放射性废料的运输

More and more low - level radioactive waste is carried by sea, rail and highways. These materials are generated by public uilities, industries, universities and hospitals throughout the world, The waste is transported to available low - level waste disposal sites, primarily by ships in containers designed for transportation of low - level waste. Carriers.     

Physical processes in the ROFI regime

The distinctive feature of all ROFI (Regions Of Freshwater Influence) systems is the input of significant amounts of buoyancy as freshwater from river sources. If the spatial scale is unrestricted by coastal topography and stirring is weak, this input tends to drive a coast-parallel flow in which the Coriolis force constrains a wedge of low density water against the coastal boundary. Without frictional effects, this flow is subject to baroclinic instability which induces large meanders and eddies in the flow but in, many ROFIs, the tidal flow induces frictional effects which stabilise the density driven flow.In the absence of the effects of rotation and stirring, the buoyancy input tends to induce stratification through an estuarine circulation in the direction of the gradient. When stirring is applied, by the action of wind, waves or tidal flow, the density current is suppressed but is rapidly re-established when stirring ceases, as in the Linden-Simpson (1988) laboratory tank experiments. In real ROFI systems, a combination of all these processes operates so that the structure of the water column and the flow is the result of a competition between the stratifying influence of buoyancy input and the net stirring effect of the wind, waves and the tides. This competition is more difficult to analyse than the heating-stirring competition, because freshwater buoyancy input is not spatially uniform but enters at discrete sources along the coast and its subsequent spreading has to be determined.While the springs-neaps cycle in tidal stirring imposes a regular fortnightly modulation on vertical mixing, the influence of the wind is irregular and depends, not just on the magnitude of the stress, but also on the direction in which it acts. In some exposed shallow water situations there may also be significant stirring due to waves generated by non-local winds.ROFI systems are further complicated by the action of tidal straining in which differential advection, due to vertical shear in the tide, interacts with the density gradient to generate fluctuations in vertical stability at the tidal frequency which, in some cases, are of sufficient amplitude to switch the water column between stable stratification and vertical density homogeneity each tidal cycle. This straining along with the other ROFI processes have been incorporated into a series of 1-D models to provide a more objective test of the hypotheses about the mechanisms involved. Comparison of model hindcasts with observations indicate that we now have a first-order understanding of the complex behaviour of ROFIs.On a global scale it is clear that ROFIs represent an important component of the shelf-sea environment of particular concern in relation to the impact of pollutant discharges. To date, most studies of ROFI's have concentrated on systems in temperate latitudes but attention needs to be focused on the very extensive ROFIs in tropical regions where most of the world's river discharge enters the ocean. In monsoonal regions, these inputs exhibit strong seasonal modulation which may, in competition with tidal stirring, result in an annual cycle of stratification and the formation of fronts.     

Biological effects of dilution of Dead Sea brine with seawater: implications for the planning of the Red Sea–Dead Sea “Peace Conduit”

The Dead Sea is a severely disturbed ecosystem. Its water level has been decreasing at a rate of nearly 1 m per year during the last decade due to anthropogenic intervention in its water balance. Since the peace treaty between Israel and Jordan was established in 1994, a proposal for the construction of a water carrier, the “Peace Conduit,” between the Gulf of Aqaba (Red Sea) and the Dead Sea is being investigated. This water carrier is intended to mitigate damaging processes that currently occur in the Dead Sea and its surrounding area. The difference in elevation of about 416 m could be exploited for seawater desalination by reverse osmosis. To examine the possible effects of the mixing of Dead Sea brines with seawater and seawater concentrates on the Dead Sea as an ecosystem, we have set up simulation experiments under field conditions in experimental ponds at Sedom, in which Dead Sea water was diluted with Red Sea water. The main components of the Dead Sea biota are the unicellular green alga Dunaliella and several types of red halophilic Archaea. Phosphate is the limiting inorganic nutrient. Massive Dunaliella blooms developed, accompanied by dense communities of red halophilic Archaea, in some of the experimental ponds, imparting a brown-red coloration to the brines. The extent of biological development depended on the extent of dilution and on phosphate availability. The results of the simulation experiments show that biological phenomena and their impact on the Dead Sea ecosystem should be taken into consideration during the planning of the “Peace Conduit.”     

