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Friedt J-M, Retornaz T, Alzuaga S, Baron T, Martin G, Laroche T, Ballandras S, Griselin M, Simonnet J-P, . (2011). Surface acoustic wave devices as passive buried sensors
. Journal of Applied Physics, 109(3), 034905–9.
Keywords: delay lines, electrical conductivity, ground penetrating radar, moisture, permittivity, surface acoustic wave sensors, temperature measurement, wireless sensor networks,
Programme: 304
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Hao Wang, John D. Nagy, Olivier Gilg, Yang Kuang. (2009). The roles of predator maturation delay and functional response in determining the periodicity of predator–prey cycles (Vol. 221).
Abstract: Population cycles in small mammals have attracted the attention of several generations of theoretical and experimental biologists and continue to generate controversy. Top-down and bottom-up trophic regulations are two recent competing hypotheses. The principal purpose of this paper is to explore the relative contributions of a variety of ecological factors to predator–prey population cycles. Here we suggest that for some species – collared lemmings, snowshoe hares and moose in particular – maturation delay of predators and the functional response of predation appear to be the primary determinants. Our study suggests that maturation delay alone almost completely determines the cycle period, whereas the functional response greatly affects its amplitude and even its existence. These results are obtained from sensitivity analysis of all parameters in a mathematical model of the lemming–stoat delayed system, which is an extension of Gilg’s model. Our result may also explain why lemmings have a 4-year cycle whereas snowshoe hares have a 10-year cycle. Our parameterized model supports and extends May’s assertion that time delay impacts cycle period and amplitude. Furthermore, if maturation periods of predators are too short or too long, or the functional response resembles Holling Type I, then population cycles do not appear; however, suitable intermediate predator maturation periods and suitable functional responses can generate population cycles for both prey and predators. These results seem to explain why some populations are cyclic whereas others are not. Finally, we find parameterizations of our model that generate a 38-year population cycle consistent with the putative cycles of the moose–wolf interactions on Isle Royale, Michigan.
Keywords: Delay differential equation Lemming–stoat Moose–wolf Population cycle Predator–prey Snowshoe hare–lynx
Programme: 1036
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Deborah Verfaillie, Joanna Charton, Irene Schimmelpfennig, Zoe Stroebele, Vincent Jomelli, François Bétard, Vincent Favier, Julien Cavero, Etienne Berthier, Hugues Goosse, Vincent Rinterknecht, Claude Legentil, Raphaelle Charrassin, Georges Aumaître, Didier L. Bourlès, Karim Keddadouche. (2021). Evolution of the Cook Ice Cap (Kerguelen Islands) between the last centuries and 2100 ce based on cosmogenic dating and glacio-climatic modelling (Vol. 33).
Abstract: The Cook Ice Cap (CIC) on the sub-Antarctic Kerguelen Islands recently experienced extremely negative surface mass balance. Further deglaciation could have important impacts on endemic and invasive fauna and flora. To put this exceptional glacier evolution into a multi-centennial-scale context, we refined the evolution of the CIC over the last millennium, investigated the associated climate conditions and explored its potential evolution by 2100 ce. A glaciological model, constrained by cosmic ray exposure dating of moraines, historical documents and recent direct mass balance observations, was used to simulate the ice-cap extents during different phases of advance and retreat between the last millennium and 2100 ce. Cosmogenic dating suggests glacial advance around the early Little Ice Age (LIA), consistent with findings from other sub-Antarctic studies, and the rather cold and humid conditions brought about by the negative phase of the Southern Annular Mode (SAM). This study contributes to our currently limited understanding of palaeoclimate for the early LIA in the southern Indian Ocean. Glaciological modelling and observations confirm the recent decrease in CIC extent linked to the intensification of the SAM. Although affected by large uncertainties, future simulations suggest a complete disappearance of CIC by the end of the century.
Keywords: degree-day glaciological model future projections glacial fluctuations in situ cosmogenic chlorine-36 dating moraines sub-Antarctic islands
Programme: 1048
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Roman Sulzbach, Hartmut Wziontek, Michael Hart-Davis, Henryk Dobslaw, Hans-Georg Scherneck, Michel Van Camp, Ove Christian Dahl Omang, Ezequiel D. Antokoletz, Christian Voigt, Denise Dettmering, Maik Thomas. (2022). Modeling gravimetric signatures of third-degree ocean tides and their detection in superconducting gravimeter records (Vol. 96).
