Influence of tropical cyclones on sea surface temperature seasonal cycle and ocean heat transport     

Emmanuel M. Vincent  Gurvan Madec  Matthieu Lengaigne  Jérôme Vialard  Ariane Koch-Larrouy 《Climate Dynamics》2013,41(7-8):2019-2038

Recent studies suggested that tropical cyclones (TCs) contribute significantly to the meridional oceanic heat transport by injecting heat into the subsurface through mixing. Here, we estimate the long-term oceanic impact of TCs by inserting realistic wind vortices along observed TCs tracks in a 1/2° resolution ocean general circulation model over the 1978–2007 period. Warming of TCs’ cold wakes results in a positive heat flux into the ocean (oceanic heat uptake; OHU) of ~480 TW, consistent with most recent estimates. However, ~2/5 of this OHU only compensates the heat extraction by the TCs winds during their passage. Another ~2/5 of this OHU is injected in the seasonal thermocline and hence released back to the atmosphere during the following winter. Because of zonal compensations and equatorward transport, only one-tenth of the OHU is actually exported poleward (46 TW), resulting in a marginal maximum contribution of TCs to the poleward ocean heat transport. Other usually neglected TC-related processes however impact the ocean mean state. The residual Ekman pumping associated with TCs results in a sea-level drop (rise) in the core (northern and southern flanks) of TC-basins that expand westward into the whole basin as a result of planetary wave propagation. More importantly, TC-induced mixing and air-sea fluxes cool the surface in TC-basins during summer, while the re-emergence of subsurface warm anomalies warms it during winter. This leads to a ~10 % reduction of the sea surface temperature seasonal cycle within TCs basins, which may impact the climate system.  相似文献   

Morphometry of micrite particles in cretaceous microporous limestones of the Middle East: Influence on reservoir properties   总被引：2，自引：0，他引：2  

Matthieu Deville de Periere  Christophe DurletEmmanuelle Vennin  Laurent LambertRaphael Bourillot  Bruno CalineEmmanuelle Poli 《Marine and Petroleum Geology》2011,28(9):1727-1750

Microporosity may account for a significant part of the total porosity of Cretaceous limestone reservoirs of the Middle East. In these microporous facies porosity is moderate to excellent (up to 35%) while permeability is poor to moderate (up to 190 mD). Micritic limestones also may form dense layers with very low porosity and permeability values.Micritic samples were collected from three fields of the Habshan and Mishrif Formations, to examine the spatial relationship with their porosity, permeability and pore throat radius distributions. Two key parameters of the micritic particles are studied using scanning electron microscopy: their morphology (shape and inter-crystal contacts), and their crystallometry.Results reveal that micrite matrixes can be subdivided into three petrophysical classes. Class C (strictly microporous limestones with coarse punctic-to-partially coalescent micrites) is made up of coarse (>2 μm) polyhedral to rounded micritic crystals, it has good to excellent porosity (8-28%), poor to moderate permeability (0.2-190 mD) and a mean pore threshold radius of more than 0.5 μm. The class C is usually observed in rudist shoal facies where relatively high hydrodynamic energy disfavoured deposition of the finer micritic crystals. It also developed within meteoric leaching intervals below exposure surfaces. Class F (strictly microporous limestones with fine punctic-to-partially coalescent micrites) is composed of fine (<2 μm) polyhedral to rounded micrites with poor to excellent porosity (3-35%), but permeability values of less than 10 mD and a mean pore threshold radius of less than 0.5 μm. It is mostly observed in sediments deposited in a low energy muddy inner platform setting. Class D (strictly microporous mud-dominated facies with compact anhedral to fused dense micrites) comprises subhedral to anhedral crystals with sutured contacts forming a dense matrix. It has very low porosity and permeability. Class D is only found in low energy muddy inner platform facies and forms inter-reservoir or caps rock layers in close association with stylolites and clay contents that usually exceed 10%.  相似文献   

Morphodynamics and sedimentary structures of bedforms under supercritical‐flow conditions: New insights from flume experiments     

Matthieu J.B. Cartigny  Dario Ventra  George Postma  Jan H. van Den Berg 《Sedimentology》2014,61(3):712-748

