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1.
P. N. Golovin 《Russian Meteorology and Hydrology》2012,37(11-12):752-761
The comparative analysis of hydrometeorological and topographic conditions of the formation and runoff of dense shelf waters on the shelves and continental slopes in different water areas of the Arctic and Antarctic demonstrates that they are similar in many aspects but there are some differences as well. In the Antarctic, these conditions are more favorable. The thermohaline conditions of the formation and runoff of shelf waters in the Arctic and Antarctic are also similar. The similarity of different conditions enables to construct the adaptive physical model of the shelf and slope cascading of shelf waters generalized for different polar water areas. It is based on the analysis of historical and present-day in situ data in the areas of margins of shelves and slopes in the Arctic and Antarctic, observations in the areas of flaw polynyas, and passing ice and meteorological observations, as well as on taking account of some general results of laboratory and theoretical investigations of the dense liquid runoff along the inclined bottom. 相似文献
2.
G. V. Shevchenko E. A. Vilyanskaya V. N. Chastikov 《Russian Meteorology and Hydrology》2011,36(1):55-64
An average long-term distribution of temperature and salinity is analyzed for different months (May–November) computed on the basis of materials accumulated at standard oceanological sections of the northern part of the Tatar Strait. The main attention is paid to the section Korsakov Cape-Cape Syurkum crossing the water area under study practically in the middle. In early spring, the cold waters with salinity of more than 33‰ are registered at the section Korsakov Cape-Cape Syurkum. The waters with smaller salinity are revealed only in late spring, in June. In the same period, the intensification of cold intermediate layer occurs, first of all, in the western part of the section. The waters in the surface layer near the Sakhalin coast are warmed more than at the continental shelf. During the summer, this difference gradually decreases and the surface layer temperature becomes even in September. On the contrary, the spatial salinity gradients increase. In the fall, under the influence of northern and northwestern winds being typical of this period, the upwelling is formed near the Sakhalin coast and the cold dense waters emerge in the narrow coastal strip. The direction of alongshore flow changes from northern to the southern one. At the section Korsakov Cape-Cape Syurkum in November, the influence of small-salinity waters associated with the Amur River runoff is significantly revealed. 相似文献
3.
Abstract An examination of the temperature and current measurements from the NE Newfoundland Shelf indicates significant frontal variability at about a 7‐day period during the months of June‐September 1989. The oscillations recorded in 1989 appeared to have propagated into the region from the Labrador Shelf. Significant variability in the position of the shelf water/slope water front in the Bonavista area is also found between years and within the same year. Time series measurements also indicated that the transition from winter to summer conditions in the inshore region may be occurring during late July to early August. 相似文献
4.
Abstract Estimates of the rate of dissipation of turbulent energy,?v, were made on the continental shelf off the southwest coast of Vancouver Island throughout the diurnal tidal cycle at six stations. If turbulent mixing takes place away from boundaries, and a constant fraction of the energy supplied to turbulence is converted into potential energy, this dissipation rate per unit volume, ?v, is shown to be proportional to the rate of turbulent mass and nutrient flux across the isopycnals. We compute these fluxes to determine the source of nutrients in the upper mixed layer on the shelf. It is found that tidal mixing on the shelf throughout the water column contributes less than 10% of the flux of nutrients supplied by the estuarine outflow out of Juan de Fuca Strait. Strong winds during upwelling events supply nutrients at rates greater than those due to tidal mixing, but at rates that are likely smaller than the Juan de Fuca source. Therefore, the nutrient‐rich waters observed in the euphotic zone in spring and summer on this shelf derive mainly from Juan de Fuca Strait. Nutrients in bottom water derive from upwelling along shelf‐break canyons. 相似文献
5.
《Journal of Atmospheric & Ocean Science》2005,10(4):343-359
Two consecutive multidisciplinary surveys, covering the north and north-western part of the Iberian shelf and slope during spring 2000, showed a dramatic change in the oceanographic conditions as a result of a southern water intrusion that replaced shelf and slope waters down to 300 m depth. The intrusion covered an alongshore distance of ∼400 km from the north of Cape Finisterre to the centre of the Cantabrian Sea, and was developed in less than a month between the two occupations of the same area. The analysis of surface currents from several buoys moored over the slope allow us to associate the emerging oceanographic configuration after the event with a strong and well-defined slope current, although during winter 1999-2000 the entrance of the Iberian Poleward Current (IPC) in the Bay of Biscay was very weak. The rapid development of the intrusion is discussed in relation with the unusual strong wind forcing pulse that occurred between the cruises. Our results highlight the importance of variability scales below seasonal (event-scale) in the Iberian margin. 相似文献
6.
