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Contribution of momentum advection to the formation of the low frequency fields of the Baltic Sea levels and currents is estimated using numerical experiments with a hydrodynamic model and statistical analysis of the experimental results. It is found that momentum advection has a significant influence on the formation of the mean level and its seasonal and synoptic variability in Neva Bay of the Gulf of Finland. The results show that nonlinear effects associated with advective accelerations can essentially contribute to the Neva River flood formation. 相似文献
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A comparative contribution of the sea level oscillations of various time scales (long-term, seasonal, synoptic, and mesoscale)
to the formation of the Neva River floods is estimated. The identification of the Neva River flood waves as the long gravity
ones existing nowadays is called in question. The comparison of estimated characteristics of flood waves with the theoretical
variance relations of different types of long waves is carried out. This comparison as well as the results of analysis of
meteorological information and numerical experiments carried out before on the basis of the hydrodynamic model of the Baltic
Sea demonstrate that the Neva River flood waves are identified as the forced baroclinic topographic waves generated as a result
of the resonance between the anemobaric forces in atmospheric cyclones and low-frequency eigenmodes of the open Baltic Sea-Gulf
of Finland system. 相似文献
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Old and modern data are given and discussed. They allow us to decide where the real position of the south marginal suture
of the East European Craton is. According to the geophysical and aerogeophysical studies, Paleozoic deposits of the Karpinskii
Ridge are bedded upon deeply sunken continuation of Archean-Proterozoic complexes comprising the Voronezh massif and crystalline
rocks belonging to the Astrakhan Dome. The latter have a pre-Riphean age. It is possible that the crust in the southeastern
part of ridge in a narrow zone with >20 km depth of the basement surface (BS) and, partially, in the Sarpinskii trough has
oceanic origin. 相似文献
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The series of long-term observations of synoptic-scale currents obtained by instrumental measurements at the moorings in the Gotland Basin of the Baltic Sea are analyzed. The results of the statistical analysis of the currents reveal their wave structure. The characteristics of the low-frequency waves received on the basis of the cross-spectral analysis show that, in the range of periods from 2 to 20 days, they propagated in the southwestern, southeastern, and northwestern directions with phase speeds of 0.02–2.08 m/s and have lengths from 28 to 431 km. It is suggested that the distinguished wavelike perturbations of the synoptic-scale currents are related to topographic waves. The analysis of the meteorological conditions and the results of the numerical hydrodynamic modeling of the Baltic Sea free low-frequency fluctuations led us to conclude that the most possible mechanism of the generation of the intense wave-like oscillations of synoptic-scale currents in the Gotland Basin is the resonance between the anemobaric forces and the relatively slow-moving anticyclones over the open Baltic Sea and the eigenmode of the basin. 相似文献
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Water Resources - The data of shipboard measurements of oxygen concentration at international monitoring stations in the Baltic Sea were used to assess the year-to-year variations of oxygen regime... 相似文献
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The within-Iranian backarc basins, including the largest Sebzawar Basin, opened in the Mid-Cretaceous. Spreading in this basin
was completed by the end of the Cretaceous. The basin closed in the Eocene with the formation of subduction zones and volcanic-plutonic
belts. Data on North Afghanistan and the Central Pamirs have allowed us to reconstruct the eastern continuation of the Sebzawar
Basin up to the west of the Central Pamirs. No fragments of oceanic crust are retained in Afghanistan and the Pamirs, but
by analogy with the Sebzawar Basin, thick Paleogene flysch sequences and volcanic-plutonic complexes indicate setting of the
active margin and subduction. It is suggested that the belt of mantle seismicity that extends for 550 km to the south of the
Central Pamirs is related to the plunging and deformation of the lithosphere once underlying the Cretaceous-Paleogene basin.
The extremely vigorous seismicity of the Hindu Kush megasource at the western termination of the seismic belt is caused by
a number of specific tectonic features that predetermined the early onset of plunging of the subducted sheet (slab). In the
megasource, the slab sank to a depth of 300 km and became vertical; its active deformation has proceeded up to the present.
In the eastern part of the seismic belt, the slab started to plunge much later and therefore has retained a gentle slope,
so that the depth of the hypocenters is shallower (down to 200 km), and earthquakes are less strong. 相似文献
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Based on vector-algebraic analysis of random processes, we study the statistical structure of the synoptic variability of currents measured by an ADCP in the upper mixed layer in the central part of the continental slope of the Laptev Sea in 2006–2007. The results of statistical analysis show that in some cases the synoptic currents in the surface layer of the sea are signs of wind drift currents. This is indicated by the high correlation between the tangential friction of wind and currents, as well as the reversal of the depth of current vectors and the major axes of the ellipses of the mean-square deviation of the Ekman spiral. Due to the large variability of wind flows and stratification of water masses, the penetration depth of these currents is small and varies from 6 to 30 m, with pronounced seasonal variation. In deeper layers, no relationship between the currents and anemobaric forces is traced. It is concluded that the fluctuations of synoptic scale currents in the area of the continental slope of the Laptev Sea represent a superposition of Ekman drift currents and movements associated with free baroclinic Kelvin waves. These currents are the dominant contributor in the upper 30-m layer of the ocean, while waves play a key role in deeper waters. 相似文献
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Doklady Earth Sciences - 相似文献