Éditeur(s) : HAL CCSD
Résumé : Les populations envahissantes sont généralement confrontées à un monde hétérogène où les conditions abiotiques, la distribution et la disponibilité en ressource et les densités d’espèces natives varient à la fois dans le temps et dans l’espace. Une telle hétérogénéité environmentale peut jouer un rôle décisif dans le succès d’établissement et sur la vitesse d’expansion d’une invasion. Des capacités de dispersion dans le temps et dans l’espace sont attendues pour permettre aux populations envahissantes de faire face à ces contraintes. Les Hyménoptères spécialistes des graines du genre Megastigmus (Torymidae) sont des modèles invasifs intéressants parce-qu’ils exploitent des populations d’arbres qui sont réparties en patchs discontinus dans le paysage et qui montrent des variations inter-annuelles synchronisées et de forte amplitude dans la production de graines (masting). Nous nous sommes intéressés à l’invasion récente des forêts de cèdre de l’Atlas du sud-est de la France par M. schimitscheki, qui montre de fortes propensions à : (i) la dispersion passive par le vent (dispersion spatiale), et (ii) la diapause prolongée, une forme de dormance larvaire pouvant durer de 3 à 5 années consécutives (dispersion temporelle). Dans un premier temps, nous montrons que, malgré une distribution très fragmentée de son hôte obligatoire à l’échelle du paysage, M. schimitscheki a pu envahir la quasi-totalité des cédraies de la région PACA par des évènements de dispersion à longue distance depuis sa zone d’introduction, à la faveur d’un vent régional dominant (le Mistral). Dans un second temps, nous montrons que, à l’échelle d’une population, la diapause prolongée peut constituer un refuge temporel démographique et génétique pour des cohortes soumises aux variations extrêmes de disponibilité en ressources, qui résultent du masting de leur hôte obligatoire.
Colloque de lancement du GdR ‘Invasions Biologiques’
Rennes, France

hal-01601706
https://hal.archives-ouvertes.fr/hal-01601706
PRODINRA : 404855

Éditeur(s) : HAL CCSD Geological Society of America
Résumé : International audience
On the New Jersey shelf (offshore North America), the presence of pore water fresher than seawater is known from a series of boreholes completed during the 1970s and 1980s. To account for this fresh water, a fi rst hypothesis involves possible present-day active dynamic connections with onshore aquifers, while a second involves meteoritic and/or sub- ice-sheet waters during periods of lowered sea level. Expedition 313 drilled three boreholes on the middle shelf, offering a unique opportunity for the internal structure of the siliciclastic system to be accessed, at scales ranging from the depositional matrix to the continental margin. This enables the stratigraphic architecture to be correlated with the spatial distribution and salinity of saturating fl uids. Expedition 313 revealed both very low salinities (<3 g/L) at depths exceeding 400 m below the seafl oor and evidence for a multilayered reservoir organization, with freshand/ or brackish-water intervals alternating vertically with salty intervals. In this study we present a revised distribution of the salinity beneath the middle shelf. Our observations suggest that the processes controlling salinity are strongly infl uenced by lithology, porosity, and permeability. Saltier pore waters generally occur in coarse-grained intervals and fresher pore waters occur in fi ne-grained intervals. The transition from fresher to saltier intervals is often marked by cemented horizons that probably act as permeability barriers. In the lowermost parts of two holes, the salinity varies independently of lithology, suggesting different mechanisms and/or sources of salinity. We present an interpretation of the sedimentary facies distribution, derived from core, logs, and seismic profi le analyses, that is used to discuss the marginscale two-dimensional reservoir geometry and permeability distribution. These proposed geometries are of primary importance when considering the possible pathways and emplacement mechanisms for the fresh and salty water below the New Jersey shelf.
EISSN: 1553-040X

insu-00858241
https://hal-insu.archives-ouvertes.fr/insu-00858241
DOI : 10.1130/GES00855.1