Abstract The mid‐to‐bottom waters of the Labrador Shelf are shown to exhibit an anomalous along‐shelf temperature gradient, with warmer waters found in the north. This feature is present in summer and autumn but appears to reverse in December. Inadequate data are available during winter and spring to draw firm conclusions regarding this feature. A time averaged heat loss of the shelf waters to the atmosphere would result on average, in colder waters in the south (because of north‐south advection); however, it is shown that there is a net annual‐mean input of heat to the shelf waters. An examination of the seasonal temperature cycle at standard depths reveals that its phase is almost uniform below 30‐m depth on the northern banks of the Labrador Shelf. The limited phase variation suggests the influence of a plume of well mixed water originating near Hudson Strait. It thus appears that mixing at the entrance to Hudson Strait imparts a phase anomaly to the seasonal cycle in the north that contributes to the observed inversion of the expected latitudinal temperature gradient. 相似文献
7.
Seasonal variations of hydrological conditions in the area adjoining the southeastern coast of Sakhalin Island are described based on the analysis of monthly mean temperature and salinity obtained over standard oceanic sections Makarov-Cape Georgii and Cape Svobodny-the sea and from nine oceanic surveys. The Poronai River runoff that promotes the formation of a warm surface layer with low salinity largely influences the water area of Terpeniya Bay in the northern part of the area studied. In spring, these waters primarily spread southward along the coast; in summer, they flow southeastward, forming a weak vortex structure at 144° E. In the fall, major changes occur below 20 m, where waters of the cold intermediate layer are replaced by warmer waters (4–6°C) of low salinity connected with the Amur River runoff. The destruction of the CIL core near the shelf edge at depths of about 100 m resulting from the fall intensification of the East Sakhalin Current is pronounced in the southern, abyssal part of the region. The coastal area is covered by waters with salinity below 32‰ connected with the Amur River runoff. The volume of low-salinity waters coming through the Cape Svobodny-the sea section into the southern part of the Sea of Okhotsk is estimated at 3000 km3 taking into account instrumental measurements of flow rates. 相似文献
8.
An examination of current‐meter data gathered in 1967/68 on the continental shelf and slope off Nova Scotia has shown that meteorological forcing is an important source of energy. The response of currents to wind forcing is concentrated in a frequency band of 2.5 to 7 days. Daily mean currents of up to 25 cm/s appear to be associated with wind‐stress events. The highest correlations between wind and current are for the alongshore components of these variables. Wind‐induced currents may have been responsible for an intrusion of slope water onto the shelf which was observed in hydrographic sections from October and December 1968. Long data series (up to 167 days) formed by patching together shorter records demonstrate the existence of distinct low‐frequency variability at periods greater than 10 days. Some aspects of these motions suggest the presence of topographic Rossby waves on the shelf and slope. However, spatial and temporal coverage of data are not sufficient to define the sources of this variability. 相似文献
9.
A study of the circulation in the northern South China Sea （SCS） is carried out with the aid of a three-dimensional, high-resolution regional ocean model. One control and two sensitivity experiments are performed to qualitatively investigate the effects of surface wind forcing, Kuroshio intrusion, and bottom topographic influence on the circulation in the northern SCS. The model results show that a branch of the Kuroshio in the upper layer can intrude into the SCS and have direct influence on the circulation over the continental shelf break in the northern SCS. There are strong southward pressure gradients along a zonal belt largely seaward of the continental slope. The pressure gradients are opposite in the southern and northern parts of the Luzon Strait, indicating inflow and outflow through the strait, respectively. The sensitivity experiments suggest that the Kuroshio intrusion is responsible for generating the imposed pressure head along the shelf break and has no obvious seasonal variations. The lateral forcing through the Luzon Strait and Taiwan Strait can induce the southwestward slope current and the northeastward SCS Warm Current in the northern SCS. Without the lateral forcing, there is the continental slope. The wind forcing mainly causes the The wind-induced water pile-up results in the southward no high-pressure-gradient zonal belt seaward of seasonal variation of the circulation in the SCS. high pressure gradient along the northwestern boundary of the basin. Without the blocking of the plateau around Dongsha Islands, the intruded Kuroshio tends to extend northwest and the SCS branch of the Kuroshio becomes wider and stronger. The analyses presented here are qualitative in nature but should lead to a better understanding of the oceanic responses in the northern SCS to these external influence factors. 相似文献
10.
