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41.
Asgeir Sorteberg Vladimir Kattsov John E. Walsh Tatyana Pavlova 《Climate Dynamics》2007,29(2-3):131-156
Ensembles of simulations of the twentieth- and twentyfirst-century climate, performed with 20 coupled models for the Intergovernmental
Panel on Climate Change (IPCC) Fourth Assessment, provide the basis for an evaluation of the Arctic (70°–90°N) surface energy
budget. While the various observational sources used for validation contain differences among themselves, some model biases
and across-model differences emerge. For all energy budget components in the twentieth-century simulations (the 20C3M simulation),
the across-model variance and the differences from observational estimates are largest in the marginal ice zone (Barents,
Kara, Chukchi Seas). Both downward and upward longwave radiation at the surface are underestimated in winter by many models,
and the ensenmble mean annual net surface energy loss by longwave radiation is 35 W/m2, which is less than for the NCEP and ERA40 reanalyses but in line with some of the satellite estimates. Incoming solar radiation
is overestimated by the models in spring and underestimated in summer and autumn. The ensemble mean annual net surface energy
gain by shortwave radiation is 39 W/m2, which is slightly less than for the observational based estimates, In the twentyfirst-century simulations driven by the
SRES A2 scenario, increased concentrations of greenhouse gasses increase (average for 2080–2100 minus average for 1980–2000
averages) the annual average ensemble mean downward longwave radiation by 30.1 W/m2. This was partly counteracted by a 10.7 W/m2 reduction in downward shortwave radiation. Enhanced sea ice melt and increased surface temperatures increase the annual surface
upward longwave radiation by 27.1 W/m2 and reduce the upward shortwave radiation by 13.2 W/m2, giving an annual net (shortwave plus longwave) surface radiation increase of 5.8 W/m2 , with the maximum changes in summer. The increase in net surface radiation is largely offset by an increased energy loss
of 4.4 W/m2 by the turbulent fluxes. 相似文献
42.
Samples of macrobenthic organisms were obtained at seven stations on a presumed pollution gradient from the head of Vancouver Harbour through to outer Howe Sound. Polychaetes (83 apparent species) and molluscs (43 apparent species) were the most abundant faunal groups numerically (44.8 and 47.9%, respectively). Molluscs accounted for most of the biomass (87.9%). The following univariate and multivariate methods were used to investigate structural changes in the benthic communities: ANOVA, Abundance-Biomass Comparisons and related statistics, cluster analysis, multidimensional scaling, and the BIOENV procedure. Most of the analyses divided the seven stations into three groups: Port Moody Arm (Inner Harbour): two stations; Inner and Outer Harbour: four stations, and Gibsons (Howe Sound): one station. Further cause-effect investigations are needed to determine the sensitivity to organic pollution of indicator species identified in the survey. However our data correlating benthic community changes to sediment chemistry suggest the inner harbour was dominated by pollution-tolerant species. Depth and sediment grain size were confounding factors for the interpretations. 相似文献
43.
Variations in species diversity and abundance of polychaete taxocenes that occurred in 1980–1989 under different contamination
levels of bottom sediments were studied in three areas of Peter the Great Bay. The most polluted area was shown to be the
Golden Horn Inlet where contaminant contents in the bottom sediments exceed the threshold values of negative biota alterations.
Amursky Bay is characterized by a moderate level of contamination, while Ussuriysky Bay has the lowest level of contamination.
Pollutant contents vary considerably within the same areas and their separate patches are polluted differently. An integral
index characterizing the contamination of bottom sediments is proposed. This index is an average grade of the rank value of
contaminant contents in sediments. The index was used to compare the contamination level and data on polychaete species diversity
and abundance. The highest species diversity of polychaetes is found in the least affected zones. Monotonous decrease of the
species number, as well as decrease in the indices of diversity and evenness, is correlated with pollution level increases.