Inorganic carbon fluxes through the boundaries of the Greenland Sea Basin based on in situ observations and water transport estimates

A carbon budget for the exchange of total dissolved inorganic carbon C_T between the Greenland Sea and the surrounding seas has been constructed for winter and summer situations. An extensive data set of C_T collected over the years 1994–1997 within the European Sub-polar Ocean Programmes (ESOP1 and ESOP2) are used for the budget calculation. Based on these data, mean values of C_T in eight different boxes representing the inflow and outflow of water through the boundaries of the Greenland Sea Basin are estimated. The obtained values are then combined with simulated water transports taken from the ESOP2 version of the Miami Isopycnic Coordinate Ocean Model (MICOM). The fluxes of inorganic carbon are presented for three layers; a surface mixed layer, an intermediate layer and a deep layer, and the imbalance in the fluxes are attributed to air–sea exchange, biological fixation of inorganic carbon, and sedimentation. The main influx of carbon is found in the surface and the deep layers in the Fram Strait, and in the surface waters of direct Atlantic origin, whereas the main outflux is found in the surface layer over the Jan Mayen Fracture Zone and the Knipovich Ridge, transporting carbon into the Atlantic Ocean via the Denmark Strait and towards the Arctic Ocean via the Norwegian Sea, respectively. The flux calculation indicates that there is a net transport of carbon out of the Greenland Sea during wintertime. In the absence of biological activity, this imbalance is attributed to air sea exchange, and requires an oceanic uptake of CO₂ of 0.024±0.006 Gt C yr⁻¹. The flux calculations from the summer period are complicated by biological fixation of inorganic carbon, and show that data on organic carbon is required in order to estimate the air–sea exchange in the area.     

Controls on stratification in the Rhine ROFI system

Stratification in the Rhine ROFI is very variable; the mean water column stability is controlled by the combined effect of tidal, wind and wave stirring which, at times, brings about complete vertical homogeneity. Control by the mixing variables has been elucidated by a regression analysis of mean stratification on the components of the windstress and significant wave height. There is strong partial correlation with all three variables which explains between 56% and 65% of the variance in two time series of observations in October 1990 and September 1992, respectively. During periods of low stirring the water column was observed to re-stratify over the whole inshore region through the relaxation of the horizontal gradients under gravity and with the influence of rotation. Superimposed on the mean stratification there is strong semi-diurnal variation, occurring throughout the stratified region at times of reduced mixing. The amplitude of this semi-diurnal variation is of the same order as the mean stability and frequently results in conditions being mixed or nearly mixed once per tide. This semi-diurnal variation results primarily from cross-shore tidal straining which interacts with the main density gradient to induce stratification. The hypothesis that water column stability is controlled by the combination of these processes has been tested using a reduced physics model which has been successful in reproducing the main features of both the mean and semi-diurnal components of stratification.     

Modelling physical processes of haline stratification in ROFIs with application to the Rhine outflow region

A physical and numerical study is made of the processes governing the stratification and circulation in ROFIs (Regions of Freshwater Influence) where there is an important impact of wind and tides. Observations in the Rhine ROFI showed that the salinity field consists of a mean and a tidally oscillating part. The physical processes are first analysed using the analytical solutions from a one-dimensional two-layer model. A justification is given for the neglection of non-linear advective terms in the equations of momentum and salinity. The dimensionless forms of the solutions can be expressed in terms of a series of dimensionless numbers. It is shown in particular that stratification and cross-shore circulation largely depend on the balance between rotation and turbulent diffusion, which depends in turn on parameters such as the Ekman number, the bottom friction coefficient, the eddy viscosity ratio and the depth of the layer interface. Surface winds either enhance or destroy stratification depending on the wind angle. The response to wind forcing is discussed using classical Ekman theory. To verify the analytical theory numerical tests are performed with a point model including an advanced turbulence closure scheme. Differences arise due to the non-linear interaction between turbulence on the one hand and current shear and stratification on the other hand. It is shown in particular that the amplitude of the tidal forcing and the off-shore horizontal salinity gradient strongly affect the semi-diurnal and semi-monthly variation of stratification. The effect of the wind is found to be in good agreement with the analysis of the two-layer model. Finally, the numerical model is compared with existing observational data in the Rhine ROFI for October 1990.     

