首页 | 本学科首页   官方微博 | 高级检索  
相似文献
 共查询到20条相似文献，搜索用时 62 毫秒
1.
Dependences have been determined which connect the parameters of the dispersion relation of the lowest mode of internal waves with the integral characteristics of the seasonal thermocline when 10 min30 min, 20 mh150 m, and 0·4 m2/s2 Q5·2 m2/s2.Translated by Mikhail M. Trufanov.  相似文献   

2.
Exact and approximate formulae are proposed to evaluate the errors of spatial/temporal digitization (aliasing) of then-dimensional random fields withm-power spectra atn=1, , 4 and 1m5, which satisfactorily approximate temperature, velocity, density, and other fields in the sea and atmosphere.Translated by Vladimir A. Puchkin.  相似文献   

3.
On the basis of the generalization of the concept of standard ocean to the Black Sea, we deduce practical formulas for the conversion of pressure into depth and vice versa depending on the latitude of the place with regard for the equation of state for 1980. The error of these relations for the standard Black Sea (whose salinity is equal to 22.2 at a temperature of +9°C from the surface to the bottom) does not exceed ±0.2m and ±0.2dbar. The difference between the practical and actual depths in winter and summer periods does not exceed ±0.35m for depths varying within range 0–2000m. The proposed practical formulas enable one to simplify the procedure of rapid evaluation of depth (or pressure) in real time by excluding the procedure of integration over a specific volume.  相似文献   

4.
The maximum uptake rate (max) and affinity constant (K s) for nitrate and ammonium were estimated in the surface water of offshore Oyashio in May (spring) and September (summer), 1990. The average max/Chl.a for ammonium was 2.1 times larger than that of nitrate in both seasons. The average max/Chl.a for both nitrogens were 3.5 times larger in summer than in spring. Water temperature and size composition of phytoplankton population were related to the seasonal difference in the max/Chl.a. Phytoplankton population showed high affinity for both nitrogens in the spring and summer. In addition, the contribution of new production to total production was estimated by max[max–No3/(max–NO3+max–NH4)]. The spring value was in the range of 0.26 to 0.45 (mean±SD=0.35±0.092), and the values in spring bloom were especially a little over 0.4. The summer value was in the range of 0.30 to 0.37 (0.34±0.04).  相似文献   

5.
The geometry and internal structures of modern sediments on the inner shelf off the southeastern coast of Korea were investigated by means of analysing high-frequency (3.5 kHz) seismic records. The records reveal a wedge-shaped sediment body, tapering off toward the sea. On the basis of reflection patterns, the sediments can be classified into two units; foreset (prodelta) unit and bottomset unit, consisting of sandy muds and clays, respectively. The lateral transition from foreset to bottomset deposits suggests a prograding delta system of the Nakdong River since the late Holocene.  相似文献   

6.
The amount of penetration of a western boundary current into a marginal sea which is connected to an open ocean by two narrow straits is estimated from a linear, steady and barotropic theoretical model. In this model the western boundary current in the open ocean is driven by a wind stress imposed at the sea surface. The inflow of the water of the open ocean into the marginal sea is caused by the pressure difference between two straits produced by the wind-driven circulation in the open ocean.Main external parameters are combined into two non-dimensional parameters; and (the ratio of the depth of the marginal sea to that of the open ocean), whereb is the distance between north and south boundaries of the ocean,D 0 is the depth of the open ocean, is the latitudinal variation of the Coriolis parameter andR is the coefficient of friction. The friction is assumed to be proportional to the flow velocity.In the limit of infinite the volume transport into the marginal sea is not affected by the width of two straits and . It is mainly controlled by the wind stress and the positions of two straits. For finite values of , however, the volume transport depends considerably on and the width of the straits.Guided by both this model and physical considerations, we obtained a relation between the volume transport into the marginal sea and the external parameters. This relation predicts that about 2 % of the volume transport of the Kuroshio penetrates into the Japan Sea.  相似文献   