Abstract: We employ the barotropic, data-unconstrained ocean tide model TiME to derive an atlas for degree-3 tidal constituents including monthly to terdiurnal tidal species. The model is optimized with respect to the tide gauge data set TICON-td that is extended to include the respective tidal constituents of diurnal and higher frequencies. The tide gauge validation shows a root-mean-square (RMS) deviation of 0.9–1.3 mm for the individual species. We further model the load tide-induced gravimetric signals by two means (1) a global load Love number approach and (2) evaluating Greens-integrals at 16 selected locations of superconducting gravimeters. The RMS deviation between the amplitudes derived using both methods is below $$0.5 \ $$nGal ($$1 \ $$nGal $$= 0.01 \frac{\text {nm}}{\text {s}^2}$$) when excluding near-coastal gravimeters. Utilizing ETERNA-x, a recently upgraded and reworked tidal analysis software, we additionally derive degree-3 gravimetric tidal constituents for these stations, based on a hypothesis-free wave grouping approach. We demonstrate that this analysis is feasible, yielding amplitude predictions of only a few 10 nGal, and that it agrees with the modeled constituents on a level of 63–80% of the mean signal amplitude. Larger deviations are only found for lowest amplitude signals, near-coastal stations, or shorter and noisier data sets.
Keywords: Degree-3 tides Superconducting gravimetry Tidal analysis Tidal modeling Tide gauge data
Programme: 688
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Sionneau T, Bout-Roumazeilles V, Flower BP, Bory A, Tribovillard N, Kissel C, Van Vliet-Lanoë B, Montero Serrano JC, . (2010). Provenance of freshwater pulses in the Gulf of Mexico during the last deglaciation
. Quaternary Research, 74(2), 235–245.
Abstract: During the last deglaciation, the decaying Laurentide Ice Sheet (LIS) delivered huge volumes of meltwater toward the Gulf of Mexico. The present investigation of clay mineralogy and grain-size characteristics of terrigenous sediments deposited in the Orca Basin (Gulf of Mexico) offers a unique opportunity to link the marine record of these meltwater floods with the reconstructed continental glacial history and the modeled drainage patterns. Five peculiar sedimentary levels, characterized by high smectite content and low CaCO3 content, were identified and occurred simultaneously with major meltwater floods. According to recently published clay mineral distribution maps for North America, these results help to pinpoint the southwestern margin of the LIS as a main contributor to most of the meltwater discharges. In addition, the peculiar mineralogical composition (illite and chlorite-rich) of the sediments characterizing the meltwater episode associated with Heinrich event 1 suggests a provenance from the Great Lakes area, supporting the interpretation of destabilization of the LIS southeastern margin during this event. Decreased terrigenous contribution associated with changing provenance of sediments after 12.9 cal ka BP suggests strong modifications of the continental hydrography in relation to Lake Agassiz history and changes in the morphology of Mississippi delta due to rising sea level.
Keywords: Deglaciation, Meltwater pulse, Laurentide Ice Sheet, Clay minerals, Orca Basin, Mississippi River,
Programme: 316
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Portier E., Mercier D., Decaulne A. (2023). Les glissements de terrain dans les Westfjords et les fjords de l'Est d'Islande : inventaire, morphométrie et variables explicatives.
