An Antarctic view of Beryllium-10 and solar activity for the past millennium   总被引：1，自引：1，他引：0  

Gilles Delaygue  Edouard Bard 《Climate Dynamics》2011,36(11-12):2201-2218

Beryllium-10 in ice provides a valuable proxy of solar activity. However, complex production pathways, atmospheric transport, and deposition processes impede its quantitative interpretation. Here, we examine the influence of deposition processes on two Be-10 ice core records from Central Antarctica (South Pole and Dome Fuji stations), covering the last millennium. We try to quantify how Be-10 variations in ice relate to variations in Be-10 production, and the bias associated to this relationship. An independent bias estimation is provided by comparing atmospheric radiocarbon variations reconstructed from tree rings and deduced from Be-10 variations. Both techniques suggest an uncertainty of the order of 10% in Be-10 production. This uncertainty estimate does not account for the geographical origin of Be-10, which remains a major issue. Because both Be-10 records are so similar, we propose to average them as a means to decrease the unshared (non solar) variability. This average record provides a new reconstruction of solar modulation parameter ?? and total solar irradiance over the last ~1,300?years. The lowest solar activity is found during the so-called Sp?rer Minimum (around AD 1450). The highest activities are found during the 8th century and over the last decades: as shown in previous studies, our results suggest that the recent solar activity is not exceptionally high for the last millennium.  相似文献   

Monsoon intraseasonal oscillation and land�Catmosphere interaction in an idealized model     

Gilles Bellon 《Climate Dynamics》2011,37(5-6):1081-1096

A simple coupled model is used in a zonally-symmetric configuration to investigate the effect of land?Catmosphere coupling on the Asian monsoon intraseasonal oscillation. The atmospheric model is a version of the Quasi-equilibrium Tropical Circulation Model with a prognostic atmospheric boundary layer, as well as two free-tropospheric modes in momentum, and one each in moisture and temperature. The land model is the simple one-layer model SLand. The complete nonlinear version and a linear version of the model are used to understand how land?Catmosphere interaction influences the northward-propagating intraseasonal oscillation that has been documented in the atmospheric model (Bellon and Sobel in J Geophys Res 113, 2008a, J Atmos Sci 65:470?C489, 2008b). Our results show that this interaction damps the intraseasonal variability in most cases. The small heat capacity of land surfaces is the main factor that intervenes directly in the dynamics of the intraseasonal oscillation and explains the damping of intraseasonal variability. But in a few peculiar cases, the small heat capacity of land can also cause a strong interaction between the intraseasonal oscillation and the mean state via the nonlinearity of precipitation, that enhances the monsoon intraseasonal variability. High land albedo indirectly influences the intraseasonal variability by setting the seasonal mean circulation to conditions unfavorable for the monsoon intraseasonal oscillation.  相似文献   

Measurement and modeling of mercury complexation by dissolved organic matter isolates from freshwater and effluents of a major wastewater treatment plant     

Bogdan Muresan  Benoît Pernet-Coudrier  Daniel Cossa  Gilles Varrault 《Applied Geochemistry》2011,26(12):2057-2063

Dissolved organic matter (DOM) samples were obtained from a low-density urbanized area located upstream of Paris (along the Marne River, France) and from the treated effluents at the Paris main wastewater treatment plant. These samples were then fractionated according to their hydrophobicity. DOM fractions consisted of nanomolar to sub-micromolar fresh organic substances with extremely strong Hg-complexing ligands. The conditional stability constants (i.e. ; pH ∼ 6.8, I_NaCl = 0.5 M, T = 25 °C) of the Hg-DOM complexes formed were greater than 10²⁴ M⁻¹, for the reaction Hg²⁺ + L = HgL (with L as ligand). For upstream of Paris, thermodynamic calculations indicated that the vast majority of Hg-DOM was associated with hydrophobic DOM. In contrast, in the Paris main wastewater treatment plant effluents, Hg-DOM was mainly bound to hydrophilic DOM. Simple dilution calculations highlighted that due to the large DOM loading of urban discharges, the hydrophilic urban DOM ligands may commonly dominate Hg-DOM speciation in the downstream Seine River, except under extreme dilution (i.e. high water episodes or floods).  相似文献   