Supercritical‐flow phenomena are fairly common in modern sedimentary environments, yet their recognition and analysis remain difficult in the stratigraphic record. This fact is commonly ascribed to the poor preservation potential of deposits from high‐energy supercritical flows. However, the number of flume data sets on supercritical‐flow dynamics and sedimentary structures is very limited in comparison with available data for subcritical flows, which hampers the recognition and interpretation of such deposits. The results of systematic flume experiments spanning a broad range of supercritical‐flow bedforms (antidunes, chutes‐and‐pools and cyclic steps) developed in mobile sand beds of variable grain sizes are presented. Flow character and related bedform patterns are constrained through time‐series measurements of bed configurations, flow depths, flow velocities and Froude numbers. The results allow the refinement and extension of some widely used bedform stability diagrams in the supercritical‐flow domain, clarifying in particular the morphodynamic relations between antidunes and cyclic steps. The onset of antidunes is controlled by flows exceeding a threshold Froude number. The transition from antidunes to cyclic steps in fine to medium‐grained sand occurs at a threshold mobility parameter. Sedimentary structures associated with supercritical bedforms developed under variable aggradation rates are revealed by means of combining flume results and synthetic stratigraphy. The sedimentary structures are compared with examples from field and other flume studies. Aggradation rate is seen to exert an important control on the geometry of supercritical‐flow structures and should be considered when identifying supercritical bedforms in the sedimentary record.  相似文献   

Elliptical Descriptors: Some Simplified Morphometric Parameters for the Quantification of Complex Outlines     

Matthieu Schmittbuhl  Bernard Allenbach  Jean-Marie Le Minor  André Schaaf 《Mathematical Geology》2003,35(7):853-871

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Calcification rate influence on trace element concentrations in aragonitic bivalve shells: Evidences and mechanisms     

Matthieu Carré  Ilhem Bentaleb  Elmer Ordinola  Michel Fontugne 《Geochimica et cosmochimica acta》2006,70(19):4906-4920

Trace elements in calcareous organisms have been widely used for paleoclimatic studies. However, the factors controlling their incorporation into mollusc shells are still unclear. We studied here the Sr, Mg, Ba and Mn serial records in the shells of two aragonitic marine bivalve species: Mesodesma donacium and Chione subrugosa from the Peruvian Coast. The elemental concentrations were compared to local temperature and salinity records. The relationships with crystal growth rate G were investigated thanks to well defined periodic growth structures providing a precise shell chronology. Our results show that for both species, environmental parameters only have minor influence, whereas crystal growth rate strongly influences trace elements concentrations, especially for Sr (explaining up to 74% of the variance). The relationship between G and Sr/Ca exhibits variability among the shells as well as inside the shells. For a same growth rate value, Sr/Ca values are higher in more curved shell sections, and the growth rate influence is stronger as well. We show that intercellular and Ca²⁺-pump pathways cannot support the calcification Ca²⁺ flux, leading us to propose an alternative mechanism for ionic transport through the calcifying mantle, implying a major role for calcium channels on mantle epithelial cell membranes. In this new calcification model, Sr/Ca shell ratios is determined by Ca²⁺-channel selectivity against Sr²⁺, which depends (i) on the electrochemical potential imposed by the crystallisation process and (ii) on the Ca²⁺-channel density per surface unit on mantle epithelia.  相似文献   

Small Antarctic micrometeorites: A mineralogical and in situ oxygen isotope study     

Matthieu GOUNELLE  Ccile ENGRAND  Michel MAURETTE  Gero KURAT  Kevin D. McKEEGAN  Franz BRANDSTTTER 《Meteoritics & planetary science》2005,40(6):917-932

Abstract— We have investigated the texture, bulk chemistry, mineralogy, as well as the anhydrous minerals oxygen isotopic composition of 67 small Antarctic micrometeorites (AMMs) collected at Cap Prudhomme, Antarctica, and belonging to the currently poorly studied size fraction 25–50 μm. When compared to larger (50–400 μm) micrometeorites collected at the same site in Antarctica with the same techniques, no significant differences are found between the two populations. We therefore conclude that the population of Cap Prudhomme AMMs is homogeneous over the size range 25–400 μm. In contrast, small AMMs have different textures, mineralogy, and oxygen isotopic compositions than those of stratospheric interplanetary dust particles (IDPs). Because small AMMs (<50 μm) overlap in size with IDPs, the differences between these two important sources of micrometeorites can no longer be attributed to a variation of the micrometeorite composition with size. Physical biases introduced by the collection procedures might account for these differences.  相似文献   

Enregistrements sismologiques de l'explosion sur le site de l'usine AZF (Toulouse,France)Seismological records of an explosion at the AZF chemical complex in Toulouse,France     

Annie Souriau  Matthieu Sylvander  Valérie Maupin  Jean-François Fels  Alexis Rigo 《Comptes Rendus Geoscience》2002,334(3):155-161

