Shoreline evolution under climate change wave scenarios   总被引：1，自引：1，他引：0  

Anna Zacharioudaki  Dominic E. Reeve 《Climatic change》2011,108(1-2):73-105

This paper investigates changes in shoreline evolution caused by changes in wave climate. In particular, a number of nearshore wave climate scenarios corresponding to a ??present?? (1961?C1990) and a future time-slice (2071?C2100) are used to drive a beach evolution model to determine monthly and seasonal statistics. To limit the number of variables, an idealised shoreline segment is adopted. The nearshore wave climate scenarios are generated from wind climate scenarios through point wave hindcast and inshore transformation. The original wind forcing comes from regional climate change model experiments of different resolutions and/or driving global climate models, representing different greenhouse-gas emission scenarios. It corresponds to a location offshore the south central coast of England. Hypothesis tests are applied to map the degree of evidence of future change in wave and shoreline statistics relative to the present. Differential statistics resulting from different global climate models and future emission scenarios are also investigated. Further, simple, fast, and straightforward methods that are capable of accommodating a great number of climate change scenarios with limited data reduction requirements are proposed to tackle the problem under consideration. The results of this study show that there are statistically significant changes in nearshore wave climate conditions and beach alignment between current and future climate scenarios. Changes are most notable during late summer for the medium-high future emission scenario and late winter for the medium-low. Despite frequent disagreement between global climate change models on the statistical significance of a change, all experiments agreed in future seasonal trends. Finally, a point of importance for coastal management, material shoreline changes are generally linked to significant changes in future wave direction rather than wave height.  相似文献   

Late Holocene changes in cyanobacterial community structure in maritime Antarctic lakes     

Rafael Fernandez-Carazo  Elie Verleyen  Dominic A. Hodgson  Stephen J. Roberts  Krzysztof Waleron  Wim Vyverman  Annick Wilmotte 《Journal of Paleolimnology》2013,50(1):15-31

Despite the dominance of cyanobacteria in polar freshwater aquatic ecosystems, little is known about their past biodiversity and response to climate and environmental changes. We explored the use of light microscopy of microfossils, high performance liquid chromatography of the fossil pigment composition and denaturing gradient gel electrophoresis of fossil 16S rRNA genes to study past and present-day differences in cyanobacterial community structure in response to climate changes in two adjacent maritime Antarctic lakes with contrasting depths (4 and 26 m) and light climates. Light microscopy was of limited use because of degradation of cell structures. Fossil cyanobacterial pigment concentrations were below the detection limits of our method in several sediment samples in the deep lake, but abundant and diverse in the sediment core from the shallow pond, probably as a consequence of increased light availability and/or a more diverse and abundant benthic cyanobacterial flora. Total carotenoid and chlorophyll concentrations were highest in both lakes between ca. 2,950 and 1,800 cal yr BP, which coincides with the late Holocene climate optimum recognised elsewhere in maritime Antarctica. Cyanobacterial molecular diversity was higher in the top few centimeters of the sediments in both lakes. In deeper sediments, the taxonomic turnover of cyanobacteria appeared to be relatively small in response to past climate anomalies in both lakes, underscoring the broad tolerance of cyanobacteria to environmental variability. This, however, may in part be explained by the low taxonomic resolution obtained with the relatively conserved 16S rRNA gene and/or the preferential preservation of particular taxa. Our results highlight the potential of fossil DNA in lake sediments to study colonization and succession dynamics of lacustrine cyanobacteria and warrant further investigation of the factors that affect preservation of cyanobacterial DNA.  相似文献   

Palaeoecological tools for improving the management of coastal ecosystems: a case study from Lake King (Gippsland Lakes) Australia   总被引：2，自引：0，他引：2  

Krystyna M. Saunders  Dominic A. Hodgson  Jennifer Harrison  Andrew McMinn 《Journal of Paleolimnology》2008,40(1):33-47