Significant growth of the average polychaete biomass and polychaete density is observed in the case of an increase of contamination
from low to moderate levels. Conversely, the biomass and abundance of polychaetes decline following an increase in contamination. 相似文献
44.
Viktoria K. Kis Tatyana Shumilova Victor Masaitis 《Physics and Chemistry of Minerals》2016,43(9):661-670
High-resolution transmission electron microscopy was applied for the detailed nanostructural investigation of Popigai impact diamonds with the aim of revealing the nature of the amorphous carbon of the matrix. The successful application of two complementary specimen preparation methods, focused ion beam (FIB) milling and mechanical cleavage, allowed direct imaging of nanotwinned nanodiamond crystals embedded in a native amorphous carbon matrix for the first time. Based on its stability under the electron beam, native amorphous carbon can be easily distinguished from the amorphous carbon layer produced by FIB milling during specimen preparation. Electron energy loss spectroscopy of the native amorphous carbon revealed the dominance of sp 2-bonded carbon and the presence of a small amount of oxygen. The heterogeneous size distribution and twin density of the nanodiamond crystals and the structural properties of the native amorphous carbon are presumably related to non-graphitic (organic) carbon precursor material. 相似文献
45.
Tatyana Novikova Gerassimos A. Papadopoulos Vassilios Karastathis 《Natural Hazards》2007,40(3):537-552
In the present paper we analyze the effect of local geology on ground motion by means of numerical calculations (numerical
models) using total (TS) and effective stress (ES) methods. These numerical calculations have been applied to the site of
Itea, Corinth Gulf, which was chosen based on liquefaction susceptibility criteria and field inspection. Data from seismic
refraction experiments and cone penetration test N-values as well as selected records of ground motion in nearby areas were
used to construct the input file for the numerical model. By means of␣dynamic analysis such characteristics of ground motion
as acceleration time histories, response spectra, and amplification function were evaluated. A one-dimensional soil amplification
effect was clearly shown. Liquefaction probability at the Itea site was predicted based on the safety factor and the calculation
of the induced settlement at the test site. Results of the TS and ES modeling lead us to conclude: (1) the presence of soft
soil at Itea caused significant amplification (almost 2.5-fold higher magnitude) of the underlying bedrock motion and, therefore,
can contribute to damage; (2) the area of Itea is highly susceptible to liquefaction due to presence of silty sand deposits
at depths between 2.48 m (the position of the water table) and 12 m that demonstrate the rapid growth of the excess pore water
pressure (EPWP) ratio with an increase in peak ground acceleration values. 相似文献
46.
Tatyana A. Zotina Alexander P. Tolomeyev Nadezhda N. Degermendzhy 《International Journal of Salt Lake Research》1999,8(3):211-232
The specific composition, vertical distribution and daily migration of plankton in a meromictic salt lake, Lake Shira, have been investigated. The main structural components of the ecosystem are bacteria, algae and crustaceans. Since the late 1970s, blue-green algae are reported as dominant. Nowadays the phytoplankton is dominated by Lyngbya contorta, Microcystis ichtyoblabe (Cyanophyta), Cyclotella tuberculata (Bacillariophyta) and Dictyosphaerium tetrachotomum (Chlorophyta). The zooplankton of Lake Shira comprises Arctodiaptomus salinus (Copepoda), Brachionus plicatilis and Hexarthra oxiuris (Rotatoria). Investigation revealed a stratified vertical distribution of all dominant species except Cyclotella with a maximum at a depth of 12--15 m during the summer growth period. Zooplanktons differ in the pattern of distribution and daily migration, but most zooplankton tend to concentrate near the surface. The possible reasons for the vertical distribution of the plankton are discussed. 相似文献
47.
