Éditeur(s) : Amer Meteorological Soc
Résumé : Salinity measurements from 119 surface drifters in 2007-12 were assessed; 80% [Surface Velocity Program with a barometer with a salinity sensor (SVP-BS)] and 75% [SVP with salinity (SVP-S)] of the salinity data were found to be usable, after editing out some spikes. Sudden salinity jumps are found in drifter salinity records that are not always associated with temperature jumps, in particular in the wet tropics. A method is proposed to decide whether and how to correct those jumps, and the uncertainty in the correction applied. Northeast of South America, in a region influenced by the Amazon plume and fresh coastal water, drifter salinity is very variable, but a comparison with data from the Soil Moisture and Ocean Salinity satellite suggests that this variability is usually reasonable. The drifter salinity accuracy is then explored based on comparisons with data from Argo floats and from thermosalinographs (TSGs) of ships of opportunity. SVP-S/SVP-BS drifter records do not usually present significant biases within the first 6 months, but afterward biases sometimes need to be corrected (altogether, 16% of the SVP-BS records). Biases start earlier after 3 months for drifters not protected by antifouling paint. For the few drifters for which large corrections were applied to portions of the record, the accuracy cannot be proven to be better than 0.1 psu, and it cannot be proven to be better than 0.5 psu for data in the largest variability area off northeast South America. Elsewhere, after excluding portions of the records with suspicious salinity jumps or when large corrections were applied, the comparisons rule out average biases in individual drifter salinity record larger than 0.02 psu (midlatitudes) and 0.05 psu (tropics).
Journal Of Atmospheric And Oceanic Technology (0739-0572) (Amer Meteorological Soc), 2014-04 , Vol. 31 , N. 4 , P. 967-983

Droits : 2014 American Meteorological Society
http://archimer.ifremer.fr/doc/00190/30095/28748.pdf
DOI:10.1175/JTECH-D-13-00158.1
http://archimer.ifremer.fr/doc/00190/30095/

Éditeur(s) : Elsevier
Résumé : In biological modelling of the coastal phytoplankton dynamics, the light attenuation coefficient is often expressed as a function of the concentrations of chlorophyll and mineral suspended particulate matter (SPM). In order to estimate the relationship between these parameters over the continental shelf of the northern Bay of Biscay, a set of in situ data has been gathered for the period 1998-2003 when SeaWiFS imagery is available. These data comprise surface measurements of the concentrations of total SPM, chlorophyll, and irradiance profiles from which is derived the attenuation coefficient of the photosynthetically available radiation, K-PAR. The performance of the IFREMER look-up table used to retrieve the chlorophyll concentration from the SeaWiFS radiance is evaluated on this new set of data. The quality of the estimated chlorophyll concentration is assessed from a comparison of the variograms of the in situ and satellite-derived chlorophyll concentrations. Once the chlorophyll concentration is determined, the non living SPM, which is defined as the SPM not related to the dead or alive endogenous phytoplankton, is estimated from the radiance at 555 nm by inverting a semi-analytic model. This method provides realistic estimations of concentrations of chlorophyll and SPM over the continental shelf all over the year. Finally, a relationship, based on non living SPM and chlorophyll, is proposed to estimate K-PAR on the continental shelf of the Bay of Biscay. The same formula is applied to non living SPM and chlorophyll concentrations, observed in situ or derived from SeaWiFS radiance.
Remote Sensing of Environment (0034-4257) (Elsevier), 2005-03 , Vol. 95 , N. 1 , P. 29-46

Droits : 2004 Elsevier Inc. All rights reserved
http://archimer.ifremer.fr/doc/2005/publication-1172.pdf
DOI:10.1016/j.rse.2004.11.007
http://archimer.ifremer.fr/doc/00000/1172/