Age of river basins in Guadeloupe impacting chemical weathering rates and land use     

Sétareh Rad  Olivier Cerdan  Karine Rivé  Gilles Grandjean 《Applied Geochemistry》2011

The Lesser Antilles have very high chemical weathering rates, with values that can reach 1290 t/km²/a. The tropical environment induces high precipitation rates, high temperature, dense vegetation, with sharp relief and thick soils. Because of volcanic activity, frequent pyroclastic flows produce very erodible and porous materials. In addition, agriculture induces important land use changes which replace existing native forest cover with banana and sugar cane plantations. Their surface can cover as much as 40% of the total area of a river basin. The aim of this study is to identify key parameters, either natural or anthropogenic, that control chemical weathering rates. Among the combined impact of all parameters (climate, runoff, slopes, vegetation etc.), basin age seems to be the control parameter: the younger the basin, the higher the weathering rate. A correlation between the chemical weathering rate and the basin age suggests that young volcanic rocks are more easily weathered than old ones: young fresh material is easily mobilized by erosion, while for older rocks with thick soil covers, chemical rates are much lower. A combined effect between the higher erodibility and a higher climate erosivity of the younger relief could be observed. Moreover, a correlation between banana plantations and the chemical weathering rates that can be explained by an increase of infiltration, due to stem flow processes is shown here. Banana plantations also have a correlation with the basin age, older basins being more favorable terrains for cultivation.  相似文献   

Separation of phytoplanktonic pigments by HPLC for the study of phyto-zooplankton trophic relationships     

Catherine Quiblier  Gilles Bourdier  Christian Amblard  Denise Pepin 《Aquatic Sciences - Research Across Boundaries》1994,56(1):29-39

Phyto-zooplankton trophic relationships were studied using phytoplanktonic pigments (chlorophylls and carotenoids) as organic natural markers. Pigments were separated by high-pressure liquid chromatography (HPLC).Comparison of pigment profiles from monospecific cultures of various taxonomic groups (Chlorophyceae, Bacillariophyceae and Cyanobacteria) and from Cladocera crustaceans (Daphnia magna) fed with these cultures, showed that the characteristic pigment associations of the different taxa are conserved during their transfer from primary producers to secondary consumers.Chromatographic profiles of the Bacillariophyceae and Chlorophyceae type were obtained fromDaphnia respectively fed with mixtures of a Chlorophyceae and a diatom species and mixture of a Chlorophyceae and a Cyanobacterium. This showed the importance of this method in demonstrating a possible selective feeding by the herbivorous zooplankton.The observation of pigment profiles of the Dinophyceae type following feeding of a zooplankton assemblage from Lake Pavin within this natural medium (phytoplankton dominated by a Dinophyceae) and of a Chlorophyceae type profile as the same assemblage was fed in the laboratory on phytoplankton from Lake Villerest (composed of about 80% Cyanobacteria and 20% Chlorophyceae), suggested that this method could be applied to the natural environment.  相似文献   

The relationship between collision-related calcalkaline, and within-plate alkaline volcanism in the Karacadağ Area (Konya-Türkiye, Central Anatolia)     

Hüseyin Kurt  Kürad Asan  Gilles Ruffet 《Chemie der Erde / Geochemistry》2008,68(2):155-176