7.
The reflection and breaking of internal waves on a sloping beach were studied in a small wavetank filled with water and petroleum. The dependence of the reflection coefficient of the internal waves on wave steepness and on beach slope is found to be very similar to that of surface waves. The reflection coefficient is small for the very gentle slope, increases rapidly as the slope increases, and becomes almost constant for the steep slope. The reflection coefficient decreases with increase of the wave steepness. Also, the transition slope at which the coefficient curve has the maximum gradient increases with increase of the wave steepness. Breaking pattern of the internal waves is classified into four types; breaking, semi-breaking, wrinkle-generating, and non-breaking. Their dependence on beach slope and wave steepness is examined. The regular sequence of the four breaking types from breaking to non-breaking is observed with decrease of wave steepness or with increase of beach slope.  相似文献   

8.
The downward short- and long-wave radiation fluxes at the sea surface (S, L) were measured aboard the R/VHakuho Maru, University of Tokyo, for the period of 117 days on six cruises from 1981 to 1985 in the western North Pacific near Japan. The upward fluxes of short- and long-wave radiation (S, L) were calculated by Payne's (1972) table and the Stefan-Boltzmann's law, respectively. The sensible and laten heat fluxes (Q h ,Q e ) were also estimated from an aerodynamic bulk method.From April to August, the daily mean value ofS varied with the amplitude of 100200 Wm–2. The value ofS was estimated approximately 6% ofS in all seasons. The difference betweenL andL was so small that the net radiation flux (Q n ) was dominated byS. In addition, the net heat flux at the sea surface was also dominated byS due to small values ofQ h andQ e , and then the ocean was warmed at the rate of 111 Wm–2 in April and 63 Wm–2 in August in the Oyashio Area, and 132 Wm–2 in May and 164 Wm–2 in June in the Kuroshio Area, respectively.From September to March, a remarkable negative correlation between the day to day variation ofS and that ofL was observed except when an intense cold air outbreak occurred. It was found that the correlation was caused by the cloud climatological feature of the western North Pacific in this period.S was not a dominant factor in the net heat flux. The value ofQ h +Q e in the Kuroshio Area ranged from 260 Wm–2 to 630 Wm–2, much larger thanQ n which ranged from –8 Wm–2 to 92 Wm–2 in the leg mean values (each leg period was about 10 days). Then the ocean was cooled at the rate of –160–620 Wm–2 during this period. The net heat flux in the Kuroshio Area averaged over five legs from late November to February was –473 Wm–2. This value is 50100% larger than the climatological values reported so far.The temporal and spatial variability of radiation fluxes and heat fluxes during each leg was also discussed.  相似文献   

9.
Values of root mean square slope 0 and its variations -0 are estimated using the brightness field of an image of the surface of the sea near a speck of light. When 0 and -0 are defined it is highly important to take into account direct as well as dissipated solar radiation.The space-time analysis of the structure of the image brightness field is performed. This gives an opportunity to estimate dispersion relationship and the running effect of a brightness contrast packet. Comparison of the parameters obtained with the theoretical dispersion ratio of internal waves (IW) allows one to make a conclusion that IW surface manifestations are recorded in a frame.UDK 551.463.5  相似文献   