Abstract: Les Westfjords et fjords de l’Est de l’Islande concentrent de nombreux glissements de terrain. Ces phénomènes visibles par observation à distance d’images satellites et d’un Modèle Numérique de Terrain (MNT) ont été inventoriés, puis mesurés et analysés. Au total, 251 et 290 glissements de terrain ont été recensés respectivement dans les Westfjords et les fjords de l’Est, au sein d’une base de données et dans un Système d’Informations Géographiques (SIG). Pour chaque glissement de terrain, sa localisation, sa morphométrie (longueur, largeur, superficie, épaisseur, volume estimé, …), ainsi que de potentielles variables de contrôle, notamment géologiques (lithologie, pendage), ou explicatives (orientation, âge de la déglaciation du versant affecté par le glissement de terrain) ont été relevées. Ces variables et la répartition des glissements ont été étudiées par analyse spatiale et statistique. Ce travail fournit un inventaire complémentaire des glissements de terrain pour ces deux secteurs. Cependant, les facteurs de déclenchement habituellement identifiés ne permettent pas une explication satisfaisante à leur répartition. Néanmoins, des pistes de réflexions se dessinent et l’élargissement de la base de données à l’échelle de l’Islande permet de les comparer d’un secteur à l’autre. Cette étude met en avant des foyers principaux de glissements de terrain : pour les Westfjords, une plus forte densité de glissements de terrain dans le nord-ouest de la zone étudiée et dans la partie la plus étroite de la péninsule ; et pour les fjords de l’Est, une plus forte densité dans le Nord de la zone étudiée. Ces foyers pourraient s’expliquer par les directions d’écoulement de la calotte glaciaire passée. D’autre part, un des constats est une surreprésentation des glissements orientés vers l’ouest et le sud pour les fjords de l’Est, et vers le sud et l’est pour les Westfjords. L’hypothèse proposée est un contrôle climatique : les versants davantage ensoleillés auraient subi une déglaciation plus rapide favorisant l’instabilité des versants. Les données recueillies suggèrent également que la lithologie (basaltes tertiaires) est une variable de contrôle et que la période pendant laquelle la zone de glissement de terrain est déglacée est une variable explicative de l'initiation du glissement de terrain. Les glissements de terrain observés s’inscriraient ainsi dans une dynamique paraglaciaire d’instabilité des versants après la phase de déglaciation
Keywords: Deglaciation Iceland Landslides Paraglacial
Programme: 1266
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Emilie Portier, Denis Mercier, Armelle Decaulne, Etienne Cossart. (2024). Schmidt-hammer exposure-age dating of seven paraglacial rock-slope failures in the Bolungarvík-Suðureyri area (Westfjords, Iceland) (Vol. 457).
Abstract: Many rock-slope failures (RSF) impact Iceland's Westfjords morphology. Five RSF areas, totalling seven RSFs, were studied in the western fjords around Bolungarvík-Suðureyri: Óshólar, Minni-Hlið, Meira-Hraun, the Vatnadalur valley and part of the Sunddalur valley. The aim of this article is to provide chronological data of the RSFs and to subsequently obtain a better chronosequence of post-glacial events, none of which have yet been dated in the Westfjords. More particularly, we discuss a paraglacial hypothesis of their occurrence. For this purpose, the Schmidt-hammer exposure-age dating (SHD) method is used on the RSF deposits, and the rebound values obtained from the impacted blocks are converted to age estimates using radiocarbon ages obtained from the different sites in order to calculate a SHD age calibration. Then, we establish a chronology of the setting up of the events. In this way, seven RSFs have been dated and different chronological generations of deposit emplacement have been exhibited for some of them. Thus, various periods of instability affected mountain slopes. The Óshólar RSF is thought to have been deposited firstly at around 12,500 cal BP, the Minni-Hlið RSF at ∼9800 cal BP, the Meira-Hraun RSF at ∼8700 cal BP, the Vatnadalur RSFs at ∼9000 cal BP, ∼ 6900 cal BP, and ∼ 4300 cal BP, and the Sunddalur RSF at ∼9600 cal BP. These RSFs therefore correspond to so-called paraglacial events, which took place at the beginning of deglaciation of the area during the first half of the Holocene.
Keywords: Deglaciation Holocene Landslide Rock-slope failures Schmidt-hammer exposure-age dating
Programme: 1266
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Emilie Portier, Denis Mercier, Armelle Decaulne. (2023). Spatial analysis and controlling factors of landslides in East Icelandic fjords (Vol. 29).
