Sediment budget controls on foredune height: Comparing simulation model results with field data          下载免费PDF全文

Robin Davidson‐Arnott  Patrick Hesp  Jeff Ollerhead  Ian Walker  Bernard Bauer  Irene Delgado‐Fernandez  Thomas Smyth 《地球表面变化过程与地形》2018,43(9):1798-1810

The form, height and volume of coastal foredunes reflects the long‐term interaction of a suite of nearshore and aeolian processes that control the amount of sand delivered to the foredune from the beach versus the amount removed or carried inland. In this paper, the morphological evolution of more than six decades is used to inform the development of a simple computer model that simulates foredune growth. The suggestion by others that increased steepness of the seaward slope will retard sediment supply from the beach to the foredune due to development of a flow stagnation zone in front of the foredune, hence limiting foredune growth, was examined. Our long‐term data demonstrate that sediment can be transferred from the beach to the foredune, even with a steep foredune stoss slope, primarily because much of the sediment transfer takes place under oblique rather than onshore winds. During such conditions, the apparent aspect ratio of the dune to the oncoming flow is less steep and conditions are not as favourable for the formation of a stagnation zone. The model shows that the rate of growth in foredune height varies as a function of sediment input from the beach and erosion due to storm events, as expected, but it also demonstrates that the rate of growth in foredune height per unit volume increase will decrease over time, which gives the perception of an equilibrium height having been reached asymptotically. As the foredune grows in size, an increasing volume of sediment is needed to yield a unit increase in height, therefore the apparent growth rate appears to slow. Copyright © 2018 John Wiley & Sons, Ltd.  相似文献   

Probing crustal anisotropy by receiver functions at the deep continental drilling site KTB in Southern Germany     

Irene Bianchi  Götz Bokelmann 《Geophysical Prospecting》2019,67(9):2450-2464

Seismic anisotropy is a unique observational tool for remotely studying deformation and stress within the Earth. Effects of anisotropy can be seen in seismic data; they are due to mineral alignment, fractures or layering. Seismic anisotropy is linked to local stress and strain, allowing modern geophysics to derive geomechanical properties from seismic data for supporting well planning and fracking. For unravelling anisotropic properties of the crust, the teleseismic receiver functions methodology has started to be widely applied recently due to its ability in retrieving the three-dimensional characteristics of the media sampled by the waves. The applicability of this technique is tested here by a field test carried out around the Kontinental Tiefbohrung site in southeastern Germany. We compare our results to previous investigations of the metamorphic rock pile of the Zone Erbendorf-Vohenstrauss, drilled down to 9 km depth, which sampled an alternating sequence of paragneiss and amphibolite, in which a strong foliation has been produced by ductile deformation. The application of the receiver functions reveals the presence of two distinct anisotropic layers within the metamorphic rock pile at 0–4 km and below 6 km depth, with up to 8% anisotropy; the depth of these two layers corresponds to the location of mica-rich paragneiss which show intense foliation, and finally proves the relation between the signal in the receiver functions, rock texture and presence of cracks. We have now the capability of providing insights from passive seismic data on geomechanical properties of the rocks, useful for geological exploration and engineering purposes, which will help influencing expensive drilling decisions thanks to future application of this seismic technique.  相似文献   

Modelling inter-annual and spatial variability of ice cover in a temperate lake with complex morphology     

Irene Caramatti  Frank Peeters  David Hamilton  Hilmar Hofmann 《水文研究》2020,34(3):691-704

The formation of ice cover on lakes alters heat and energy transfer with the water column. The fraction of surface area covered by ice and the timing of ice-on and ice-off therefore affects hydrodynamics and the seasonal development of stratification and related ecosystem processes. Multi-year model simulations of temperate lake ecosystems that freeze partially or completely therefore require simulation of the formation and duration of ice cover. Here we present a multi-year hydrodynamic simulation of an alpine lake with complex morphology (Lower Lake Constance, LLC) using the three-dimensional (3D) model Aquatic Ecosystem Model (AEM3D) over a period of 9 years. LLC is subdivided into three basins (Gnadensee, Zeller See and Rheinsee) which differ in depth, morphological features, hydrodynamic conditions and ice cover phenology and thickness. Model results were validated with field observations and additional information on ice cover derived from a citizen science approach using information from social media. The model reproduced the occurrence of thin ice as well as its inter-annual variability and differentiated the frequency and extent of ice cover between the three sub-basins. It captured that full ice cover occurs almost each winter in Gnadensee, but only rarely in Zeller See and Rheinsee. The results indicate that the 3D model AEM3D is suitable for simulating long-term dynamics of thin ice cover in lakes with complex morphology and inter-annual changes in spatially heterogeneous ice cover.  相似文献   