10.
The Central Spreading Ridge (CSR) is located in the central part of the North Fiji Basin, a complex back-arc basin created 12 Ma ago between the Pacific and Indo-Australian plates. The 3.5 Ma old CSR is the best developed, for both structure and magmatism, of all the spreading centers identified in the basin, and may be one of the largest spreading systems of the west Pacific back-arc basins. It is more than 800 km long and 50–60 km wide, and has been intensively explored during the French-Japanese STARMER project (1987–1991).The CSR is segmented into three first order segments named, from north to south, N160°, N15° and N-S according to their orientation. This segmentation pattern is similar to that found at mid-ocean ridges. The calculated spreading rate is intermediate and ranges from 83 mm/yr at 20°30 S to 50 mm/yr at 17°S. In addition, there is a change in the axial ridge morphology and gravity structure between the northern and southern sections of the CSR. The axial morphology changes from a deep rift valley (N160° segment), to a dome split by an axial graben (N15° segment) and to a rectangular flat top high (N-S segment). The Mantle Bouguer Anomalies obtained on the northern part of the CSR (N160°/N15° segments) show bull's eye structures associated with mantle upwelling at the 16°50S triple junction and also in the middle of the segments. The Mantle Bouguer Anomalies of the southern part of the ridge (N-S segment) are more homogeneous and consistent with the observed smooth topography associated with axial isostatic compensation.At these intermediate spreading rates the contrast in bathymetry and gravity structure between the segments may reflect differences in heat supply. We suggest that the N160° and N15° segments are cold with respect to the hot N-S segment. We use a non-steady-state thermal model to test this hypothesis. In this model, the accretion is simulated as a nearly steady-state seafloor spreading upon which are superimposed periodic thermal inputs. With the measured spreading rate of 50 mm/yr, a cooling cycle of 200,000 yr develops a thermal state that permits to explain the axial morphology and gravity structure observed on the N160° segment. A spreading rate of 83 mm/yr and a cooling cycle of 120,000 yr would generate the optimal thermal structure to explain the characteristics of the N-S segment. The boundaries between the hot N-S segment and its cold bounding segments are the 18°10 S and 20°30 S propagating rifts. A heat propagation event along the N-S segment at the expense of the adjacent colder failing segments, can explain the sharp changes in the observed morphology and structure between the segments.  相似文献   

11.
Inversion modelling of marine gravity anomalies to derive predicted seafloor topography has provided significant advance in delineating deep-ocean bathymetry where the seafloor both conforms to the half-space cooling model of seafloor spreading, and largely sediment-free. Similar modelling for elevated ridges and seamounts, that are formed by processes other than seafloor spreading and/or have proximal sediment sources (e.g., continental margins and volcanic arcs), have significantly higher errors when validated against modern shipborne echo-sounding data. A three-dimensional, five-layer gravity model is emulated for the cases of both synthetic and real seamounts, with varying degrees of sediment burial, to establish the sensitivity of variable sediment cover as a source of error. A simple `Gaussian' seamount with base radius of 30 km, 2000 m of relief, has a maximum 140–160 mGal anomaly, that decreases to 50 mGal with the addition of 1 km of sediment cover with simple `flood' geometry. Complete burial, with a typical sediment density of 2300 kg m–3, results in a 120 mGal difference from a sediment-free seamount model. Increasing sediment density results in an exponential decay of the seamount anomaly. More complex synthetic geometries of varying basement relief and sediment thickness show that the anomaly amplitude remains significant, especially where the latter is >700–800 m thick. For the real case, seamounts of the Three Kings Ridge (northern New Zealand) imaged with seismic reflection data, with varying degrees of sediment cover of up to 1 km, when modelled both with and with-out the inclusion of a sediment layer, typically have rms differences of 30 mGal between observed and modelled gravity anomalies. Significantly, the rms errors are reduced by 50% with the inclusion of a sediment layer that corresponds to a reduction of predicted seafloor topography rms errors of 192–684 m to 78–360 m.  相似文献   

12.
The heat lability of succinic dehydrogenase, malic dehydrogenase and lactate dehydrogenase in cell-free extracts ofVibrio marinus MP-1 grown at 15C was compared for the tris buffer suspended enzymes and the NaCl suspended enzymes. The tris buffer suspended enzymes lost 50 percent activity at low thermal exposure between 5C and 27C. No activity was evident on thermal exposure between 32C and 39C. The enzyme extracts suspended in NaCl at 36 % were more heat stable, losing 50 percent activity after exposure between 16C and 40C. The enzymes lost all activity on thermal exposure between 33C and 42C in the presence of NaCl.  相似文献   

