|
Miyashita, Y.; Ieda, A.; Kamide, Y.; Machida, S.; Mukai, T.; Saito, Y.; Liou, K.; Meng, C.-I.; Parks, G.K.; McEntire, R.W.; Nishitani, N.; Lester, M.; Sofko, G.J.; Villain, J.-P. (2005). Plasmoids observed in the near-Earth magnetotail at X ? ?7 RE. J. Geophys. Res., 110.
Keywords: plasmoid; Geotail; 2723 Magnetospheric Physics: Magnetic reconnection; 2744 Magnetospheric Physics: Magnetotail; 2790 Magnetospheric Physics: Substorms; 2704 Magnetospheric Physics: Auroral phenomena; 2736 Magnetospheric Physics: Magnetosphere/ionosphere interactions
Programme: 312;911
|
|
|
De Lauretis, M.; Francia, P.; Vellante, M.; Piancatelli, A.; Villante, U.; Di Memmo, D. (2005). ULF geomagnetic pulsations in the southern polar cap: Simultaneous measurements near the cusp and the geomagnetic pole. J. Geophys. Res., 110.
Keywords: polar cap phenomena; cusp; MHD waves and turbulence; solar wind/magnetosphere interactions; 2776 Magnetospheric Physics: Polar cap phenomena; 2706 Magnetospheric Physics: Cusp; 2784 Magnetospheric Physics: Solar wind/magnetosphere interactions; 2752 Magnetospheric Physics: MHD waves and instabilities; 2740 Magnetospheric Physics: Magnetospheric configuration and dynamics
Programme: 1130
|
|
|
Fain, X.; Ferrari, C.P.; Gauchard, P.-A.; Magand, O.; Boutron, C. (2006). Fast depletion of gaseous elemental mercury in the Kongsvegen Glacier snowpack in Svalbard. Geophysical research letters, 33.
Keywords: 0317 Atmospheric Composition and Structure: Chemical kinetic and photochemical properties; 0322 Atmospheric Composition and Structure: Constituent sources and sinks; 0330 Atmospheric Composition and Structure: Geochemical cycles; 0365 Atmospheric Composition and Structure: Troposphere: composition and chemistry; 0736 Cryosphere: Snow
Programme: 399
|
|
|
Lambotte, S.; Rivera, L.; Hinderer, J. (2006). Rupture length and duration of the 2004 Aceh-Sumatra earthquake from the phases of the Earth's gravest free oscillations. Geophysical research letters, 33.
Abstract: The Aceh-Sumatra 2004 earthquake strongly excited the Earth's free oscillations. Well separated split multiplets provide useful information on the earthquake source. Particularly, the phases of split singlets constrain the duration, rupture length and mean rupture velocity. We analyze the initial phases of some of the Earth's gravest free oscillations (0
S
2, 0
S
3, 0
S
0 and 1
S
0) in order to constrain the space-time finiteness of the source. We use recordings of vertical broadband seismometers and superconducting gravimeters from several worldwide geophysical networks. We estimate a rupture length of about 1220 km, a source time duration of about 500 s, and a mean rupture velocity of 2.4 km/s.
Keywords: 3255 Mathematical Geophysics: Spectral analysis; 7209 Seismology: Earthquake dynamics; 7215 Seismology: Earthquake source observations; 7255 Seismology: Surface waves and free oscillations; 7260 Seismology: Theory
Programme: 133;906
|
|
|
Andersen, O.B.; Seneviratne, S.I.; Hinderer, J.; Viterbo, P. (2005). GRACE-derived terrestrial water storage depletion associated with the 2003 European heat wave. Geophysical research letters, 32.
Abstract: The GRACE twin satellites reveal large inter-annual terrestrial water-storage variations between 2002 and 2003 for central Europe. GRACE observes a negative trend in regional water storage from 2002 to 2003 peaking at ?7.8 cm in central Europe with an accuracy of 1 cm. The 2003 excess terrestrial water storage depletion observed from GRACE can be related to the record-breaking heat wave that occurred in central Europe in 2003. We validate the measurements from GRACE using two independent hydrological estimates and direct gravity observations from superconducting gravimeters in Europe. All datasets agree well with the GRACE measurements despite the disparity of the employed information; the difference between datasets tends to be within GRACE margin of error. The April-to-August terrestrial water storage depletion is found to be significantly larger in 2003 than in 2002 from both models and observations.
Keywords: 1640 Global Change: Remote sensing; 1655 Global Change: Water cycles; 1836 Hydrology: Hydrological cycles and budgets; 1812 Hydrology: Drought
Programme: 337
|
|
|
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
|
|
|
Legagneux, L.; Domine, F. (2005). A mean field model of the decrease of the specific surface area of dry snow during isothermal metamorphism. J. Geophys. Res., 110.
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.
