Risk Assessment of Soil Compaction in the Walloon Region in Belgium   总被引：1，自引：0，他引：1  

Dimitri D’Or  Marie-France Destain 《Mathematical Geosciences》2016,48(1):89-103

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Stability Analysis of the Climate-Vegetation System in the Northern High Latitudes   总被引：6，自引：0，他引：6  

Victor Brovkin  Samuel Levis  Marie-France Loutre  Michel Crucifix  Martin Claussen  Andrey Ganopolski  Claudia Kubatzki  Vladimir Petoukhov 《Climatic change》2003,57(1-2):119-138

The stability of the climate-vegetation system in the northern high latitudesis analysed with three climate system models of different complexity: A comprehensive 3-dimensional model of the climate system, GENESIS-IBIS, and two Earth system models of intermediate complexity (EMICs), CLIMBER-2 andMoBidiC. The biogeophysical feedback in the latitudinal belt 60–70° N, although positive, is not strong enough to support multiple steady states: A unique equilibriumin the climate-vegetation system is simulated by all the models on a zonal scale for present-day climate and doubled CO₂ climate.EMIC simulations with decreased insolation also reveal a unique steady state. However, the climate sensitivity to tree cover, T_F, exhibits non-linear behaviour within the models. For GENESIS-IBIS and CLIMBER-2, T_F islower for doubled CO₂ climate than for present-day climate due to a shorter snow season and increased relative significance ofthe hydrological effect of forest cover. For the EMICs, T_F is higher for low tree fraction than for high treefraction, mainly due to a time shift in spring snow melt in response to changes in tree cover. The climate sensitivity to tree coveris reduced when thermohaline circulation feedbacks are accounted for in the EMIC simulations. Simpler parameterizations of oceanic processes have opposite effects on T_F: T_F is lower in simulations with fixed SSTs and higher in simulations with mixed layer oceans. Experiments with transient CO₂ forcing show climate and vegetation not in equilibrium in the northern high latitudes at the end of the 20thcentury. The delayed response of vegetation and accelerated global warming lead to rather abrupt changes in northern vegetation cover in the first halfof the 21st century, when vegetation cover changes at double the present day rate.  相似文献   

Multi-technique monitoring of ocean tide loading in northern France     

Muriel Llubes  Nicolas Florsch  Jean-Paul Boy  Martine Amalvict  Pascal Bonnefond  Marie-Noëlle Bouin  Stphane Durand  Marie-France Esnoult  Pierre Exertier  Jacques Hinderer  Marie-Franoise Lalancette  Frdric Masson  Laurent Morel  Joëlle Nicolas  Mathilde Vergnolle  Guy Wppelmann 《Comptes Rendus Geoscience》2008,340(6):379-389

We have organised afield study of ocean tide loading in the northwestern part of France, where tidal amplitudes are known to be among the highest in the world. GPS and gravimetric techniques have already proved their capability to measure such weak and high-frequency signals. In this study, these classical observations are complemented with less usual techniques, such as tiltmeter and Satellite Laser Ranging (SLR) measurements. We present here the preliminary results for a common period of observations spanning from 12–19 May 2004. Additional measurements from the French Transportable Laser Ranging Station (FTLRS) were available during September and October 2004. Observation residuals are computed as the difference between the observed and the predicted time signals. We obtain small RMS residuals for GPS measurements (2.5/3.1/4.5 mm for the eastward, northward and upward components), for absolute and relative gravimetry (9 nm/s² and 13 nm/s²) and for tiltmeters (0.05 μrad for EW component). We also fit the amplitude of the main M2 tidal constituent to FTLRS observations and we find a value of 3.731 cm, which is comparable to the theoretical value.  相似文献   

Spatio-temporal variation of suspended and sedimentary organic matter quality in the Bay of Marseilles (NW Mediterranean) assessed by biochemical and isotopic analyses     

Cresson P  Ruitton S  Fontaine MF  Harmelin-Vivien M 《Marine pollution bulletin》2012,64(6):1112-1121