13.
Ishiwatari  R.  Hirakawa  Y.  Uzaki  M.  Yamada  K.  Yada  T. 《Journal of Oceanography》1994,50(2):179-195
Organic geochemical study of bulk organic matter (OM), hopanoid hydrocarbon and normal hydrocarbon (C23C35) was conducted for a 936-cm-long sediment core sample from the Oki Ridge of the Japan Sea (Core KH-79-3, C-3; 37°03.5 N, 134°42.6E, water depth 935 m). Stable carbon isotopic ratios were also measured for both bulk OM and individual hydrocarbons. The following results were obtained: (1) The weight ratios of total organic carbon to total nitrogen range from 6.2 to 9.4 in the core. The 13C values of bulk OM range from –25.1–20.7%.. The 13C values of OM in the sections of 140190 cm are lower (–25–24) than those in the other sections (–23–21). This result indicates that OM in the core except for the 140190 cm sections is essentially of marine origin. (2) The 13C value of diploptene (a hopanoid hydrocarbon) in the last glacial maximum (LGM), is –66.3 (vs. PDB), which indicates it originating in methanotrophic bacteria. This result provides evidence to support for the previous ideas (Oba et al., 1980, 1984; Masuzawa and Kitano, 1984) that the bottom waters in the Japan Sea were anoxic in LGM. (3) Long chain (C23C35) n-alkanes of higher-plant wax origin were found throughout the core. Their concentration is high in 140190 cm in depth, suggesting that eolian dust load was high in LGM. (4) The n-alkane/TOC ratio increases with decreasing 13C values of bulk OM. This result indicates that the load of terrestrial (probably eolian dust-derived) OM to the Japan Sea became higher in colder climates. (5) The CPI values of long-chain n-alkanes are different in different 13O stages of paleoclimate, probably reflecting variations in species of terrestrial higher plants as a result of climatological adaptations.  相似文献   

14.
The winter water mass distributions in the western Gulf of Mexico, affected by the collision of a Loop Current anticyclonic ring, during January 1984 are analyzed. Two principal modes of Gulf Common Water (GCW) formation, arising from the dilution of the Caribbean Subtropical Underwater (SUW), are identified. Within the western gulf continental slope to the east of Tamiahua, the GCW is formed by the collision of anticyclonic rings. During these collision events, the SUW, entrapped at the core (200 m depth) of these features, is diluted by low salinity (36.1S36.3) water from the uppermost layer of the main thermocline. The end product of this mixture is GCW, which is further diluted by low salinity coastal water within the western gulf continental shelf. The second GCW formation mode is associated to the northerly wind stress which propagates over the western gulf during winter. During January, 1984, this wind stress gave rise to a 175 m mixed layer. This convective mixing destroyed the static stability of the summer thermocline and allowed for the partial dilution of the SUW with low salinity (S36.3) water from the western gulf continental shelf. Within the western gulf's upper 2000 m, the following water masses were identified to be present: GCW, SUW, Tropical Atlantic Central Water and associated dissolved oxygen minimum stratum, Antarctic Intermediate Water remnant, a mixture of the Caribbean Intermediate Water and the upper portion of North Atlantic Deep Water (NADW), and the NADW itself. The topographic distribution of these water masses' strata was dictated by the cyclonic-anticyclonic baroclinic circulation that evolved from the anticyclone's collision to the east of Tamiahua. Between the cyclonic and anticyclonic domains, the maximum pressure differential of these water masses' core occurrences was 150 to 280 dbar. The topographic transition zone defined by these strata occurred between the cyclonic and anticyclonic domains and coincided unambiguously with the anticyclone's collision zone. Within the continental shelf, we identified low temperature (12°C) and low salinity (31) coastal waters contributed by river runoff. Driven by the northerly wind stress, these coastal waters were advected toward the south hugging the coastline. The coastal and continental shelf waters demarcated a sea surface temperature, salinity, and dissolved oxygen discontinuity region that coincided with the horizontal baroclinic flow transition zone associated to the anticyclone's collision.  相似文献   

15.
The problem of reflexion and critical level absorption of barotropic non-divergent Rossby waves in a lateral shear flow is considered with a ray tracing method. The results are compared with those of a normal mode approach. Some oceanographical applications are suggested.  相似文献   

16.
The storm surges which occurred in Tosa Bay in August 21, 1970 were numerically simulated. First of all NOAA's model SPLASH (Special Program to List Amplitudes of Surges from Hurricanes) was used and the effects of the typhoon's parameters, the bottom topography, the coastal configuration and the coordinate systems of storm surges were examined. SPLASH was then modified to suit computations of storm surges in the open sea and open boundary conditions were studied. Finally a two layer model was developed and the effects of the two layer system on surges were investigated.  相似文献   

