Impact of doubled CO2 on the interaction between the global and regional water cycles in four study regions     

Zhao Li  Uma S. Bhatt  Nicole Mölders 《Climate Dynamics》2008,30(2-3):255-275

Results from a suite of 30-year simulations (after spin-up) of the fully coupled Community Climate System Model version 2.0.1 are analyzed to examine the impact of doubling CO₂ on interactions between the global water cycle and the regional water cycles of four similar-size, but hydrologically and thermally different study regions (the Yukon, Ob, St Lawrence, and Colorado river basins and their adjacent land). A heuristic evaluation based on published climatological data shows that the model generally produces acceptable results for the control 1× CO₂ concentration, except for mountainous regions where it performs like other modern climate models. After doubling CO₂, the Northern Hemisphere receives significantly (95% confidence level) more moisture from the Southern Hemisphere during the boreal summer than under 1× CO₂ conditions, and the phase of the annual cycle of net moisture transport to areas north of 60°N shifts to a month later than in the reference simulation. Precipitation and evapotranspiration in the doubled CO₂ simulation increase for the Yukon, Ob, and St Lawrence, but decrease, on average, for the Colorado region compared to the reference simulation. For all regions, interaction between global and regional water cycles increases under doubled CO₂, because the amount of moisture entering and leaving the regions increases in the warmer climate. The degree of change in this interaction depends on region and season, and is related to slight shifts in the position/strength of semi-permanent highs and lows for the Yukon, Ob, and St Lawrence; in the Colorado region, higher temperatures associated with doubling CO₂ and the anticyclone located over the region increase the persistence of dry conditions.  相似文献   

The magmatic plumbing system beneath El Hierro (Canary Islands): constraints from phenocrysts and naturally quenched basaltic glasses in submarine rocks   总被引：1，自引：1，他引：0  

Nicole A. Stroncik  Andreas Klügel  Thor H. Hansteen 《Contributions to Mineralogy and Petrology》2009,157(5):593-607

A thermobarometric and petrologic study of basanites erupted from young volcanic cones along the submarine portions of the three El Hierro rift zones (NE-Rift, NW-Rift and S-Ridge) has been performed to reconstruct magma plumbing and storage beneath the island. Mineral-melt thermobarometry applied to naturally quenched glass and clinopyroxene rims yields pressures ranging from 350 to 1070 MPa with about 80% of the calculated pressures being in the range of 600–800 MPa. This corresponds to a depth range of 19–26 km, implying that the main level of final crystal fractionation is within the uppermost mantle. No systematic dependence between sample locality and fractionation pressures could be observed. Olivine and clinopyroxene crystals in the rocks are complexly zoned and have, on an inter-sample as well as on an intra-sample scale, highly variable core and rim compositions. This can best be explained by mixing of multiply saturated (olivine, magnetite, clinopyroxene, ilmenite), moderately evolved magmas with more mafic magmas being either only saturated with olivine + spinel or with olivine + spinel + clinopyroxene. The inter-sample differences indicate derivation from small, isolated magma chambers which have undergone distinct fractionation and mixing histories. This is in contrast to oceanic intraplate volcanoes situated on plumes with high melt supply rates, e.g. Kilauea Volcano (Hawaii), where magma is mainly transported through a central conduit system and stored in a shallow magma chamber prior to injection into the rift zones. The plumbing system beneath El Hierro rather resembles the magma storage systems beneath, e.g. Madeira or La Palma, indicating that small, intermittent magma chambers might be a common feature of oceanic islands fed by plumes with relatively low fluxes, which results in only limited and periodic magma supply.  相似文献   

Iron biomineralization by anaerobic neutrophilic iron-oxidizing bacteria   总被引：1，自引：0，他引：1  

Jennyfer Miot  Karim Benzerara  Andreas Kappler  Martin Obst  Fériel Skouri-Panet  Nicole Posth  Gordon E. Brown Jr.  François Guyot 《Geochimica et cosmochimica acta》2009,73(3):696-1446