Palaeozoic sequences and evolution of the Calabrian-Peloritan Arc (Southern Italy)     

P. Acquafredda  S. Lorenzoni  E. Zanettin Lorenzoni 《地学学报》1994,6(6):582-594

Three Palaeozoic sequences belonging to three different basins crop out in the Calabrian–Peloritan Arc. Their age covers the time span from middle (?) Cambrian to early Carboniferous. The sequences comprise terrigenous, volcanic and carbonate rocks, and show low-grade metamorphism. The basement is of pre-middle Cambrian age, crops out in the Calabrian–Peloritan Arc, and was metamorphosed prior to the opening to the Palaeozoic basins. The Palaeozoic basins existed no later than the middle Carboniferous, with inferred maximum crustal extension in the Cambro-Ordovician. By Devonian time, the tectonic regime was compressional overall with middle Devonian island-arc type volcanic activity that continued until the closure of the basins. Approximately 330 Myr, the Palaeozoic sequences experienced low-pressure greenschist facies metamorphism and continuing subduction controlled the Variscan tectonogenesis with 280 Myr island-arc type intrusive magmas. Subduction ceased and late-stage 280–270 Myr granitic magmas were emplaced during continental collision. The crustal sector carrying the Palaeozoic basins is interpreted as comprising fragments of an active continental margin, one of the several microplates, located at the southern margin of the Euro-Asia continent which faced a large (at least 1500 km in width) ocean basin.  相似文献   

Processes in the Pacific La Niña onset triggered by the Atlantic Niño     

Irene Polo  Marta Martin-Rey  Belen Rodriguez-Fonseca  Fred Kucharski  Carlos Roberto Mechoso 《Climate Dynamics》2015,44(1-2):115-131

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Variability in storm climate along the Gulf of Cadiz: the role of large scale atmospheric forcing and implications to coastal hazards     

Theocharis A. Plomaritis  Javier Benavente  Irene Laiz  Laura Del Río 《Climate Dynamics》2015,45(9-10):2499-2514

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Intersexuality incidence, sex ratio fluctuations and intersex reproductive output as factors affecting the temporal variation of intersexed populations of the marine amphipod Echinogammarus marinus     

Irene Martins  Alex T. Ford  Teresa F. Fernandes 《Marine environmental research》2009,68(4):163-169

The occurrence of intersexuality in populations of the marine amphipod Echinogammarus marinus has been related to several causes, including anthropogenic contamination, microsporidian parasites and environmental sex determination (ESD). At the individual-level, the costs of intersexuality in E. marinus are reflected in reduced reproductive output of intersexes compared to normal specimens. The impacts of intersexuality and other reproductive disorders in nature will only be fully understood when individual-level effects are upscale to the population-level, which can be achieved through ecological models. The aim of the present work is to simulate the density variation of real populations of E. marinus with different intersexuality incidence, proportions of phenotypes and intersex female reproductive rates. To achieve that, we have incorporated empirical data obtained at the individual-level from three intersexed populations of E. marinus into a population dynamic model. The original model was calibrated and validated for a long-term stable population without intersexuality and sex ratio 1. In the present version, the model includes an extra population group, intersex females, but the total sum of flow rates from juveniles to adults was kept the same as in the original model to respect the previous validation. In these circumstances, results indicate that the male-biased population is very sensitive to intersexuality, even at low incidence levels, and exhibits significant density decrease if conditions do not change. On the contrary, the two populations with a preponderance of female-biased sex ratios, low or moderate intersexuality incidence (up to an average value of 9% of the population) and with intersex reproductive rates corresponding to 80% the value of normal specimens, exhibit long-term persistence.The model is highly sensitive to adult female parameters (e.g. mortality), indicating that small variations on its values can significantly change population responses.Overall the present results suggest that, in spite the costs of intersexuality in E. marinus, the temporal variation of intersexed populations depend on intersex incidence level, sex ratio fluctuations and reproductive output of intersexes. Simulations also suggest that other processes (e.g. mortality rates of normal females) may play important roles in the maintenance of populations with intersexuality. In the future, it will be crucial to improve and validate this type of models with long-term observations and monitoring of intersexed populations.  相似文献   