Éditeur(s) : HAL CCSD Springer Verlag
Résumé : International audience
Selected high-resolution seismic-reflection profiles and multibeam bathymetry acquired along the convergent Ecuador margin during the ATACAMES cruise on onboard the R/V L’Atalante (Jan.15–Feb.18, 2012) allow a preliminary evaluation of the neotectonic development and stratigraphic evolution of the margin based on the sismo-stratigraphic analysis of Quaternary sediment preserved on the margin shelf and upper slope. We present three major preliminary results. (1) The evolution of the Esmeraldas, Guayaquil and Santa Elena canyons. The head of the Esmeraldas canyon is the location of a continuous significant sediment transport. The Guayaquil canyon shows several episodes of deposition and incision. Aggrading sedimentation pattern in the canyon records several changes in relative sea-level. The subsidence of the Gulf of Guayaquil probably contributes to the good preservation of the canyon filling stages. The Santa Elena canyon is controlled by a SW–NE trending normal fault. (2) Variations of sediment accumulation and relative vertical motions are shown along-strike the shelf edge. Offshore the uplifted Manta peninsula, a pronounced subsidence of the shelf edge is documented by sedimentary clinoforms that have deposited in a morphological reentrant, and have migrated upslope testifying of a local subsidence meanwhile the adjacent La Plata Island area underwent uplift. In the Esmeraldas canyon area, a local uplift of the shelf is documented. (3) Two neotectonic fault systems with a possible transcurrent component are imaged across the shelf edge and upper margin slope offshore Jama, and Cape Galera. This possible transcurrent motion could be related to the reactivation of ancient faults of the upper plate by the subduction. These preliminary results indicate that the ATACAMES data set has a strong potential to evaluate the spatial and temporal contribution of tectonic and climate changes on the structural development and stratigraphic evolution of the Ecuador continental margin.
ISSN: 0025-3235

insu-01131151
https://hal-insu.archives-ouvertes.fr/insu-01131151
DOI : 10.1007/s11001-014-9231-y

Éditeur(s) : HAL CCSD American Chemical Society
Résumé : International audience
Four bicyclic and three pentacyclic guanidine alkaloids (1–7) were isolated from a French Polynesian Monanchora n. sp. sponge, along with the known alkaloids monalidine A (8), enantiomers 9–11 of known natural product crambescins, and the known crambescidins 12–15. Structures were assigned by spectroscopic data interpretation. The relative and absolute configurations of the alkaloids were established by analysis of 1H NMR and NOESY spectra and by circular dichroism analysis. The new norcrambescidic acid (7) corresponds to interesting biosynthetic variation within the pentacyclic core. All compounds exhibited antiproliferative and cytotoxic efficacy against KB, HCT116, HL60, MRC5, and B16F10 cancer cells, with IC50 values ranging from 4 nM to 10 μM.
ISSN: 0163-3864

hal-01584556
https://hal.archives-ouvertes.fr/hal-01584556
DOI : 10.1021/acs.jnatprod.6b00168

Éditeur(s) : HAL CCSD IEEE
Résumé : International audience
This paper proposes a novel automated approach for the categorization of cells in fluorescence microscopy images. Our supervised classification method aims at recognizing patterns of unlabeled cells based on an annotated dataset. First, the cell images need to be indexed by encoding them in a feature space. For this purpose, we propose tailored bio-inspired features relying on the distribution of contrast information. Then, a supervised learning algorithm is proposed for classifying the cells. We carried out experiments on cellular images related to the diagnosis of autoimmune diseases, testing our classification method on the HEp-2 Cells dataset of Foggia et al (CBMS 2010). Results show classification precision larger than 96% on average, thus confirming promising application of our approach to the challenging application of cellular image classification for computer-aided diagnosis.
ICPR 2012
Tsukuba, Japan

hal-00958856
https://hal.archives-ouvertes.fr/hal-00958856
https://hal.archives-ouvertes.fr/hal-00958856/document
https://hal.archives-ouvertes.fr/hal-00958856/file/icpr_2012.pdf