Isotopic and biochemical features of suspended particulate organic matter (POM) in the water column and of sedimentary organic matter (SOM) were investigated seasonally in the Bay of Marseilles. Biochemical compounds (carbohydrates, lipids and proteins) were consistently more concentrated in POM than in SOM, with SOM mainly composed of insoluble carbohydrates. POM displayed lower δ(13)C and higher δ(15)N values than SOM. Phytoplanktonic production represented the major contributor of POM year-round with spatial and seasonal variations. Climatic parameters and wind-induced currents created differences in POM contributions, with more important inputs of terrestrial OM at one sampling site. Spatial and seasonal variations were lower for SOM. The composition of this pool appeared to be linked with the permanent inputs of phytoplankton and Posidonia oceanica detritus. The combined use of biochemical and isotopic analyses was a useful tool to characterize OM pools and would help understanding the trophic functioning of this coastal environment.  相似文献   

The role of forcing and internal dynamics in explaining the “Medieval Climate Anomaly”     

Hugues Goosse  Elisabeth Crespin  Svetlana Dubinkina  Marie-France Loutre  Michael E. Mann  Hans Renssen  Yoann Sallaz-Damaz  Drew Shindell 《Climate Dynamics》2012,39(12):2847-2866

Proxy reconstructions suggest that peak global temperature during the past warm interval known as the Medieval Climate Anomaly (MCA, roughly 950–1250 AD) has been exceeded only during the most recent decades. To better understand the origin of this warm period, we use model simulations constrained by data assimilation establishing the spatial pattern of temperature changes that is most consistent with forcing estimates, model physics and the empirical information contained in paleoclimate proxy records. These numerical experiments demonstrate that the reconstructed spatial temperature pattern of the MCA can be explained by a simple thermodynamical response of the climate system to relatively weak changes in radiative forcing combined with a modification of the atmospheric circulation, displaying some similarities with the positive phase of the so-called Arctic Oscillation, and with northward shifts in the position of the Gulf Stream and Kuroshio currents. The mechanisms underlying the MCA are thus quite different from anthropogenic mechanisms responsible for modern global warming.  相似文献   

Effect of N content and soil texture on the decomposition of organic matter in forest soils as revealed by solid-state CPMAS NMR spectroscopy     

Marie-France Dignac  Heike Knicker  Ingrid Kgel-Knabner 《Organic Geochemistry》2002,33(12):157

N has a controlling effect on litter biodegradation in the forest floor, while stabilization of organic matter in the mineral soil may be influenced by physical parameters related to soil texture. In this study, in order to understand the processes involved in soil organic matter (SOM) formation, the chemical composition of SOM was followed and evaluated with regards to N contents and soil texture. Samples were taken on sites covered with Norway spruce and displaying contrasting values of C/N ratios in the forest floor. The chemical structure of OM was characterized using solid-state CPMAS ¹³C and ¹⁵N nuclear magnetic resonance (NMR) spectroscopy, along with Proton Spin Relaxation Editing (PSRE) sequences. Four groups of sampling sites were defined based on the NMR spectra of Oh and A horizons. In each group displaying similar NMR characteristics, N content and soil texture could be highly different among sites. Some Oh horizons with similar NMR spectra had very different N contents. Highly humified OM in Oh horizons were observed mainly on sites with low N contents. Some A horizons with different soil texture displayed similar OM chemical structure. High contents of O-alkyl C in some A horizons could originate from higher fresh root material input.  相似文献   

Amorce de la Sédimentation Synorogénique dans les PyrénéesVarisques. Données Chronologiques; Implications Paléogéographiques     

Professeur Dr. Raymond Mirouse  Gilbert Barrouquère  Gilbert Bessière  Jean-Jacques Delvolvé  Marie-France Perret 《International Journal of Earth Sciences》1983,72(1):253-281

Conodont associations and recent macrofaunal discoveries, allow us to date the beginning of detrital deposits going with the Variscan uplift in the Pyrenean marine basins during the Lower Carboniferous. Thus, the establishing of synorogenic conditions seems to have progressed from the East to the West; there appears the picture of a kind of north-Pyrenean axis already individualized in the wide Cantabrico-Pyrenean foreland.  相似文献   

A 17,900-year multi-proxy lacustrine record of Lago Puyehue (Chilean Lake District): introduction     

