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53.
The fishery harbor of Karaburun coastal village is located at the south west coast of the Black Sea. The significant waves coming from north eastern direction cause considerable rate of sediment transport along 4 km sandy beach towards the fishery harbor in the region. The resulting sediment deposition near and inside the harbor entrance prevents the boat traffic and cause a vital problem for the harbor operations. In order to determine the level and reasons of the sediment transport, the long-term observations of shoreline changes, the long-term statistical analysis of wind and wave characteristics in the region, and sediment properties have been performed. The data obtained from observations, measurements and analysis were discussed. The long-term statistics of deep water significant wave heights for each direction was discussed by comparing the results obtained from different data sources and methods. For shoreline evolution, the numerical study using one-line model was applied to describe the shoreline changes with respect to probable wave conditions. Initial shoreline was obtained from the digitized image in 1996 since there was no previous shoreline measurement of the site. The results were compared using the techniques of remote sensing obtained from sequent images using IKONOS and IRS1C/D satellites. 相似文献
54.
Patrik Kraufvelin Ari T. Ruuskanen Niko Nappu Mikko Kiirikki 《Estuarine, Coastal and Shelf Science》2007,72(4):665-674
During the reproduction period of Fucus vesiculosus, which occurs only once a year (in May–June) along the Finnish coast of the northern Baltic Sea, a thick carpet of filamentous algae often covers hard substrates suitable for zygote settlement. By placing out artificial substrates into the field, monthly over a period of eight months prior to F. vesiculosus settlement (October 2001–June 2002), we investigated the autumn/winter/spring colonisation and succession of filamentous algae and their possible relationships with the settlement success of F. vesiculosus under naturally variable field conditions. The substrates exposed in October 2001 became covered by filamentous brown algal Pilayella littoralis mats, which persisted over the settlement period of F. vesiculosus, but now also were accompanied by large amounts of the filamentous green alga Cladophora glomerata. The substrates exposed from November 2001 onwards hosted smaller amounts of P. littoralis during the winter and different filamentous algal communities at the time of F. vesiculosus settlement, i.e. less P. littoralis and C. glomerata, but Dictyosiphon foeniculaceus, Ceramium tenuicorne and Ulva intestinalis instead. We observed recruits of F. vesiculosus on all substrates, except on the ones placed out in October 2001. Significantly more P. littoralis and C. glomerata on the October substrates may explain the failed F. vesiculosus recruitment, although we could not establish direct causal or correlational relationships between filamentous algae and F. vesiculosus settlement. We compared the results with a previous un-replicated pilot study in the same area demonstrating similar response patterns. 相似文献
55.
Ka Lok Li Ólafur Gudmundsson Ari Tryggvason Reynir Bödvarsson Bryndís Brandsdóttir 《Journal of Seismology》2016,20(3):771-786
Seismicity is generally concentrated on faults or in fault zones of varying, sometimes complex geometry. An earthquake catalog, compiled over time, contains useful information about this geometry, which can help understanding the tectonics of a region. Interpreting the geometrical distribution of events in a catalog is often complicated by the diffuseness of the earthquake locations. Here, we explore a number of strategies to reduce this diffuseness and hence simplify the seismicity pattern of an earthquake catalog. These strategies utilize information about event locations contained in their overall catalog distribution. They apply this distribution as an a priori constraint on relocations of the events, or as an attractor for each individual event in a collapsing scheme, and thereby focus the locations. The latter strategy is not a relocation strategy in a strict sense, although event foci are moved, because the movements are not driven by data misfit. Both strategies simplify the seismicity pattern of the catalog and may help to interpret it. A synthetic example and a real-data example from an aftershock sequence in south west Iceland are presented to demonstrate application of the strategies. Entropy is used to quantify their effect. 相似文献
56.
Evolution and degradation of flat‐top mesas in the hyper‐arid Negev,Israel revealed from 10Be cosmogenic nuclides
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Ronen Boroda Ari Matmon Rivka Amit Itai Haviv Maurice Arnold Georges Aumaître Didier L. Bourlès Karim Keddadouche Yehuda Eyal Yehouda Enzel 《地球表面变化过程与地形》2014,39(12):1611-1621
Mesas are ubiquitous landforms in arid and semiarid regions and are often characterized by horizontal stratified erodible rocks capped by more resistant strata. The accepted conceptual model for mesa evolution and degradation considers reduction in the width of the mesa flat‐top plateau due to cliff retreat but ignores possible denudation of the mesa flat‐top and the rates and mechanism of erosion. In this study we examine mesas in the northeastern hyperarid Negev Desert where they appear in various sizes and morphologies and represent different stages of mesa evolution. The variety of mesas within a single climatic zone allows examination of the process of mesa evolution through time. Two of the four sites examined are characterized by a relatively wide (200–230 m) flat‐top and a thick caprock whereas the other two are characterized by a much narrower remnant flat‐top (several meters) and thinner caprock. We use the concentration of the cosmogenic nuclide 10Be for: (a) determining the chronology of the various geomorphic features associated with the mesa; and (b) understanding geomorphic processes forming the mesa. The 10Be data, combined with field observations, suggest a correlation between the width of flat‐top mesa and the denudation and cliff retreat rates. Our results demonstrate that: (a) cliff retreat rates decrease with decreasing width of the flat‐top mesa; (b) vertical denudation rates increase with decreasing width of the flat‐top mesa below a critical value (~60 m, for the Negev Desert); (c) the reduction in the width of the flat‐top mesa is driven mainly by cliff retreat accompanied by extremely slow vertical denudation rate which can persist for a very long time (>106 Ma); and (d) when the width of the mesa decreases below a certain threshold, its rate of denudation increases dramatically and mesa degradation is completed in a short time. Copyright © 2014 John Wiley & Sons, Ltd. 相似文献
57.