Microstructure and hydrological profiles were collected along two cross-shelf sections from the deep slope to the shallow water in the north of Taiwan Island in the summer of 2006. While the tidal currents on the shelf were dominated by the barotropic tide with the current ellipse stretched across the shelf, significant internal tides were observed on the slope. The depth-mean turbulent kinetic energy(TKE) dissipation rate on the shelf was 10~(-6)W kg-1, corresponding to a diapycnal diffusivity of 10~(-2)m~2s~(-1). The depth-mean TKE dissipation rate on the slope was 1 × 10~(-7)W kg-1, with diapycnal diffusivity of 3.4 × 10~(-4)m~2s~(-1). The shear instability associated with internal tides largely contributed to the TKE dissipation rate on the slope from the surface to 150 m, while the enhanced turbulence on the shelf was dominated by tidal or residual current dissipations caused by friction in the thick bottom boundary layer(BBL). In the BBL, the Ekman currents associated with the northeastward Taiwan Warm Current were identified, showing a near-bottom velocity spiral, which agreed well with the analytical bottom Ekman solution. 相似文献
11.
R. Pawlowicz 《大气与海洋》2017,55(4-5):264-283
The west coast of Vancouver Island (WCVI) is an important marine ecosystem in which concentrations of dissolved oxygen can reach hypoxic levels at certain times of the year. Although the general features of its oceanography are well understood, little is known in particular about the seasonal cycle of oxygen in shelf areas and its interannual variability. It is possible that high temporal resolution monitoring efforts could be carried out relatively easily in sheltered fjords adjacent to the shelf, but the linkages between conditions in these fjords and those on the shelf are also not known. Here a 10-year time series of monthly hydrographic stations in Barkley Sound, British Columbia, is used to identify the seasonal cycle of temperature, salinity, density, dissolved oxygen, and chlorophyll fluorescence in a WCVI fjord. Analysis suggests that there is a standard estuarine circulation in surface and near-surface waters of the Sound, as well as a deep renewal cycle in intermediate and deep waters, and that the two are largely independent. The deep basin in the Sound undergoes annual summer renewals in response to wind-driven upwelling on the shelf, separated by stagnation and hypoxia during fall, winter, and spring downwelling periods. Other than for the stagnant deep waters in winter, residence times in different parts of the Sound are only a few weeks. Barkley Sound characteristics thus adjust rapidly to shelf conditions, and inshore measurements can be used with care as a proxy for some shelf properties. However, phytoplankton biomass does not appear to be affected by the onset of deep renewal and the associated reversal of along-shore winds and instead responds to local factors. Finally, once the seasonal cycle has been accounted for, interannual variations in temperature, density, and dissolved oxygen are uncoupled, possibly in response to longer-term changes in the characteristics of source waters offshore and/or to changes in shelf processes. 相似文献
12.
An ocean circulation model for the British Columbia continental shelf is run with future initial conditions and forcing fields downscaled from the North American Regional Climate Change Assessment Program archive. Average seasonal sea surface temperatures for the period 2065 to 2078 are projected to increase by between 0.5° and 2.0°C with respect to analogous averages from 1995 to 2008. Seasonal sea surface salinities are projected to decrease by as much as 2.0 over the same period, though there are some regions where and periods when small increases are projected. Though stronger winter winds result in larger Haida Eddies, slightly stronger summer winds along the western Vancouver Island shelf do not result in appreciable changes to either the cross-shelf upwelling or to the magnitude of Juan de Fuca Eddies or the timing of their formation. However, increased flows are projected in some seasons for the Rose Spit, Middle Bank, and Goose Island Bank eddies. More precipitation over the watersheds emptying into coastal waters produces larger freshwater discharges and, in particular, a stronger estuarine flow in Juan de Fuca Strait and a stronger Vancouver Island Coastal Current. Generally increasing winds and decreasing density mean that the winter minus summer range of sea surface heights is projected to increase all along the coast. 相似文献
13.
