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381.
Masashi Kusakabe Andrey Andreev Vyacheslav Lobanov Igor Zhabin Yuichiro Kumamoto Akihiro Murata 《Journal of Oceanography》2002,58(5):691-701
Data from the R/V Mirai cruise (May–June 2000) have been examined to discover how mesoscale processes associated with eddy dynamics direct affect
the water masses, the distributions and the vertical fluxes of the dissolved oxygen, nutrients and dissolved inorganic carbon
in the western subarctic Pacific. Using maps of the temperature, salinity, dissolved oxygen, nutrients, chlorophyll and sea-air
pCO2 difference we show that the boundaries of the anticyclone eddies in the study region were composed of high productivity coastal
Oyashio water. The coastal waters were wrapped around the anticyclone eddies (thus creating a high productivity belt) and
intruded inside of them. Using SeaWifs data we demonstrate that temporal variations in the position and the strength of anticyclone
eddies advected the Kuril island coastal high productivity waters to the pelagic part, resulting in temporal variations of
the chlorophyll in the Oyashio region. Computed vertical fluxes of the dissolved oxygen (DO), inorganic carbon (DIC) and silicate
show that the anticylonic eddies in the Kuroshio-Oyashio Zone are characterized by enhanced vertical fluxes of the DO and
DIC between the upper (σθ = 26.7–27.0) and lower (σθ = 27.1–27.5) intermediate layer, probably due to the intrusions of the Oyashio waters into the eddies.
This revised version was published online in August 2006 with corrections to the Cover Date. 相似文献
382.
Igor Tsukrov Oleg Eroshkin David Fredriksson M. Robinson Swift Barbaros Celikkol 《Ocean Engineering》2003,30(2):251-270
A consistent finite element is proposed to model the hydrodynamic response of net panels to environmental loading. This equivalent net element is constructed to reproduce the drag, buoyancy, inertial and elastic forces exerted on the netting by current and waves. To evaluate the accuracy of the proposed finite element modeling, numerical predictions have been compared with the experimental observations and (simplified) analytical results of other authors. This new modeling technique has been applied to evaluate the performance of a tension leg fish cage in the open ocean environment. 相似文献
383.
Inter-annual to inter-decadal changes of hydrographic structure and circulation in the subpolar North Atlantic are studied using a coarse resolution ocean circulation model. The study covers 1949 through 2001, inclusive. A “time-mean state nudging” method is applied to assimilate the observed hydrographic climatology into the model. The method significantly reduces model biases in the long-term mean distribution of temperature and salinity, which commonly exist in coarse-resolution ocean models. By reducing the time-mean biases we also significantly improve the model’s representation of inter-annual to inter-decadal variations. In the central Labrador Sea, the model broadly reproduces the heat and salt variations of the Labrador Sea Water (LSW) as revealed by hydrographic observations. Model sensitivity experiments confirm that the low-frequency hydrographic changes in the central Labrador Sea are closely related to changes in the intensity and depth of deep convection. Changes in surface heat flux associated with the winter North Atlantic Oscillation (NAO) index play a major role in driving the changes in T–S and sea surface height (SSH). Changes in wind stress play a secondary role in driving these changes but are important in driving the changes in the depth-integrated circulation. The total changes in both SSH and depth-integrated circulation are almost a linear combination of the separate influences of variable buoyancy and momentum fluxes. 相似文献
384.
Karst aquifers represent one of the main sources of water supply in Serbia. Wide distributions of karstic areas, abundant
reserves, and excellent quality of karst groundwater have been the reasons for its extensive use in water supply systems throughout
the country. In Serbia, 70 karstic sources have been tapped for centralized water supply, with the assessed minimal capacity
exceeding 4.5 m3/s. Most of the large cities of Eastern and Western Serbia currently use karst groundwater for water supply; however, due
to unstable flow regime when only natural springflow is tapped, numerous problems arise during the recession period (summer–autumn).
During the last two decades, after favorable conditions had been confirmed through hydrogeological survey and feasibility
studies, several newly constructed systems for artificial control of karst aquifers (mostly in Eastern Serbia) resulted in
significantly improved water supply. 相似文献
385.