Minerals formed by bio-oxidation of ferrous iron (Fe(II)) at neutral pH, their association with bacterial ultrastructures as well as their impact on the metabolism of iron-oxidizing bacteria remain poorly understood. Here, we investigated iron biomineralization by the anaerobic nitrate-dependent iron-oxidizing bacterium Acidovorax sp. strain BoFeN1 in the presence of dissolved Fe(II) using electron microscopy and Scanning Transmission X-ray Microscopy (STXM). All detected minerals consisted mainly of amorphous iron phosphates, but based on their morphology and localization, three types of precipitates could be discriminated: (1) mineralized filaments at distance from the cells, (2) globules of 100 ± 25 nm in diameter, at the cell surface and (3) a 40-nm thick mineralized layer within the periplasm. All of those phases were shown to be intimately associated with organic molecules. Periplasmic encrustation was accompanied by an accumulation of protein moieties. In the same way, exopolysaccharides were associated with the extracellular mineralized filaments. The evolution of cell encrustation was followed by TEM over the time course of a culture: cell encrustation proceeded progressively, with rapid precipitation in the periplasm (in a few tens of minutes), followed by the formation of surface-bound globules. Moreover, we frequently observed an asymmetric mineral thickening at the cell poles. In parallel, the evolution of iron oxidation was quantified by STXM: iron both contained in the bacteria and in the extracellular precipitates reached complete oxidation within 6 days. While a progressive oxidation of Fe in the bacteria and in the medium could be observed, spatial redox (oxido-reduction state) heterogeneities were detected at the cell poles and in the extracellular precipitates after 1 day. All these findings provide new information to further the understanding of molecular processes involved in iron biomineralization by anaerobic iron-oxidizing bacteria and offer potential signatures of those metabolisms that can be looked for in the geological record.  相似文献   

The variations in eccentricity and apse precession rate of a narrow ring perturbed by a close satellite     

Nicole Borderies  Peter Goldreich  Scott Tremaine 《Icarus》1983,53(1):84-89

We derive a Hamiltonian which describes the first-order perturbations of orbital eccentricity and apse precession rate of a narrow ring due to a close satellite whose orbit is also eccentric. Our treatment covers cases in which the satellite crosses the ring. The level curves of the Hamiltonian are displayed for several values of the parameters. We apply our results to the interaction of Saturn's F ring with its inner shepherd satellite.  相似文献   

Caractérisation des variations lithologiques saisonnières des sédiments de la baie de Seine orientale ; impact des crues de la Seine (France)Characterisation of seasonal lithological variations of the superficial sediment in the eastern part of the Bay of Seine: impact of floods Seine River (France)     

Sébastien Garnaud  Patrick Lesueur  Sandric Lesourd  Nicole Poupinet  Jean-Claude Brun-Cottan 《Comptes Rendus Geoscience》2002,334(5):323-330

This paper presents the first results obtained during cruises since 1995 in the southeastern part of the Bay of Seine. New sedimentological data concerning sediment samples, box cores and water column measurements have been obtained recently in the framework of the Research Programme PNEC (French National Coastal Environment Programme). Fine sediments are deposited on form of temporary veneers of fluid-to-soft mud formed during high floods episodes. In the subtidal area (<10 m water depth), mobility of fine sediments is important and temporary mud deposited during high discharge period composes part of the distal estuarine system of the Seine River. To cite this article: S. Garnaud et al., C. R. Geoscience 334 (2002) 323–330.  相似文献   

Homogénéisation et validation des corrections de terrain gravimétriques jusqu'à la distance de 167 km sur l'ensemble de la FranceUpdating and validating the French gravity terrain corrections out to a distance of 167 km     

Guillaume Martelet  Nicole Debéglia  Catherine Truffert 《Comptes Rendus Geoscience》2002,334(7):449-454

For regional and national study purposes, there is a high need for updating the terrain corrections (TC) in the French gravity database. We have recomputed the TC for all the French gravity stations from 50 m out to a distance of 167 km. We compute the TC with a flat-top-prism algorithm and three DEM with grid spacing of 50, 250 and 1000 m, used in the zones 53 m/3 km, 3 km/10 km et 10 km/167 km, respectively. Analysing the DEM/station Δz and comparing our results to the ones previously obtained in the Alps area, we estimate the accuracy of our TC to be better than 1 mGal. To cite this article: G. Martelet et al., C. R. Geoscience 334 (2002) 449–454.  相似文献   

Horizontal distribution of the rotifer plankton of Lake Aydat (France)   总被引：2，自引：0，他引：2  

Nicole Lair  Hassan Taleb  Patricia Reyes-Marchant 《Aquatic Sciences - Research Across Boundaries》1996,58(3):253-268

We investigated the causes of the shift which occurs in the horizontal distribution of planktonic rotifers of Lake Aydat. A normalised PCA was used to analyse the spatio-temporal distribution of 18 rotifer species. They are more numerous in the littoral zone, but seasonal changes remain higher than spatial changes. Results illustrate the capability of rotifers to take efficiently advantage of available space and food. The digestive tracts of fry and juvenile roach was also analysed and the index of Ivlev was used to determine prey selection. Fish predation occurs in the nearshore zone and the interactions between invertebrate predators and their prey are illustrated by the quantitative changes in community dynamics. Among the complex cascade of events varying in the course of the year, and despite of resource partitioning, predator-prey interactions as well as the exploitative competition between rotifers and crustaceans produce gradients exhibited in the horizontal distribution of rotifers in Lake Aydat.  相似文献   

Dynamics of post-flare ejections and magnetic loop geometry     

Pierre Mein  Nicole Mein 《Solar physics》1982,80(1):161-171

Flare-associated mass ejections have been observed at the solar limb on June 29, 1980 in the H line, with the Multichannel Subtractive Double Pass spectrograph of the Meudon solar tower. Radial velocities were measured as a function of time in a two dimensional field, and kinematics investigated in one selected fine structure. A simple model of locally dipole-type magnetic field increasing with time can be fitted to the data. It can be checked from extrapolation that the model is consistent with an ejection starting roughly from the same point at the same time. Height of the loops ( 135 000 km) is consistent with other determinations. Magnetic field is found to be increasing locally by a factor 1.14 within 10 min.