Seasonal variability in sea surface oceanographic conditions in the Aegean Sea (Eastern Mediterranean): an overview

Seasonal variability and the spatial distribution of sea surface temperatures (SST) and salinities (SSS) are reviewed, in relation to the prevailing climatological conditions, heat fluxes, water budget and general water circulation patterns. Within this context, consideration is given to: sea surface temperatures; air temperatures; precipitation; evaporation; wind speeds and directions; freshwater (mainly riverine) discharges throughout the Aegean; and the exchange of water masses with the Black Sea and eastern Mediterranean Sea. The investigation of satellite images, covering a 6-yr period (1988–1994), has enabled a synthesis of the monthly sea surface thermal distribution to be established.The climate of the Aegean Sea is characterised by annual air temperatures of 16–19.5°C, precipitation of about 500 mm yr⁻¹ and evaporation of some 4 mm d⁻¹. The Aegean has a negative heat budget (approximately −25 W m⁻²) and positive water balance (+ 1.0 m yr⁻¹), when inflow from the Black Sea is considered. During the summer, the (northerly) Etesians are the dominant winds over the Sea.Mean monthly sea surface temperatures (SST) vary from 8°C in the north during winter, up to 26°C in the south during summer. SST depends mainly upon air temperature; there is a month's delay between the former and latter maxima. The sea surface salinity (SSS) varies also spatially and seasonally, ranging from less than 31 psu, in the north, to more than 39 psu, in the southeast; lower values (< 25 psu) occur adjacent to the river mouths. SSSs present their maximum differences during summer, whilst during winter and autumn the distribution of SSS is more uniform. The overall spatial SST and SSS distribution pattern is controlled by: distribution of the (colder) Black Sea Waters; advection of the (warmer) Levantine Waters, from the southeastern part of the Aegean; upwelling and downwelling; and, to a lesser extent, but locally important, freshwater riverine inflows.     

Numerical analysis of water circulation and thermohaline structures in the Caspian Sea

The Caspian Sea has a unique ecosystem that consists of endemic species. The deterioration of the unique ecosystem has become increasingly worrisome since a wide variety of pollutants have been released into the water. Water circulation plays a key role in advection and diffusion of these pollutants. In the present study, water circulation and thermohaline structures in the Caspian Sea were analyzed by means of a three dimensional numerical simulation. The effects of meteorological changes, river inflow, and an icing event were taken into account as boundary conditions. Numerical simulation was carried out for 20 years to achieve stable seasonal variations in model variables. As a result, the horizontal distributions of water temperature and salinity could be reproduced; the gradient of water temperature in the north–south direction, the decrease in water temperature along the east coast of the middle Caspian Sea due to coastal upwelling, and low salinity in the northern Caspian Sea. The icing event kept the water temperature in the northern Caspian Sea from decreasing to an unrealistic value. The observed cyclonic gyres were basically formed by the density-driven current due to thermohaline structure.     

集装箱船的大型化开发及其引发的问题

首先概要介绍近年来世界集装箱船大型化的发展，接着分析指出，远洋运输成本低廉是集装箱船大型化发展的驱动力，然后提出大型化发展中出现的3个问题值得讨论。第一个问题是大型化发展受港口航道水深、码头装卸机械等条件制约。第二个问题是设计制造超大型集装箱船的主机不易。最后一个问题是，为解决超大型集装箱船的巨量货物的“集疏运”，必须开发电子信息技术。作者最后提出，21世纪初对大型集装箱船的箱量定位应为8000标准箱。     

Using OMP analysis to observe temporal variability in water mass distribution

Previous optimum multiparameter analyses have investigated spatial distribution of water masses and reported successful results. This study tests the method further with application to a time series to examine temporal variability in water mass distribution. Observations collected from the Sargasso Sea are utilised, mainly to detect well-documented property changes that have occurred in Labrador Sea Water, but also possible fluctuations in water mass contributions as a whole.The results show much structure and variability in the contributions of Central Water and upper deep waters in the depth range 900–2000 m. It is proposed that the passage of warm and cold core eddies is indicated by these changes in relative contributions of water masses, although quantitative comparison of satellite altimetry data with the model results is not conclusive.Significant irregularities in the distribution of Labrador Sea Water are also revealed by the model. Through-flow of modified (since the early 1990s) Labrador Sea Water is denoted in the results by an apparent absence from mid-1995 to early 1998. This suggests a transit time of 5–6 years between the Labrador Sea and Bermuda, which is consistent with observational findings described in the literature.     

The PROFILE project: an overview

The EC MAST project PROFILE (Processes in Regions of Freshwater Influence, ROFIs) aims to develop process understanding and tested numerical models for ROFIs. This includes the role of physical processes controlling water-property distributions, suspended sediments controlling the availability of light, nutrients and phytoplankton growth. The project comprises: (1) construction of a 3D nearshore model, with high resolution (1 h and one km approx.) and a framework coupling modules for hydrodynamics (tides, effects of winds and waves, currents, temperature, salinity, turbulence and diffusivity), sediments, plankton, nutrients and oxygen, (2) investigation of methods to include ROFI model detail in coarser shelf-wide models, (3) specific tests of model components against measurements, (4) tests of model calculations against measurements in contrasted ROFIs, (5) systematic observations suitable for these model tests (time-series over a seasonal cycle for dynamics and intermittency, good vertical resolution and spatial surveys) of the contrasted Rhine, Clyde and Thermaikos Bay ROFIs, complementing earlier measurements in the ROFI areas of the Rhine, German Bight and Po, (6) interpretation and comparison of the contrasted ROFIs' behaviour, (7) a defined set of observations, model code and output suitable for subsequent integration and promulgation as test data and a nearshore model for wider use.     

