Risk,wealth and agrarian change in India. Household-level hazards vs. late-modern global risks at different points along the risk transition     

Sarah Jewitt  Kathleen Baker 《Global Environmental Change》2012,22(2):547-557

The global poor often prioritise immediate hazards of food insecurity over temporally more distant risks like global warming. Yet the influence of socio-economic factors, temporal and spatial distance on risk perception remains under-researched. Data on risk perception and response were collected from two sets of Indian villages. Participatory approaches were used to investigate variations by socio-economic status, food security, age and gender. Villagers’ risk priorities reflected clear spatial and temporal patterns depending on land ownership, community group and education levels. Poorer groups prioritised household-level risks to health and food security while global environmental risks were mentioned by only three of the wealthiest respondents. The paper concludes that household risk perceptions and responses vary greatly with socio-economic status, age, gender and the spatial or temporal distance of the risk. These factors need to be better understood if the most significant contributors to the global burden of disease are to be reduced.  相似文献   

Causes of recent changes in western North American snowpack     

Sarah Kapnick  Alex Hall 《Climate Dynamics》2012,38(9-10):1885-1899

Monthly snow water equivalent (SWE) station observations and gridded temperature data are used to identify mechanisms by which warming affects the temporal and geographical structure of changes in western North American mountain snowpack. We first exploit interannual variability to demonstrate the sensitivity of snowpack to temperature during the various phases of the snow season. We show that mechanisms whereby temperature affects snowpack emerge in the mid to late portion of the snow season (March through May), but are nearly absent during the earliest phase (February), when temperatures are generally well below freezing. The mid to late snow season is precisely when significant loss of snowpack is seen at nearly all locations over the past few decades, both through decreases in snow accumulation and increases in snowmelt. At locations where April 1st SWE has been increasing over the past few decades, the increase is entirely due to a significant enhancement of accumulation during the earliest phase of the snow season, when the sensitivity analysis indicates that temperature is not expected to affect snowpack. Later in the snow season, these stations exhibit significant snowpack loss comparable to the other stations. Based on this analysis, it is difficult to escape the conclusion that recent snowpack changes in western North America are caused by regional-scale warming. Given predictions of future warming, a further reduction in late season snowpack and advancement in the onset of snowmelt should be expected in the coming decades throughout the region.  相似文献   

Quantitative assessment of precipitation seasonality and summer surface wetness using ombrotrophic sediments from an Arctic Norwegian peatland   总被引：1，自引：0，他引：1  

Jonathan E. Nichols  Marie Walcott  Raymond Bradley  Jon Pilcher  Yongsong Huang   《Quaternary Research》2009,72(3):443-451

Seasonality of precipitation is an important yet elusive climate parameter in paleoclimatological reconstructions. This parameter can be inferred qualitatively from pollen and other paleoecological methods, but is difficult to assess quantitatively. Here, we have assessed seasonality of precipitation and summer surface wetness using compound specific hydrogen and carbon isotope ratios of vascular plant leaf waxes and Sphagnum biomarkers extracted from the sediments of an ombrotrophic peatland, Bøstad Bog, Nordland, Norway. Our reconstructed precipitation seasonality and surface wetness are consistent with regional vegetation reconstructions. During the early Holocene, 11.5–7.5 ka, Fennoscandia experienced a cool, moist climate. The middle Holocene, 7.5–5.5 ka, was warm and dry, transitioning towards cooler and wetter conditions from the mid-Holocene to the present. Changes in seasonality of precipitation during the Holocene show significant coherence with changes in sea surface temperature in the Norwegian Sea, with higher SST corresponding to greater percentage of winter precipitation. Both high SST in the Norwegian Sea and increased moisture delivery to northern Europe during winter are correlated with a strong gradient between the subpolar low and subtropical high over the North Atlantic (positive North Atlantic Oscillation).  相似文献   

Dendrochronological reconstruction of snow avalanche activity in the Lahul Himalaya,Northern India   总被引：1，自引：0，他引：1  

Sarah C. Laxton  Dan J. Smith 《Natural Hazards》2009,49(3):459-467

Mass wasting and avalanche events substantially impact the landscape morphology and consequently human habitation throughout the Himalaya. There is, however, a paucity of snow avalanche documentation for the region. The application of dendrochronologic research methods introduces a sensitive approach to document the recurrence of snow avalanche events in a region where historical records are either non-existent or difficult to access. An exploratory dendrochronologic study was undertaken in the Lahul Himalaya of Northern India during the summer of 2006. Included within the fieldwork was an assessment of avalanche track morphology to enable identification of the slope characteristics that might be associated with an increase in avalanche activity. Thirty-six trees growing on the Ratoli avalanche track were sampled. The oldest tree was a Cedrus deodara with a pith date of 1950. A tree-ring-derived avalanche response curve highlights four avalanche events that occurred from 1972 to 2006. The successful scientific results based on the application of the method used provide the basis for local planners to quantify slope failure hazards in forested areas throughout the western Himalaya.  相似文献   

