In situ and satellite observations of the eastward migration of the Western Alboran Sea Gyre     

M.M. Flexas  D. Gomis  S. Ruiz  A. Pascual  P. Len 《Progress in Oceanography》2006,70(2-4):486

During October 2003 an intensive oceanographic survey (BIOMEGA) was carried out in the Alboran Sea, coinciding with a migration event of the Western Alboran Sea Gyre (WAG). The observations gathered during that cruise constitute the first field evidence of a migrated stage of the WAG. In this work we present the main differences between the 3D hydrodynamic fields observed during BIOMEGA and those corresponding to a WAG located at its usual position. The migration of the gyre was followed by satellite (altimetry and sea surface temperature) imagery. The causes of the gyre migration are explored in terms of the quasi-geostrophic tendency equation, in particular of the dynamics governing scales larger than the Rossby radius of deformation. It is shown that the steady state gyre must be almost equivalent barotropic and that the key process to break down the stationarity would be a density advection at gyre scale. The mechanisms to explain the migration of the WAG proposed by previous authors are discussed in light of the explanation proposed in this work.  相似文献   

Trends,drivers and impacts of changes in swidden cultivation in tropical forest-agriculture frontiers: A global assessment     

Nathalie van Vliet  Ole Mertz  Andreas Heinimann  Tobias Langanke  Unai Pascual  Birgit Schmook  Cristina Adams  Dietrich Schmidt-Vogt  Peter Messerli  Stephen Leisz  Jean-Christophe Castella  Lars Jørgensen  Torben Birch-Thomsen  Cornelia Hett  Thilde Bech-Bruun  Amy Ickowitz  Kim Chi Vu  Kono Yasuyuki  Jefferson Fox  Christine Padoch  Alan D. Ziegler 《Global Environmental Change》2012,22(2):418-429

This meta-analysis of land-cover transformations of the past 10–15 years in tropical forest-agriculture frontiers world-wide shows that swidden agriculture decreases in landscapes with access to local, national and international markets that encourage cattle production and cash cropping, including biofuels. Conservation policies and practices also accelerate changes in swidden by restricting forest clearing and encouraging commercial agriculture. However, swidden remains important in many frontier areas where farmers have unequal or insecure access to investment and market opportunities, or where multi-functionality of land uses has been preserved as a strategy to adapt to current ecological, economic and political circumstances. In some areas swidden remains important simply because intensification is not a viable choice, for example when population densities and/or food market demands are low. The transformation of swidden landscapes into more intensive land uses has generally increased household incomes, but has also led to negative effects on the social and human capital of local communities to varying degrees. From an environmental perspective, the transition from swidden to other land uses often contributes to permanent deforestation, loss of biodiversity, increased weed pressure, declines in soil fertility, and accelerated soil erosion. Our prognosis is that, despite the global trend towards land use intensification, in many areas swidden will remain part of rural landscapes as the safety component of diversified systems, particularly in response to risks and uncertainties associated with more intensive land use systems.  相似文献   

Climate change and infectious diseases: Can we meet the needs for better prediction?     

Xavier Rodó  Mercedes Pascual  Francisco J. Doblas-Reyes  Alexander Gershunov  Dáithí A. Stone  Filippo Giorgi  Peter J. Hudson  James Kinter  Miquel-Àngel Rodríguez-Arias  Nils Ch. Stenseth  David Alonso  Javier García-Serrano  Andrew P. Dobson 《Climatic change》2013,118(3-4):625-640

The next generation of climate-driven, disease prediction models will most likely require a mechanistically based, dynamical framework that parameterizes key processes at a variety of locations. Over the next two decades, consensus climate predictions make it possible to produce forecasts for a number of important infectious diseases that are largely independent of the uncertainty of longer-term emissions scenarios. In particular, the role of climate in the modulation of seasonal disease transmission needs to be unravelled from the complex dynamics resulting from the interaction of transmission with herd immunity and intervention measures that depend upon previous burdens of infection. Progress is also needed to solve the mismatch between climate projections and disease projections at the scale of public health interventions. In the time horizon of seasons to years, early warning systems should benefit from current developments on multi-model ensemble climate prediction systems, particularly in areas where high skill levels of climate models coincide with regions where large epidemics take place. A better understanding of the role of climate extremes on infectious diseases is urgently needed.  相似文献   

Late Quaternary (Marine Isotope Stage 3 to Recent) sedimentary evolution of the Basque shelf (southern Bay of Biscay)     

Blanca Martínez‐García  Arantxa Bodego  Jone Mendicoa  Ana Pascual  Julio Rodríguez‐Lázaro 《Boreas: An International Journal of Quaternary Research》2014,43(4):973-988