This study presents a detailed analysis of the seismic records of a strong explosion that occurred on 21 September 2001 at a chemical complex located south of Toulouse, France, and provoked important damages. The explosion, which is equivalent to a 3.4 magnitude earthquake, has been recorded at most of the stations of the National Seismological Network, as well as at a station under test at the ‘Observatoire Midi-Pyrénées’, 4.2 km away from the epicentre. The main seismic phases are interpreted using the known crustal structures, and a modelling with synthetic seismograms is performed. To cite this article: A. Souriau et al., C. R. Geoscience 334 (2002) 155–161.  相似文献   

Bedforms and associated sedimentary structures formed under supercritical water flows over aggrading sand beds   总被引：5，自引：0，他引：5  

J. Alexander  J. S. Bridge  R. J. Cheel  & S. F. Leclair 《Sedimentology》2001,48(1):133-152

Bedforms and associated sedimentary structures, formed under supercritical water flow over an aggrading sand bed, were studied in a laboratory flume. Although the geometry and hydraulic characteristics of these bedforms (antidunes, chutes-and-pools) are well known, their internal structures are not. The objectives of the study were to: (1) describe the three-dimensional geometry of the sedimentary structures and examine their mode of origin; (2) develop a relationship between the geometries of the sedimentary structures and the formative bedforms and; (3) identify criteria that distinguish these sedimentary structures from similar types, such as hummocky and swaley cross-strata. Sedimentary structures associated with antidunes are primarily lenticular laminasets with concave-upward erosional bases (troughs) in which laminae generally dip upstream or fill the troughs symmetrically. These laminasets are associated with growth and upstream migration of water-surface waves and antidunes, and with surface-wave breaking and filling of antidune troughs respectively. In addition, sets of downstream-dipping laminae are produced by rapid migration of asymmetrical bedwaves immediately after wave breaking. Rare convex-upward laminae define the shape of antidunes that developed under stationary water-surface waves. The laminasets and internal laminae extend across the width of the flume, but vary in thickness and inclination, indicating that the antidunes have some degree of three dimensionality. The length and maximum thickness of the lenticular laminasets are approximately half of the length and height of formative antidunes, providing a potentially useful tool for palaeohydraulic reconstructions. The sets of downstream-dipping laminae formed under antidunes are distinctive and do not occur in hummocky and swaley cross-strata. Sedimentary structures associated with chutes-and-pools are sets of upstream-dipping laminae and structureless sand.  相似文献   

“There is No Program Without Farmers”: Interactive Radio for Forest Landscape Restoration in Mount Elgon Region,Uganda     

Karen Hampson  Mark Leclair  Askebir Gebru  Lynne Nakabugo  Chris Huggins 《社会与自然资源》2017,30(5):642-657

Increase in ownership and use of radios and mobile phones in Uganda may present opportunities for interactive and efficient agricultural extension services. Yet the impact of interactive radio on rural development has rarely been evaluated. In a participatory project, the International Union for the Conservation of Nature together with Farm Radio International and stakeholders from local government, radio, and community-based organizations promoted the increased use of forest landscape restoration activities though interactive rural radio programs, including innovative methods to reach populations not covered by radio. An evaluation found that 98% of people who listened to most or all of the broadcasts carried out one of the practices, whereas 84% of those who had listened to only one episode had used one of the practices. Inclusion of a wide range of community stakeholders from project inception was vital for presenting the project and embedding it within local institutional contexts.  相似文献   

The Rwenzori Mountains,a landslide-prone region?     

Liesbet Jacobs  Olivier Dewitte  Jean Poesen  Damien Delvaux  Wim Thiery  Matthieu Kervyn 《Landslides》2016,13(3):519-536

With its exceptionally steep topography, wet climate, and active faulting, landslides can be expected to occur in the Rwenzori Mountains. Whether or not this region is prone to landsliding and more generally whether global landslide inventories and hazard assessments are accurate in data-poor regions such as the East African highlands are thus far unclear. In order to address these questions, a first landslide inventory based on archive information is built for the Rwenzori Mountains. In total, 48 landslide and flash flood events, or combinations of these, are found. They caused 56 fatalities and considerable damage to road infrastructure, buildings, and cropland, and rendered over 14,000 persons homeless. These numbers indicate that the Rwenzori Mountains are landslide-prone and that the impact of these events is significant. Although not based on field investigations but on archive data from media reports and laymen accounts, our approach provides a useful complement to global inventories overlooking this region and increases our understanding of the phenomenon in the Rwenzori Mountains. Considering the severe impacts of landslides, the population growth and related anthropogenic interventions, and the likelihood of more intense rainfall conditions, there is an urgent need to invest in research on disaster risk reduction strategies in this region and other similar highland areas of Africa.  相似文献