Impact of winter dense water formation on shelf sediment erosion (evidence from the Gulf of Lions,NW Mediterranean)     

François Bourrin  Xavier Durrieu de Madron  Serge Heussner  Claude Estournel 《Continental Shelf Research》2008

A 1-year survey of sediment dynamics on the Têt inner-shelf in the south-western part of the Gulf of Lions was conducted as part of the EUROSTRATAFORM program (European Margin Strata Formation) from October 2004 to November 2005. Several bottom instruments (ADCP, wave gauge and altimeters) were deployed at 28 m water depth on the Têt prodelta to measure forcing responsible for sediment erosion and transport on the inner-shelf.  相似文献   

Seasonal and event-controlled export of organic matter from the shelf towards the Gulf of Lions continental slope     

Joan Fabres  Tommaso Tesi  Jose Velez  Fabian Batista  Cindy Lee  Antoni Calafat  Serge Heussner  Albert Palanques  Stefano Miserocchi 《Continental Shelf Research》2008

To investigate the role of coastal canyons in the transfer of organic matter from the shelf to the slope and basin, we deployed sediment trap/current meter pairs at the head of five canyons in the Gulf of Lions (GoL) between November 2003 and May 2004. Analysis of organic carbon, biogenic silica, Corg isotopic composition, Corg/total nitrogen, chloropigments, and amino acids clearly shows the seasonal influence and effect of extreme meteorological events on the composition of collected particles. The sampling period was divided into three “scenarios”. The first corresponded to a large easterly storm and flood of the Rhone river during stratified water column conditions; the composition of material collected during this event was influenced by increased transfer of riverine and coastal particulate matter, with a lower Corg content. During the second “fall-winter” scenario, northern and northwestern winds blowing over the shelf caused cooling and homogenization of the shelf water column; particles collected at this time reflected the homogeneous source of particulate matter transported through canyons; particles sitting in the vicinity of canyon heads are most likely swept downslope by the general south-westward circulation. Organic tracers indicate a degraded origin for organic matter transported during this period. A third “spring” scenario corresponded to northern winds alternating with eastward windstorms that triggered and/or enhanced the cascading of dense waters accumulated on the bottom of the shelf due to previous cooling. These conditions occurred in conjunction with increased phytoplankton productivity in shelf surface waters. Organic matter advected mainly by dense shelf water cascading was fresher due to the transport of newly produced particles and a variable terrestrial fraction; this fraction depended on the proportion of resuspended material accumulated during previous high discharge periods that was involved in each transport pulse. The tight link shown between meteorological conditions and organic matter transport is important for continental margin geochemical studies as future changes in climatic conditions may lead to dramatic changes in carbon sequestration capability and in the ecosystems of deep margin environments.  相似文献   

Rhythmic pelagic successions and terrestrial orbital variations. The example of the Lower Cretaceous from Angles (SE France)     

Michel Rio  Pierre Cotillon  Serge Ferry 《地学学报》1989,1(5):449-450

An harmonic analysis of limestone bed and marl interbed thicknesses of pelagic Berriasian-Barremian interval from the Angles area (SE France) shows that marly parts of the succession contain frequencies significantly different from calcareous ones. Some of the resulting periods are in the Milankovitch frequency band but many others are different from those predicted by the orbital theory.  相似文献   

Observation and photometry of an outer ring of saturn     

Audouin Dollfus  Serge Brunier 《Icarus》1982,49(2):194-204

A faint outer ring (E ring), which lies outside the classical rings A, B, C, and F, has been detected out to eight Saturn radii. We first observed it on November 1, 1979, and thereby confirmed the 1966 observation by Feibelman. Our plates were taken with a coronographic design and are specially intended for photometry. They are directly scaled in reflectance by reference to the Saturn disk which is properly attenuated. Photometry of the edge-on ring E lineament shows a strong brightness increase at small phase angles, which is compatible with scattering by particles of several microns in radius. The excess reflectivity in blue compared to the B ring implies a significant contribution of small particles in the scattering process. The E ring shows brightness and radial gradient changes, with condensations, which differ between east and west limbs and are not always the same from night to night. The E ring is probably a flat structure with a condensation centered at a distance of 4 R_s, but without a simple axial symmetry. It is probably shaped by segments or lumps and may have streamerlike structures.  相似文献   