Late Quaternary (MIS 3 to Recent) oceanographic evolution of the Basque shelf has been analysed for the first time based on the sedimentological analysis of three cores obtained from the middle and outer shelves. The cores are located in two interfluves separated by the San Sebastian canyon. The variability of the percentage of the planktonic foraminifera species Neogloboquadrina pachyderma sin. and of δ¹⁸O_bull allowed us to identify the influence of colder and warmer waters in the Basque shelf during the late Quaternary. From ～56 cal. ka BP to the end of the Last Glacial Maximum (19 cal. ka BP) the sedimentary record shows a decreasing trend in the mean grain size that correlates with the eustatic sea‐level fall. The last Deglaciation (19–11.5 cal. ka BP) is characterized by a sea‐level rise that produced an important hiatus in the western outer shelf. During the Holocene, the middle and outer shelves present different behaviours. From 11.5 to 6.7 cal. ka BP, in the outer shelf the sea‐level rise that started during the Deglaciation produced a hiatus, whereas in the middle shelf the sedimentary succession records the presence of warm to temperate waters. Between 6.7–4.9 cal. ka BP, the entrance of cold surface water‐masses that only affected the middle shelf has been identified, and temperate to warm waters occurred in the outer shelf. The cold surface water‐masses retreated during 4.9–4.3 cal. ka BP in the middle shelf. Finally, from 4.3 cal. ka BP to Recent, the middle shelf registers a hiatus due to sea‐level stabilization after a generalized transgression, synchronous to a decrease in the energy of the water‐masses in the outer shelf. In conclusion, the environmental changes detected in the Basque shelf are attributed to both regional and eustatic sea‐level changes.  相似文献   

Growth forms,dispersal strategies and taxonomic spectrum in a semi-arid shrubland in SE Spain     

T. Navarro  V. Pascual  C.L. Alados  B. Cabezudo 《Journal of Arid Environments》2009,73(1):103-112

We have identified the dispersal strategies of major growth forms in a semi-arid Mediterranean shrubland of Cabo de Gata Natural Park (SE Spain), testing (1) whether dispersal strategies and antitelechoric mechanisms vary among growth forms and families, and (2) whether dispersal traits that identify dispersal strategies can be used to predict different ways of plant survival in response to seasonal changes in their habitat. In the survey, the data of 17 dispersal traits were collected of 140 species and analysed using cluster analysis and nonlinear principal components analysis. For shrubs and forbs, low diaspore release height, spheroidal diaspores with a low mass and small size and a low to high diaspore number were associated with restricted spatial dispersal. In contrast, medium to high release height, relatively large and heavy diaspores varying in shape and a high diaspore number were associated with developed spatial dispersal (telechory). Telechory is higher in shrubs than in forbs and grasses, where atelechory/antitelechory predominate. Dispersal was synchronized mainly with the drought period (July and August) and the beginning of the rainy season (October–December). 68% of shrubs and 61.6% of forbs were anemochores, whereas zoochory (6% of shrubs) and ballistic species (8% of shrubs and 6.9% of forbs) were less common. Ombrohydrochory was well represented among forbs (27.3%) but rare among shrubs (4%). The main antitelechoric mechanisms were: bradyspory (30.7%), myxospermy (15.7%) and trypanocarpy (29.4%, only for grasses). Species with restricted spatial dispersal and antitelechoric mechanisms are well adapted to survival in semi-arid climatic conditions, and should be taken into consideration in conservation planning.  相似文献   

Frontal dynamics boost primary production in the summer stratified Mediterranean sea   总被引：1，自引：1，他引：0  

Antonio Olita  Arthur Capet  Mariona Claret  Amala Mahadevan  Pierre Marie Poulain  Alberto Ribotti  Simón Ruiz  Joaquín Tintoré  Antonio Tovar-Sánchez  Ananda Pascual 《Ocean Dynamics》2017,67(6):767-782