Spatialities of ageing: The co-construction and co-evolution of old age and space   总被引：1，自引：0，他引：1  

Tim Schwanen  Irene Hardill  Susan Lucas 《Geoforum》2012,43(6):1291-1295

This editorial introduction to the themed issue is divided into four parts. We begin with outlining five reasons for more sustained attention to ageing and old age in human geography and go onto discuss two major challenges for geographical inquiry into ageing and later life. One of these is examining embodiment in ways that keep both its social/cultural aspects and its biological/physiological dimensions in sharp focus; the other concerns the challenge of considering time, or rather spatiotemporality, in all its facets. With regard to the latter we argue that the life-course concept can be helpful in this regard, especially if attention is paid to transitions as well as to slow, difficult-to-identify forms of change and if life-courses are understood in terms of folds. Thinking in these terms opens up a perspective according to which ageing and space can be analysed as entwined becomings. We conclude by positioning the contributions in this issue vis-à-vis the perspective developed in this piece.  相似文献   

Characterization of environmental impact on resources, using strategic assessment of environmental impact and management of natural spaces of “Las Batuecas-Sierra de Francia” and “Quilamas” (Salamanca, Spain)     

A. M. Martínez-Graña  J. L. Goy y Goy  Irene De Bustamante Gutiérrez  C. Zazo Cardeña 《Environmental Earth Sciences》2014,71(1):39-51

A new procedure is proposed for joint strategic environmental assessment and environmental impact assessment using simultaneous characterizations in the protected natural area studied to analyse the importance and extent of the impact of human activities within this area on the various natural resources. GIS techniques were used to define territorial models, including environmental information criteria in thematic layers to facilitate environmental diagnosis in the early planning stages in the areas of concern or of higher quality for conservation at different working levels (municipal, district, provincial or national). Traditional conventional environmental impact assessment methods were improved, using spatial analysis to compare scenarios based on the spatial and temporal variability of the impacts identified and their evaluation. This method was applied to the natural space of Las Batuecas-S. de Francia and Quilamas, where in an initial stage the different anthropogenic activities (landfills, etc.) with the potential to cause direct (sewage waters, etc.) or indirect (leachate, etc.) impacts were identified, using checklists and double-entry matrices to analyse actions likely to cause impacts, developing the cartography and identifying environmental impacts potentially damaging to the natural environment. Next, thematic and interpretive mappings were drawn up (surface water quality, aquifer vulnerability to pollution and vulnerability to municipal solid waste) to assess the effects upon resources (water, soil, air, etc.). Finally, by overlapping the impact identification and vulnerability mappings (municipal solid waste, pollution of aquifers and surface water quality) the impact characterization mapping was obtained, showing the absorption capacity of the different sectors to help the responsible bodies set out preventive and/or corrective measures. The essence of this paper is, in methodological terms, its use of two methods simultaneously (strategic environmental assessment and environmental impact assessment) in a protected natural area, allowing it to be extrapolated to any area where territorial management and planning studies need to be carried out.  相似文献   

Analysis of trends and sudden changes in long-term environmental data from King George Island (Antarctica): relationships between global climatic oscillations and local system response     

A. Valeria Bers  Fernando Momo  Irene R. Schloss  Doris Abele 《Climatic change》2013,116(3-4):789-803

The Western Antarctic Peninsula is one of the most rapidly warming regions on earth. It is therefore important to analyze long-term trends and inter-annual patterns of change in major environmental parameters to understand the process underlying climate change in Western Antarctica. Since many polar long-term data series are fragmented and cannot be analysed with common time series analysis tools, we present statistical approaches that can deal with missing values. We applied U-statistics after Pettit and Buishand to detect abrupt changes, dynamic factor analysis to detect functional relationships, and additive modelling to detect patterns in time related to climatic cycles such as the Southern Annular Mode and El Niño Southern Oscillation in a long-term environmental data set from King George Island (WAP), covering 20 years. Our results not only reveal sudden changes for sea surface temperature and salinity, but also clear patterns in all investigated variables (sea surface temperature, salinity, suspended particulate matter and Chlorophyll a) that can directly be related to climatic cycles. Our results complement previous findings on climate related changes in the King George Island Region and provide insight into the environmental conditions and climatic drivers of system change in the study area. Hence, our statistical analyses may prove valuable for other polar environmental data sets and contribute to a better understanding of the regional variability of climate change and its impact on coastal systems.  相似文献