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971.
We present the results of experimental investigations of the characteristics of turbulence in the layer of wave-induced mixing.
The data on the fluctuations of velocity, temperature, and conductivity are obtained with the help of a Sigma-1 measuring complex. The computed values of the dissipation rate of turbulent energy are compared with different models proposed
for the subsurface layer. It is shown that the available models fail to guarantee satisfactory agreement of the numerical
results with the experimental data for the layer of active wave action and, in particular, in the presence of swell. This
leads us to the conclusion concerning the necessity of parametrization and assimilation of more complete data on the state
of the sea surface, the structure of currents, and the surface layer of the atmosphere in the models.
__________
Translated from Morskoi Gidrofizicheskii Zhurnal, No. 2, pp. 15–28, March–April, 2007. 相似文献
972.
973.
Walker O. Smith Jr Amy R. Shields Jennifer C. Dreyer Vernon Asper 《Deep Sea Research Part I: Oceanographic Research Papers》2011,58(2):147-159
The vertical flux of particulate matter from the surface of the Ross Sea, Antarctica, has been suggested as being large, with substantial seasonal and spatial variations. We conducted a study in which vertical flux was quantified using sediment traps deployed at 200 m and compared to estimates calculated from one-dimensional budgets of nutrients (nitrogen and silicon). Estimates of flux were collected at two locations in the southern Ross Sea from late December to early February during four years: 2001-2002, 2003-2004, 2004-2005, and 2005-2006. Phytoplankton biomass and vertical flux varied substantially seasonally and spatially between the two sites, and among years. The greatest flux was observed in 2001-2002, with a short-term maximum organic carbon flux of 3.13 mmol m−2 d−1, and the summer mean organic carbon flux equal to 0.93 mmol m−2 d−1. In contrast, the mean carbon flux at the same site in 2003-2004 was over an order of magnitude less, averaging 0.19 mmol m−2 d−1, despite the fact that productivity in that year was substantially greater. In 2005-206 the contribution of fecal pellets to flux was smallest among all years, and the pellet contribution ranged from <1 to more than 50% of organic flux. As the moorings also had surface layer fluorometers, the relationship between surface biomass and sediment trap flux was compared. Temporal lags between surface fluorescence and flux at 200 m maxima in 2003-2004 and 2004-2005 ranged from two to six days; however, in 2005-2006 the temporal offset between biomass and flux was much longer, ranging from 11 to 27 days, suggesting that fecal pellet production appeared to increase the coupling between flux and surface production. Estimates of export from the upper 200 m based on one-dimensional nutrient budgets were greater than those recorded by the sediment traps. Nutrient budgets also indicated that siliceous production averaged ca. 40% of the total annual production. The variations observed in the flux of biogenic matter to depth in the Ross Sea are large, appear to reflect different forcing among years, and at present are not adequately understood. However, such variability needs to be both understood and represented in biogeochemical models to accurately assess and predict the effects of climate change on biogeochemical cycles. 相似文献
974.
George O. Marmorino W.D. MillerGeoffrey B. Smith Jeffrey H. Bowles 《Deep Sea Research Part I: Oceanographic Research Papers》2011,58(3):316-321
Airborne hyperspectral and thermal infrared imagery collected over the Florida Current provide a view of the disintegration of a Sargassum drift line in 5 m s−1 winds. The drift line consists mostly of rafts 20-80 m2 in size, though aggregations larger than 1000 m2 also occur. Rafts tend to be elongated, curved in the upwind direction, and 0.1-0.5 °C warmer than the surrounding ocean surface. Long weed ‘trails’ extending upwind from the rafts are evidence of plants dropping out and being left behind more rapidly drifting rafts. The raft line may be a remnant of an earlier Sargassum frontal band, which is detectible as an upwind thermal front and areas of submerged weed. Issues are identified that require future field measurements. 相似文献
975.
On the basis of the wind-energy method, we estimate the distributions of the parameters of a longshore flux of sediments formed
near the west coast of the Bakal’skaya Spit (in the northwest part of the Crimea) under the conditions of heavy storms whose
action caused a significant erosion of the west coast of the spit and retreat of the coastline in January and November 2007.
The calculations are carried out by using the actual directions and velocities of the winds recorded in the investigated region.
We analyze the trends of changes in the formation of the coastal zone caused by the nonuniform distribution of the intensity
of longshore transportation of sediments. In analyzing the causes of formation of gullies in the barrier of the Bakal’skoe
Lake and in the narrow distal part of the body of the spit, we make an attempt of interpretation of the quantities characterizing
the force of the frontal action of waves. The obtained numerical results are confirmed by the data of field observations. 相似文献
976.
I. F. Gablina L. L. Demina O. B. Dmitrenko N. S. Os’kina E. A. Popova T. A. Khusid V. V. Shilov 《Oceanology》2011,51(3):476-490
The first thorough analysis of microfossils from ore-bearing sediments of the Ashadze-1 hydrothermal field in the Mid-Atlantic
Ridge sampled during cruise 26 of the R/V Professor Logachev in 2005 revealed the substantial influence of hydrothermal processes on the preservation of planktonic calcareous organisms,
as well as on the preservation and composition of the benthic foraminifers. From the lateral and vertical distribution patterns
and the secondary alterations of the microfossils, it is inferred that the main phase of the hydrothermal mineralization occurred
in the Holocene. Heavy metals (Cu, Co, Cr, and Ag) were accumulated by foraminiferal tests and in their enveloping Fe-Mn crusts.
The distribution of authigenic minerals replacing foraminiferal tests demonstrates local zoning related to the hydrothermal
activity. There are three mineral-geochemical zones defined: the sulfide zone, the zone with an elevated Mg content, and zone
of Fe-Mn crusts. 相似文献
977.
978.
Interaction of solitary waves with emergent, rigid vegetation 总被引:3,自引:0,他引:3
In this study, solitary wave interaction with emergent, rigid vegetation was studied numerically and experimentally. Laboratory experiments were carried out in a wave flume with vegetation models of different lengths and porosities; the Boussinesq equations with the effects of the vegetation being modeled by a quadratic drag law are used to simulate the wave scattering by and the wave propagation through vegetation. Effects of incident wave height, vegetation density, and vegetation length are discussed. An empirical expression for the mean drag coefficient of emergent, rigid vegetation is presented and compared with other available data. The results are useful for studying tsunami hazard mitigation by coastal forests. 相似文献
979.
O.A. Montasir 《Ocean Engineering》2011,38(13):1417-1429
Spar platform has been regarded as a competitive floating structure for deep and ultra deep water oil and gas production. In this paper, an efficient methodology has been developed to determine the slow motion responses of slender floating offshore structures due to wave forces. Based on this methodology, a MATLAB program named ‘TRSPAR’ was developed to predict the dynamic responses in time domain and it was used in this study to obtain the numerical results of a typical truss spar platform connected to sea bed using nine taut mooring lines. The difference frequency forces were calculated using the principles of the extension of Morison equation for an inclined cylinder and the wave kinematics were predicted using hyperbolic extrapolation. Mooring lines were modelled as nonlinear springs and their stiffness was obtained by conducting the static offset simulation. Because of the lack of detailed calculations in literature, most of the equations used were derived and presented in this paper. The effects of the different sources of the second order difference frequency forces were compared for inertia and drag forces in terms of response spectra. To validate the TRSPAR code, its results were compared to results of a typical truss spar model test. 相似文献
980.