Bio-physical glider measurements from a unique process-oriented experiment in the Eastern Alboran Sea (AlborEx) allowed us to observe the distribution of the deep chlorophyll maximum (DCM) across an intense density front, with a resolution (～ 400 m) suitable for investigating sub-mesoscale dynamics. This front, at the interface between Atlantic and Mediterranean waters, had a sharp density gradient (Δρ ～ 1 kg/m³ in ～ 10 km) and showed imprints of (sub-)mesoscale phenomena on tracer distributions. Specifically, the chlorophyll-a concentration within the DCM showed a disrupted pattern along isopycnal surfaces, with patches bearing a relationship to the stratification (buoyancy frequency) at depths between 30 and 60 m. In order to estimate the primary production (PP) rate within the chlorophyll patches observed at the sub-surface, we applied the Morel and Andrè (J Geophys Res 96:685–698 1991) bio-optical model using the photosynthetic active radiation (PAR) from Argo profiles collected simultaneously with glider data. The highest production was located concurrently with domed isopycnals on the fresh side of the front, suggestive that (sub-)mesoscale upwelling is carrying phytoplankton patches from less to more illuminated levels, with a contemporaneous delivering of nutrients. Integrated estimations of PP (1.3 g C m^?2d^?1) along the glider path are two to four times larger than the estimations obtained from satellite-based algorithms, i.e., derived from the 8-day composite fields extracted over the glider trip path. Despite the differences in spatial and temporal sampling between instruments, the differences in PP estimations are mainly due to the inability of the satellite to measure DCM patches responsible for the high production. The deepest (depth > 60 m) chlorophyll patches are almost unproductive and probably transported passively (subducted) from upper productive layers. Finally, the relationship between primary production and oxygen is also investigated. The logarithm of the primary production in the DCM interior (chlorophyll (Chl) > 0.5 mg/m³) shows a linear negative relationship with the apparent oxygen utilization, confirming that high chlorophyll patches are productive. The slope of this relationship is different for Atlantic, mixed interface waters and Mediterranean waters, suggesting the presence of differences in planktonic communities (whether physiological, population, or community level should be object of further investigation) on the different sides of the front. In addition, the ratio of optical backscatter to Chl is high within the intermediate (mixed) waters, which is suggestive of large phytoplankton cells, and lower within the core of the Atlantic and Mediterranean waters. These observations highlight the relevance of fronts in triggering primary production at DCM level and shaping the characteristic patchiness of the pelagic domain. This gains further relevance considering the inadequacy of optical satellite sensors to observe DCM concentrations at such fine scales.  相似文献   

P-T evolution of eclogites from the Agualada Unit (Ordenes Complex, northwest Iberian Massif, Spain): Implications for crustal subduction     

R. Arenas  J. Abati  J.R. Martí  nez Catal  n  F. Dí  az Garcí  a  F.J. Rubio Pascual 《Lithos》1997,40(2-4):221-242

Eclogite lenses in the Agualada Unit (western Ordenes Complex, Spain) contain the peak mineral assemblage garnet (prograde rim: Alm = 48 mol%, Prp = 30 mol%), omphacite (Jd max = 36 mol%), quartz, rutile and rare zoisite, which equilibrated at T = 700 °C and P > 12–14 kbar. Garnet shows discontinuous growth zoning, with a pyrope-poor intermediate zone (Alm = 51 mol%, Prp = 10 mol%) between a core zone where pyrope is slightly higher (Alm = 46 mol%, Prp = 16 mol%) and areas just inward from the rims where the maximum pyrope contents (Alm = 48 mol%, Prp = 30 mol%) are recorded. In atoll interiors, garnet contains inclusions of a first generation of omphacite (Jd max = 40 mol%). This omphacite is replaced in the matrix by a second generation (Jd max = 36 mol%) with higher Fe/Fe + Mg ratio. The compositions of garnet and omphacite suggest a complex syneclogitic tectonothermal evolution for the Agualada Unit, characterized by: (1) eclogite-facies metamorphism (T = 585 °C, P > 12–13 kbar), followed by (2) cooling during a slight decompression (T = 500 °C, P > 11–12 kbar), and (3) a final increase in P and T to form the garnet rim-matrix omphacite mineral assemblage. The Agualada Unit is part of a subduction complex which affected the Gondwana margin at the beginning of the Variscan cycle. The P-T evolution of the Agualada eclogites is closely related to the structural evolution of the accretionary complex and the whole orogenic wedge. The cooling event recorded by the Agualada eclogites may have resulted from the accretion of a new colder crustal slice under the unit, whereas the final progradation reflects the emplacement of the Agualada Unit directly under the mantle wedge. This evolution fits well with previously presented the retical models, both for the tectonothermal evolution of accretionary complexes and for the dynamic evolution of orogenic wedges. P-T paths such as the one for the Agualada Unit eclogites, probably reflect a prolonged structural evolution. Although evidently rarely preserved, such paths are probably the rule rather than the exception during plate convergence.  相似文献   

Magmatism in the Iberian Pyrite Belt: petrological constraints on a metallogenic model     

