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Debayle, E.; Sambridge, M. (2004). Inversion of massive surface wave data sets: Model construction and resolution assessment. J. Geophys. Res., 109, B02316.
Abstract: A new scheme is proposed for the inversion of surface waves using a continuous formulation of the inverse problem and the least squares criterion. Like some earlier schemes a Gaussian a priori covariance function controls the horizontal degree of smoothing in the inverted model, which minimizes some artifacts observed with spherical harmonic parameterizations. Unlike earlier schemes the new approach incorporates some sophisticated geometrical algorithms which dramatically increase computational efficiency and render possible the inversion of several tens of thousands of seismograms in few hours on a typical workstation. The new algorithm is also highly suited to parallelization which makes practical the inversion of data sets with more than 50,000 ray paths. The constraint on structural and anisotropic parameters is assessed using a new geometric approach based on Voronoi diagrams, polygonal cells covering the Earth's surface. The size of the Voronoi cells is used to give an indication of the length scale of the structures that can be resolved, while their shape provides information on the variation of azimuthal resolution. The efficiency of the scheme is illustrated with realistic uneven ray path configurations. A preliminary global tomographic model has been built for SV wave heterogeneities and azimuthal variations through the inversion of 24,124 fundamental and higher-mode Rayleigh waveforms. Our results suggest that the use of relatively short paths (<10,000 km) in a global inversion should minimize multipathing, or focusing/defocusing effects and provide lateral resolution of a few hundred kilometers across the globe.
Keywords: 7218 Seismology: Lithosphere and upper mantle; 7255 Seismology: Surface waves and free oscillations; 7260 Seismology: Theory and modeling; 8180 Tectonophysics: Tomography
Programme: 133;906
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. (2008). King penguin population threatened by Southern Ocean warming. Proceedings of the National Academy of Sciences, 105(7), 2493–2497.
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Whinam, J.; Copson, G.; Chapuis, J.-L. (2006). Subantarctic Terrestrial Conservation and Management.
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Rousseau, D.-D.; Duzer, D.; Etienne, J.-L.; Cambon, G.; Jolly, D.; Ferrier, J.; Schevin, P. (2004). Pollen record of rapidly changing air trajectories to the North Pole. J. Geophys. Res., 109.
Abstract: Tracing modern atmospheric dynamics is important for constraining models used in past climate reconstruction. However, these models must be verified by modern observations. We present the rapid changeover of two different air trajectories to the North Pole determined by studying the long distance transport of pollen. Samples were collected on a manned floating capsule drifting southward on the sea ice from the North Pole in 2002. It was observed that an air mass at 3000 m altitude transported birch and pine pollen released in Western Europe during week 22 (May 27). Two weeks later, during week 24 (June 10), alder, birch and willow pollen from eastern Siberia reached the drifting station with an air mass at 1000 m altitude. These particular patterns support independent investigations of air trajectories in the Arctic, especially the transport of anthropogenic pollutants such as sulfate and nitrate.
Keywords: 0305 Atmospheric Composition and Structure: Aerosols and particles; 0315 Atmospheric Composition and Structure: Biosphere/atmosphere interactions; 1620 Global Change: Climate dynamics; 3322 Meteorology and Atmospheric Dynamics: Land/atmosphere interactions
Programme: 349
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Magand, O.; Picard, G.; Brucker, L.; Fily, M.; Genthon, C. (2008). Snow melting bias in microwave mapping of Antarctic snow accumulation. TCD, 2(2), 255–273.
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Genthon, C.; Cosme, E. (2003). Intermittent signature of ENSO in west-Antarctic precipitation. Geophysical research letters, 30.
Abstract: Precipitation data from the new ERA40 reanalyses and from a 200-year simulation confirm a robust main mode of precipitation variability in west Antarctica. An intermittently strong ENSO signature is found in this mode. However, high correlation with ENSO indices appears infrequent. Thus, the high correlation found in ERA40, and previously in other chronologically realistic data, in the late 1980s and the 1990s may not be expected to last. Unlike previously suggested by others, the sign of the correlation between ENSO indices and west Antarctic precipitation, when significant, does not appear to change in time: Precipitation variability at the ENSO pace in the Bellingshausen-Weddell (Ross-Amunsden) region is consistently in phase (phase opposition, respectively) with the Southern Oscillation Index. This is consistent with a tropospheric wave train connecting the tropical Pacific and west Antarctic regions, which modulates in phase opposition the advection of air and moisture in the 2 regions.