Igor Brovchenko Julia Kanarska Vladimir Maderich Katerina Terletska 《Acta Geophysica》2007,55(1):47-55
New three-dimensional numerical non-hydrostatic model with a free surface that was designed for modelling the bottom and bank
stability subjected by ship propeller jets is presented. Unlike all known models, it describes three-dimensional fields of
velocities generated by ship propellers, turbulence intensity and length scale in the given domain of arbitrary bottom and
coastal topography. Results of simulations are compared with the laboratory experiments. 相似文献
386.
Time series of hydrographic sections in the northern North Atlantic from the period 1990 to 2004 are analyzed for changes
in the characteristics and distribution of water masses that are involved in the thermohaline circulation (THC). During the
1990s, the North Atlantic Oscillation (NAO) alternates from a positive phase (strong westerlies) to a negative phase (weak
westerlies). The reduced ocean heat loss confined the convection in the Labrador Sea to the upper 1,200 m, generating a new
salinity minimum layer characterizing the Upper Labrador Sea Water (ULSW), and led to a warming and salinization of the older
LSW below due to lateral mixing. The Lower LSW, formed in the first half of the 1990s, spread in the subpolar gyre and reached
the Newfoundland and Irminger basins after about 1 to 2 years, where the associated isopycnal doming contributed to eastward
frontal shifts in the upper layer. After 5 and 6 years, it arrived in the Iceland and West European basins, respectively.
The collapse of the isopycnal dome in the Labrador Sea, associated with the drainage of the Lower LSW, resulted in a slowing
of the cyclonic circulation of the subpolar gyre. This was accompanied in the upper layer by a westward shift of the southeastern
extension of the gyre and a northward advection of warm and saline subtropical water in its eastern part, which finally reached
the Labrador Sea after about 7 years. In the upper layer of the Labrador Sea, the advection of warm and saline water dominated
over the heat loss to the atmosphere and the freshwater gain from melting ice and precipitation in the NAO-low period, so
that no accumulation of freshwater but an increase of the heat and salt contents were observed, as in the whole eastern part
of the subpolar gyre. Within 1 to 2 years after the drop of the NAO in the winter of 1995/1996, the Subarctic (Subpolar) Front
shifted northward and westward north of about 50°N, favored by the retreat of the low-salinity tongue extending eastward from
the southern Labrador Sea, and it shifted southward and eastward in the Newfoundland Basin. Therefore, the enhanced northward
advection of subtropical waters in the northeastern North Atlantic is balanced by the enhanced southward advection of subarctic
waters, including Lower LSW in the Newfoundland Basin, indicating a strong response of the gyre component of the THC. 相似文献
387.
Hernando Tavera Efraín Fernández Isabel Bernal Yanet Antayhua Consuelo Agüero Henry Salas Simeón Rodríguez Luis Vilcapoma Yolanda Zamudio David Portugal Adolfo Inza Julia Carpio Freddy Ccallo Igor Valdivia 《Journal of Seismology》2006,10(2):171-195
The western border of South America is one of the most important seismogenic regions in the world. In this region the most damaging earthquake ever recorded occurred. In June 23rd, 2001, another very strong earthquake (Mw = 8.1–8.2) occurred and produced death and damages in the whole southern region of Peru. This earthquake was originated by a friction process between Nazca and South American plates and affected an area of about 300 km × 120 km defined by the distribution of more than 220 aftershocks recorded by a local seismic network that operated 20 days. The epicenter of the main shock was localized in the northwestern extremity of the aftershock area, which suggests that the rupture propagated towards the SE direction. The modeling of P-wave for teleseismic distances permitted to define a focal mechanism of reverse type with NW-SE oriented nodal planes and a possible fault plane moving beneath almost horizontally in NE direction. The source time function (STF) suggests a complex process of rupture during 85 sec with 2 successive sources. The second one of greater size, and located approximately 100–120 km toward the SE direction was estimated to have a rupture velocity of about 2 km/sec on a 28°-dipping plane to the SE (N135°). A second event happened 45 sec after the first one with an epicenter 130km farther to the SE and a complex STF. This event and the second source of the main shock caused a Tsunami with waves from 7 to 8 meters that propagated almost orthogonally to the coast line, by affecting mainly the Camaná area.Three of all the aftershocks presented magnitudes greater or equal to Mw = 6.6, two of them occurred in front of the cities of Ilo and Mollendo (June 26th and July 7th) with focal mechanisms similar to the main seismic event. The aftershock of July 5th shows a normal mechanism at a depth of 75 km, and is therefore most likely located within the subducting Nazca plate and not in the coupling. The aftershocks of June 26th (Mw = 6.6) and July 5th (Mw = 6.6) show simple short duration STF. The aftershock of July 7th (Mw = 7.5) with 27-second duration suggests a complex process of energy release with the possible occurrence of a secondary shock with lower focal depth and focal mechanism of inverse type with a great lateral component. Simple and composed focal mechanisms were elaborated for the aftershocks and all have similar characteristics to the main earthquake.The earthquake of June 23rd caused major damages in the whole southern Peru. The damage in towns of Arequipa, Moquegua allow to consider maximum intensities from 6 to 7 (MSK79). In Alto de la Alianza and Ciudad Nueva zones from Tacna, the maximum intensity was of 7− (MSK79). 相似文献
388.