Éditeur(s) : HAL CCSD Wiley
Résumé : International audience
Projections of climate change impacts on coral reefs produced at the coarse resolution (~1°) of Global Climate Models (GCMs) have informed debate but have not helped target local management actions. Here, projections of the onset of annual coral bleaching conditions in the Caribbean under Representative Concentration Pathway (RCP) 8.5 are produced using an ensemble of 33 Coupled Model Intercomparison Project phase-5 models and via dynamical and statistical downscaling. A high-resolution (~11 km) regional ocean model (MOM4.1) is used for the dynamical downscaling. For statistical downscaling, sea surface temperature (SST) means and annual cycles in all the GCMs are replaced with observed data from the ~4-km NOAA Pathfinder SST dataset. Spatial patterns in all three projections are broadly similar ; the average year for the onset of annual severe bleaching is 2040–2043 for all projections. However, downscaled projections show many locations where the onset of annual severe bleaching (ASB) varies 10 or more years within a single GCM grid cell. Managers in locations where this applies (e.g., Florida, Turks and Caicos, Puerto Rico, and the Domini-can Republic, among others) can identify locations that represent relative albeit temporary refugia. Both downscaled projections are different for the Bahamas compared to the GCM projections. The dynamically downscaled projections suggest an earlier onset of ASB linked to projected changes in regional currents, a feature not resolved in GCMs. This result demonstrates the value of dynamical downscaling for this application and means statistically downscaled projections have to be interpreted with caution. However, aside from west of Andros Island, the projections for the two types of downscaling are mostly aligned; projected onset of ASB is within AE10 years for 72% of the reef locations.
ISSN: 1354-1013

Droits : http://creativecommons.org/licenses/by-nc/
hal-01223492
https://hal-univ-perp.archives-ouvertes.fr/hal-01223492
https://hal-univ-perp.archives-ouvertes.fr/hal-01223492/document
https://hal-univ-perp.archives-ouvertes.fr/hal-01223492/file/Hooidonk_et_al-2015-Global_Change_Biology.pdf
DOI : 10.1111/gcb.12901

Éditeur(s) : HAL CCSD
Résumé : International audience
ISSN: 0974875X

hal-01313378
https://hal.archives-ouvertes.fr/hal-01313378

Éditeur(s) : HAL CCSD Institute of Electrical and Electronics Engineers
Résumé : International audience
Tailoring nearest neighbors algorithms to boosting is an important problem. Recent papers study an approach, UNN, which provably minimizes particular convex surrogates under weak assumptions. However, numerical issues make it necessary to experimentally tweak parts of the UNN algorithm, at the possible expense of the algorithm's convergence and performance. In this paper, we propose a lightweight alternative algorithm optimizing proper scoring rules from a very broad set, and establish formal convergence rates under the boosting framework that surprisingly compete with those known for UNN. It is an adaptive Newton-Raphson algorithm, which belongs to the same lineage as the popular Gentle Adaboost. To the best of our knowledge, no such boosting-compliant convergence rates were previously known for these algorithms. We provide experiments on a dozen domains, including the challenging Caltech and SUN computer vision databases. They display that GNNB significantly outperforms UNN, both in terms of convergence rate and quality of the solution obtained, and GNNB provides a simple and efficient contender to techniques that can be used on very large domains, like stochastic gradient descent -- for which little is known to date. Experiments include a divide-and-conquer improvement of GNNB which exploits the link with proper scoring rules optimization.
ISSN: 0162-8828

hal-00958809
https://hal.archives-ouvertes.fr/hal-00958809
https://hal.archives-ouvertes.fr/hal-00958809/document
https://hal.archives-ouvertes.fr/hal-00958809/file/PAMI.pdf
DOI : 10.1109/TPAMI.2014.2307877

Éditeur(s) : HAL CCSD
Résumé : International audience
It is an admitted fact that mainstream boosting algorithms like AdaBoost do not perform well to estimate class conditional probabilities. In this paper, we analyze, in the light of this problem, a recent algorithm, unn, which leverages nearest neighbors while minimizing a convex loss. Our contribution is threefold. First, we show that there exists a subclass of surrogate losses, elsewhere called balanced, whose minimization brings simple and statistically efficient estimators for Bayes posteriors. Second, we show explicit convergence rates towards these estimators for unn, for any such surrogate loss, under a Weak Learning Assumption which parallels that of classical boosting results. Third and last, we provide experiments and comparisons on synthetic and real datasets, including the challenging SUN computer vision database. Results clearly display that boosting nearest neighbors may provide highly accurate estimators, sometimes more than a hundred times more accurate than those of other contenders like support vector machines.
European Conference on Machine Learning and Principles and Practice of Knowledge Discovery in Databases (ECML PKDD)
Bristol, United Kingdom

hal-00702771
https://hal.archives-ouvertes.fr/hal-00702771
https://hal.archives-ouvertes.fr/hal-00702771/document
https://hal.archives-ouvertes.fr/hal-00702771/file/ecml12-dnbnb-sub.pdf