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
Programme: 437
|
|
|
. (2005). Interior structure of terrestrial planets: Modeling Mars' mantle and its electromagnetic, geodetic, and seismic properties. J. Geophys. Res., 110.
Abstract: We present a new procedure to describe the one-dimensional thermodynamical state and mineralogy of any Earth-like planetary mantle, with Mars as an example. The model parameters are directly related to expected results from a geophysical network mission, in this case electromagnetic, geodetic, and seismological processed observations supplemented with laboratory measurements. We describe the internal structure of the planet in terms of a one-dimensional model depending on a set of eight parameters: for the crust, the thickness and the mean density, for the mantle, the bulk volume fraction of iron, the olivine volume fraction, the pressure gradient, and the temperature profile, and for the core, its mass and radius. Currently, available geophysical and geochemical knowledge constrains the range of the parameter values. In the present paper, we develop the forward problem and present the governing equations from which synthetic data are computed using a set of parameter values. Among all Martian models fitting the currently available knowledge, we select eight candidate models for which we compute synthetic network science data sets. The synergy between the three geophysical experiments of electromagnetic sounding, geodesy, and seismology is emphasized. The stochastic inversion of the synthetic data sets will be presented in a companion paper.
Keywords: internal structure; Mars; network science; 5430 Planetary Sciences: Solid Surface Planets: Interiors; 6225 Planetary Sciences: Solar System Objects: Mars; 3672 Mineralogy and Petrology: Planetary mineralogy and petrology
Programme: 905;907
|
|
|
Alexander, B.; Park, R.J.; Jacob, D.J.; Li, Q.B.; Yantosca, R.M.; Savarino, J.; Lee, C.C.W.; Thiemens, M.H. (2005). Sulfate formation in sea-salt aerosols: Constraints from oxygen isotopes. J. Geophys. Res., 110.
Keywords: atmospheric chemistry; aerosol formation; isotopes; 0305 Atmospheric Composition and Structure: Aerosols and particles; 0312 Atmospheric Composition and Structure: Air/sea constituent fluxes; 0365 Atmospheric Composition and Structure: Troposphere: composition and chemistry; 0490 Biogeosciences: Trace gases; 1041 Geochemistry: Stable isotope geochemistry
Programme: 399
|
|
|
Masson-Delmotte, V.; Landais, A.; Stievenard, M.; Cattani, O.; Falourd, S.; Jouzel, J.; Johnsen, S.J.; Dahl-Jensen, D.; Sveinsbjornsdottir, A.; White, J.W.C.; Popp, T.; Fischer, H. (2005). Holocene climatic changes in Greenland: Different deuterium excess signals at Greenland Ice Core Project (GRIP) and NorthGRIP. J. Geophys. Res., 110.
Abstract: Water stable isotope measurements (?D and ?18O) have been conducted on the Holocene part of two deep Greenland ice cores (Greenland Ice Core Project (GRIP) and NorthGRIP), located ?320 km apart. These combined measurements provide the first two continuous Greenland Holocene deuterium excess profiles (d = ?D ? 8?18O), a parameter strongly influenced by changes in moisture sources. We discuss here temporal and regional fluctuations of the deuterium excess within central to north Greenland, with a mean temporal resolution of ?4 years. Although GRIP and NorthGRIP exhibit similar annual mean surface temperatures and ?18O levels, a significant offset of modern deuterium excess is observed between the two sites. We attribute this offset to a different mix of modern moisture sources, pointing to regional-scale differences in moisture advection toward Greenland. The common long-term deuterium excess Holocene increasing trend is probably related to the increased relative contribution of low-latitude moisture to Greenland snowfall, in response to the change in the Earth obliquity, as symmetrically observed in Antarctica. Three abrupt declines punctuate the GRIP excess record (8.2, 4.5, and 0.35 ka BP), suggesting associated reorganizations of the northern high latitudes hydrological cycle. The 8.2 ka BP event is characterized by (1) a rapid cooling followed by a progressive warming and (2) a deuterium excess cooling restricted to GRIP, therefore totally different from rapid events during glacial times. By contrast, the NorthGRIP deuterium excess record is more stable. We propose that a slightly larger proportion of moisture supplied by local storm tracks to GRIP induces an isotopic compensation mechanism between simultaneous site and source temperature coolings, resulting in a rather temperature-insensitive ?18O profile, together with well-marked deuterium excess amplitudes. NorthGRIP ?18O seems less biased by isotopic processes and should provide a more reliable past temperature record.
Keywords: paleoclimate; polar ice sheet; water cycle; 1041 Geochemistry: Stable isotope geochemistry; 0724 Cryosphere: Ice cores; 1620 Global Change: Climate dynamics; 1655 Global Change: Water cycles; 3344 Atmospheric Processes: Paleoclimatology
Programme: 458
|
|