Marc De Batist  Nathalie Fagel  Marie-France Loutre  Emmanuel Chapron 《Journal of Paleolimnology》2008,39(2):151-161

This paper introduces the background and main results of a research project aimed at unravelling the paleolimnological and paleoclimatological history of Lago Puyehue (40° S, Lake District, Chile) since the Last Glacial Maximum (LGM), based on the study of several sediment cores from the lake and on extensive fieldwork in the lake catchment. The longest record was obtained in an 11-m-long piston core. An age-depth model was established by AMS ¹⁴C dating, ²¹⁰Pb and ²³⁷Cs measurements, identification of event-deposits, and varve-counting for the past 600 years. The core extends back to 17,915 cal. yr. BP, and the seismic data indicate that an open-lake sedimentary environment already existed several thousands of years before that. The core was submitted to a multi-proxy analysis, including sedimentology, mineralogy, grain-size, major geochemistry and organic geochemistry (C/N ratio, δ¹³C), loss-on-ignition, magnetic susceptibility, diatom analysis and palynology. Along-core variations in sediment composition reveal that the area of Lago Puyehue was characterized since the LGM by a series of rapid climate fluctuations superimposed on a long-term warming trend. Identified climate fluctuations confirm a.o. the existence of a Late-Glacial cold reversal predating the northern-hemisphere Younger Dryas cold period by 500–1,000 years, as well as the existence of an early southern-hemisphere Holocene climatic optimum. Varve-thickness analyses over the past 600 years reveal periodicities similar to those associated with the El Niño Southern Oscillation and the Pacific Decadal Oscillation, as well as intervals with increased precipitation, related to an intensification of the El Niño impact during the southern-hemisphere equivalent of the Little Ice Age.  相似文献   

Variations de l’âge des sédiments calcaires et « Culm » carbonifère dans la chaîne varisque du Sud de la France : migration de l’orogenèse varisque     

Jean-Jacques Delvolvé  Marie-France Perret 《Geodinamica Acta》2013,26(2):117-126

Résumé

Dans le Sud de la France et les Pyrénées espagnoles, les calcaires sous-jacents aux roches détritiques du Culm carbonifère ont fait l’objet d’une datation systématique par conodontes. Il en ressort que le dépôt de ces niveaux carbonates s’est poursuivi de plus en plus tardivement de l’Est vers l’Ouest : du Viséen inférieur (V3b) en Montagne Noire, au Namurien supérieur (G2) en Pays basque.

Les roches détritiques à caractère flyschoïde du Culm remanient, localement, des éléments de calcaire de plate-forme. La datation de ces éléments par foraminifères, algues, pseudo-algues et végétaux supérieurs montre qu’ils sont de plus en plus récents d’Est en Ouest : leur âge s’échelonne du Viséen 3bp-Namurien A en Montagne Noire, au Westphalien C (Kachirien) au Pays basque (Massif des Cinco-Villas).

Ces divers résultats montrent que les manifestations tectoniques, responsables des premiers épandages détritiques du Culm puis de la resédimentation des calcaires de plate-forme dans le bassin, ont commencé de plus en plus tardivement de la Montagne Noire au Pays basque.

Dans sa branche Sud, l’orogenèse varisque, si l’on s’en tient à la position actuelle de ses segments observables, a migré progressivement du Nord vers le Sud, en Montagne Noire et dans le Massif de Mouthoumet, puis vers l’Ouest, des Pyrénées centrales aux Pyrénées orientales.  相似文献   

Etude physico-chimique des résidus de pyrolyse de la sporopollénine     

Pierre Libert  André Marchand  Marie-France Achard 《Geochimica et cosmochimica acta》1976,40(2):143-148

Two parameters are chosen to characterize the pyrolysis residues of sporopollenin: the first one is the $\text{d}{}_{1600}\text{d}{}_{1700}$ ratio, where d₁₆₀₀ and d₁₇₀₀ are the optical densities of the absorption bands at 1600 and 1700 cm^?1, respectively; the second one is the paramagnetic susceptibility χ_p measured by E.P.R.Those two quantities increase rapidly above 300°C, which confirms previous results that the sporopollenin structure undergoes important modifications at this temperature. A striking similarity is observed between the properties of sporopollenin residues and those of natural kerogens.  相似文献