Éditeur(s) : HAL CCSD National Academy of Sciences
Résumé : International audience
Natal philopatry, the return of individuals to their natal area for reproduction, has advantages and disadvantages for animal populations. Natal philopatry may generate local genetic adaptation, but it may also increase the probability of inbreeding that can compromise persistence. Although natal philopatry is well documented in anadromous fishes, marine fish may also return to their birth site to spawn. How philopatry shapes wild fish populations is, however, unclear because it requires constructing multigenerational pedigrees that are currently lacking for marine fishes. Here we present the first multigenerational pedigree for a marine fish population by repeatedly genotyping all individuals in a population of the orange clownfish (Amphiprion percula) at Kimbe Island (Papua New Guinea) during a 10-y period. Based on 2927 individuals, our pedigree analysis revealed that longitudinal philopatry was recurrent over five generations. Progeny tended to settle close to their parents, with related individuals often sharing the same colony. However, successful inbreeding was rare, and genetic diversity remained high, suggesting occasional inbreeding does not impair local population persistence. Local reproductive success was dependent on the habitat larvae settled into, rather than the habitat they came from. Our study suggests that longitudinal philopatry can influence both population replenishment and local adaptation of marine fishes. Resolving multigenerational pedigrees during a relatively short period, as we present here, provides a framework for assessing the ability of marine populations to persist and adapt to accelerating climate change.
ISSN: 0027-8424

hal-01417471
https://hal-univ-perp.archives-ouvertes.fr/hal-01417471
DOI : 10.1073/pnas.1611797113

Éditeur(s) : HAL CCSD Publisher : Baltimore : Williams & Wilkins, c1950-. Latest Publisher : Bethesda, MD : American Association of Immunologists
Résumé : International audience
Schistosome infection is a major public health concern affecting millions of people living in tropical regions of Africa, Asia, and South America. Schistosomes cause mild clinical symptoms in most subjects, whereas a small proportion of individuals presents severe clinical disease (as periportal fibrosis (PPF)) that may lead to death. Severe PPF results from an abnormal deposition of extracellular matrix proteins in the periportal spaces due to a chronic inflammation triggered by eggs and schistosome Ags. Extracellular matrix protein production is regulated by a number of cytokines, including IFN-gamma. We have now screened putative polymorphic sites within this gene in a population living in an endemic area for Schistosoma mansoni. Two polymorphisms located in the third intron of the IFN-gamma gene are associated with PPF. The IFN-gamma +2109 A/G polymorphism is associated with a higher risk for developing PPF, whereas the IFN-gamma +3810 G/A polymorphism is associated with less PPF. The polymorphisms result in changes in nuclear protein interactions with the intronic regions of the gene, suggesting that they may modify IFN-gamma mRNA expression. These results are consistent with the results of previous studies. Indeed, PPF is controlled by a major locus located on chromosome 6q22-q23, closely linked to the gene encoding the alpha-chain of the IFN-gamma receptor, and low IFN-gamma producers have been shown to have an increased risk of severe PPF. Together, these observations support the view that IFN-gamma expression and subsequent signal transduction play a critical role in the control of PPF in human hepatic schistosome infection (S. mansoni).
ISSN: 0022-1767

Droits : http://creativecommons.org/licenses/by-nc-nd/
hal-01211760
https://hal.archives-ouvertes.fr/hal-01211760
https://hal.archives-ouvertes.fr/hal-01211760/document
https://hal.archives-ouvertes.fr/hal-01211760/file/J%20Immunol-2003-Chevillard-5596-601.pdf
DOI : 10.4049/jimmunol.171.10.5596

