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Author |
Samuel Veilleux, Najat Bhiry, Armelle Decaulne |
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Title |
Talus slope characterization in Tasiapik Valley (subarctic Québec): Evidence of past and present slope processes |
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Journal |
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Year |
2020 |
Publication |
Geomorphology |
Abbreviated Journal |
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Volume |
349 |
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Pages |
106911 |
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Keywords  |
Morphometry Nunavik Periglacial Slope dynamics Snow avalanches |
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Abstract |
Topographic, granulometric, morphometric, petrographic and vegetation surveys were conducted on the slopes of Tasiapik Valley, near Umiujaq (Nunavik), to document mass wasting processes and their geomorphological impact. Talus slopes, widespread at the foot of the steep rockwalls of Tasiapik Valley, are an important landscape feature in the area. The lithology of the slope deposits attest their local origin, namely the result of rockfalls coming from the adjacent wall. Locally, poor vegetation covering the clasts exhibits recently fallen debris; elsewhere, dense shrub cover has colonized the slopes demonstrating the low activity nowadays. On-going periglacial processes have led to extensive dismantling of the rockface, enabling for debris supply. Following the last deglaciation, paraglacial processes have potentially favoured slope instabilities. The use of automatic cameras during the winter 2017–2018 resulted in the observation of many snow-avalanche events; however few rockfall events have been observed. Spring snow avalanches have carried rock debris to the talus at the foot of the slope; snow also enabled debris redistribution on the slopes. |
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1148 |
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0169-555X |
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yes |
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Serial |
8261 |
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Hannah J. Kriesell, Thierry Aubin, Víctor Planas‐Bielsa, Marine Benoiste, Francesco Bonadonna, Hélène Gachot‐Neveu, Yvon Le Maho, Quentin Schull, Benoit Vallas, Sandrine Zahn, Céline Le Bohec |
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Title |
Sex identification in King Penguins Aptenodytes patagonicus through morphological and acoustic cues |
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Journal |
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Year |
2018 |
Publication |
Ibis |
Abbreviated Journal |
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Volume |
160 |
Issue |
4 |
Pages |
755-768 |
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Keywords |
morphology penguins seabird sexing methods sexual selection vocal sex recognition |
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Abstract |
In the context of sexual selection, animals have developed a variety of cues conveying information about the sex of an individual to conspecifics. In many colonial seabird species, where females and males are monomorphic and do not show obvious differences in external morphology, acoustic cues are an important signal for individual and sex recognition. Here, we study the vocal and morphological sex dimorphism in the King Penguin Aptenodytes patagonicus, a colonial, monomorphic seabird for which our knowledge about the role of vocalizations and morphology in mate choice is very limited. Data were collected at Possession Island, Crozet Archipelago, in a breeding colony consisting of about 16 000 breeding pairs. Using measurements of six morphological features and analysing acoustic parameters of call recordings of adult individuals, we show that King Penguins can be sexed based on a single morphological measurement of the beak with an accuracy of 79%. We found a sex-specific syntax in adult King Penguin calls that provided a 100% accurate method to distinguish between the sexes in our study population. To confirm the method at the species level, we analysed calls recorded from King Penguin adults in Kerguelen Island, 1300 km away from our study population and found the same accuracy of the sex-specific syntax. This sex-specific syllable arrangement is rare in non-passerines and is a first step in understanding the mate choice process in this species. Furthermore, it offers a cost-effective, non-invasive technique for researchers to sex King Penguins in the field. |
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137,354 |
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Bachelor's thesis |
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1474-919X |
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1474-919X |
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yes |
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Serial |
7100 |
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Author |
Reymond D, Crusem R, Barriot J P, |
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Title |
Empirical approaches for fast robust inversion of seismic moment tensor from surface waves
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Journal Article |
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Year |
2010 |
Publication |
Geophysical Research Letters |
Abbreviated Journal |
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Volume |
37 |
Issue |
7 |
Pages |
L07307- |
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Keywords |
moment tensor, robust inversion, IRLS, 3260 Inverse theory, 7255 Surface waves and free oscillations, 7215 Earthquake source observations, |
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Abstract |
We present a method of robust inversion (also called IRLS: Iterative Reweighted Least Squares) which is surprisingly insensitive to outlier data points, as it discards automatically the aberrant points, without the necessity for careful human inspection and control of data quality. Different criteria based on residuals and signal-to-noise ratio are injected into the covariance matrix (acting like a weighting function), to perform the robust inversion using the iterative generalized discrete inverse method of Tarantola-Valette. From a practical point of view, this algorithm is used as the Preliminary Determination of Focal Mechanism (PDFM) method, which is a project for rapid estimation of source parameters of strong earthquakes in the context of tsunami warning. The input data to be inverted are spectra of long period surface waves, and as an output, the computed result is the seismic moment tensor, from which focal geometry of an earthquake, and principal stress axes are obtained. This method can be applied to any other method of non-linear (iterative) inversions confronted to the problem of outlier points polluting the data sets.
