Coupled strata and granulometry detection on indurated cores by gray-level image analysis     

Nazha?SelmaouiEmail author  Bernard?Repetti  Christine?Laporte-Magoni  Michel?Allenbach 《Geo-Marine Letters》2004,24(4):241-251

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Is a management framework based on spawning-stock biomass indicators sustainable? A viability approach     

De Lara  Michel; Doyen  Luc; Guilbaud  Therese; Rochet  Marie-Joelle 《ICES Journal of Marine Science》2007,64(4):761-767

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Local Multiscale Approximations of Geostrophic Oceanic Flow: Theoretical Background and Aspects of Scientific Computing     

Willi Freeden  Dominik Michel  Volker Michel 《Marine Geodesy》2005,28(4):313-329

In modern geoscience, understanding the climate depends on the information about the oceans. Covering two-thirds of the Earth, oceans play an important role. Oceanic phenomena are, for example: oceanic circulation; water exchanges between atmosphere, land, and ocean; or temporal changes of the total water volume. All these features require new methods in constructive approximation, since they are regionally bounded and not globally observable. This article deals with a new and alternative method of handling data with locally supported basis functions, modeling them in a multiscale scheme involving a wavelet approximation and presenting the main results for the dynamic topography and the geostrophic flow, e.g., in the Northern Atlantic. Further, it is demonstrated that compressional rates of the occurring wavelet transforms can be achieved by using of locally supported wavelets and investigating the signal distribution within different frequency bands.  相似文献   

Contourite drift construction influenced by capture of Mediterranean Outflow Water deep-sea current by the Portimão submarine canyon (Gulf of Cadiz, South Portugal)     

Elodie Marchès  Thierry Mulder  Michel Cremer  Cédric Bonnel  Vincent Hanquiez  Eliane Gonthier  Pascal Lecroart 《Marine Geology》2007,242(4):247-260

The margin of the Gulf of Cadiz is swept by the deep current formed by the Mediterranean Outflow Water (MOW) flowing from the Mediterranean to the Atlantic. On the northern margin of the Gulf (Algarve Margin, South Portugal), the MOW intensity is low and fine-grained contourite drifts are built up with an alongslope development. From new sedimentological data, this study emphasizes the presence of two types of contourite drifts separated only by a deep submarine canyon incising the slope with a north-south orientation (Portimão Canyon). High-resolution seismic and bathymetry interpretation shows that on the eastern side of the canyon, the MOW forms a thick and large detached drift (Albufeira Drift) prograding toward both north and west, as shown in seismic profiles, with a high sedimentation rate. On this side of the canyon, the MOW intensity is high enough to erode the slope forming a moat channel (Alvarez Cabral). On the western side of Portimão Canyon, the MOW energy is lower, preventing moat channel erosion. Only flat and thin drift develops (Portimão and Lagos Drifts) with slow aggradation and a low sedimentation rate. This difference in drift development is due to the presence of the canyon which generates an important change in hydrodynamic of the MOW, confirmed by temperature-density measurements showing that MOW flows down Portimão Canyon. The canyon is responsible for the deviation of the direction of the MOW as it partly catches the deep-sea current flowing westward (i.e. capture phenomenon). It creates, thus, a decrease of the flow energy, competency and capacity between the east and west sides of the canyon. Through this phenomenon of MOW deep-sea current capture, the canyon constitutes a morphologic feature generating an important change in the contourite deposition pattern.In addition to already known climatic and oceanographic influences, our results show the role of canyons on contourite drift building. This study provides new elements on autocyclic factors influencing the contourite sedimentation, which are important to consider in future sedimentary paleo-reconstruction interpretations.  相似文献   

Trophic structure and pathways of biogenic carbon flow in the eastern North Water Polynya   总被引：1，自引：0，他引：1  

Jean-ric Tremblay  Hiroshi Hattori  Christine Michel  Marc Ringuette  Zhi-Ping Mei  Connie Lovejoy  Louis Fortier  Keith A. Hobson  David Amiel  Kirk Cochran 《Progress in Oceanography》2006,71(2-4):402