D. Thiéblemont  E. Pascual  G. Stein 《Mineralium Deposita》1997,33(1-2):98-110

Igneous formations associated with massive sulphide deposits in the Iberian Pyrite Belt (IPB) are essentially composed of basic lavas and dolerites, and dacitic to rhyolitic volcanites; intermediate lavas are subordinate. The basic rocks show variable geochemical characteristics: lavas and dolerites comparable to recent within-plate alkaline basalts seem restricted to the western and southern parts of the IPB, whereas basic rocks comparable to continental tholeiites or arc-related basalts occur across the whole belt. The felsic rocks are classified as calc-alkaline and belong to the “low-Al₂O₃ and high-Yb type”. At given SiO₂, Al₂O₃ and TiO₂ contents, they show variable Zr, Nb, and HREE contents. Heavy-rare-earth element fractionation decreases from the dacites to the rhyolites ([Gd/Yb]_N ∼ 1), whereas the negative Eu-anomaly becomes more pronounced. The characteristics of the rhyolites are typical of sulphide-fertile volcanic packages. Trace-element modelling suggests that the felsic rocks evolved from a dacitic parent magma through fractional crystallization of hornblende and plagioclase. Partial melting of an amphibolite protolith, which appears as the most probable model for the origin of this dacitic magma, requires a high T/P gradient in the crust. The occurrence of alkaline basalts and continental tholeiites is consistent with formation of the IPB in a tensional tectonic setting. However, the associated island-arc tholeiites suggest a location in a domain of plate convergence. Emplacement in a fore-arc basin over a recently accreted crustal segment is envisaged as a possible hypothesis to account for the geological and petrological constraints. A high geothermal gradient and eruption in a submarine tensional basin could have been two key ingredients for the development of massive sulphide deposits within the IPB.

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Resumen (translated by E. Pascual) Las formaciones ígneas asociadas con los depósitos de sulfuros masivos de la Faja Pirítica Ibérica (IPB) se componen esencialmente de doleritas y lavas básicas y de rocas volcánicas dacíticas a riolíticas; las lavas intermedias son poco abundantes. Las rocas básicas muestran caracteres geoquímicos variables: lavas y doleritas comparables a basaltos alcalinos intraplaca recientes parecen hasta ahora restringidos a las partes W y S de la IPB, mientras que rocas básicas de caracteres comparables a las de toleítas continentales o basaltos relacionados con arcos aparecen en toda la zona. Las rocas ácidas se clasifican como calcoalcalinas del tipo “low-Al₂O₃, high-Yb”. Para un contenido dado en SiO₂, Al₂O₃ y TiO₂, muestran contenidos variables en Zr, Nb y REE. El contenido en tierras raras pesadas decrece de dacitas a riolitas ([Gd/Yb]_N ∼ 1), al tiempo que la anomalía de Eu se hace más pronunciada. La modelización de elementos trazas sugiere que las rocas evolucionaron a partir de un magma parental dacítico mediante cristalización fraccionada de hornblenda y plagioclasa. La fusión parcial de un protolito anfibolítico, que parece el modelo más plausible para el origen del magma dacítico, requiere un elevado gradiente T/P en la corteza. La existencia de basaltos alcalinos y de toleítas continentales es congruente con la formación de la IPB en un entorno tectónico distensivo. El emplazamiento en una cuenca “fore-arc”, en un segmento cortical de reciente acreción, se contempla como una hipótesis posible para explicar los caracteres geológicos y petrológicos. Un alto gradiente térmico, junto con la erupción en una cuenca submarina extensional, pueden haber sido los dos ingredientes clave en el desarrollo de los depósitos de sulfuros masivos en la IPB.

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Received: 3 March 1996 / Accepted: 7 April 1997  相似文献   

Aggregata octopiana (Protista: Apicomplexa): a dangerous pathogen during commercial Octopus vulgaris ongrowing     

Gestal  Camino; Guerra  Angel; Pascual  Santiago 《ICES Journal of Marine Science》2007,64(9):1743-1748

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Hydrogeological and mineralogical analysis of the pre‐Romanesque monument of Santa María del Naranco,Asturias, Spain     

Beatriz Gonzlez Fernndez  Celia Marcos Pascual  Eduardo Menndez Casares 《Geoarchaeology》2010,25(4):497-513

The church of Santa María del Naranco is an important monument from the pre‐Romanesque period of Asturian art. Here we present research that locates the probable source of travertine used in the construction of a vault within this monument. Since the genesis of this travertine is associated with spring activity, and archival evidence suggests that stone procurement during this period tended to be local, we surveyed existing carbonated aquifers within a 5‐km radius of the monument. We identified a spring (Sopeña) with an associated outcrop of discontinuous travertine that appeared to have been quarried in the past. We conducted X‐ray powder diffraction, electron microprobe, and inductively coupled plasma mass spectrometry analyses of samples extracted from the suspected travertine source, an additional more distant travertine quarry for comparison, and the vault. Matching mineralogy and geochemistry indicate that the Sopeña travertine was the probable source of rock material used in the construction of the vault. This study provides insight into local ancient monument construction and can assist in procuring original stone material for historical restoration. © 2010 Wiley Periodicals, Inc.  相似文献