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133 |
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ISSN |
1944-8007 |
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yes |
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Serial |
403 |
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Author |
Dufumier H. |
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Title |
On the limits of moment tensor inversions of teleseismic body wave spectra. |
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Journal Article |
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Year |
1996 |
Publication |
Pure and applied geophysics |
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Volume |
147 |
Issue |
3 |
Pages |
467-482 |
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Keywords |
Moment tensor, inversion, body waves, conditioning, resolution, information, single-station |
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Abstract |
The limits of linear moment-tensor inversions from long-period teleseismic body waves are analysed in detail, using inverse methods. We focus our attention on single-station and few-stations methods. Information on the feasibility of full or deviatoric moment-tensor determinations prior to inversion are deduced from the system conditioning. The resolution and correlation of the momenttensor components are analysed using the resolution matrix. Conclusions on the importance and independence of the data are drawn from the information matrix. The single--station case and its implications are discussed in greater detail, as well as possible constraints on the inversion. |
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133 |
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ISSN |
0033-4553 |
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yes |
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Serial |
262 |
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Author |
Vignati E, Facchini MC, Rinaldi M, Scannell C, Ceburnis D, Sciare J, Kanakidou M, Myriokefalitakis S, Dentener F, O'Dowd CD, |
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Title |
Global scale emission and distribution of sea-spray aerosol: Sea-salt and organic enrichment
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Journal Article |
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Year |
2010 |
Publication |
Atmospheric Environment |
Abbreviated Journal |
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Volume |
44 |
Issue |
5 |
Pages |
670 -677 |
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Keywords |
Modelling, Marine aerosols, Organics, Emissions, |
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Abstract |
The chemical composition of marine aerosols as a function of their size is an important parameter for the evaluation of their impact on the global climate system. In this work we model fine particle organic matter emitted by sea spray processes and its influence on the aerosol chemical properties at the global scale using the off-line global Chemistry-Transport Model TM5. TM5 is coupled to a microphysical aerosol dynamics model providing size resolved information on particle masses and numbers. The mass of the emitted sea spray particles is partitioned between water insoluble organic matter (WIOM) and sea salt components in the accumulation mode using a function that relates the emitted organic fraction to the surface ocean chlorophyll-a concentrations. The global emission in the submicron size range of organic matter by sea spray process is 8.2 Tg yr-1, compared to 24 Tg yr-1 sea-salt emissions. When the marine sources are included, the concentrations of modeled primary particulate organic matter (POM) increase mainly over the oceans. The model predictions of WIOM and sea salt are evaluated against measurements carried out at Mace Head (Northern Hemisphere) and Amsterdam Island (Southern Hemisphere), showing that in clean marine conditions WIOM marine emissions contribute significantly to POM values. An estimation of the sea spray organic source in the coarse mode is carried out on the basis of field observations as well as laboratory experiments: the mass of sea spray organic matter in the coarse size range is ca 52% of the total primary organic fraction, leading to a total marine POM emission of 17.2 Tg yr-1. |
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415 |
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ISSN |
1352-2310 |
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yes |
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Serial |
68 |
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Author |
Legagneux, L.; Domine, F. |
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Title |
A mean field model of the decrease of the specific surface area of dry snow during isothermal metamorphism |
Type |
Journal Article |
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Year |
2005 |
Publication |
Journal of geophysical research-atmospheres |
Abbreviated Journal |
J. Geophys. Res. |
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Volume |
110 |
Issue |
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Pages |
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Keywords |
model; isothermal snow metamorphism; Ostwald ripening; 0736 Cryosphere: Snow; 3947 Mineral Physics: Surfaces and interfaces; 1847 Hydrology: Modeling; 5112 Physical Properties of Rocks: Microstructure |
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Abstract |