The Karacadağ (Kulu-Konya) area is one of the main volcanic provinces in Central Anatolia. The Karacadağ volcanites are composed of large volumes of andesitic-dacitic lavas associated with pyroclastics and small volumes of alkali basalt, trachybasalt and trachyandesite lavas. Two groups of volcanic rocks can be distinguished: (1) calcalkaline rocks including andesites and dacites, and (2) alkaline rocks including basalts, trachybasalts and trachyandesites. ⁴⁰Ar/³⁹Ar ages show that the Karacadağ volcanites were erupted during Early Miocene (ca.18–19 Ma) and suggest that alkaline volcanites succeed shortly afterwards calcalkaline volcanites. Major oxides and trace elements plotted versus SiO₂ suggest fractionation of hornblende, Fe–Ti oxide and apatite for calcalkaline volcanic rocks and olivine, clinopyroxene and Fe–Ti oxide for alkaline volcanic rocks in the magmatic evolution. The incompatible trace element patterns of the calcalkaline volcanites show enrichment of LILEs (Sr, K, Rb, Ba and Th) and negative HFSEs (Nb, Ta) anomalies suggesting an enriched lithospheric source by a subduction-related process. On the other hand, alkaline volcanites show enrichment of both LILEs and HFSEs suggesting an enriched lithospheric source by small volume melts from the asthenosphere. The rocks also have moderately fractionated REE patterns with (La/Lu)_N ratios of 7–24 for calcalkaline and 6–17 for alkaline volcanites. Moreover, the volcanites have relatively low ⁸⁷Sr/⁸⁶Sr(t) ratios for between 0.703782 and 0.705129, and high ε_Nd(t) values between +2.25 and +4.49. Generally, the Sr–Nd isotopic compositions of the rocks range from the mantle array to bulk earth. All of these observations and findings suggest that the calcalkaline volcanites were formed in a subduction modified orogenic setting, and the alkaline volcanites in a within-plate setting.  相似文献   

Quantifying the spatial distribution of sediment transport in an experimental gully system using the morphological method     

Wen Dai  Liyang Xiong  Gilles Antoniazza  Guoan Tang  Stuart N. Lane 《地球表面变化过程与地形》2021,46(6):1188-1208

Whilst time-series of sediment transport in gullies in both laboratory experimental and field settings can be determined through instrumentation, quantifying the spatial distribution of transport rates remains challenging. The morphological method, which was proposed for estimating bed-material transport in both one- and two-dimensions in rivers, provides an alternative. Here, we developed this method for gully systems. A laboratory catchment was used to simulate gully erosion. High-resolution topographical data were acquired by close-range digital photogrammetry. Morphological changes were determined using high-resolution topographic data and an associated level of detection. Based on measured morphological changes, one-dimensional (1D) and two-dimensional (2D) sediment transport rates were calculated via cross-section by cross-section routing (1D) and cell by cell routing (2D). The 1D application provided a general trend of longitudinal variation of sediment transport for the whole gully system, increased gradually from zones of headward extension to a zone downstream where erosion and deposition were in balance, and sediment transport rates less variable in space. For the 2D application, hydrological and blended hydrological-hydraulic routing solutions were compared. We found that the level of negative transport was insensitive to whether or not a blended hydrological-hydraulic routing was used and that results from applying the hydrological routing throughout were not significantly degraded. We also found that consideration should be given to spatial and temporal resolution of the topographic data. The 2D application provided spatial patterns of sediment transport that vary with gully evolution. The main gully remained a high transport corridor but branch transport became more important through time. The framework we report provides an additional tool for both experimental and field quantification of the spatial patterns of sediment transport in gullies; and quantification of how these patterns change under different forcing factors.  相似文献   

Mesozoic paleostress evolution in the Saharian platform (southern Tunisia)     

Eric Barrier  Samir Bouaziz  Jacques Angelier  Gilles Creuzot  Jamel Ouali  Pierre Tricart 《Geodinamica Acta》2013,26(1):39-57

Abstract

A detailed analysis of brittle deformations in the Saharian platform of southern Tunisia is based on studies of fault-slip data sets and joint sets. It allows reconstruction of the Mesozoic paleostress evolution. During the Permo-Triassic, N-S extensions occurred with high late Permian subsidence rates. During the Norian, strike-slip movements reactivated former normal faults. During the Jurassic and the Cretaceous a succession of extensional events was characterized by : (1) a N-S extension which dominated from late Triassic to early Aptian. We relate this extension to the Africa-Eurasia divergence; (2) a ENE-WSW extension during the Cenomanian. We relate this extension to the opening of «he African basins ; (3) a NE-SW Senonian extension that continued during the Cenozoic in the Jeffara and in the Gabes Gulf, during the further evolution of the northern African margin. The various compressional trends recorded in the platform are attributed to Cenozoic events.  相似文献   

Paleofluid analysis from fracture-fill cements in the Asmari limestones of the Kuh-I-Mond field, SW Zagros, Iran   总被引：1，自引：1，他引：0  

