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排序方式: 共有285条查询结果,搜索用时 15 毫秒
51.
Carmen E. Morales Humberto E. González Gabriel Yuras Leonardo R. Castro 《Progress in Oceanography》2007,75(3):452-469
The oceanographic setting and the planktonic distribution in the coastal transition zone off Concepción (∼35-38°S, ∼73-77°W), an area characterized by its high biological production, were assessed during two different seasons: austral spring with equatorward upwelling favorable winds and austral winter with predominately northerly winds. Oceanographic and biological data (total chlorophyll-a, particulate organic carbon, microplankton, large mesozooplankton >500 μm as potential consumers of microplankton) were obtained during two cruises (October 1998, July 1999) together with satellite imagery for wind stress, geostrophic flow, surface temperature, and chlorophyll-a data. The physical environment during the spring sampling was typical of the upwelling period in this region, with a well-defined density front in the shelf-break area and high concentrations of surface chlorophyll-a (>5 mg m−3) on the shelf over the Itata terrace. During the winter sampling, highly variable though weakly upwelling-favorable winds were observed along with lower surface chlorophyll-a values (<2 mg m−3) on the shelf. In the oceanic area (>100 km from the coast), cyclonic and anti-cyclonic eddies were evident in the flow field during both periods, the former coinciding with higher chlorophyll-a contents (∼1 mg m−3) than in the surrounding waters. Also, a cold, chlorophyll-a rich filament was well defined during the spring sampling, extending from the shelf out to 350-400 km offshore. Along a cross-shelf transect, the micro- and meso-planktonic assemblages displayed higher coastal abundances during the spring cruise but secondary peaks appeared in the oceanic area during the winter cruise, coinciding with the distribution of the eddies. These results suggest that the mesoscale features in this region, in combination with upwelling, play a role in potentially increasing the biological productivity of the coastal transition zone off Concepción. 相似文献
52.
Bas J. van Ruijven Marc A. Levy Arun Agrawal Frank Biermann Joern Birkmann Timothy R. Carter Kristie L. Ebi Matthias Garschagen Bryan Jones Roger Jones Eric Kemp-Benedict Marcel Kok Kasper Kok Maria Carmen Lemos Paul L. Lucas Ben Orlove Shonali Pachauri Tom M. Parris Anand Patwardhan Arthur Petersen Benjamin L. Preston Jesse Ribot Dale S. Rothman Vanessa J. Schweizer 《Climatic change》2014,122(3):481-494
This paper discusses the role and relevance of the shared socioeconomic pathways (SSPs) and the new scenarios that combine SSPs with representative concentration pathways (RCPs) for climate change impacts, adaptation, and vulnerability (IAV) research. It first provides an overview of uses of social–environmental scenarios in IAV studies and identifies the main shortcomings of earlier such scenarios. Second, the paper elaborates on two aspects of the SSPs and new scenarios that would improve their usefulness for IAV studies compared to earlier scenario sets: (i) enhancing their applicability while retaining coherence across spatial scales, and (ii) adding indicators of importance for projecting vulnerability. The paper therefore presents an agenda for future research, recommending that SSPs incorporate not only the standard variables of population and gross domestic product, but also indicators such as income distribution, spatial population, human health and governance. 相似文献
53.
The molluscan macrofauna living in shallow muddy bottoms with the green algae Caulerpa prolifera was studied monthly between February 1994 and January 1996 in the inner Bay of Cádiz (SW Spain). The molluscan assemblage followed a similar pattern over the 2 years, displaying seasonal trends in species richness, abundance and structure. During the autumn and winter months, a decrease in abundance, species richness and diversity and an increase in evenness occurred. During the spring and summer months, the molluscan assemblage was characterised by an increase in species richness, abundance and diversity. These seasonal trends were supported statistically by the presence of significantly different groupings of seasonal samples in multivariate analyses.Despite human impacts in the bay (e.g. aquaculture activities, sewage), the presence of repetitive seasonal trends, based on the qualitative and quantitative data, indicates the stability of the molluscan assemblage over 2 years. Benthic characteristics from the inner Bay of Cádiz, such as shallow soft bottoms with the presence of macrophytes and current dynamics, seem to be key factors influencing the composition and seasonality of this molluscan assemblage. 相似文献
54.
55.
Andrés Folguera Emilio Rojas Vera Germán Bottesi Gonzalo Zamora Valcarce Victor A. Ramos 《Journal of Geodynamics》2010,49(5):287-295
The Loncopué Trough is located in the hinterland Andean zone between 36°30′ and 39°S. It constitutes a topographic low bounded by normal faults and filled by lavas and sediments less than 5 Ma old. Reprocessed seismic lines show wedge-like depocenters up to 1700 m deep associated with high-angle faults, correlated with the 27–17 Ma Cura Mallín basin deposits, and buried beneath Pliocene to Quaternary successions and Late Miocene foreland sequences. The southern Central Andes seem to have been under extension in the hinterland zone some 27 Ma ago and again at approximately 5 Ma ago. This last extensional period could have been the product of slab steepening after a shallow subduction cycle in the area, although other alternatives are discussed. Orogenic wedge topography, altered by the first extensional stage in the area, was recovered through Late Miocene inversion, and was associated with foreland sequences. However, since the last extension (<5 Ma) the Andes have not recovered their characteristic contractional behavior that controlled past orogenic growth. 相似文献
56.