In the eastern North Water, most of the estimated annual new and net production of carbon (C) occurred during the main diatom bloom in 1998. During the bloom, at least 30% of total and new phytoplankton production occurred as dissolved organic carbon (DOC) and was unavailable for short-term assimilation into the herbivorous food web or sinking export. Based on particle interceptor traps and ²³⁴Th deficits, 27% of the particulate primary production (PP) sank out of the upper 50 m, with only 7% and 1% of PP reaching the benthos at shallow (≈200 m) and deep (≈500 m) sites, respectively. Mass balance calculations and grazing estimates agree that ≈79% of PP was ingested by pelagic consumers between April and July. During this period, the vertical flux of biogenic silica (BioSi) at 50 m was equivalent to the total BioSi produced, indicating that all of the diatom production was removed from the euphotic zone as intact cells (direct sinking) or empty frustules (grazing or lysis). The estimated flux of empty frustules was consistent with rates of herbivory by the large, dominant copepods and appendicularians during incubations. Since the carbon demand of the dominant planktivorous bird, Alle alle, amounted to ≈2% of the biomass synthesized by its main prey, the large copepod Calanus hyperboreus, most of the secondary carbon production was available to pelagic carnivores. Stable isotopes indicated that the biomass of predatory amphipods, polar cod and marine mammals was derived from these herbivores, but corresponding carbon fluxes were not quantified. Our analysis shows that a large fraction of PP in the eastern North Water was ingested by consumers in the upper 50 m, leading to substantial carbon respiration and DOC accumulation in surface waters. An increasingly early and prolonged opening of the Artic Ocean is likely to promote the productivity of the herbivorous food web, but not the short-term efficiency of the particulate, biological CO₂ pump.  相似文献   

The effects of a water-soluble petroleum fraction on the neuroid electrical activity of the hydroid coelenterate Tubularia crocea     

William C Michel  James F Case 《Marine environmental research》1986,19(4)

Several properties of the excitable epithelium of the hydroid coelenterate, Tubularia crocea, are affected by a water-soluble fraction (WSF) of Platform Holly, Monterey Formation, crude oil (100% WSF= 20 ppm total hydrocarbons). In a flowing seawater system, 0·5 ml pulses of 1 WSF cause a significant increase in the epithelial pulse activity, while a 10·min exposure to 0·1% WSF produces a significant increase in the epithelial pulse frequency. Electrophysiological responses to the volatile and non-volatile subfractions are equal, but significantly lower than those to the whole WSF. Behaviorally, the 100% WSF elicits a more vigorous proximal tentacle closure than either its volatile or non-volatile subfraction. However, the closure response to the volatile subfraction exceeds that for the non-volatile component.Of the two epithelial neuroid pulse systems, the hydranth pulse (HP) system is affected to a greater extent than the neck pulse (NP) system. During 10 minutes' treatment with 100% WSF the amplitude of the neck pulses and hydranth pulses declined by 50% and 80%, respectively. The maximum ³H-toluene uptake from 100% WSF also occurs within this period, and sodium and calcium concentrations fluctuate rapidly. These results suggest that a rapid bioaccumulation of hydrocarbons by T. crocea alters membrane permeability, upsetting critical ion gradients which, in turn, alter the firing frequency of the epithelial conducting systems. This study demonstrates that concentrations of WSF approaching environmentally realistic levels (in areas of chronic pollution) alter the epithelial conducting systems that co-ordinate important elements of behavior in Tubularia. This system provides a sensitive neuroid-behavioral assay for aquatic contaminants.  相似文献   

Karst groundwater resources in the countries of eastern Mediterranean: the example of Lebanon   总被引：1，自引：0，他引：1  

Michel Bakalowicz  Massaad El Hakim  Ahmad El-Hajj 《Environmental Geology》2008,54(3):597-604

The hydrogeological study of some karst systems in Lebanon shows important storage capacity, up to 27 billions m³ for Zarka system, the spring of Orontes River. Their geological and morphological settings, as well as their hydrodynamic function, show structures developed below the level of present springs, probably up to several hundreds meters at depth. Since Miocene, those carbonate formations were subject to a remarkable instability of their base levels. Variations of sea level, of which the Messinian salinity crisis is the major phase, and effects of the alpine orogenesis, combined with climate variations to develop complex, multiphased karst systems. Karstification occurs frequently in the whole formation, often deeply below sea level or underneath sediment filling of continental basins. The surface karst landscape is often intensely eroded. Those multiple, superimposed karst phases give the carbonate aquifers their large extension and storage capacity. These karst aquifers show the typical easy restoration of storage. They have the ability to bear large interannual recharge variations and support exploitation under high pumping rates. However, these aquifers have some disadvantages for sustainable management. In some regions, successful boreholes, which allow high pumping rates also induce uncontrolled exploitation. Another consequence is natural seawater intrusion, as well as the submarine discharge of fresh groundwater, in coastal aquifers. Those carbonate aquifers are subject to important economical stress which jeopardizes their durability. The systematic study and understanding of carbonate aquifers in Eastern Mediterranean is a preliminary condition to any integrated and sustainable management of water resources. Studies in progress in Lebanon may serve as examples to the whole region.  相似文献   

Cosmo-SkyMed X-band SAR data for classification of ice-free areas and glacier facies on Potter Peninsula,King George Island Antarctica     