Abstract: Les fjords de l’est de l’Islande concentrent de nombreux glissements de terrain. Ces phénomènes visibles par observation à distance d’images satellites et d’un Modèle Numérique de Terrain (MNT) ont été inventoriés dans cette étude, puis mesurés et analysés. Au total, 290 glissements de terrain ont été recensés au sein d’une base de données sous forme de tableur et dans un Système d’Informations Géographiques (SIG). Pour chaque glissement de terrain ont été relevées sa localisation, sa morphométrie (longueur, largeur, superficie, épaisseur, volume estimé, etc.), ainsi que de potentielles variables de contrôle notamment géologiques (lithologie, pendage), ou explicatives (orientation, âge de la déglaciation du versant affecté par le glissement de terrain). Ces variables et leur répartition ont été étudiées par analyse spatiale et statistique. Cette étude met en avant une plus forte densité de glissements de terrain dans le nord de la zone étudiée, qui pourrait s’expliquer par les directions d’écoulement de la calotte glaciaire passée, qui auraient renforcé la pression exercée sur les versants entraînant le phénomène de décompression postglaciaire. Un autre constat est une surreprésentation de glissements orientés vers l’ouest et le sud, amenant l’hypothèse d’un contrôle climatique : les versants davantage ensoleillés auraient subi une déglaciation plus rapide favorisant l’instabilité des versants. Les données recueillies suggèrent également que la lithologie (basaltes tertiaires) est une variable de contrôle et que la période pendant laquelle la zone de glissement de terrain est déglacée est une variable explicative de l'initiation du glissement de terrain. Les glissements de terrain observés s’inscriraient ainsi dans une dynamique paraglaciaire d’instabilité des versants après leur déglaciation.
Keywords: déglaciation glissements de terrain Islande paraglaciaire
Programme: 1266
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Tocheport, A.; Rivera, L.; Chevrot, S. (2007). A systematic study of source time functions and moment tensors of intermediate and deep earthquakes. J. Geophys. Res., 112.
Abstract: We developed an inversion algorithm to determine the Source Time Function and Moment Tensor of intermediate and deep earthquakes from a set of teleseismic body wave records. The method proceeds in two stages. First, a nonlinear inversion by simulated annealing is performed to simultaneously (a) align the waveforms in time, (b) determine a common source time function, and (c) measure a collection of observed station amplitudes. The station amplitudes are then used, in a second stage, as secondary observables to invert for the moment tensors. We perform three different inversions to estimate the complete moment tensor solution, the pure deviatoric solution, and the double-couple solution. All the calculations are extremely simple and, in particular, it is not necessary to compute synthetic seismograms. The method requires well-isolated phases at different stations, which restricts its application to intermediate and deep events. The algorithm is applied to the FDSN broadband records corresponding to the period 1990–2005 of worldwide intermediate and deep seismicity (depth $\ges$100 km) of magnitude greater than 6.5. The source time functions are compared to those obtained from other studies of intermediate and deep events. The moment tensors are also systematically compared to the Harvard-CMT and USGS solutions. Both show a very good agreement with previous studies.
Keywords: Deep earthquakes; body waves inversion; source parameters; 7203 Seismology: Body waves; 7215 Seismology: Earthquake source observations; 7209 Seismology: Earthquake dynamics; 8120 Tectonophysics: Dynamics of lithosphere and mantle: general
Programme: 133
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F. Pitout, A. Marchaudon, K. J. Trattner, J. Berchem, H. Laakso, C. P. Escoubet. (2020). Simultaneous Polar and Cluster Observations in the Northern and Southern Middle-Altitude Polar Cusps Around Equinox (Vol. 125).
Abstract: We present an event of simultaneous observations of the northern and southern middle-altitude polar cusps by the Polar spacecraft and Cluster fleet that occurred on 23 September 2004. We examine the possible asymmetries in the fields and plasma parameters, although the proximity of the equinox should limit these asymmetries. Ion sensors reveal two dispersions in both cusps, and data analysis leads to the conclusion that those dispersions are due to pulsed reconnection at a single X-line, which runs along the subsolar magnetopause. While the electromagnetic and particle energy fluxes injected in both cusp are globally very similar, we report significant differences in ion dispersions, width of the low-latitude boundary layer, and peak convection velocities. We ascribe these differences to the dipole tilt that introduces an asymmetry in the magnetosheath flow at the exterior cusps.
Keywords: dayside magnetosphere hemispheric asymmetry polar cusp
Programme: 312
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