approved yes  
  Call Number Serial 514  
Permanent link to this record
 

 
Author Laparie M, Larvor V, Frenot Y, Renault D, doi  openurl
  Title Starvation resistance and effects of diet on energy reserves in a predatory ground beetle (Merizodus soledadinus; Carabidae) invading the Kerguelen Islands Type Journal Article
  Year 2012 Publication Comparative Biochemistry and Physiology Part A: Molecular & Integrative Physiology Abbreviated Journal  
  Volume 161 Issue 2 Pages 122-129  
  Keywords (down) Invasive insect, Glucose, Metabolic stores, Prey selection, Sub-Antarctic island, Trehalose, Triglyceride, Trophic stress,  
  Abstract The relationship between nutritional requirements and the availability or quality of food is a prime parameter in determining the geographical expansion of invasive insects. At the sub-Antarctic Kerguelen Islands, the invasive ground beetle Merizodus soledadinus becomes the main invertebrate predator when it colonizes new habitats, leading to the local extinction of native fly species. Such changes in the structure of prey communities may alter the energy management (storage and expenditure) of this predator. In this species, we monitored survival and body mass during food deprivation, in addition to evaluating the effects of two distinct diets (maggots versus enchytraeids) on the consumption and restoration of body reserves (sugars and triglycerides). We found that adults can starve for more than 60 days, and feed every 3.76 days on average when food is available. We recorded higher predation rates on maggots, associated with steeper body mass variations, compared to enchytraeids. Sugars and triglycerides were significantly consumed during food deprivation and restored after refeeding, but varied similarly among individuals supplied on the distinct diets. Other parameters may determine the food preferences observed, such as salt content in prey tissues, because M. soledadinus mainly feeds in hypersaline foreshore habitats, and may limit the consumption of osmotic conformers.  
  Programme 136  
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  Language Summary Language Original Title  
  Series Editor Series Title Abbreviated Series Title  
  Series Volume Series Issue Edition  
  ISSN 1095-6433 ISBN Medium  
  Area Expedition Conference  
  Notes Approved yes  
  Call Number Serial 4110  
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Author Matthias Vignon, Mingsha Zhou, Angus R. McIntosh, Cristian Correa, Peter A. H. Westley, Lisa Jacquin, Jacques Labonne, Andrew P. Hendry doi  openurl
  Title Trait variation in a successful global invader: a large-scale analysis of morphological variance and integration in the brown trout Type Journal
  Year 2023 Publication Biological Invasions Abbreviated Journal  
  Volume 25 Issue 5 Pages 1659-1677  
  Keywords (down) Invasion Morphological integration Phenotypic variation Population size  
  Abstract In ecology and evolution, the small population paradigm posits that reduced genetic variation will result in limited phenotypic variation that, in turn, will affect population resilience and potential for adaptation. Over the last decade though, such a paradigm has been questioned, with evidence that mechanisms independent of genetic variation may be also important in shaping phenotypic variation. However, there are few large-scale empirical examples, especially from aquatic ecosystems. Using the large-scale natural experiment afforded by the global invasion of brown trout (Salmo trutta), we quantify standing phenotypic variation in morphology among different introduced ranges, relative to the native range. By using shape variation and morphological integration as indicators of phenotypic variation, we show that neither founding population size nor time since founding (i.e., effect of selection regime) are correlated to the amount of morphological variation, contrarily to common expectations. Beyond founding population size and time since founding, the amount of morphological variation is mostly controlled by factors at the population level rather than at the region level, and is not lower in invaded regions compared to the native range. These results suggest that the dynamics of phenotypic variation may be largely independent of population size and mostly determined by site-specific patterns of selection.  
  Programme 1041  
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  Corporate Author Thesis  
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  Language Summary Language Original Title  
  Series Editor Series Title Abbreviated Series Title  
  Series Volume Series Issue Edition  
  ISSN 1573-1464 ISBN Medium  
  Area Expedition Conference  
  Notes Approved yes  
  Call Number Serial 8649  
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Author Lecomte Frédéric, Beall Edward, Chat Joëlle, Davaine Patrick, Gaudin Philippe, doi  openurl
  Title The complete history of salmonid introductions in the Kerguelen Islands, Southern Ocean Type Journal Article
  Year 2013 Publication Abbreviated Journal  
  Volume 36 Issue 4 Pages 457-475-  
  Keywords (down) Introductions, Colonization, Salmo, Oncorhynchus, Salvelinus, Kerguelen Islands,  
  Abstract  
  Programme 1041  
  Campaign  
  Address  
  Corporate Author Thesis  
  Publisher Springer-Verlag Place of Publication Editor  
  Language Summary Language Original Title  
  Series Editor Series Title Abbreviated Series Title  
  Series Volume Series Issue Edition  
  ISSN 0722-4060 ISBN Medium  
  Area Expedition Conference  
  Notes Approved yes  
  Call Number Serial 4782  
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