Éditeur(s) : HAL CCSD Pôle de Recherche pour l'Organisation et la diffusion de l'Information Géographique
Résumé : International audience
The Amazon has recently experienced a dramatic decline in deforestation coupled with economic development. However, this process is uneven. While large and medium-sized producers are intensifying and diversifying their production systems in the already cleared areas, thus apparently abandoning expansion strategies at the moment, family farming remains aloof from this decoupling between production and deforestation. In this article, the commitments of public authorities and sectors, their effects on deforestation and inequalities of adaptation are analyzed at the scale of the Legal Amazon and in a municipality considered as a model because involved in a Município Verde initiative: Paragominas, in the Eastern Amazon.
L’Amazonie a amorcé depuis quelques années une baisse de la déforestation couplée à un développement économique. Le processus est cependant inégal. Si les grands et moyens producteurs font évoluer leurs systèmes de production vers l’intensification et la diversification dans les espaces déjà ouverts, délaissant en apparence les stratégies d’expansion, l’agriculture familiale reste à l’écart du découplage entre production et déforestation. Dans cet article, les engagements des pouvoirs publics et des filières, leurs effets en matière de déforestation et les inégalités d’adaptation sont analysés à l’échelle de l’Amazonie Légale et à celle d’une municipalité considérée comme un modèle car à l’initiative d’une démarche de Município Verde : Paragominas, en Amazonie orientale.
ISSN: 1963-1197

halshs-01609039
https://halshs.archives-ouvertes.fr/halshs-01609039
DOI : 10.4000/echogeo.15035

Éditeur(s) : HAL CCSD
Résumé : National audience
Le standard d’eau de rivière naturelle SLRS-5 (NRC-CNRC) est uneréférence de contrôle qualité en analyse d’eau de routine pour la communautéinternationale. Dix laboratoires français étudiant les élémentsmajeurs et en trace dans les solutions naturelles (groupe de travail del’atelier du CNRS « Isotrace ») valident leurs mesures avec les 19 élémentscertifiés par le producteur. Or, d’autres éléments non certifiés sontrégulièrement analysés par ces laboratoires qui ont comparé et compilé2 années de leurs mesures sur ce standard d’eau. La plupart desmesures sont réalisées par ICP-MS (Inductively Coupled Plasma Mass-Spectrometry).Dans un premier temps, il a été vérifié que les résultats obtenus étaientcohérents pour les éléments certifiés par le producteur. Ainsi Ba présenteune valeur compilée de 14,2 1,4 g/l (330 mesures issues de 9laboratoires participants) en accord avec la valeur certifiée de 14 0,5g/l.Ensuite, des valeurs moyennes et leurs incertitudes associées sont proposéespour des éléments non certifiés par NRC-CNRC tels que le siliciumet 35 éléments en trace (terres rares, Ag, B, Bi, Cs, Ga, Ge, Li, Nb,P, Rb, Rh, Re, S, Sc, Sn, Th, Ti, Tl,W, Y et Zr). Le rapport isotopique deSr est aussi proposé à partir de mesures par TIMS (Thermo IonisationMass Spectrometry).Il apparaît que les mesures individuelles et compilées varient dequelques ng/l à 2400 g/l avec des incertitudes associées comprisesentre 2 et 240%. Les fortes incertitudes associées ne sont pas proportionnellesaux concentrations puisque certaines mesures s’accordent mêmeà de faibles teneurs tels que Bi (0,9 0,3 ng/l valeur compilée). Danscertains cas, un ou deux laboratoires ont caractérisé l’élément impliquantmoins de mesures et une incertitude associée plus élevée quelleque soit la concentration en l’élément. C’est le cas, par exemple, de Ge(0,015 0,014 g/l valeur compilée) caracterisé par seulement 2 laboratoires(34 mesures) et de P (8,19 3,40 g/l) issu de 8 mesuresd’un seul laboratoire. Les terres rares et onze autres éléments (B, Bi,Cs, Li, Rb, Si, Th, Ti, Tl, Y et Zr) ont été déterminés par au moins 3laboratoires différents et apportent des informations complémentairesessentielles à l’utilisation
24 ème Réunion des sciences de la Terre 2014
Pau, France

insu-01080879
https://hal-insu.archives-ouvertes.fr/insu-01080879

Éditeur(s) : HAL CCSD Springer
Résumé : Third International Workshop, MLMI 2012, Held in Conjunction with MICCAI 2012
International audience
Universal Nearest Neighbours (unn) is a classifier recently proposed, which can also effectively estimates the posterior probability of each classification act. This algorithm, intrinsically binary, requires the use of a decomposition method to cope with multiclass problems, thus reducing their complexity in less complex binary subtasks. Then, a reconstruction rule provides the final classification. In this paper we show that the application of unn algorithm in conjunction with a reconstruction rule based on the posterior probabilities provides a classification scheme robust among different biomedical image datasets. To this aim, we compare unn performance with those achieved by Support Vector Machine with two different kernels and by a k Nearest Neighbours classifier, and applying two different reconstruction rules for each of the aforementioned classification paradigms. The results on one private and five public biomedical datasets show satisfactory performance.
Machine Learning in Medical Imaging
Nice, France