Résumé : Notre étude s’est proposée d’analyser l’incidence du paludisme et son évolution dans le temps et dans l’espace, ainsi que de rechercher les facteurs de risque d’accès palustres chez les enfants d’un village du Moyen-Oyapock (Camopi), peuplé d’Amérindiens wayampi et émerillon, d’une part, et d’un village du Haut-Maroni (Antecume Pata), peuplé d’Amérindiens wayana, d’autre part. L’approche a été multiple avec, pour chacun des deux sites d’étude :- Une analyse de survie (modèle de Cox) à partir des accès palustres confirmés biologiquement dans une cohorte d’enfants de moins de sept ans régulièrement suivis, ainsi qu’un questionnaire de type Connaissances, Attitudes et Pratiques (CAP), puis les caractéristiques des habitats et la description de leur environnement immédiat.- Une analyse spatiale avec une classification de l’occupation du sol à partir d’images satellites SPOT 5, l’extraction de variables environnementales d’intérêt, l’étude de leur effet sur la transmission du paludisme et la mise au point d’une méthode objective de sélection d’un rayon d’observation autour des habitations pour la caractérisation de l’environnement.- Une étude de séries temporelles (ARIMA) afin de déterminer l’effet des évènements climatiques et hydrologiques sur le paludisme, aux niveaux local et plus global (El Niño).Les taux d’incidence d’accès palustres sur la période 2001-2009 se sont révélés particulièrement élevés chez les jeunes enfants, notamment à Camopi avec une moyenne de 773‰ par année. Une diminution brutale de l’incidence a eue lieu en 2007 sur le Haut-Maroni et ce phénomène est observé à Camopi depuis 2010. Une prémunition se développe assez rapidement au cours de la vie (2-3 ans), surtout contre les reviviscences à Plasmodium vivax. Les facteurs environnementaux se sont avérés être les plus nombreux et les plus fortement liés à l’incidence palustre. En effet, le dégagement des alentours du carbet de toute végétation et une certaine distance de celui-ci à la forêt sont des facteurs protecteurs. La composante géographique est également apparue essentielle à Camopi avec une incidence qui variait selon le fleuve d’habitation et en fonction de la distance au hameau principal. Les facteurs météorologiques locaux (température et niveau du fleuve) se sont également révélés être liés à l’incidence du paludisme à court terme (0-3 mois). Par ailleurs, nos résultats ont permis d’émettre un certain nombre d’hypothèses quant à la transmission et au(x) vecteur(s) local(ux), et notamment de suggérer la participation d’un vecteur autre qu’An. darlingi dans la transmission du paludisme à Camopi. Nous avons également prouvé par ce travail que la télédétection et les systèmes d’information géographique sont très prometteurs pour la prise en compte de la dimension spatiale et environnementale dans l’étude des maladies transmissibles, notamment dans les zones d’accès difficile de Guyane.
The aim of our study was to analyze the incidence of malaria in children and its evolution through time and space, as well as to search for risk factors in a village in Mid-Oyapock (Camopi), populated by Amerindians Wayampi and Emerillon, on the one hand, and a village in Upper-Maroni (Antecume Pata), populated by Amerindians Wayana, on the other hand. The approach was multiple with, for both study sites:- A survival analysis (Cox modelling) completed out of biologically confirmed malaria attacks in a cohort of children under seven, as well as a Knowledge, Attitudes, Practices and Behavior (KAPB) questionnaire, and also the characteristics of the houses and the description of their immediate environment.- A spatial analysis with a land cover classification from SPOT 5 satellite images, the extraction of environmental variables, the study of their effect on malaria transmission and the development of an objective method for picking the proper observation horizon around houses in order to characterize the environment.- A time series study (ARIMA) to determine the effect of climatic and hydrological events on malaria at local and global (El Niño) scales.The incidence rates of malaria attacks during the period 2001-2009 were particularly high among young children, especially in Camopi with an average of 773‰ by year. A sharp decline in incidence occurred in 2007 on the Upper Maroni and this phenomenon has been observed in Camopi since 2010. An acquired immunity develops quite rapidly during the life (2-3 years old), especially against P. vivax relapses. Environmental factors were found to be the most strongly associated with malaria incidence. Indeed, living in a hut cleared from the surrounding vegetation and at a larger distance from the forest are protective factors. The geographic component also appeared essential in Camopi with an incidence which varied with the river of living and with the distance from the main hamlet. The local meteorological factors (temperature and river level) also proved to be linked to malaria incidence in the short term (0-3 months). Moreover, our results have allowed issuing a number of assumptions about the transmission and the local vector(s), in particular to suggest the involvement of another vector than An. darlingi in the malaria transmission in Camopi. We also proved by this work that remote sensing and geographic information systems hold great promise for the inclusion of the spatial and environmental dimensions in the study of transmitted diseases, especially in areas of difficult access in French Guiana.