Zeinab Shariatinia  Manouchehr Haghighi  Sadat Feiznia  Don Hall  Gilles Levresse  Ali Mousavi Dehghani  Masoud Rashidi 《Arabian Journal of Geosciences》2013,6(7):2539-2556

Kuh-I-Mond field in the Zagros foreland basin is a conventional heavy oil resource and is composed of fractured carbonates whose fractures were filled by calcite, dolomite, and anhydrite cements. Oil inclusions occurred within the fracture-fill cements indicate that fractures were open and played an active role during oil migration and charge. The highest measured values for secondary porosities belong to fractures in Asmari Formation, which is characterized by significant amounts of vug- and fracture-filling cements. Fractures facilitated fluid circulation and subsequently dissolution of allochems and high Mg carbonates. In contrast, fine-grained carbonate facies were less cemented, and thus, porosity enhancement by cement dissolution was insignificant. Temperature profiles of oil inclusions in the dolomite, calcite, and anhydrite minerals characterized by distinct variations in the homogenization temperatures (Th) that are divided into two ranges below 50°C in anhydrites and from 45°C to 125°C in dolomites and calcites. The lower Th ranges for anhydrite suggests that it may have formed at shallower burial depths during early to middle diagenesis. The oil inclusions display trend for increasing temperature downward which conform to Formation geothermal gradient. In other word, the decreasing trend of Th temperatures upward within Asmari Formation that can be observed in Th versus depth plot is consistent with the uplift events at Late Miocene time and later that caused removal of about 1,300 m of the crest of the Kuh-I-Mond anticline. Vitrinite reflectance data from source rock intervals in the field area do not support vertical migration of locally generated hydrocarbons into the Kuh-I-Mond accumulation, and long-distance lateral oil migration and charge from a source kitchen to the southwest is proposed. Vitrinite reflectance data from this dolomite and limestone reservoir suggest low maturation levels corresponding to paleotemperatures less than 50°C. The observed maturation level (<0.5% Ro) does not exceed values for simple burial maturation based on the estimated burial history. Also, homogenization temperatures from fluid inclusion populations in calcite and dolomites show expected good correlation with reflectance-derived temperatures. The Th data represent pore fluids became warmer and more saline during burial. As aqueous fluid inclusions in calcite veins were homogenized between 22°C and 90°C with a decrease in salinity from 22 to 18 eq.?wt.% NaCl. The Th values suggest a change in water composition and that dolomite and calcite cements might have precipitated from petroleum-derived fluids. The hydrocarbon fluid inclusions microthermometry data suggest that the reservoir was being filled by heavy black oils in reservoir during Cenozoic. Aqueous fluid inclusions hosted by calcite equant sparry/fossil cavity fills suggest low cementation temperatures (<45°C) and high salinities (19 eq.?wt.% NaCl), while those in dolostones are characterized by highly variable homogenization temperature (52°C to 125°C) and salinities (6.5 to 20 eq.?wt.% NaCl).  相似文献   

A GIS‐based Vehicle Mobility Estimator for Operational Contexts     

Audrey Hohmann  Gilles Grandjean  Vincent Mardhel  Gilles Schaefer  Nicolas Desramaut 《Transactions in GIS》2013,17(1):78-95

A vehicle mobility estimator has been developed to produce decision aid maps for projecting civil or military forces on operational theatres. Based on the exploitation of classical geographical sources (e.g. digital elevation models, optical images, and vector databases) and thematic sources (e.g. climate, meteorological, pedological and land cover databases), the system computes speed maps for different kinds of vehicles moving both on‐road and off‐road. Such computations are realized through a ground‐vehicle interaction module that estimates the vehicle performance from experimental results, numerical simulations and empirical relationships. The system's architecture is built using a GIS interface that manages the data, the computation and the presentation layers. An operational version of this tool has been tested and validated on several operational theatres in France and in northern Africa. The results show good agreement between the predicted mobility performance of various vehicles and those observed on the field. A case study is presented to illustrate the mobility maps and demonstrate their relevance in the decision‐making chain depending on different climate contexts. A short application to itinerary optimization is presented as a promising future application.  相似文献