We explored the variability of the Egyptian shelf zone circulation connected to atmospheric forcing by means of a numerical simulation of the general circulation. A high resolution model grid was used at 1/60° horizontal resolution and 25 sigma layers. The simulation was carried out using the most recent version of the Princeton Ocean Model (POM). The initialised model was run the whole year of 2006 using the analysis forcing data for the same year obtained from ECMWF and MFS (Mediterranean Forecasting System, Pinardi et al., 2003). The model skills were evaluated by means of the root mean square error (RMSE) and correlations. The Egyptian Shelf Model (EGYSHM) simulation suggests the presence of an Egyptian Shelf Slope Current (ESSC), which is flowing eastward at different depths in the domain. We found that the maximum velocity of the ESSC [0.25 m/s] is located near the continental slope during the summer time, while in winter the velocity of ESSC is weaker [0.12 m/s] in the same location. The ESSC appears to be directly affected by Mersa-Matruh gyre system. EGYSHM reproduced the main region circulation patterns, especially after adding the Nile River outflow. We found that wind stress is crucial to force the circulation of the Egyptian shelf zone. EGYSHM SST was significantly correlated to satellite SST in all months at a 95% confidence limit, with a maximum of 0.9743 which was obtained in May 2006. The RMSE between EGYSHM and Argo floats salinity data was about 0.09. We compared our results with satellite altimetry to verify the positions and shapes of mesoscale features. 相似文献
14.
V. A. Sosnin P. Ya. Tishchenko A. N. Salyuk N. Biebow 《Russian Meteorology and Hydrology》2008,33(2):106-111
The field data show that the ventilation of waters in the Sea of Okhotsk occurs the year round as a cyclic process and consists of several phases. During the initial phase, the shelf waters enter the offshore subsurface layers. Later, they appear at intermediate depths and spread southward as cold intrusions mixing with surrounding waters on their way. During the last phase of the cycle, the shelf waters do not penetrate the deep-sea layers, and in the vertical structure of temperature field near the northeast coast of Sakhalin, a local phenomenon of “warm” dichothermal layer is observed. 相似文献
15.
南海夏季海流的数值模拟 总被引：3，自引：0，他引：3
用一个水平分辨率较高的区域海洋模式计算了中国海的海流。本文给出了南海７月份的上层环流的数值模拟结果。结果表明:在南海北部的陆架区，一支较强的东北向海流穿过台湾海峡流入东海；在海南岛东南和越南沿岸以东海域有一个气旋式的涡旋；南海南部被一个反气旋式的大涡旋所占据。计算得到的这些环流特征与观测结果十分一致。另外，数值模拟结果还显示出，黑潮的一个分支通过巴士海峡的南部进入南海，虽然一部分海水不断被陆架诱导流向东北，但是仍有一部分海水可以一直向西流到海南岛以东海域。 相似文献
16.
Seasonal Variability of the Yellow Sea／East China Sea Surface Fluxes and Thermohaline Structure 总被引：1，自引：0，他引：1
We use the U.S. Navy‘s Master Oceanographic Observation Data Set (MOODS) for the Yellow Sea/East China Sea (YES) to investigate the climatological water mass features and the seasonal and non-seasonal variabilities of the thermohaline structure, and use the Comprehensive Ocean-Atmosphere Data Set (COADS) from 1945 to 1989 to investigate the linkage between the fluxes (momentum, heat, and moisture) across the air-ocean interface and the formation of the water mass features. After examining the major current systems and considering the local bathymetry and water mass properties, we divide YES into five regions: East China Sea (ECS) shelf, Yellow Sea (YS) Basin, Cheju bifurcation (CB) zone,Taiwan Warm Current (TWC) region, Kuroshio Current (KC) region. The long term mean surface heat balance corresponds to a heat loss of 30 W m^-2 in the ESC and CB regions, a heat loss of 65 W m^-2 in the KC and TWC regions, and a heat gain of 15 W m^-2 in the YS region. The surface freshwater balance is defined by precipitation minus evaporation. The annual water loss from the surface for the five subarea sranges from 1.8 to 4 cm month^-1. The fresh water loss from the surface should be compensated for from the river run-off. The entire water column of the shelf region (ECS, YS, and CB) undergoes an evident seasonal thermal cycle with maximum values of temperature during summer and maximum mixed layer depths during winter. However, only the surface waters of the TWC and KC regions exhibit a seasonal thermal cycle. We also found two different relations between surface salinity and the Yangtze River run-off,namely, out-of-phase in the East China Sea shelf and in-phase in the Yellow Sea. This may confirm an earlier study that the summer fresh water discharge from the Yangtze River forms a relatively shallow, low salinity plume-like structure extending offshore on average towards the northeast. 相似文献
17.
Ingrid Peterson 《大气与海洋》2013,51(4):402-415
Abstract Ice floes along the Labrador Coast were tracked using visible NOAA satellite images on two consecutive days (26 and 27 April, 1984) when the ice‐pack extended beyond the Labrador Current, and winds were weak. The resulting “snapshot” of the velocity field reveals strong topographic steering of the Labrador Current, such that the current speed and width in different areas are dependent on the steepness of the continental slope, and the current deflects into and out of Hopedale Saddle. Between 55 and 58°N, the main core of the current is 60–90 km wide, with speeds of 30–55 cm s?1. The overall circulation pattern is in good agreement with historical water mass analyses over the shelf and slope, and with estimates of the speed of the Labrador Current obtained by other methods. 相似文献
18.