hal-00958909
https://hal.archives-ouvertes.fr/hal-00958909
https://hal.archives-ouvertes.fr/hal-00958909/document
https://hal.archives-ouvertes.fr/hal-00958909/file/Miccai.pdf
DOI : 10.1007/978-3-642-35428-1_15

Éditeur(s) : HAL CCSD
Résumé : International audience
ICPRAM
Rome, Italy

hal-01313380
https://hal.archives-ouvertes.fr/hal-01313380

Éditeur(s) : HAL CCSD Elsevier Elsevier Masson
Résumé : New field and micropalaeontological investigations have been conducted in four of the Pliocene rias of the internal zone of the Rif in Morocco, on the southern margin of the Alboran Sea. We found that marine sediments outcropping in these rias were deposited mainly during the Early Zanclean, between 5.04 and 3.8 Ma. After a transgressive episode that led to the deposition of terrestrial to marine conglomerates, dark clays deposited first at shallow palaeo-depths and then at bathyal palaeo-depths. The rias were then infilled with a shallowing upward succession comprising marine clays and sandstone and, locally, terrestrial sediments that indicate their final emersion. No Gilbert-deltas were observed in these rias. The presence of transgressive deposits at the bottom of the rias, also identified in other basins of the external zone of the Rif, and the absence of Gilbert deltas question a catastrophic reflooding after the Messinian Salinity Crisis in this area.
ISSN: 1631-0713

hal-01115243
https://hal.archives-ouvertes.fr/hal-01115243
DOI : 10.1016/j.crte.2014.03.002

Éditeur(s) : HAL CCSD Centers for Disease Control and Prevention
Résumé : International audience
To assess the prevalence of malaria among illegal gold miners in the French Guiana rainforest, we screened 205 miners during May-June 2014. Malaria prevalence was 48.3%; 48.5% of cases were asymptomatic. Patients reported self-medication with artemisinin-based combination therapy. Risk for emergence and spread of artemisinin resistance among gold miners in the rainforest is high.
ISSN: 1080-6040

Droits : http://creativecommons.org/licenses/by/
pasteur-01305106
https://hal-pasteur.archives-ouvertes.fr/pasteur-01305106
https://hal-pasteur.archives-ouvertes.fr/pasteur-01305106/document
https://hal-pasteur.archives-ouvertes.fr/pasteur-01305106/file/15-1957.pdf
DOI : 10.3201/eid2205.151957.

Éditeur(s) : HAL CCSD Public Library of Science
Résumé : International audience
Growth charts are an essential clinical tool for evaluating a child's health and development. The current French reference curves, published in 1979, have recently been challenged by the 2006 World Health Organization (WHO) growth charts. To evaluate and compare the growth of French children who were born between 1981 and 2007, with the WHO growth charts and the French reference curves currently used. Anthropometric measurements from French children, who participated in 12 studies, were analyzed: 82,151 measurements were available for 27,257 children in different age groups, from birth to 18 years. We calculated and graphically compared mean z-scores based on the WHO and French curves, for height, weight and Body Mass Index (BMI) according to age and sex. The prevalence of overweight using the WHO, the French and International Obesity Task Force definitions were compared. Our population of children was on average 0.5 standard deviations taller than the French reference population, from the first month of life until puberty age. Mean z-scores for height, weight and BMI were closer to zero based on the WHO growth charts than on the French references from infancy until late adolescence, except during the first six months. These differences not related to breastfeeding rates. As expected, the prevalence of overweight depended on the reference used, and differences varied according to age. The WHO growth charts may be appropriate for monitoring growth of French children, as the growth patterns in our large population of French children were closer to the WHO growth charts than to the French reference curves, from 6 months onwards. However, there were some limitations in the use of these WHO growth charts, and further investigation is needed.
ISSN: 1932-6203

hal-01134193
https://hal-univ-rennes1.archives-ouvertes.fr/hal-01134193
DOI : 10.1371/journal.pone.0120806
PUBMED : 25761138
PUBMEDCENTRAL : PMC4356547