17.
In 1983 a combined SeaMARC I, Sea Beam swath mapping expedition traversed the East Pacific Rise from 13°20 N to 9°50 N, including most of the Clipperton Transform Fault at 10°15 N, and a chain of seamounts at 9°50 N which runs obliquely to both the ridge axis and transform fault trends. We collected temperature, salinity and magnetic data along the same track. These data, combined with Deep-Tow data and French hydrocasts, are used to construct a thermal section of the rise axis from 13°10 N to 8°20 N.Thermal data collected out to 25 km from the rise axis and along the Clipperton Transform Fault indicate that temperatures above the rise axis are uniformly warmer by 0.065°C than bottom water temperatures at equal depths off the axis. The rise axis thermal structure is punctuated by four distinct thermal fields with an average spacing of 155 km. All four of these fields are located on morphologic highs. Three fields are characterized by lenses of warmed water 20 km in length and 300 m thick. Additional clues to hydrothermal activity are provided in two cases by high concentrations of CH4, dissolved Mn and 3He in the water column and in another case by concentrations of benthic animals commonly associated with hydrothermal regions.We use three methods to estimate large-scale heat loss. Heat flow estimates range from 1250 MW to 5600 MW for one thermal field 25 km in length. Total convective heat loss for the four major fields is estimated to lie between 2100 MW and 9450 MW. If we add the amount of heat it takes to warm the rest of the rise axis (489 km in length) by 0.065.°C, then the calculated axial heat loss is from 12,275 to 38,525 MW (19–61% of the total heat theoretically emitted from crust between 0 and 1 m.y. in age).  相似文献   

18.
We compare the results obtained by using theoretical and semiempirical models developed for the evaluation of the dissipation rate of turbulent energy in a stratified ocean with independent distribution of this quantity established by the authors for the active layer of the Black Sea (50–300 m) by using a one-dimensional model taking into account the balance of heat, salt, and fluid inside the layer. It is shown that, in a layer with gradual variation of the Väisälä–Brunt frequency N as a function of depth, the predominant sink of the energy of motion into dissipation N 2 is ensured by the flow of energy through the spectrum of internal waves toward low frequencies and small vertical scales. On the contrary, in layers with abrupt drops of density as a function of depth (layers with jumps of density), an important role is played by the interface-type waves and the dependence of on N transforms into N .  相似文献   

19.
Transmission and reflection problems when kissing≓ occurs among planetary and topographic Rossby waves in a two-layer ocean are studied. The slope parameterS(=dh 2/dx, whereh 2is the thickness of the lower layer) is assumed to have constant values in the regionsx 0 andxL and to vary linearly with the increase ofx in the region0xL (refer to Fig. 2 in the text). Furthermore, a wave is entered fromx=– and kissing is assumed to occur in the region (0<)x axxb(<L).It is found that a wave of the same type as the incident wave is mainly transmitted when the width of the region in which kissing occurs,L kiss(=tx b–xa), is smaller than kiss=2/(¦K¦+ y/2), whereK is a representative wavenumber in the regionx ab, y is they-component of , and is the frequency. WhenL kiss is larger than kiss, on the other hand, the main wave transmitted is of a different type to the incident wave. As an application, transmission and reflection problems of planetary Rossby waves are considered, and it is shown that when an external (internal) planetary Rossby wave is entered, an internal (external) one can be transmitted due to the effect of kissing.  相似文献   

20.
In an analysis of video observations of gravel transport in the West Slent, UK, collective and individual characteristics of 458 bursts of bedload have been examined and the transport velocity and distance of 1680 individual particles in a consecutive succession of burst events determined. Infrequent, long duration, high stress events account for 60% of total transport in only 24% of the total time with the mean free path and transport velocity for particles being 0.16 m and 0.22 m/s, respectively. Clear links between intense intermittent turbulence and bedload transport revealed in this study, suggest progress in modelling requires a clearer understanding of near bed flow structure.  相似文献   

设为首页 | 免责声明 | 关于勤云 | 加入收藏

Copyright©北京勤云科技发展有限公司  京ICP备09084417号