It is shown how symmetric dipolar vortices can be formed by the action of an impulsive jet in a homogeneous single layer of fluid in a rotating tank. These dipoles are allowed to interact with a constant topographic slope, which can model a β-plane or a continental shelf. A dipole's trajectory bends toward the right when climbing a slope and to the left when descending, as predicted by numerical simulations and analytical arguments. The maximum penetration of the dipoles over a slope, the adjustment to the slope, and formation of trailing lobes are compared with both numerical simulations and a two-point vortex model. The results suggest that Rossby wave radiation plays an important role in the interaction process. 相似文献
19.
西太平洋副热带高压东西位置异常与华北夏季酷暑 总被引：18，自引：0，他引：18
文中研究了副热带高压 (副高 )东西位置异常与中国东部地区夏季气温的关系。发现两者之间有很高的正相关 ,当西太平洋副高偏西时 ,大片的北方地区气温会降低 ;而当副高偏东时 ,该地区的气温将偏高。西太平洋副高东西位置的异常对应着亚洲太平洋地区的长波位置和强度的很大变化 ,从而影响到中国北方地区的气温。更重要的是 ,副高西端位移所产生的扰动还会以波列的形式向极地和北美方向传播 ,从而从更大的范围内影响西风带环流。对 2 0 0 2年夏季中国北方出现的持续高温天气进行了分析。该年夏季副高持续偏东。西风带大槽也处于偏东的位置。西部的大陆副高东移扩展 ,与槽后的高压脊打通 ,造成该地区的持续高温。副高的东西位置决定了季风气流 (也就是水汽的主要通道 )的北向转折的路径。当副高偏东时 ,向北折向的位置随之东移 ,东亚大陆的水汽供应变为负距平 ,特别是中国北方地区 ,变得十分干燥。引起中国北方高温的直接系统是大陆高压中的极强的下沉气流 ,副高的偏东位置为大陆副高的东进和加强提供了大尺度的背景条件 相似文献
20.
The boundary currents over the Western Australian continental shelf and slope consist of the poleward flowing Leeuwin Current (LC) and the equatorward flowing Leeuwin Undercurrent (LUC). Key properties of the LC are its poleward strengthening, deepening to the south, and shelfbreak intensification. The alongshore flow reverses direction below about 300 m, forming the LUC at greater depths. To investigate the processes that cause these features, we obtain solutions to an idealized, regional ocean model of the South Indian Ocean. Solutions are forced by relaxing surface density to a prescribed, meridionally varying density profile ρ*(y) with a timescale of δt. In addition, vertical diffusion is intensified near the ocean surface. This diffusion establishes the minimum thickness over which density is well-mixed. We define this thickness as the “upper layer”. Solutions are obtained with and without a continental shelf and slope off Western Australia and for a range of values of δt and mixing parameters. Within this upper layer, there is a meridional density gradient that balances a near-surface, eastward geostrophic flow. The eastward current downwells near the eastern boundary, leading to westward flow at depth. The upper layer's meridional structure and zonal currents crucially depend on coastal processes, including the presence of topography near the eastern boundary. Kelvin waves inhibit the upper layer from deepening at the coast. Rossby waves propagate the coastal density structure offshore, hence modifying the interior currents. A comparison of the solutions with or without a continental shelf and slope demonstrate that topographic trapping of Rossby waves is a necessary process for maintaining realistic eastern boundary current speeds. Significant poleward speeds occur only onshore of where the upper layer intersects the slope, that is, at a grounding line. Its poleward transport increases when surface-enhanced vertical mixing is applied over a greater depth. When the timescale δt is sufficiently short, the poleward current is nearly barotropic. The current's spatial structure over the shelf is controlled by horizontal mixing, having the structure of a Munk layer. Increasing vertical diffusion deepens the upper layer thickness and strengthens the alongshore current speed. Bottom drag leads to an offshore flow along the bottom, reducing the net onshore transport and weakening the current's poleward acceleration. When δt is long, poleward advection of buoyancy forms a density front near the shelf break, intensifying poleward speeds near the surface. With bottom drag, a bottom Ekman flow advects density offshore, shifting the jet core offshore of the shelf break. The resulting cross-shelf density gradient reverses the meridional current's direction at depth, leading to an equatorward undercurrent. 相似文献