http://www.theses.fr/2011AGUY0448/document

Éditeur(s) : HAL CCSD Oxford University Press (OUP): Policy P - Oxford Open Option A Oxford University Press (OUP)
Résumé : International audience
While the kinematics of Anatolia plate and the North Anatolian Fault System (NAFS) has been studied extensively, the slip rate and locking depth along the NAFS are usually assumed constant in the analyses due to the lack of sufficient data. This is also partly due to the reasonably good fit of Euler small circle and partly due to the lack of spatial resolution of observations to determine slip rates independently from locking depths. On the other hand, recent geodetic studies show a contrast for locking depth between Marmara and other parts of the NAFS, implying a non-uniform locking depth across the NAFS. In this study, we analyse new GPS data and homogenously combine available data sets covering the eastern part of the NAFS to form the most complete data set. In particular, we incorporate the first results of Turkish Real-Time Kinematic GPS Network (CORS-TR) into our data set. A detailed analysis of three profiles within the NAFS reveals an increase of locking depth in the middle profile to 19.1 ± 3.4 km from 11.9 ± 3.5 km in the easternmost profile while the slip rate is nearly constant (20–22 mm yr−1), which implies a variation of strain rate of ∼100 nanostrain yr−1. Assuming a constant locking depth throughout whole NAFS gives an average locking depth of 14.3 ± 1.7 km. Our best estimates of slip rates in block modelling which takes the variation of locking depths into account are in the range between 22.5 and 22.8 mm yr−1 over eastern part of the NAFS.
ISSN: 0956-540X

hal-01218392
https://hal.archives-ouvertes.fr/hal-01218392
DOI : 10.1093/gji/ggv274

Éditeur(s) : Inter-Research
Résumé : Macrobrachium rosenbergii nodavirus (MrNV) and extra small virus (XSV) were purified from diseased freshwater prawns M rosenbergii and used to infect healthy post-larvae (PL) by an immersion method. Three groups of prawns were challenged with various combined doses of MrNV and XSV. Signs of white-tail disease (WTD) were observed in Groups 1 and 2, which had been challenged with combinations containing relatively high proportions of MrNV and low proportions of XSV. By contrast there was little sign of WTD in Group 3, which had been challenged with a higher proportion of XSV than MrNV. A 2-step Taqman real-time RT-PCR was developed and applied to quantify viral copy numbers in each challenged PL. Results showed that genomic copies of both viruses were much higher in Groups 1 and 2 than they were in Group 3, indicating that MrNV plays a key role in WTD of M rosenbergii. The linear correlation between MrNV and XSV genome copies in infected prawns demonstrated that XSV is a satellite virus, dependent on MrNV, but its role in pathogenicity of WTD remains unclear.
Diseases of aquatic organisms (0177-5103) (Inter-Research), 2006-07 , Vol. 71 , N. 1 , P. 11-17

Droits : Inter-Research 2006
http://archimer.ifremer.fr/doc/2006/publication-3568.pdf
DOI:10.3354/dao071011
http://archimer.ifremer.fr/doc/00000/3568/

