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881.
E. M. Lemeshko A. N. Morozov S. V. Stanichnyi L. D. Mee G. I. Shapiro 《Physical Oceanography》2008,18(6):319-331
The profiles of absolute current velocity obtained by using a lowered acoustic doppler current profiler (LADCP) are presented. In the course of the BSERP-3 expedition, the measurements were carried out in the regions of the Rim Current, anticyclonic eddy, and northwest shelf.
In the core of the Rim Current, a unidirectional motion of waters is traced in layers below the main pycnocline down to depths
greater than 500 m. Its characteristic velocity can be as high as 0.08 m/sec. It is shown that the direct action of the eddy
is detected in the shelf region at distances larger than 20 km from the outer edge of the shelf in the zone bounded by an
isobath of 100 m. The formation of multilayer vertical structures in the field of current velocities is revealed in the region
of interaction of the anticyclonic eddy with irregularities of the bottom on the side of the shelf. A two-layer structure
of currents with specific features in the layer of formed seasonal pycnocline is observed in the region of the shelf down
to an isobath of 100 m. The profiles of the moduli of vertical shears of currents averaged over the casts ensemble are presented
for the abyssal and shelf parts of the sea. It is shown that the shears induced by the geostrophic currents and wave processes
in the region of the main pycnocline are comparable. Below the pycnocline, the shears are mainly determined by the wave processes.
Translated from Morskoi Gidrofizicheskii Zhurnal, No. 6, pp. 25–37, November–December, 2008. 相似文献
882.
883.
The Climatic variability of the seasonal water exchange in the Strait of Gibraltar and the spatial structure of the tongue of the Mediterranean Waters (MW) in the Atlantic Ocean are studied. The analysis is based on the results of a numerical experiment using a 3D ocean circulation model developed at the Institute of Computational Mathematics (ICM RAS) with a resolution of the dataset over the latitude and longitude equal to 0.25 degree. The seasonal evolution of the salinity and density fields is calculated in the North Atlantic (from 20 °S, including the Mediterranean Sea) and in the Arctic Ocean (including the Bering Sea). The comparison of the model estimates with the results of field observations demonstrated good agreement. The transport of the MW into the Atlantic is close to the observed data (during the year, it varies from 1.8 Sv in the winter to 0.9 Sv in the summer). The complex pattern of the currents in the region of the MW spreading is confirmed. The alternating character of the saline MW tongue at the 1000-m level is shown for the first time. It is found that the zones of maximum salinities in the open part of the ocean coincide with the main trajectories of migration of MW lenses and the regions of their decomposition. 相似文献
884.
A numerical model of baroclinic circulation based on the use of a double sigma coordinate system is presented and its application
to the simulation of flows and temperature and salinity fields in the Dnieper-Bug Estuary is described. The model reproduces
the salinity and temperature fields surveyed in 1998. The results of simulations reveal the existence of a global influence
of the relatively narrow and deep ship channel (through which Black-Sea waters can penetrate deep into the estuary) on the
transport processes.
Translated from Morskoi Gidrofizicheskii Zhurnal, No. 6, pp. 66–77, November–December, 2008. 相似文献
885.