Isabel Abad Gabriel Gutirrez-Alonso Fernando Nieto Igor Gertner Alex Becker Ana Cabero 《Tectonophysics》2003,365(1-4):103
Geological mapping and structural analysis of the Talas Ala Tau (Tien Shan, Kyrgyz Republic) have revealed a complex structure composed of folds with axial-plane cleavage and thrust faults verging towards the NE. The main structures of the range correspond to minor Tertiary and Carboniferous–Permian deformation superimposed on the main deformation event that took place during the Baikalian orogeny. The pervasive axial-plane cleavage diminishes in penetrativity from the hinterland to the foreland in both the Uzunakhmat and Karagoin sheets. The main thrusts developed phyllonitic shear-related rocks on the hangingwall immediately above the thrust planes. A crystal-chemical study of the phyllosilicates growth during the Baikalian deformation event along a cross-section revealed changes in the crystallinity, composition and lattice parameters of them. The phyllosilicates present in the Talas Ala Tau rocks were crystallized in very low-grade metamorphic conditions, that is below 300 °C, as indicated by their Kübler Index (KI), which decreases from SW towards the NE. Detailed TEM study of the phyllosilicates reveals a clear textural difference at the lattice level between samples with higher or lower KI parameters. There is also a clear difference in crystal-chemical parameters (KI and b) and composition between the phyllosilicates growth in relation to the axial-plane cleavage and the ones belonging to the thrust-related phyllonites. The first ones are more affected by the ferrimuscovitic vector than the phyllosilicates of phyllonites, closer to the theoretical phengitic component. Huge ranges of values of phengitic content of micas at sample level are interpreted as the result of a decompression path from at least 8 kbar. We propose a subduction geodynamic environment for the regional deformation and the origin of the phyllosilicates, as they are similar to those obtained in more recent accretionary complexes. 相似文献
389.
We design a velocity–porosity model for sand-shale environments with the emphasis on its application to petrophysical interpretation of compressional and shear velocities. In order to achieve this objective, we extend the velocity–porosity model proposed by Krief et al., to account for the effect of clay content in sandstones, using the published laboratory experiments on rocks and well log data in a wide range of porosities and clay contents. The model of Krief et al. works well for clean compacted rocks. It assumes that compressional and shear velocities in a porous fluid-saturated rock obey Gassmann formulae with the Biot compliance coefficient. In order to use this model for clay-rich rocks, we assume that the bulk and shear moduli of the grain material, and the dependence of the compliance on porosity, are functions of the clay content. Statistical analysis of published laboratory data shows that the moduli of the matrix grain material are best defined by low Hashin–Shtrikman bounds. The parameters of the model include the bulk and shear moduli of the sand and clay mineral components as well as coefficients which define the dependence of the bulk and shear compliance on porosity and clay content. The constants of the model are determined by a multivariate non-linear regression fit for P- and S-velocities as functions of porosity and clay content using the data acquired in the area of interest. In order to demonstrate the potential application of the proposed model to petrophysical interpretation, we design an inversion procedure, which allows us to estimate porosity, saturation and/or clay content from compressional and shear velocities. Testing of the model on laboratory data and a set of well logs from Carnarvon Basin, Australia, shows good agreement between predictions and measurements. This simple velocity-porosity-clay semi-empirical model could be used for more reliable petrophysical interpretation of compressional and shear velocities obtained from well logs or surface seismic data. 相似文献
390.
1. Introduction In spite of the progress achieved in global climatemodelling during the last few decades, the models stillshow considerable errors even for the surface air tem-perature ?eld (Covey et al., 2000; IPCC, 2001; Lam-bert and Boer, 2001). As i… 相似文献