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Résumé Des éjections de matière associées à une éruption ont été observées au bord solaire le 29 Juin 1980, dans la raie H, avec le spectrographe à Double Passage Soustractif Multicanaux de la Tour Solaire de Meudon. Les vitesses radiales ont été mesurées au cours du temps sur un champ bidimensionnel, et la cinématique a été analysée pour une structure fine particulière. Un modèle simple de champ magnétique, localement dipolaire et croissant au cours du temps, peut être ajusté aux données. Par extrapolation, on peut vérifier que le modèle est compatible avec une éjection déclenchée sensiblement au même point et au même instant. La hauteur des boucles ( 135 000 km) est en accord avec d'autres déterminations. On trouve que le champ magnétique croît localement d'un facteur 1.14 en 10 min.

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Velocity waves in the quiet solar chromosphere     

Nicole Mein  Pierre Mein 《Solar physics》1976,49(2):231-248

Propagation of velocity waves are investigated in the solar chromosphere, with a special view to high frequencies (periods 60 s). Four line profiles have been observed during 27 mn with the Sacramento Peak vacuum telescope (H, 3933, 8498 and 8542 Ca ii). Three Fourier analysis are performed according to the location in the cells of the chromospheric network. Phase-shifts and amplitude ratios between the line Doppler shifts are computed as functions of frequency. The pollution of high frequency results by energetic low frequency oscillations is investigated.H Doppler shifts are probably affected by the large width of line formation layers (low transfer function). Using formation altitudes for Doppler shifts previously computed for the infra-red lines, we show that acoustic waves propagating upwards cannot account for the observations. In particular, the phase-shifts between oscillations in different chromospheric layers are much smaller than theoretical predictions. As a first attempt for a qualitative agreement, we suggest that most of the high frequency oscillations (10–15 mHz) are magnetoacoustic waves, travelling in layers where the gradient of the Alfvén-speed cannot be neglected, and reflected at the top of the chromosphere. The amplitudes of these waves are probably underestimated as derived from the observed Doppler shifts.  相似文献   

Atmospheric deposition and isotope biogeochemistry of zinc in ombrotrophic peat   总被引：1，自引：0，他引：1  

Dominik J. Weiss  Nicole Rausch  Thomas F.D. Mason  Jamie J. Wilkinson  Liisa Ukonmaanaho  Tiina M. Nieminen 《Geochimica et cosmochimica acta》2007,71(14):3498-3517

Zinc isotope ratios were measured in the top sections of dated ombrotrophic peat cores in Finland to investigate their potential as proxies for atmospheric sources and to constrain post depositional processes affecting the geochemical record. The peat deposits were located in Hietajärvi, a background site well away from any point pollution source and representing ‘background’ conditions, in Outokumpu, next to a mining site, and in Harjavalta, next to a smelter. Measured total concentrations, calculated excess concentrations and mass balance considerations suggest that zinc is subjected to important biogeochemical cycling within the peat. Significant isotopic variability was found in all three peat bogs, with heavier zinc in the deeper and lighter zinc in the upper sections. Isotope ratios and concentrations correlated in the two peats located next to dominant point sources, i.e. the smelting and mining site, suggesting that zinc isotopes trace pollution sources. Concentration and isotope peaks were offset from the period of mining and smelting activity, supporting migration of zinc down the profile. The δ⁶⁶Zn_JMC (where δ⁶⁶Zn = [(⁶⁶Zn/⁶⁴Zn)_sample/(⁶⁶Zn/⁶⁴Zn)_JMC-standard − 1] × 10³) of the top section sample at the remote Hietajärvi site was 0.9‰ and we suggest this represents the regional background isotope signature of atmospheric zinc. The deeper sections of the peat cores show isotopically heavier zinc than any potential atmospheric source, indicating that post depositional processes affected the isotopic records. The large variations encountered (up to 1.05‰ for δ⁶⁶Zn) and Rayleigh modelling imply that multiple fractionation of zinc during diagenetic alterations occurs and nutrient recycling alone cannot explain the fractionation pattern.We propose that zinc isotopes are amenable to identify different atmospheric zinc sources, including zinc derived from anthropogenic activities such as mining and smelting, but multiple biogeochemical processes seriously affect the record and they need to be evaluated and assessed carefully if zinc isotopes are used in terrestrial paleorecords.  相似文献