This paper explores the relationship between disaster risk reduction and long-term adaptive capacity building in two climate vulnerable areas—the Cayman Islands in the Caribbean and Ceará, in NE Brazil. Drawing on past applications of the disaster risk reduction framework, we identify four critical factors that have led to reductions in risk: flexible, learning-based, responsive governance; committed, reform-minded and politically active actors; disaster risk reduction integrated into other social and economic policy processes; and a long-term commitment to managing risk. We find that while the presence of these factors has reduced overall risk in both regions, in Ceará, disaster response as it is currently practiced, has fallen short of addressing the fundamental causes of vulnerability that leave those prone to hazards able to cope in the short term, yet enmeshed in poverty and at risk from the longer-term changes associated with climate change. Although calls for integration of disaster risk management with poverty eradication are not new, there has been insufficient attention paid in the literature on how to foster such integration. Based on the two case studies, we argue that the adoption of good governance mechanisms (such as stakeholder participation, access to knowledge, accountability and transparency) in disaster risk reduction policy may create the policy environment that is conducive to the kind of structural reform needed to build long-term adaptive capacity to climate-driven impacts. We conclude that without a synergistic two-tiered approach that includes both disaster risk reduction and structural reform, disaster risk reduction, in the face of climate changes, will prove to be an expensive and ineffective palliative treatment of changing risks. 相似文献
57.
Pablo H. Alasino Juan A. Dahlquist Carmen Galindo Cesar Casquet Julio Saavedra 《International Journal of Earth Sciences》2010,99(5):1051-1065
The La Costa pluton in the Sierra de Velasco (NW Argentina) consists of S-type granitoids that can be grouped into three igneous
facies: the alkali-rich Santa Cruz facies (SCF, SiO2 ~67 wt%) distinguished by the presence of andalusite and Na- and Li-rich cordierite (Na2O = 1.55–1.77 wt% and Li2O = 0.14–0.66 wt%), the Anillaco facies (SiO2 ~74 wt%) with a significant proportion of Mn-rich garnet, and the Anjullón facies (SiO2 ~75 wt%) with abundant albitic plagioclase. The petrography, mineral chemistry and whole-rock geochemistry of the SCF are
compatible with magmatic crystallization of Na- and Li-rich cordierite, andalusite and muscovite from the peraluminous magma
under moderate P–T conditions (~1.9 kbar and ca. 735°C). The high Li content of cordierite in the SCF is unusual for granitic rocks of intermediate
composition. 相似文献
58.
Jos Luis Orgeira Mariela del Carmen Alderete Yohana Gisell Jimnez Juan Cruz Gonzlez 《极地研究(英文版)》2015,(2)
The Scotia Sea is one of the most biologically rich regions of Antarctica, and it hosts a large community of upper trophic-level predators. Long-term at-sea monitoring provides valuable information on ... 相似文献
59.
Saturn's southern pole was observed at high resolution by the Cassini Imaging Science Subsystem (ISS) during the spacecraft insertion orbit in July 2004. Cloud tracking of individual features on images taken at a wavelength of 938 nm reveal the existence of a strong polar vortex enclosed by a jet with maximum speed of relative to System III rotation frame, and peak at 87 °S planetographic latitude. Radiative transfer models of the reflected light, based on the Cassini images complemented by Hubble Space Telescope images from March 2004, indicate that the aerosol particles in the vortex are structured vertically in three detached layers. We find two hazes and one dense cloud distributed in altitude between ∼500 mbar (top of the dense cloud) and few mbar (top of the stratospheric haze), spanning a vertical altitude range of ∼200 km. The vortex area coincides with a thermal hot spot recently reported, indicating that winds decrease with altitude above polar clouds. 相似文献
60.
Victoria Ochoa Carmen Riva Melissa Faria Carlos Barata 《Marine pollution bulletin》2013,66(1-2):135-142
Marine bivalves such as oysters are widely used as bioindicators to monitor marine coastal pollution. This study aimed to use B-esterase activity responses in oysters (Crassostrea gigas) cultured in Ebro Delta bays to monitor environmental effects of pesticides. The B esterases investigated were acetylcholinesterase, propionylcholinesterase, and carboxylesterase and their activities were measured in adductor muscle and gills from oysters transplanted in Ebro Delta bays where the are traditionally grown. Enzyme activities were related with physico-chemical parameters and pesticide levels measured in water. Cholinesterase activities measured in gills were unaffected across sites and periods. Conversely, carboxylesterase activities in oyster gills varied across periods and sites and were negatively correlated with residue levels of organophoshporous and carbamate pesticides in water. Therefore, inhibition of carboxylesterase activities can be considered a good indicator of exposure to anti-cholinergic pesticides in oysters. 相似文献