Determination of the separability of coastal community assemblages of the Al Wajh Barrier Reef, Red Sea, from hyperspectral data     

Sarah Hamylton 《Central European Journal of Geosciences》2009,1(1):95-105

Remote sensing provides a practical means by which coral reefs and their associated communities are commonly mapped. The availability of spectral information is a key determinant of the detail discernable in the mapping process and consequent detail presented in output maps. Testament to this is the increasing utility of hyperspectral sensors, which typically yield datasets of higher resolution, spectrally continuous wavebands. Image classification algorithms distinguish between the different and unique reflectance characteristics of target features. While the availability of more wavebands provides the opportunity to apply analysis techniques that treat the data as spectrally continuous, such a large number of data dimensions also present a considerable computing burden. Through multiple discriminant function analysis, this paper identifies an optimal subset of wavelengths for resolving the reflectance of key terrestrial and marine coverages at the Al Wajh Barrier reef system, Saudi Arabia, Red Sea. The goal of such analysis is to facilitate the processing of high resolution, spectrally continuous remote sensing data of coastal landscapes.  相似文献   

Stratigraphic architecture resulting from dune interactions: White Sands Dune Field,New Mexico          下载免费PDF全文

Sarah C. Brothers  Gary Kocurek  Thomas C. Brothers  Ilya V. Buynevich 《Sedimentology》2017,64(3):686-713

Aeolian dune interactions provide the dynamics for field‐scale pattern emergence and evolution within a set of boundary conditions. Although morphologies for a spectrum of dune interactions are recognized, associated stratigraphic architectures are unknown and have probably been misidentified in the rock record. A unique data set for the White Sands Dune Field in New Mexico (USA) allowed for a detailed analysis in which the morphological evolution of defect and bedform repulsion interactions is chronicled over a decadal time‐series of images and coupled with the resulting stratigraphic architecture, documented from cross‐strata exposed in interdune areas and ground‐penetrating radar imaging of dune interiors. Defect and bedform repulsions represent a class of interactions in which the faster‐migrating dune termination or defect (defect repulsion), or pair of defects (bedform repulsion), collides with the target dune downwind. Results document that during the collision, the defect(s) of the impactor dune recombine(s) with a segment of the target dune, and the redundant target dune segment is ejected as a parabolic‐shaped ejecta dune. The ejecta dune assumes a more barchanoid shape as it migrates downwind. The interaction architecture consists of lateral truncation of the target set by an interaction bounding surface. Defect cross‐strata tangentially approach the surface in plan‐view, and downlap onto the surface in cross‐section. The orientation of the defect cross‐strata is at an acute angle to the trend of the interaction surface. Orientations of the defect cross‐strata, which represent the defect approach angle, and the target dune cross‐strata, which represent the general dune migration direction, diverge at a high angle. Defect cross‐strata typically consist of wind‐ripple laminae, in contrast to the target set that may house grainflow cross‐strata. In the transport direction, the erosional interaction surface curves to become subparallel to subjacent and superjacent cross‐strata where the defect and target unify into a single lee face.  相似文献   

Hybrid event beds dominated by transitional‐flow facies: character,distribution and significance in the Maastrichtian Springar Formation,north‐west Vøring Basin,Norwegian Sea          下载免费PDF全文

Sarah J. Southern  Ian A. Kane  Michał J. Warchoł  Kristin W. Porten  William D. McCaffrey 《Sedimentology》2017,64(3):747-776

Hybrid event beds comprising clay‐poor and clay‐rich sandstone are abundant in Maastrichtian‐aged sandstones of the Springar Formation in the north‐west Vøring Basin, Norwegian Sea. This study focuses on an interval, informally referred to as the Lower Sandstone, which has been penetrated in five wells that are distributed along a 140 km downstream transect. Systematic variations in bed style within this stratigraphic interval are used to infer variation in flow behaviour in relatively proximal and distal settings, although individual beds were not correlated. The Lower Sandstone shows an overall reduction in total thickness, bed amalgamation, sand to mud ratio and grain size in distal wells. Turbidites dominated by clay‐poor sandstone are at their most common in relatively proximal wells, whereas hybrid event beds are at their most common in distal wells. Hybrid event beds typically comprise a basal clay‐poor sandstone (non‐stratified or stratified) overlain by banded sandstone, with clay‐rich non‐stratified sandstone at the bed top. The dominant type of clay‐poor sandstone at the base of these beds varies spatially; non‐stratified sandstone is thickest and most common proximally, whereas stratified sandstone becomes dominant in distal wells. Stratified and banded sandstone record progressive deposition of the hybrid event bed. Thus, the facies succession within hybrid event beds records the longitudinal heterogeneity of flow behaviour within the depositional boundary layer; this layer changed from non‐cohesive at the front, through a region of transitional behaviour (fluctuating non‐cohesive and cohesive flow), to cohesive behaviour at the rear. Spatial variation in the dominant type of clay‐poor sandstone at the bed base suggests that the front of the flow remained non‐cohesive, and evolved from high‐concentration and turbulence‐suppressed to increasingly turbulent flow; this is thought to occur in response to deposition and declining sediment fallout. This research may be applicable to other hybrid event bed prone systems, and emphasizes the dynamic nature of hybrid flows.  相似文献   

