Browsing by Issue Date, starting with "2013-03"
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- Impact of atmospheric circulation patterns on coastal dune dynamics, NW SpainPublication . González-Villanueva, Rita; Costas, Susana; Pérez-Arlucea, Marta; Jerez, Sonia; Trigo, Ricardo MachadoDunes in temperate latitudes have experienced a significant stabilization in recent times, essentially as a consequence of the expansion of dense vegetation cover. Yet, the causes for this gradual stabilization as well as the causes promoting antecedent aeolian mobilization remain poorly understood. The Traba coastal dune field, located in NW Spain, was examined to explore the causes inducing aeolian activity and subsequent stabilization since 1940. Morphological changes were identified through the combination of aerial photographs and geophysical techniques. Local wind field regimes were simulated using a regional climate model to obtain the variability of the most relevant modes of atmospheric circulation in the North Atlantic and European regions; North Atlantic Oscillation (NAO), Eastern Atlantic (EA) and Scandinavian (SCAND). This allows us to identify the impact of these circulation modes over dune dynamics. Results document an episode of aeolian activity during the 1950s followed by a gradual stabilization and fixation of the dune coincident with a decrease on storm and wind intensity. Yet, aeolian sand movement remained active in small areas (blowouts), occurring mainly during the summer. NE winds associated with a negative phase of the EA explain the movement of sand within the dune field under favorable conditions of sand supply. On the other hand, sand supply to the dune field from the beach was promoted by NW winds coincident with the summer negative phase of NAO. During winter, the negative NAO favored frequent SW winds associated with the passage of intense storms, which in turn explain sand remobilization from the beach making sediment available for the NW winds to blow inland. With this work, it is proven that to understand past and future aeolian activity requires critical consideration of the variability and impact of the two principal modes of atmospheric circulation in the North Atlantic (NAO and EA). The SCAND mode explaining a lower percentage of the local wind field variability was also included to achieve higher significance levels of explained variance.
- Identification of materials related to acid mine drainage using multi-source spectra at S. Domingos Mine, SE PortugalPublication . Quental, Lídia; Sousa, António Jorge de; Marsh, Stuart; Abreu, Maria Manuela
- The influence of coastal processes on inner shelf sediment distribution : the Eastern Algarve Shelf (Southern Portugal)Publication . Rosa, F.; Rufino, Marta M.; Ferreira, Ó.; Matias, A.; Brito, A. C.; Gaspar, M. B.
- Scarce industrial commodities : a glance at the possible rhenium availability in mining residues from the exploitation of Portuguese ore depositsPublication . Figueiredo, M. Ondina; Silva, Teresa; Batista, Maria Joao; de Oliveira, Daniel Pipa Soares; Veiga, JP
- Principais características e limitações hidrogeológicas do Aquífero Cretácico Inferior da região de Lisboa para o seu aproveitamento como recurso geotérmico de baixa entalpiaPublication . Marrero Diaz, Rayco; Costa, Augusto Marques da; Ribeiro, Maria Luísa; Ramalho, Elsa; Rosa, Carlos J. P.; Rosa, Diogo
- Metodologia para cartografar águas salgadas e salobras aprisionadas em formações geológicas na Beira, MoçambiquePublication . Fernandes, Judite; Ramalho, Elsa; Batista, Maria Joao; Quental, Lídia; Dias, Ruben Pereira; Oliveira, José Tomás; Daudi, Elias Félix; Milisse, Dino; Cune, Grácio; Ussene, Ussene Vasco; Manhiça, Vítor
- Movimentos geológicos e geotectónicos / deslizamentos - Importância da Cartografia GeológicaPublication . Dias, Ruben Pereira; Moniz, Catarina; Queiroz, S.
- Signature of fault zone deformation in near-surface soil visible in shear wave seismic reflectionsPublication . Ghose, Ranajit; Carvalho, João; Loureiro, Afonso VargasSmall-throw seismogenic fault segments hidden in the Holocene sediments are crucial but difficult targets in seismic exploration. We report here the detection of the deformation pattern and a concealed fault segment in the unconsolidated sediments at Vila Franca Xira, Portugal, through identification in shear wave reflection data of multiple signatures of ductile deformation associated with faulting. We find step-like changes in the stacking velocity along a shallow subsoil layer boundary, indicating synsedimentary faulting. We also recognize a consistent distortion in the moveout of the reflection events in the raw shear wave data. Synthetic modeling of seismic data helps in interpreting these observations and identifying backscattered energy from a steeply dipping shallow fault zone. Prior to this finding, there was no evidence for Holocene activity of this fault, although the fault is considered to be the most probable source for the disastrous 1531 earthquake.
- Biomass Fuels in SOFCPublication . Cabrita, IsabelResulting from growing concerns on climate change and resources depletion, biomass has gained increased importance. Security of supply, better environment and economic development, as worldwide goals, are usually drivers for economic growth. Technology developments have adequately not responded to challenges to diversify resources to substitute carbon-intensive fossil fuels at competitive prices. State-of-the-art energy technologies, although advanced, are facing constraints, justifying icreasing effosts in demonstrating efficient and more environmentally friendly tecnhologies.
- Geographical variation in shell shape of the pod razor shell Ensis siliqua (Bivalvia: Pharidae)Publication . Rufino, Marta M.; Vasconcelos, Paulo; Pereira, Fábio; Fernández-Tajes, Juan; Darriba, Susana; Méndez, Josefina; Gaspar, Miguel B.