Historical sediment nutrient concentrations and heavy metal distributions were studied in four estuaries in the Gulf of Finland, Baltic Sea to examine the response of these estuaries to temporal changes in human activities. Cores were collected using a 1-m Mackereth corer and dated using 210Pb and 137Cs. The cores were analyzed for total carbon (TC), total nitrogen (TN), total phosphorus (TP), organic phosphorus (OP), inorganic phosphorus (IP), biogenic silica (BSi), loss-on-ignition (LOI), Cu, Zn, Al, Fe, Mn, K, Ca, Mg and Na. Principal component analysis (PCA) was used to summarize the trends in the chemical variables and to compare the trends at the different sites. Applying the 1986 137Cs date as a reference point, 210Pb chronologies were constructed for the sites using either the CRS model or a composite model (using both CIC and CRS). Significant increases were observed in sedimentation rates, TP and TN concentrations in all of the cores. Copper showed clear increases from 1850 towards present at all sites. Furthermore, redundancy analysis (RDA) was used to correlate environmental variables (catchment land use, catchment size, estuary surface area, depth and lake percentage) to sediment geochemistry. Based on redundancy analysis (RDA), the percentage of agriculture in the catchment was the most important factor affecting the sediment accumulation rate. Urban land-use types and industry correlate well with sediment Cu and Ca concentrations. Forest areas were related to high sediment BSi concentrations. Catchment land use was the most significant factor affecting sediment geochemical composition and sediment accumulation rates in these coastal embayments. Our results demonstrate that the coastal estuaries of the Gulf of Finland respond to the increased nutrient loading with the increased sedimentation and nutrient accumulation rates. 相似文献
886.
887.
Stotts S. A Koch R. A. Joshi S. M. Nguyen V. T. Ferreri V. W. Knobles D. P. 《Oceanic Engineering, IEEE Journal of》2010,35(1):79-102
888.
The sea cucumber Holothuria scabra is a widely distributed and economically important species that has been harvested in Kenya for decades. No previous studies have been carried out on the reproduction of this species in Kenya. Standard gonad index methods were used to analyze reproductive patterns of individuals collected monthly in 1998–1999, 2000–2001 and 2006–2007. Morphological characteristics, gonad tubule lengths and fecundity were also measured. Mean monthly gonad indices were significantly correlated between males and females indicating synchronous gonad development between the sexes. Gonad indices showed a biannual pattern that was consistent in all three years with a minor spawning event occurring between August and September and a major spawning event between November and December. The pattern of gonad growth showed significant variability between years and between months. Temporal changes in gonad growth correlated significantly with gonad tubule length and absolute fecundity. Monthly gonad indices also correlated significantly with monthly measurements of air temperature and light suggesting a possible role for both factors in timing gametogenesis and spawning. There was a shift in sex ratio from unity in the 1998–1999 and 2000–2001 samples to significantly more males in the 2006–2007 samples, as well as a significant reduction in mean sizes (body wall weight) and reproductive output (gonad index) which suggests that the reproductive success of this species is potentially negatively affected by fishing. 相似文献
889.
A series of samples of inhabitants of hydrothermal vents were collected during the 12th cruise of R/V Akademik Mstislav Keldysh in Guaymas Basin (the Gulf of California) and the Axial Seamount area (Juan de Fuca Ridge). The concentrations of trace and heavy metals in the tissues of Ridgeia piscesae, Riftia pachyptila, and Paralvinella palmiformis were analyzed. The neutron-activation analysis revealed significantly higher concentrations of uranium in the tissues of Paralvinella palmiformis as compared to the ambient seawater. The possible reasons for such phenomenon are discussed. The data obtained by the neutron-activation method are compared with those obtained by the atomic-absorption method for the same tissues analyzed. 相似文献
890.
Nonlinear interactions of the internal waves of a tidal period with low-frequency synoptic-scale internal waves are studied using instrumental measurements of the current in the coastal zone of the Sea of Japan. In the course of spectral analysis of the data of instrumental measurements, it is found that a maximum in the spectrum of the kinetic energy of coastal waters in the vicinity of the semidiurnal frequency ω0 is surrounded by satellite maxima whose frequencies obey the relation ω s = ω0 ± Ω, where Ω is the characteristic frequency of synoptic-scale internal waves. The spectrum of the anticyclonic current component has a similar structure in the vicinities of the frequency ω0 and its first and second harmonics. The general theory of nonlinear interactions of weakly dispersive waves is used to solve the problem of modulation and the parametric amplification of tidal internal waves in the coastal zone using low-frequency narrow-band internal waviness. As can be judged from the literature, the effect of parametric modulation of tidal internal waves by low-frequency synoptic-scale internal waves has been recorded in the coastal zone of a tidal sea for the first time. 相似文献