The surface area of snow that is accessible to gases is an essential parameter for quantifying the exchange of trace gases between the snowpack and the atmosphere and is called the specific surface area (SSA). Snow SSA decreases during metamorphism, but this is not described in current snow models owing to the complexity of the physics and geometry of snow. In this paper, we test whether it is possible to model snow SSA changes during isothermal metamorphism without accounting for all the complexity of the three-dimensional (3-D) structure of real snow. We have developed a mean field model of snow metamorphism under isothermal conditions, grounded in the theoretical framework of transient Ostwald ripening and representing snow as a distribution of spherical particles. Analytical expressions of the growth rates of these spheres are obtained, and the evolution of two measurable parameters that characterize snow geometry, the SSA and the distribution of radii of curvature (DRC), are simulated and compared to experimental data obtained by X-ray tomography. The qualitative effects of temperature, snow density, and the condensation coefficient on the rate of SSA decrease are examined. The model predicts very well the rate of evolution of the particle size distribution, which validates our physical description of isothermal metamorphism. In particular, we find that vapor phase diffusion is rate limiting. However, the calculation of the SSA from the DRC appears delicate and evidences too crude approximations in our description of the 3-D geometry of snow. Finally, it is stressed that the initial DRC can greatly influence the rate of SSA decrease, while experimental measurements of the rate of SSA decrease suggest that all snow types evolve in a similar way. It is thus proposed that most natural fresh snows have similar DRCs. |
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437 |
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Publisher |
American Geophysical Union |
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ISSN |
0148-0227 |
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yes |
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Call Number |
IPEV @ Thierry.Lemaire @ |
Serial |
5650 |
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Author |
Aymeric Fromant, Charles-André Bost, Paco Bustamante, Alice Carravieri, Yves Cherel, Karine Delord, Yonina H. Eizenberg, Colin M. Miskelly, John P. Y. Arnould |
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Title |
Temporal and spatial differences in the post-breeding behaviour of a ubiquitous Southern Hemisphere seabird, the common diving petrel |
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Journal |
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Year |
2020 |
Publication |
Royal Society Open Science |
Abbreviated Journal |
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Volume |
7 |
Issue |
11 |
Pages |
200670 |
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Keywords |
migration moult non-breeding Procellariiformes Southern Ocean stable isotopes |
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Abstract |
The non-breeding period plays a major role in seabird survival and population dynamics. However, our understanding of the migratory behaviour, moulting and feeding strategies of non-breeding seabirds is still very limited, especially for small-sized species. The present study investigated the post-breeding behaviour of three distant populations (Kerguelen Archipelago, southeastern Australia, New Zealand) of the common diving petrel (CDP) (Pelecanoides urinatrix), an abundant, widely distributed zooplanktivorous seabird breeding throughout the southern Atlantic, Indian and Pacific oceans. The timing, geographical destination and activity pattern of birds were quantified through geolocator deployments during the post-breeding migration, while moult pattern of body feathers was investigated using stable isotope analysis. Despite the high energetic cost of flapping flight, all the individuals quickly travelled long distances (greater than approx. 2500 km) after the end of the breeding season, targeting oceanic frontal systems. The three populations, however, clearly diverged spatially (migration pathways and destinations), and temporally (timing and duration) in their post-breeding movements, as well as in their period of moult. Philopatry to distantly separated breeding grounds, different breeding phenologies and distinct post-breeding destinations suggest that the CDP populations have a high potential for isolation, and hence, speciation. These results contribute to improving knowledge of ecological divergence and evolution between populations, and inform the challenges of conserving migratory species. |
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394 |
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Approved |
yes |
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Call Number |
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Serial |
8029 |
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Author |
G. Picard, H. Löwe, F. Domine, L. Arnaud, F. Larue, V. Favier, E. Le Meur, E. Lefebvre, J. Savarino, A. Royer |
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Title |
The Microwave Snow Grain Size: A New Concept to Predict Satellite Observations Over Snow-Covered Regions |
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Journal |
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Year |
2022 |
Publication |
AGU Advances |
Abbreviated Journal |
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Volume |
3 |
Issue |
4 |
Pages |
e2021AV000630 |
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Keywords |
microstructure microwave modeling porous media remote sensing snow |
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Abstract |