Éditeur(s) : Pergamon-elsevier Science Ltd
Résumé : The south-west lagoon of New Caledonia is a wide semi-open coral reef lagoon bounded by an intertidal barrier reef and bisected by numerous deep inlets. This paper synthesizes findings from the 2000-2008 French National Program EC2CO-PNEC relative to the circulation and the transport of suspended particles in this lagoon. Numerical model development (hydrodynamic, fine suspended sediment transport, wind-wave, small-scale atmospheric circulation) allowed the determination of circulation patterns in the lagoon and the charting of residence time, the later of which has been recently used in a series of ecological studies. Topical studies based on field measurements permitted the parameterisation of wave set-up induced by the swell breaking on the reef barrier and the validation of a wind-wave model in a fetch-limited environment. The analysis of spatial and temporal variability of suspended matter concentration over short and long time-scales, the measurement of grain size distribution and the density of suspended matter (1.27 kg 1(-1)), and the estimation of erodibility of heterogeneous (sand/mud, terrigenous/biogenic) soft bottoms was also conducted. Aggregates were shown to be more abundant near or around reefs and a possible biological influence on this aggregation is discussed. Optical measurements enabled the quantification of suspended matter either in situ (monochromatic measurements) or remotely (surface spectral measurements and satellite observations) and provided indirect calibration and validation of a suspended sediment transport model. The processes that warrant further investigation in order to improve our knowledge of circulation and suspended sediment transport in the New Caledonia lagoon as well as in other coral reef areas are discussed, as are the relevance and reliability of the numerical models for this endeavour.
Marine Pollution Bulletin (0025-326X) (Pergamon-elsevier Science Ltd), 2010 , Vol. 61 , N. 7-12 , P. 269-296

Droits : 2010 Elsevier Ltd All rights reserved.
http://archimer.ifremer.fr/doc/00014/12526/9401.pdf
DOI:10.1016/j.marpolbul.2010.06.023
http://archimer.ifremer.fr/doc/00014/12526/

Éditeur(s) : IEEE
Résumé : Soil Moisture and Ocean Salinity, European Space Agency, is the first satellite mission addressing the challenge of measuring sea surface salinity from space. It uses an L-band microwave interferometric radiometer with aperture synthesis (MIRAS) that generates brightness temperature images, from which both geophysical variables are computed. The retrieval of salinity requires very demanding performances of the instrument in terms of calibration and stability. This paper highlights the importance of ocean salinity for the Earth's water cycle and climate; provides a detailed description of the MIRAS instrument, its principles of operation, calibration, and image-reconstruction techniques; and presents the algorithmic approach implemented for the retrieval of salinity from MIRAS observations, as well as the expected accuracy of the obtained results.
Proceedings of the IEEE (0018-9219) (IEEE), 2010-05 , Vol. 98 , N. 5 , P. 649-665

Droits : 2010 IEEE – All Rights Reserved
http://archimer.ifremer.fr/doc/00004/11482/8066.pdf
DOI:10.1109/JPROC.2009.2033096
http://archimer.ifremer.fr/doc/00004/11482/

Éditeur(s) : HAL CCSD American Geophysical Union
Résumé : International audience
In Taiwan, about one third of the lithospheric plate convergence between Eurasia and the Philippine Sea plate is accommodated on the eastern coast across the narrow Longitudinal Valley (LV). The Longitudinal Valley Fault (LVF) is the main seismically active fault zone in this region. However, the spatial distribution of ground deformation due to interseismic loading on locked fault segments remains widely unknown. To address this problem, we use a "permanent scatterer" (PS) interferometric synthetic aperture radar (InSAR) approach for processing the ERS satellite archives. The PS mean velocity maps allow accurately mapping and quantifying the ground deformation all along the LV. Assuming that, close to the surface, the fault plane along the central LVF creeping segment dips 55 degrees to the east, we derive a slip vector at the surface of similar to 25 mm/yr with a mean rake of 70 degrees. In agreement with our PS observations, shallow seismicity indicates a clear change in the fault mechanical behavior of the creeping segment around Fuli town. Finally, we propose a combination of the PS velocity fields for estimating a 3-D map of ground deformation. In the southern part of the LV, the vertical component reveals an uplift of the Coastal Range with respect to the LV of similar to 10 mm/yr. Moreover, between Taitung and Luyeh, the vertical deformation is essentially accommodated along the Luyeh Strand. Finally, north of Rueisuei, the Coastal Range uniformly subsides at similar to 15 mm/yr relative to the western side of the LV. However, a local uplift pattern is detected around latitude 23 degrees 42'.
ISSN: 0148-0227

hal-00595532
https://hal.archives-ouvertes.fr/hal-00595532
DOI : 10.1029/2010JB007898