André Medeiros de Andrade  Jorge Arigony-Neto  Ulisses Franz Bremer  Roberto Ferreira Machado Michel  Alice César Fassoni-Andrade  Carlos Ernesto Goncalves Reynaud Schaefer 《国际地球制图》2016,31(7):803-812

The climate change phenomena have been influencing terrestrial and glacial ecosystems around the planet. Maritime Antarctica is especially sensitive to these climate variations and over the last 50 years increasing global air temperatures have caused extensive glacial retreat. The objective of this study is to evaluate the potential use of the SAR technology in monitoring the surface dynamics of the Potter Peninsula, King George Island, maritime Antarctica. An image generated by the SAR satellite COSMO-SkyMed, obtained on 2 February 2011, was used to extract the backscattering values of targets on the surface for further processing and classification, using a supervised statistic classifier of maximum likelihood for the determination of the surface classes. The average backscattering of water bodies presented high similarity, which made its separation unattainable. On the other hand, the surface classes’ bare ice and wet snow over the glacier presented distinct average backscattering values, which allowed an efficient and precise classification using only this parameter. The classification process showed satisfactory results for periglacial environments, presenting high fidelity to the field data.  相似文献   

Searching for Added Value in Simulating Climate Extremes with a High-Resolution Regional Climate Model over Western Canada. II: Basin-Scale Results     

Charles L. Curry  Bárbara Tencer  Kirien Whan  Andrew J. Weaver  Michel Giguère  Edward Wiebe 《大气与海洋》2016,54(4):385-402

We evaluate the capacity of a regional climate model to simulate the statistics of extreme events, and also examine the effect of differing horizontal resolution, at the scale of individual hydrological basins in the topographically complex province of British Columbia, Canada. Two climate simulations of western Canada (WCan) were conducted with the Canadian Regional Climate Model (version 4) at 15 (CRCM15) and 45?km (CRCM45) horizontal resolution driven at the lateral boundaries by global reanalysis over the period 1973–1995. The simulations were evaluated with ANUSPLIN, a daily observational gridded surface temperature and precipitation product and with meteorological data recorded at 28 stations within the upper Peace, Nechako, and upper Columbia River basins. In this work, we focus largely on a comparison of the skill of each model configuration in simulating the 90th percentile of daily precipitation (PR90). The companion paper describes the results for a wider range of temperature and precipitation extremes over the entire WCan domain.

Over all three watersheds, both simulations exhibit cold biases compared with observations, with the bias exacerbated at higher resolution. Although both simulations generally display wet biases in median precipitation, CRCM15 features a reduced bias in PR90 in all three basins in summer and throughout the year in the upper Columbia River basin. However, the higher resolution model is inferior to CRCM45 with respect to rarer heavy precipitation events and also displays high spatial variability and lower spatial correlations with ANUSPLIN compared with the coarser resolution model. A reduction in the range of PR90 biases over the upper Columbia basin is noted when the 15?km results are averaged to the 45?km grid. This improvement is partly attributable to the averaging of errors between different elevation data used in the gridded observations and CRCM, but the sensitivity of CRCM15 to resolved topography is also clear from spatial maps of seasonal extremes. At the station scale, modest but systematic reductions in the bias of PR90 relative to ANUSPLIN are again found when the CRCM15 results are averaged to the 45?km grid. Furthermore, the annual cycle of inter-station spatial variance in the upper Columbia River basin is well reproduced by CRCM15 but not by ANUSPLIN or CRCM45. The former result highlights the beneficial effect of spatial averaging of small-scale climate variability, whereas the latter is evidently a demonstration of the added value at high resolution vis-à-vis the improved simulation of precipitation at the resolution limit of the model.  相似文献   

The anatomy of an active slide: the Gascons rockslide,Québec,Canada     

Catherine Cloutier  Jacques Locat  Réjean Couture  Michel Jaboyedoff 《Landslides》2016,13(2):241-258

A railroad crosses the coastal Gascons rockslide, in Quebec, Canada. This study improves the understanding of the rockslide’s failure mechanism and post-failure behaviour responsible for the deformation in the railroad. The slide is an asymmetrical wedge failure of 410,000 m³, in rocks made up of centimetre-scale beds of nodular calcilutite alternating with sandstones and limestone. The post-failure stage of the rockslide is characterised by continuous movement of blocks with speeds ranging from 6 to 110 mm/year. The main water table is just below the sliding surface, but precipitation and snowmelt can raise it above the sliding surface in the upper part of the slide. We propose a model for the rockslide, its failure mechanism, geometry and hydrogeology to provide a baseline for interpreting the near-real-time data collected since 2009.  相似文献