Since European settlement began over 200 years ago, many southeast Australian coastal lakes and lagoons have experienced substantial human impacts, including nutrient enrichment. Present day management and conservation efforts are often hampered by a lack of data on pre-impact conditions. We used a palaeoecological approach at Lake King, Gippsland Lakes, southeast Australia in order to determine its pre-impact condition and to establish the nature and direction of subsequent environmental changes, including responses to the construction of a permanent entrance to the sea in 1889. A 120 cm sediment core was analysed for diatoms, chlorophyll a, total carbon, nitrogen and sulphur, and dated using ²¹⁰Pb. Past phosphate and salinity concentrations were reconstructed using diatom-phosphate and diatom-salinity transfer functions developed from a calibration set based on 53 sites from 14 southeast Australian coastal lakes and lagoons. Results show changes in the diatom assemblage that record a shift from a brackish-water to marine diatom flora since construction of the permanent entrance. Phosphate concentrations increased at the same time and experienced major peaks in the 1940s and 1950s to >100 μg/l. Chlorophyll a concentrations were generally below 24 μg/l/gTOC in the core, but there has been a clear increase since the 1980s, peaking at 120 μg/l/gTOC, likely associated with a recorded increase in the frequency of nuisance algal blooms. These results indicate that the Lake King environment is now very different to that present during early European settlement. We conclude that by identifying the nature and direction of environmental change, palaeoecological studies can contribute towards developing realistic and well-informed management, conservation and restoration strategies in Australian coastal ecosystems.  相似文献   

Farmers’ coping response to the low flows in the lower Yellow River: A case study of temporal dimensions of vulnerability     

Chunling Liu  Dominic Golding  Gang Gong   《Global Environmental Change》2008,18(4):543

Water scarcity in northern China has been a topic of concern in China for many years, but the increased frequency and duration of “no-flow” events in the Yellow River in the 1990s created a flurry of recent activity in the academic and policy arenas. These low-flow events severely disrupted the supply of irrigation water for agriculture in the lower reaches of the Yellow River and posed a substantial threat to farmers’ livelihoods. Within a broader effort to assess farmers’ vulnerability to water shortages, this qualitative research focuses on the coping mechanisms and adaptive strategies adopted by farming households in three villages in Shandong Province (Ma, Ding, and Xing). With increasing water stress and other stresses from land degradation and lack of market access, farmers’ coping mechanisms have evolved, expanding from one-time adjustments to long-term adaptations, and switching focus from securing reliable water sources to improving irrigation efficiency and diversifying both on-farm and off-farm production. The three villages have different vulnerability profiles and adopted different patterns of adaptive processes that reveal the key roles played by community leaders and the early innovators. The research presented here contributes a temporal and dynamic dimension to the study of vulnerability which is largely missing from the current literature, and provides practical insights about how to improve farmers’ adaptive capacities in the face of water shortages in northern China.  相似文献   

Erratum to: Aquitard distribution in a northern reach of the Miami Valley aquifer,Ohio, USA: Part 2. Interpretation of facies and geostatistical results     

David F. Dominic  Robert W. Ritzi  Kenneth W. Kausch 《Hydrogeology Journal》1996,4(4):97-97

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Analysis of Water Saturation, NAPL Content, Degradation Half-Life, and Lower Boundary Conditions on VOC Transport Modeling: Implications for Closure of Soil Venting Systems     

Dominic C. DiGiulio  Ravi Varadhan 《Ground Water Monitoring & Remediation》2001,21(4):83-91

Simulations using a one-dimensional, analytical, vadose zone, solute-transport screening code (VFLUX) were conducted to assess the effect of water saturation, NAPL saturation, degradation half-life, and boundary conditions at the vadose zone/ground water interface on model output. At high initial soil concentrations, model output was significantly affected by input parameters and lower boundary conditions yet still resulted in consistent decision-making to initiate or continue venting application. At lower soil concentrations, however, typical of what is observed after prolonged venting application, differences in model input and selection of lower boundary conditions resulted in inconsistent decision-making. Specifically, under conditions of low water saturation, use of a first-type, time-dependent lower boundary condition indicated that the primary direction of mass flux was from ground water to the vadose zone, suggesting little benefit from continued venting application. Use of a finite, zero-gradient lower boundary condition, though, indicated continued mass flux from the vadose zone to ground water, suggesting a continued need for venting application. In this situation, sensitivity analysis of input parameters, selection of boundary conditions, and consideration of overall objectives in vadose zone modeling become critical in regulatory decision-making.  相似文献   