The dammed Hikurangi Trough: a channel-fed trench blocked by subducting seamounts and their wake avalanches (New Zealand–France GeodyNZ Project)     

Keith B. Lewis  Jean-Yves Collot  & Serge E. Lallem 《Basin Research》1998,10(4):441-468

The Hikurangi Trough, off eastern New Zealand, is at the southern end of the Tonga–Kermadec–Hikurangi subduction system, which merges into a zone of intracontinental transform. The trough is mainly a turbidite-filled structural trench but includes an oblique-collision, foredeep basin. Its northern end has a sharp boundary with the deep, sediment-starved, Kermadec Trench. Swath-mapping, sampling and seismic surveys show modern sediment input is mainly via Kaikoura Canyon, which intercepts littoral drift at the southern, intracontinental apex of the trough, with minor input from seep gullies. Glacial age input was via many canyons and about an order of magnitude greater. Beyond a narrow, gravelly, intracontinental foredeep, the southern trench-basin is characterized by a channel meandering around the seaward edge of mainly Plio-Pleistocene, overbank deposits that reach 5 km in thickness. The aggrading channel has sandy turbidites, but low-backscatter, and long-wavelength bedforms indicating thick flows. Levées on both sides are capped by tangentially aligned mudwaves on the outsides of bends, indicating centrifugal overflow from heads of dense, fast-moving, autosuspension flows. The higher, left-bank levée also has levée-parallel mudwaves, indicating Coriolis and/or boundary currents effects on dilute flows or tail plumes. In the northern trough, basin-fill is generally less than 2 km thick and includes widespread overbank turbidites, a massive, blocky, avalanche deposit and an extensive, buried, debris flow deposit. A line of low seamounts on the subducting plate acts as a dam preventing modern turbidity currents from reaching the Kermadec Trench. Major margin collapse probably occurred in the wake of a large subducting seamount; this seamount and its wake debris flow probably dammed the trench from 2 Ma to 0.5 Ma. Before this, similar dams may have re-routed turbidity currents across the plateau.  相似文献   

Climate change impacts on groundwater resources: modelled deficits in a chalky aquifer,Geer basin,Belgium   总被引：8，自引：4，他引：4  

Serge?BrouyèreEmail author  Guy?Carabin  Alain?Dassargues 《Hydrogeology Journal》2004,12(2):123-134

An integrated hydrological model (MOHISE) was developed in order to study the impact of climate change on the hydrological cycle in representative water basins in Belgium. This model considers most hydrological processes in a physically consistent way, more particularly groundwater flows which are modelled using a spatially distributed, finite-element approach. Thanks to this accurate numerical tool, after detailed calibration and validation, quantitative interpretations can be drawn from the groundwater model results. Considering IPCC climate change scenarios, the integrated approach was applied to evaluate the impact of climate change on the water cycle in the Geer basin in Belgium. The groundwater model is described in detail, and results are discussed in terms of climate change impact on the evolution of groundwater levels and groundwater reserves. From the modelling application on the Geer basin, it appears that, on a pluri-annual basis, most tested scenarios predict a decrease in groundwater levels and reserves in relation to variations in climatic conditions. However, for this aquifer, the tested scenarios show no enhancement of the seasonal changes in groundwater levels.

---

Resumen Se ha desarrollado un modelo hidrológico integrado (MOHISE) para estudiar el impacto del cambio climático en el ciclo hidrológico de cuencas representativas en Bélgica. Este modelo considera todos los procesos hidrológicos de forma coherente, especialmente en relación con los flujos de aguas subterráneas, que son modelados por medio de un enfoque de elementos finitos espacialmente distribuidos. Gracias a esta herramienta numérica precisa, y tras una calibración y validación detalladas, se puede obtener interpretaciones cuantitativas de los resultados del modelo del acuífero. Considerando escenarios de cambio climático IPCC, se ha aplicado el enfoque integrado a la evaluación del impacto de dicho cambio climático en el ciclo hidrológico de la cuenca del Geer. Se describe los detalles y resultados del modelo de las aguas subterráneas en términos del impacto del cambio climático en la evolución de las reservas de los acuíferos. Los resultados preliminares indican que es posible esperar déficits de aguas subterráneas en un futuro en Bélgica.