Keywords: 3349 Meteorology and Atmospheric Dynamics: Polar meteorology; 3354 Meteorology and Atmospheric Dynamics: Precipitation; 1620 Global Change: Climate dynamics; 1655 Global Change: Water cycles; 9310 Information Related to Geographic Region: Antarctica
Programme: 411
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Domine, F.; Taillandier, A.S.; Simpson, W.R.; Severin, K. (2005). Specific surface area, density and microstructure of frost flowers. Geophysical research letters, 32.
Abstract: Frost flowers often grow on new sea ice. They are thought to have a high specific surface area (SSA) that provides sites for heterogeneous reactions. We have measured the SSA of frost flowers using CH4 adsorption at 77 K and obtained a value of 185 (+80 ?50) cm2/g, much lower than inferred by others. Their density is 0.02 g/cm3. We calculate that the total surface area of frost flowers is 1.4 m2 per m2 of ice surface, so that they do not increase the ice surface area significantly. Their role as sites for enhanced heterogeneous reactions should be reconsidered. Frost flowers also commonly grow on fresh water and the saline brine seen on young sea ice is not necessary for their growth. Photo- and electro-micrographs reveal hollow and concave structures, typical of very fast growing crystals. The brine that wicks up frost flowers considerably perturbs their growth.
Keywords: 0736 Cryosphere: Snow; 0750 Cryosphere: Sea ice; 0754 Cryosphere: Leads
Programme: 437
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Reijmer, C.H.; Oerlemans, J. (2002). Temporal and spatial variability of the surface energy balance in Dronning Maud Land, East Antarctica. J. Geophys. Res., 107.
Abstract: We present data of nine Automatic Weather Stations (AWS), which are located in Dronning Maud Land (DML), East Antarctica, since the austral summer of 1997. Potential temperature and wind speed are maximum at the sites with the steepest surface slope, i.e., at the edge of the Antarctic plateau. Specific humidity and accumulation decrease with elevation and distance from the coast. The annual average energy gain at the surface from the downward sensible heat flux varies between ?3 W m?2 and ?25 W m?2, with the highest values at the sites with the largest surface inclination and wind speeds. The net radiative flux is negative and largely balances this sensible heat flux and ranges from ??2 W m?2 to ??28 W m?2; maximum values can be linked to maxima in surface slope and wind speed, and suggest a strong connection between the heat budget and the katabatic flow in DML. The average latent heat flux is generally small and negative (??1 W m?2) indicating a slight net mass loss through sublimation.
Keywords: 1827 Hydrology: Glaciology; 1863 Hydrology: Snow and ice; 3307 Meteorology and Atmospheric Dynamics: Boundary layer processes; 3349 Meteorology and Atmospheric Dynamics: Polar meteorology; 9310 Information Related to Geographic Region: Antarctica
Programme: 960
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Priestley, K.; Debayle, E. (2003). Seismic evidence for a moderately thick lithosphere beneath the Siberian Platform. Geophysical research letters, 30.
Abstract: We have built a Sv-wavespeed tomographic model for the upper mantle beneath the Siberian platform and surrounding region derived from the analysis of more than 13,000 fundamental and higher mode regional waveforms. The dense path coverage and rich higher mode content of the data allow building an upper mantle image with an horizontal resolution of a few hundred kilometers extending to ?400 km depth. The high velocity, upper mantle lid or seismic lithosphere is ?200 km thick beneath most of the Siberian platform but may extend to ?250 km depth beneath small areas. A high velocity seismic lid also underlies a large region west of the Siberian platform. Our observation of a ?200 thick seismic lithosphere beneath the Siberian platform on the slow-moving Eurasian plate, similar to the thickness of the seismic lithosphere beneath Precambrian terrains on the fast-moving Australian plate, suggests that a moderately thick seismic lithosphere beneath Precambrian terrains may be more common than previously supposed.
Keywords: 7207 Seismology: Core and mantle; 7218 Seismology: Lithosphere and upper mantle; 7255 Seismology: Surface waves and free oscillations
Programme: 133;906
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Legrand, M.; Preunkert, S.; Galy-Lacaux, C.; Liousse, C.; Wagenbach, D. (2005). Atmospheric year-round records of dicarboxylic acids and sulfate at three French sites located between 630 and 4360 m elevation. J. Geophys. Res., 110.
Keywords: dicarboxylates; secondary production; high-elevated sites; 0365 Atmospheric Composition and Structure: Troposphere: composition and chemistry; 0368 Atmospheric Composition and Structure: Troposphere: constituent transport and chemistry; 0322 Atmospheric Composition and Structure: Constituent sources and sinks
Programme: 414
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