Evidence for plunging river plume deposits in the Pahrump Hills member of the Murray formation,Gale crater,Mars     

Kathryn M. Stack  John P. Grotzinger  Michael P. Lamb  Sanjeev Gupta  David M. Rubin  Linda C. Kah  Lauren A. Edgar  Deirdra M. Fey  Joel A. Hurowitz  Marie McBride  Frances Rivera‐Hernndez  Dawn Y. Sumner  Jason K. Van Beek  Rebecca M. E. Williams  Robin Aileen Yingst 《Sedimentology》2019,66(5):1768-1802

Recent robotic missions to Mars have offered new insights into the extent, diversity and habitability of the Martian sedimentary rock record. Since the Curiosity rover landed in Gale crater in August 2012, the Mars Science Laboratory Science Team has explored the origins and habitability of ancient fluvial, deltaic, lacustrine and aeolian deposits preserved within the crater. This study describes the sedimentology of a ca 13 m thick succession named the Pahrump Hills member of the Murray formation, the first thick fine‐grained deposit discovered in situ on Mars. This work evaluates the depositional processes responsible for its formation and reconstructs its palaeoenvironmental setting. The Pahrump Hills succession can be sub‐divided into four distinct sedimentary facies: (i) thinly laminated mudstone; (ii) low‐angle cross‐stratified mudstone; (iii) cross‐stratified sandstone; and (iv) thickly laminated mudstone–sandstone. The very fine grain size of the mudstone facies and abundant millimetre‐scale and sub‐millimetre‐scale laminations exhibiting quasi‐uniform thickness throughout the Pahrump Hills succession are most consistent with lacustrine deposition. Low‐angle geometric discordances in the mudstone facies are interpreted as ‘scour and drape’ structures and suggest the action of currents, such as those associated with hyperpycnal river‐generated plumes plunging into a lake. Observation of an overall upward coarsening in grain size and thickening of laminae throughout the Pahrump Hills succession is consistent with deposition from basinward progradation of a fluvial‐deltaic system derived from the northern crater rim into the Gale crater lake. Palaeohydraulic modelling constrains the salinity of the ancient lake in Gale crater: assuming river sediment concentrations typical of floods on Earth, plunging river plumes and sedimentary structures like those observed at Pahrump Hills would have required lake densities near freshwater to form. The depositional model for the Pahrump Hills member presented here implies the presence of an ancient sustained, habitable freshwater lake in Gale crater for at least ca 10³ to 10⁷ Earth years.  相似文献   

A methodology for urban micro-scale coastal flood vulnerability and risk assessment and mapping     

Percival  Sarah  Teeuw  Richard 《Natural Hazards》2019,99(1):355-377

Natural Hazards - Wind gusts are a major cause of damage to property and the natural environment and a source of noise in seismic networks such as the USArray Transportable Array. Wind gusts cause...  相似文献   

Minerals provide tints and possible binder/extender in pigments in san rock paintings (South Africa)     

Joselito M. Arocena  Kevin Hall  Ian Meiklejohn 《Geoarchaeology》2008,23(2):293-304

Minerals such as iron oxides and clays provide high tinting strength and improve the adhesive properties of pigments. In this study, we investigated the mineral composition of pigments from samples of San rock art. We used X‐ray diffraction and scanning electron microscopy to determine the mineral composition and micromorphology of pigments. Results showed that the major minerals in pigments in San rock art are whewellite, quartz, gypsum, hematite, and various alumino‐silicate minerals. The red hue in the pigment is due to hematite; gypsum and clays provide the white coloration, whereas black might be due to amorphous manganese compounds. We believe that whewellite with globular habit was extracted from plant sap (e.g., aloe vera) and added to the pigment, perhaps as binder, extender, or whitener. Whewellite with needle‐shaped morphology was present in cracks that developed in pigments and indicated an early stage of deterioration of the rock art. We propose that conservationists should seriously evaluate any change in the environmental conditions at the art site (e.g., removal of vegetation to improve touristic view) because such changes might significantly increase thermal fluctuations in pigments and promote crack formation and hence the decay of the San rock art. © 2008 Wiley Periodicals, Inc.  相似文献