Satellite observations of snow-covered regions in the microwave range have the potential to retrieve essential climate variables such as snow height. This requires a precise understanding of how microwave scattering is linked to snow microstructural properties (density, grain size, grain shape and arrangement). This link has so far relied on empirical adjustments of the theories, precluding the development of robust retrieval algorithms. Here we solve this problem by introducing a new microstructural parameter able to consistently predict scattering. This “microwave grain size” is demonstrated to be proportional to the measurable optical grain size and to a new factor describing the chord length dispersion in the microstructure, a geometrical property known as polydispersity. By assuming that the polydispersity depends on the snow grain type only, we retrieve its value for rounded and faceted grains by optimization of microwave satellite observations in 18 Antarctic sites, and for depth hoar in 86 Canadian sites using ground-based observations. The value for the convex grains (0.6) compares favorably to the polydispersity calculated from 3D micro-computed tomography images for alpine grains, while values for depth hoar show wider variations (1.2–1.9) and are larger in Canada than in the Alps. Nevertheless, using one value for each grain type, the microwave observations in Antarctica and in Canada can be simulated from in-situ measurements with good accuracy with a fully physical model. These findings improve snow scattering modeling, enabling future more accurate uses of satellite observations in snow hydrological and meteorological applications. |
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Programme |
1110,1177 |
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Bachelor's thesis |
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ISSN |
2576-604X |
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yes |
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Serial |
8424 |
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Author |
Grob M, Maggi A, Stutzmann E, |
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Title |
Observations of the seasonality of the Antarctic microseismic signal, and its association to sea ice variability
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Type |
Journal Article |
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Year |
2011 |
Publication |
Geophys. Res. Lett. |
Abbreviated Journal |
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Volume |
38 |
Issue |
11 |
Pages |
L11302- |
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Keywords |
microseisms, sea, seismic noise, seismology, 0750 Cryosphere: Sea ice, 7299 Seismology: General or miscellaneous, 9310 Geographic Location: Antarctica, |
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Abstract |
Seismic noise spectra at all seismic stations display two peaks in the 1–20 s period band, called primary and secondary microseisms. They are caused by the coupling of ocean waves into Rayleigh waves. At most locations, microseismic power is greater during local winter (when nearby oceans are stormier) than local summer. This tendency is reversed for stations in Antarctica, where growth of local winter sea ice seems to impede microseism generation in near coastal areas. A decade of continuous data from coastal seismic stations in Antarctica show systematic seasonality in microseismic signal levels, and demonstrate associations with both broad-scale and local sea-ice conditions. Primary microseisms are known to be generated at the coast and the modulation that we observe can be associated with sea-ice variations both in the vicinity of the station and along other Antarctic coasts. The similar modulation of short-period secondary microseisms corroborates their mostly near-coastal origin, while the continued presence of long-period secondary microseisms suggests more distant source regions. These observations could be used to extend the monitoring of climate variability prior to the availability of satellite-derived climate indicators.
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906 |
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AGU |
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ISSN |
0094-8276 |
ISBN |
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Notes |
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yes |
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Call Number |
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Serial |
3292 |
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Author |
Grob M, Maggi A, Stutzmann E, |
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Title |
Observations of the seasonality of the Antarctic microseismic signal, and its association to sea ice variability
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Type |
Journal Article |
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Year |
2011 |
Publication |
Geophys. Res. Lett. |
Abbreviated Journal |
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Volume |
38 |
Issue |
11 |
Pages |
L11302- |
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Keywords |
microseisms, sea, seismic noise, seismology, 0750 Cryosphere: Sea ice, 7299 Seismology: General or miscellaneous, 9310 Geographic Location: Antarctica, |
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133 |
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Bachelor's thesis |
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AGU |
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0094-8276 |
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yes |
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Call Number |
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Serial |
3795 |
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