We analyze climate change in a cost–benefit framework, using the emission and concentration profiles of Wigley et al. (Nature
379(6562):240–243, 1996). They present five scenarios that cover the period 1990–2300 and are designed to reach stabilized concentration levels of
350, 450, 550, 650 and 750 ppmv, respectively. We assume that the damage cost in each year t is proportional to the corresponding gross world product and the square of the atmospheric temperature increase (ΔT(t)). The latter is estimated with a simple two-box model (representing the atmosphere and deep ocean). Coupling the damage
cost with the abatement cost, we interpolate between the five scenarios to find the one that is optimal in the sense of minimizing
the sum of discounted annual (abatement plus damage) costs over a time horizon of N years. Our method is simpler than ‘traditional’ models with the same purpose, and thus allows for a more transparent sensitivity
study with respect to the uncertainties of all parameters involved. We report our central result in terms of the stabilized
emission level E
o
and concentration level p
o
(i.e. their values at t = 300 years) of the optimal scenario. For the central parameter values (that is, N = 150 years, a discount rate r
dis
= 2%/year and a growth rate r
gro
= 1%/year of gross world product) we find E
o
= 8.0 GtCO2/year and p
o
= 496 ppmv. Varying the parameters over a wide range, we find that the optimal emission level remains within a remarkably
narrow range, from about 6.0 to 12 GtCO2/year for all plausible parameter values. To assess the significance of the uncertainties we focus on the social cost penalty,
defined as the extra cost incurred by society relative to the optimum if one makes the wrong choice of the emission level
as a result of erroneous damage and abatement cost estimates. In relative terms the cost penalty turns out to be remarkably
insensitive to errors. For example, if the true damage costs are three times larger or smaller than the estimate, the total
social cost of global climate change increases by less than 20% above its minimum at the true optimal emission level. Because
of the enormous magnitude of the total costs involved with climate change (mitigation), however, even a small relative error
implies large additional expenses in absolute terms. To evaluate the benefit of reducing cost uncertainties, we plot the cost
penalty as function of the uncertainty in relative damage and abatement costs, expressed as geometric standard deviation and
standard deviation respectively. If continued externality analysis reduces the geometric standard deviation of relative damage
cost estimates from 5 to 4, the benefit is 0.05% of the present value G
tot
of total gross word product over 150 years (about $3.9 × 1015), and if further research reduces the standard deviation of relative abatement costs from 1 to 0.5, the benefit is 0.03%
of G
tot
. 相似文献
58.
Antti Kilpeläinen Hilppa Gregow Harri Strandman Seppo Kellomäki Ari Venäläinen Heli Peltola 《Climatic change》2010,99(1-2):193-209
This work studied the temporal and spatial variability of the risk of snow-induced forest damage in Finland under current and changing climatic conditions until the end of this century. The study was based on a snow accumulation model in which cumulative precipitation, air temperature and wind speed were used as input variables. The risk was analyzed in terms of the number of days per year when the accumulated amount of snow exceeded 20 kg m???2. Based on the risk, the forest area and mean carbon stock of seedling, young thinning and advanced thinning stands at risk were calculated. Furthermore, the number of 5-day periods, when the accumulated amount of snow exceeded a risk limit, was calculated for the current and changing climatic conditions in order to study the frequency of damaging snowfalls. Compared to the baseline period 1961–1990, the risk of snow-induced forest damage and the amount of damaging snowfalls were predicted to decrease from the first 30-year period (1991–2020) onwards. Over the whole country, the mean annual number of risk days decreased by 11%, 23% and 56% in the first, second and third 30-year period, respectively, compared to the baseline period. In the most hazardous areas in north-western and north-eastern Finland, the number of risk days decreased from the baseline period of over 30 days to about 8 days per year at the end of the century. Correspondingly, the shares of the forest area at risk were 1.9%, 2.0% and 1.0% in the first, second and third 30-year period, respectively. The highest mean annual carbon stocks of young stands at risk were found in central, north-eastern and north-western Finland in the first and second 30-year period, varying between 0.6 and 1.2 Mg C ha???1 year???1, meaning at highest 3% of the mean carbon stock (Mg C stem wood ha???1) of those areas. This study showed that although the risk of snow-induced forest damage was mainly affected by changes in critical weather events, the development of growing stock under the changing climatic conditions also had an effect on the risk assessment. However, timely management of forest stands in the areas with a high risk of snow-induced damage contributes to the trees’ increased resistance to the damage. 相似文献
59.
Jussi Malila Antti-Pekka Hyvrinen Yrj Viisanen Ari Laaksonen 《Atmospheric Research》2008,90(2-4):303-ICNAA07
Nucleation phenomena have a great importance in many areas of science. However, the main theoretical tool to analyse these phenomena, the classical nucleation theory (CNT), has known weaknesses. A decade ago a nucleation theorem based correction to CNT was developed [McGraw, R., Laaksonen, A., 1996. Scaling properties of the critical nucleus in classical and molecular-based theories of vapor–liquid nucleation. Phys. Rev. Lett. 76, 2754–2757]. We have analysed experimental nucleation rate data of two homologous series of molecular fluids in terms of this scaling relation. Our first results suggest possible universal functional form for correction to the temperature dependence of CNT. 相似文献
60.
Summary A method of propagating the components of the displacement across interfaces in a multi-layered spherical earth model is presented. It is useful both for explosion sources and tangential dislocation sources, buried in an arbitrary layer of the model. Combined with known techniques, our method yields a useful tool for generating synthetic seismograms for earthquake sources in realistic earth models. 相似文献