Éditeur(s) : HAL CCSD
Résumé : International audience
Conférence MISTRALS PAELOMEX
Montpellier, France

hal-01683547
https://hal-univ-tlse2.archives-ouvertes.fr/hal-01683547

Éditeur(s) : HAL CCSD
Résumé : International audience
The challenge is to implement research that can estimate the consequences ofclimate changes in terms of impact on terrestrial environments and resources.Emphasis should be placed on regions dependent on natural resources and forwhich demographic pressure is strong. Simulations obtained from climate modelprojections (using different Representative Concentration Pathways (RCPs))predict that the Mediterranean basin and its southern periphery are particularlyvulnerable to water resources and environmental impact (IPCC, AR5, 2013).An annual rainfall decrease by 30% is found for the projection period 2070-2099(IPCC, AR5, 2013) associated with a decrease in water resources by 30 to 50%(Milano, 2012). In addition, several studies using regional atmospheric modelsindicate an increase in the precipitation inter-annual variability with extremeevents and a spatial heterogeneous signature, superimposed on a decrease in thetotal precipitation amount (Giorgi and Lionello, 2008; Raible et al. 2010).Currently, regional climate projections are highly sensitive to the climate modelused. In particular, spatial resolution as well as local climate conditions seemto impact significantly on the simulations (Jacob et al. 2014).The Mediterranean region, at the interface between arid and temperate climateswith several mountainous areas, is a complex climate system affected by theinteractions between mid-latitude and sub-tropical processes. In this context,Morocco, located at the transition between a temperate climate to the North anda tropical climate to the south constitutes a key area for an impact and sensitivitystudy to global climate changes. The climate is influenced by the Atlantic Ocean,the Mediterranean Sea and the Sahara, together with a very steep orography inthe Atlas region. The precipitation distribution is therefore characterised by greatspatial variability, and exhibits a marked seasonality, a strong inter-annualvariability (Ouda et al. 2005) and in general a pronounced gradient from northto south and west to east. At a broader scale, Morocco is located on the subtropicalsubsidence path and between the Acores High and the Saharan Low (Agoussine,2003). Several studies have also identified strong links with inter-annualprecipitation variability and NAO index (Knippertz, 2003) as well as remoteclimate modes (Esper et al. 2007).Continental climate variability at a local/regional scale, if it is to be integratedin climate predictions, needs to be supported by long-term observation.Meteorological stations in Morocco provide climatic data mainly for the last40 years with only a few stations located in the mountainous region (Tramblayet al. 2012; 2013; Driouech et al. 2010). This climate database is also supportedby the IAEA network providing stations for which isotope tracers have beenapplied to daily/monthly rain and water vapour samples over 2 to 3 years between2000 and 2004. Besides the poor coverage of instrumented areas, lacustrinesystems can provide a climatic data set that offers access to short and long-termtime series of climate parameters when knowledge of modern lake water balanceis combined with lacustrine sedimentary-climate records. Lake sediment recordsideally provide high resolution climate/environmental information of the last10,000 years (Magny et al. 2013). This time interval (corresponding to theHolocene) is a key period to investigate short and long-term climate variabilityand to improve prediction in a warming climate.In this study we present an integrated approach focusing on a mountainous lake(Aguelmam Azigza). The modern lake system study is based on site monitoring(2012-2016) and available regional hydro-climatic data. These data show thatlake level changes during the instrumented period were mainly driven byprecipitation following the high inter-annual variability. These data are thencompared with accurately dated short sediment cores retrieved in the same lake.Micro-scale geochemical and sedimentological analyses of these sequencesenable us to identify various sedimentary facies that can be linked with periodsof high (low) lake levels over the past decades.
The Mediterranean Region under Climate ChangeLa méditerranée face au changement climatique

insu-01394690
https://hal-insu.archives-ouvertes.fr/insu-01394690
https://hal-insu.archives-ouvertes.fr/insu-01394690/document
https://hal-insu.archives-ouvertes.fr/insu-01394690/file/Vidaletal.2016-COP22-Chap1.pdf