Tatyana I. Moiseenko Andrey N. Sharov Lubov P. Kudryavtseva Catherine Rose 《Limnologica》2009,39(1):1-13
In this study, published data on Lake Imandra, north-west Russia, have been synthesised to investigate trends in lake contamination and recovery due to changing inputs of heavy metals and nutrients over time. Records of water chemistry, phytoplankton, zooplankton and fish communities have been used to determine the status of aquatic ecosystem health in three distinct phases of Lake Imandra's recent history. Firstly, background (reference) conditions within the lake have been established to determine lake conditions prior to anthropogenic influences. Secondly, a period of ecosystem degradation due to anthropogenic inputs of toxic metals and nutrients has been described. Finally, evidence of lake recovery due to recent decreases of toxic metals and nutrients has been explored. Pollution of Lake Imandra began in the 1930s, reaching a peak in the 1980s. Increases in heavy metal and nutrient inputs transformed the typical Arctic ecosystem. During the contamination phase, there was a decrease in Arctic species and in biodiversity. During the last 10 years, pollution has decreased and the lake has been recolonised by Arctic water species. Ecosystem recovery is indicated by a change of predominant species, an increase in the individual mass of organisms and an increase in the biodiversity index of plankton communities. In accordance with Odum's ecosystem succession theory, this paper demonstrates that the ecosystem has transformed to a more stable condition with new defining parameters. This illustrates that the recovery of Arctic ecosystems towards pre-industrial reference conditions after a reduction in anthropogenic stresses occur, although a complete return to background conditions may not be achievable. Having determined the status of current ecosystem health within Lake Imandra, the effect of global warming on the recovery process is discussed. Climate warming in Arctic regions is likely to move the ecosystem towards a predominance of eurybiontic species in the community structure. These organisms have the ability to tolerate a wider range of environmental conditions than typical Arctic inhabitants and will gain advantages in development. This indicates that the full recovery of Arctic ecosystems in a warming climate may not be possible. 相似文献
48.
Sallam Emad S. Ruban Dmitry A. Mostafa Moataz T. Elkhodery Menna Kh. Alwilily Rufida L. Molchanova Tatyana K. Zorina Svetlana O. 《Arabian Journal of Geosciences》2020,13(3):1-11
Arabian Journal of Geosciences - Surface albedo is a key parameter in earth energy budget and global climate change studies. In this aspect, variation in vegetation covers is one of the most... 相似文献
49.
Mineralogy and Petrology - Complementary nano- and atomic-scale data from SEM, FIB, HRTEM, and EELS observations of after-coal impact diamonds from the giant Kara astrobleme are described,... 相似文献
50.
Oleksandr Menshov Roman Kuderavets Sergiy Vyzhva Valentyn Maksymchuk Igor Chobotok Tatyana Pastushenko 《Studia Geophysica et Geodaetica》2016,60(4):731-746
The Starunia oil-ozokerite deposit occurs in the Boryslav-Pokuttya Unit of the Carpathian Foredeep, which is the main oil- and gas-bearing part of the Ukrainian Carpathians. Starunia is of great interest in studying the relationship between the magnetic properties of rocks, soils and hydrocarbons due to extensive surface microseeps yielding oil and gas, mineral water, and clay pulp containing hydrocarbons. We identified a local negative magnetic anomaly (30–35 nT) with a width of about 700 m within the MAG1 profile. The magnetic high is associated with the area of the largest mud volcanoes in the Starunia structure. Magnetic susceptibility of the soil was measured on a site with three distinct landscape features: a patch of forest with phaeozem and mass-specific susceptibility (χ) of 20–45 × 10?8 m3/kg for the surface topsoil; an area near the volcano and Nadia-1 well with visible hydrocarbon microseepage at the surface and the topsoil showing no visible evidence of hydrocarbon presence with χ = 20–50 × 10?8 m3/kg; and a patch of lowland with gleysols and χ = 10–20 × 10?8 m3/kg. Hydrocarbon-containing clays and soils from the alluvial sediments of the Velyky Lukavets River and bedrock clays near the Nadia-1 well demonstrated high χ values (up to 250–440 × 10?8 m3/kg). 相似文献