Éditeur(s) : Copernicus Gesellschaft Mbh
Résumé : The sea surface salinity (SSS) measured from space by the Soil Moisture and Ocean Salinity (SMOS) mission has recently been revisited by the European Space Agency first campaign reprocessing. We show that, with respect to the previous version, biases close to land and ice greatly decrease. The accuracy of SMOS SSS averaged over 10 days, 100 x 100 km(2) in the open ocean and estimated by comparison to ARGO (Array for Real-Time Geostrophic Oceanography) SSS is on the order of 0.3-0.4 in tropical and subtropical regions and 0.5 in a cold region. The averaged negative SSS bias (-0.1) observed in the tropical Pacific Ocean between 5 degrees N and 15 degrees N, relatively to other regions, is suppressed when SMOS observations concomitant with rain events, as detected from SSM/Is (Special Sensor Microwave Imager) rain rates, are removed from the SMOS-ARGO comparisons. The SMOS freshening is linearly correlated to SSM/Is rain rate with a slope estimated to -0.14 mm(-1) h, after correction for rain atmospheric contribution. This tendency is the signature of the temporal SSS variability between the time of SMOS and ARGO measurements linked to rain variability and of the vertical salinity stratification between the first centimeter of the sea surface layer sampled by SMOS and the 5 m depth sampled by ARGO. However, given that the whole set of collocations includes situations with ARGO measurements concomitant with rain events collocated with SMOS measurements under no rain, the mean -0.1 bias and the negative skewness of the statistical distribution of SMOS minus ARGO SSS difference are very likely the mean signature of the vertical salinity stratification. In the future, the analysis of ongoing in situ salinity measurements in the top 50 cm of the sea surface and of Aquarius satellite SSS are expected to provide complementary information about the sea surface salinity stratification.
Ocean Science (1812-0784) (Copernicus Gesellschaft Mbh), 2013 , Vol. 9 , N. 1 , P. 183-192

Droits : Author(s) 2013. CC Attribution 3.0 License.
http://archimer.ifremer.fr/doc/00139/25073/23161.pdf
DOI:10.5194/os-9-183-2013
http://archimer.ifremer.fr/doc/00139/25073/

Éditeur(s) : Taylor & Francis
Résumé : This study is an attempt to produce an assessment of the impact of shrimp aquaculture in the Mekong Delta (Viet Nam) on mangrove ecosystems. For this exercise we selected two sub-areas (Ca Mau and Tra Vinh provinces) encompassing a variety of land uses and ecological conditions. Twenty stations in Tra Vinh and 15 stations in Ca Mau have been surveyed several times from September 2000 to March 2002. Field investigations included mangrove soils studies, measurements of pH and salinity of the water, analysis of mangrove flora, and density and structure of the vegetation. Four Systeme Probatoire de l'Observation de la Terre (SPOT) scenes were used for the discrimination of mangrove types and for the delineation of landscape units. For the first time, five ecologically distinct landscape classes were identified and delineated. Their possible links with the farming and yields of high valued species of shrimps, especially the giant tiger shrimp (Penaeus monodon) destined for export markets, need further studies. Since 1965, about 30% of mangrove ecosystems have been lost in Ca Mau Province and more than 30% of present mangroves are replanted monospecific stands. To the best of our knowledge, this is the first study which demonstrates that, in spite of deep and ancient man interactions in the Mekong Delta, five ecologically distinct classes of land use can be defined. Satellite surveys confirm a clear distribution of landscape units with possible links with shrimp aquaculture potentialities.
International Journal of Remote Sensing (0143-1161) (Taylor & Francis), 2004-11 , Vol. 25 , N. 21 , P. 4795-4812

Droits : 2004 Taylor & Francis
http://archimer.ifremer.fr/doc/2004/publication-2303.pdf
DOI:10.1080/01431160412331270858
http://archimer.ifremer.fr/doc/00000/2303/