---

Résumé Un modèle hydrologique intégré (MOHISE) a été développé afin détudier limpact du changement climatique sur le cycle hydrologique de bassins versants représentatifs de Belgique. Ce modèle prend en compte tous les processus hydrologiques dune manière physiquement consistante, plus particulièrement les écoulements souterrains qui sont modélisés par une approche spatialement distribuée aux éléments finis. Grâce à cet outil numérique précis, après une calibration et une validation détaillées, des interprétations quantitatives peuvent être réalisées à partir des résultats du modèle de nappe. Considérant des scénarios de changements climatiques de lIPCC, lapproche intégrée a été appliquée pour évaluer limpact du changement climatique sur le cycle de leau du bassin du Geer en Belgique. Le modèle de nappe est décrit en détail et les résultats sont discutés en terme dimpact du changement climatique sur lévolution des réserves souterraines. Les premiers résultats indiquent que des déficits deau souterraine peuvent apparaître dans le futur en Belgique.

  相似文献   

The giant clam Tridacna maxima communities of three French Polynesia islands: comparison of their population sizes and structures at early stages of their exploitation     

Gilbert  Antoine; Andrefouet  Serge; Yan  Laurent; Remoissenet  Georges 《ICES Journal of Marine Science》2006,63(9):1573-1589

  相似文献   

Ecosystem approach to fisheries: a review of implementation guidelines   总被引：6，自引：5，他引：6  

Garcia  Serge M.; Cochrane  Kevern L. 《ICES Journal of Marine Science》2005,62(3):311-318

  相似文献   

The remarkable population size of the endangered clam Tridacna maxima assessed in Fangatau Atoll (Eastern Tuamotu, French Polynesia) using in situ and remote sensing data     

Andrefouet  Serge; Gilbert  Antoine; Yan  Laurent; Remoissenet  Georges; Payri  Claude; Chancerelle  Yannick 《ICES Journal of Marine Science》2005,62(6):1037-1048

  相似文献   

Temporal changes of mollusc populations from a Zostera marina bed in southern Spain (Alboran Sea), with biogeographic considerations     

María del Carmen Arroyo  Carmen Salas  José Luis Rueda  & Serge Gofas 《Marine Ecology》2006,27(4):417-430

Molluscs associated with a Zostera marina bed from Cantarriján bay (Southern Spain, Alboran Sea) at 14–16 m depth were sampled monthly from October 1996 to September 1997. A total of 44,819 individuals belonging to 80 species were identified. In spite of the high species richness, only seven species of gastropods showed a dominance value (D) higher than 1%. Jujubinus striatus was the dominant species of the assemblage with 70.8% of the total abundance. The other dominant species were Rissoa membranacea (9.8%), Nassarius pygmaeus (5.8%), Mitrella minor (4%), Smaragdia viridis (1.9%), Rissoa monodonta (1.4%), Bittium reticulatum (1.3%). The dynamic pattern of the mollusc populations showed a temporal trend with monthly values of species richness and abundance ranging between 10 and 25 species and between 178 and 4412 individuals·222 m⁻². The species richness and abundance were higher in the spring and summer months than in the autumn and winter ones. The diversity (Shannon–Wiener, H’) follows a similar trend, with increases from April to September and decreases from October to March. H’ values (ranging from 0.45 to 3.10) are more influenced by the evenness (J) than by the species richness. A multivariate analysis (Cluster, Multi-dimensional Scaling) based on both presence/absence and quantitative data has also pointed out a temporal trend, with spring–summer samples significantly different from autumn–winter samples. The temporal changes in abundance seem related with the species’ biology, such as recruitment events, as well as to the canopy features and shoot density variation in the Zostera meadow. From the biogeographical point of view, most of the molluscs (65%) found in the Cantarriján bed, have a Lusitanian–Mediterranean distribution (sensu Ekman 1953 ). The proximity to Africa is shown by the presence of four species with a mainly West African distribution. Only R. membranacea has a typical Atlantic distribution, driven by that of Z. marina in NW Europe.  相似文献