Kreemer Corné, . (2009). Absolute plate motions constrained by shear wave splitting orientations with implications for hot spot motions and mantle flow
. J. Geophys. Res., 114(B10), B10405–.
Abstract: Here, I present a new absolute plate motion model of the Earth's surface, determined from the alignment of present-day surface motions with 474 published shear wave (i.e., SKS) splitting orientations. When limited to oceanic islands and cratons, splitting orientations are assumed to reflect anisotropy in the asthenosphere caused by the differential motion between lithosphere and mesosphere. The best fit model predicts a 0.2065°/Ma counterclockwise net rotation of the lithosphere as a whole, which revolves around a pole at 57.6°S and 63.2°E. This net rotation is particularly well constrained by data on cratons and/or in the Indo-Atlantic region. The average data misfit is 19° and 24° for oceanic and cratonic areas, respectively, but the normalized root-mean-square misfits are about equal at 5.4 and 5.2. Predicted plate motions are very consistent with recent hot spot track azimuths (<8° on many plates), except for the slowest moving plates (Antarctica, Africa, and Eurasia). The difference in hot spot propagation vectors and plate velocities describes the motion of hot spots (i.e., their underlying plumes). For most hot spots that move significantly, the motions are considerably smaller than and antiparallel to the absolute plate velocity. Only when the origin depth of the plume is considered can the hot spot motions be explained in terms of mantle flow. The results are largely consistent with independent evidence of subasthenospheric mantle flow and asthenospheric return flow near spreading ridges. The results suggest that, at least where hot spots are, the lithosphere is decoupled from the mesosphere, including in western North America.
Keywords: absolute plate motion, seismic anisotropy, mantle flow, hot spot, 8011 Kinematics of crustal and mantle deformation, 8158 Plate motions: present and recent, 8121 Dynamics: convection currents, and mantle plumes,
Programme: 133
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Jouventin P., Bried J. & Ausilio E. (1996). Life-history variations of the Lesser Sheathbill Chionis minor in contrasting habitats. Ibis (Lond. 1859), 138, 732–741.
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Legrand M., Feniet Saigne C., Saltzman E.S. & Germain C. (1992). Spatial and temporal variations of methanesulfonic acid and non dea salt sulfate in Antarctic ice. Journal of atmospheric chemistry, 14, 245–260.
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Barnaud G. & Chapuis J.L. (1996). Questions scientifiques et éthiques relatives à la restauration des systèmes insulaires. L'éradication des mammifères introduits dans les îles subantarctiques françaises/Scientific and ethic issues on the restorations of island ecosystems. The eradic. Vie et milieu, 46, 291–303.
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Bried J. & Mougeot F. (1994). Premier cas de mélanisme chez un procellariiforme:le Pétrel-tempête à croupion gris garrodia nereis. Alauda, 62(4), 311–312.
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Handrich Y., Gendner J.P. & Le Maho Y. (1995). Breeding penguins as indicators of marine resources: a study with minimal human disturbance..
Abstract: In: Dann P, Normann I, Reilly P (eds) The penguins: ecology and management. Surrey Beatty & Sons Pty. Ltd., pp 75–79
Programme: 137
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Ropert Coudert Y., Kato A., Baudat J., Bost C.A., Le Maho Y. & Naito Y. (2001). Feeding strategies of free-ranging Adélie penguins Pygoscelis adeliae analysed by multiple data recording. Polar Biol., 24, 460–466.
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Gilbert Caroline, McCafferty Dominic, Le Maho Yvon, Martrette Jean-Marc, Giroud Sylvain, Blanc Stéphane, Ancel André, . (2010). One for all and all for one: the energetic benefits of huddling in endotherms
. Biological Reviews, 85(3), 545–569.
Abstract: Huddling can be defined as an active and close aggregation of animals. It is a cooperative group behaviour, permitting individuals involved in social thermoregulation to minimize heat loss and thereby lower their energy expenditure, and possibly allowing them to reallocate the saved energy to other functions such as growth or reproduction. Huddling is especially important in the case of animals faced with high heat loss due to a high surface-to-volume ratio, poor insulation, or living in cold environments. Although numerous experimental studies have focused on the huddling behaviour of a wide range of species, to our knowledge, this is the first attempt to review the various implications of this widely used behavioural strategy. Huddling allows individuals to maximise energy savings by (1) decreasing their cold-exposed body surface area, (2) reducing their heat loss through warming of ambient temperatures surrounding the group, and (3) eventually lowering their body temperature through physiological processes. Huddling provides substantial energy savings and is estimated to reduce energy expenditure by between 6 and 53%. Broad variations in the energetic benefits of huddling depend on the number of individuals and species involved in huddles, the ambient temperatures to which individuals are exposed and the density of the aggregations. It has been shown that huddling individuals have increased survival, a lower food intake, a decreased body mass loss, increased growth rate, reduced water loss, and/or a more constant body temperature together with a significant reduction in metabolic rate. Though huddling has been studied widely, this review reveals the intricacies of this adaptive behaviour.
Keywords: huddling, group, social behaviour, thermoregulation, energy conservation, ambient temperature, mammals, birds,
Programme: 137
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Lévêque Jean-Jacques, Maggi Alessia, Souriau Annie, . (2010). Seismological constraints on ice properties at Dome C, Antarctica, from horizontal to vertical spectral ratios
. Antarct. Sci., 22(05), 572–579.
Abstract: The French-Italian Concordia (CCD) seismological station at Dome C is one of two observatories setup on the ice cap in the interior of the Antarctic continent. We analysed the seismic signal due to ambient noise at this station and at three temporary stations 5 km away from Concordia, in order to specify the ice properties beneath them. A method based on the horizontal to vertical (H/V) spectral ratio, commonly used to analyse soil response in seismic regions, was applied to the Antarctic stations. The main peak in the spectral ratios is observed at frequencies 6.7–8 Hz at the Dome C stations, but it is not observed at another station on the ice cap, QSPA, where the sensor is buried at 275 m depth. This peak can be explained by a 23 m thick unconsolidated snow or firn layer with a low S-wave velocity of 0.7 km s-1, overlying a consolidated layer with S-wave velocity 1.8 km s-1. Despite the non-uniqueness of the solutions obtained by fitting the H/V spectra, this model is preferred because the depth of the velocity contrast coincides with the density at which ice particles arrange themselves in a continuous, dense lattice. A small variability of this structure is observed around Dome C.
Keywords: Antarctic seismological stations, Concordia, firn, seismic ambient noise,
Programme: 133;906
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Ofman et al. (1995). Intercomparison of UV/visible spectrometers for measurements of stratospheric NO2 or the Network for the Detection of Stratospheric Change. J. Geophys. Res., 100, 16765–16791.
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