The Ecology of Cyanobacteria: Their Diversity in Time and Space, Edited by B. A. Whitton and M. Potts     

Dominic A. Hodgson 《Journal of Paleolimnology》2002,28(3):383-384

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A critical assessment of the analysis and distributions of scytonemin and related UV screening pigments in sediments   总被引：1，自引：0，他引：1  

Angela H. Squier  Dominic A. Hodgson  Brendan J. Keely   《Organic Geochemistry》2004,35(11-12):1221

High performance liquid chromatography-mass spectrometry has been used to identify the cyanophyta-derived ultraviolet screening pigment scytonemin and its reduced counterpart in an Antarctic lake sediment. The formation of an artefact during the analysis has been demonstrated, enabling the recovery of improved estimates of the scytonemin and reduced scytonemin signals. The overall pigment composition records a primary producer community comprising both oxygenic and anoxygenic photoautotrophs, with variations in the abundance of scytonemin relative to the chlorophylls and carotenoids that are consistent with changes in response to variations in the light regime over time.  相似文献   

Evidence of subduction and crust–mantle mixing from a single diamond     

Daniel J. Schulze  Ben Harte  John W. Valley  Dominic M.DeR. Channer 《Lithos》2004,77(1-4):349-358

Cathodoluminescence (CL) imaging of polished sections of a diamond from the Guaniamo region of Venezuela suggests a history of the diamond involving two periods of growth separated by a period of resorption and possibly brittle deformation. In situ electron probe analysis of multiple eclogitic garnet inclusions reveals a correlation between garnet composition and location in the stone. An early-formed garnet in the diamond core has higher Ca/(Ca+Mg) and lower Mg/(Mg+Fe) values than later garnets associated with the second period of diamond growth. This variation conforms to an extensive trend of variation in the suite of eclogitic garnets extracted from Venezuelan diamonds. The diamond is zoned in carbon isotope composition (in situ secondary ion mass spectrometry, SIMS, data). The core compositions (δ¹³C PDB), corresponding to the first stage of growth, average −17.7‰. The second period of growth is apparently in two sub-sets of CL zones with mean values of −13.0‰ and −7.9‰. Nitrogen contents of diamond are low (30–300 atomic ppm) and do not correlate with carbon isotope composition. Oxygen isotope ratios of the garnet inclusions are elevated substantially above those expected for “common mantle”; δ¹⁸O VSMOW of early garnet is approximately +10.5‰ and two late garnets average +8.8‰. The evolutionary trend of magnesium enrichment in garnet is unlikely to represent igneous fractionation. The stable isotope data are consistent with diamond formation in subducted meta-basic rocks that had interacted with sea water at low temperatures at or near the sea floor and contained a substantial biogenic carbon component. During or following subduction, diamonds continued to form in an evolving system that was progressively modified by interaction with mantle material.  相似文献   

Wave propagation and soil–structure interaction on a cliff crest during the 1999 Athens Earthquake     

Dominic Assimaki  Eduardo Kausel  George Gazetas   《Soil Dynamics and Earthquake Engineering》2005,25(7-10):513-527

During the 1999 Athens Earthquake the town of Adàmes, located on the eastern cliff of the Kifissos river canyon, experienced unexpectedly heavy damage. Despite the significant amplification potential of the slope geometry, topography effects cannot alone explain the uneven damage distribution within a 300 m zone behind the crest, characterized by a rather uniform structural quality. This paper illustrates the important role of soil stratigraphy, material heterogeneity, and soil–structure interaction on the characteristics of ground surface motion. For this purpose, we first perform elastic two-dimensional wave propagation analyses utilizing available geotechnical and seismological data, and validate our results by comparison with aftershock recordings. We then conduct non-linear time-domain simulations that include spatial variability of soil properties and soil–structure interaction effects, to reveal their additive contribution in the topographic motion aggravation.  相似文献