Ventilation of bottom water in the North Sea–Baltic Sea transition zone

The transition zone between the North Sea and the Baltic Sea is a highly dynamic region where a general estuarine circulation forms a regional scale frontal system from northern Kattegat to the Arkona Sea. This system is characterized by an upper low saline out?owing Baltic water mass from the in?owing saline Skagerrak bottom water to the Kattegat and Belt Sea area. Large and rapid ?uctuations of the frontal system are caused by barotropic transports, forced by changing sea level difference between northern Kattegat and the western Baltic Sea, and this results in high variability of the hydrographic conditions and also in frequent in- and out?ow events to the Baltic. The dynamics in the region are here analyzed by a regional model of the transition zone, covering the area from the northern Kattegat to the Arkona Sea. The model is validated against water level, temperature and salinity measurements from the region, and the transports through the Danish straits are related to previous estimates and empirical relations. A sensitivity study quantify the role of bathymetry, the tidally induced mixing and the in?owing Skagerrak bottom water for ventilating the bottom water with Skagerrak water or surface water.Furthermore, the dynamics in the region is analyzed with tracers representing the age of the water. The distribution of age tracers with different boundary conditions are analyzed, and the role of advection and mixing for ventilating the bottom water is quanti?ed in terms of the water age. It is shown that the Great Belt area is a very dynamical area where bottom water is ventilated with surface water. The interannual variation of the ventilation of bottom water in the period 2001–2003 is analyzed by various age tracers and related to observed oxygen conditions, and it is shown that the extreme hypoxic event in the autumn 2002 in the southern Kattegat, the Great Belt and in the western Baltic Sea coincide with an unusual low vertical ventilation rate in the Great Belt area, but normal advection rates of bottom water from the northern Kattegat. This indicates that during this particular event, and probably in general, ventilation of bottom water in the Great Belt has signi?cant in?uence on oxygen conditions in the southern part of the region and for ventilation of bottom waters in the western Baltic Sea. In contrast, the central Kattegat is primarily ventilated by advection of bottom water from the Skagerrak. An age tracer representing the ventilation rate of bottom water with either Skagerrak water or surface water is shown to be inversely correlated to the observed oxygen distribution in the region.     

A note on the age of radioactive tracers

The age of a water mass is often estimated experimentally using the radio-age computed from the distribution of a radioactive tracer (radiocarbon, helium–tritium). Deleersnijder et al. [J. Mar. Syst. 28 (2001) 229.] have shown that the radio-age underestimates the age of the water and is larger than the age of the radioactive tracer used for its evaluation. This result is generalized here to radio-ages computed from the ratio of two radioactive tracers. The differences between the different ages are also studied analytically and numerically as functions of the decay rate of the radioactive tracers.For small decay rates, the difference between the age of the water mass and the radio-age is shown to be proportional to the decay rate. It depends also on the level of mixing in the system; even radioactive tracers with small decay rates can provide poor estimates of the age of the water mass in a strongly diffusive flow. For small half lives, both the radio-age and the age of radioactive tracers decrease as the inverse of the square root of the decay rate.The same analysis applies to some extent to the estimates of the age of a water mass from stable tracers with known time dependent sources (e.g. chloroflurocarbons).     

On the dense water spreading off the Ross Sea shelf (Southern Ocean)

In this study, current meter and hydrological data obtained during the X Italian Expedition in the Ross Sea (CLIMA Project) are analyzed. Our data show a nice agreement with previous data referring to the water masses present in this area and their dynamics. Here, they are used to further analyze the mixing and deepening processes of Deep Ice Shelf Water (DISW) over the northern shelf break of the Ross Sea. In more detail, our work is focused on the elementary mechanisms that are the most efficient in removing dense water from the shelf: either classical mixing effects or density currents that interact with some topographic irregularity in order to drop to deeper levels, or also the variability of the Antarctic Circumpolar Current (ACC) which, in its meandering, can push the dense water off the shelf, thus interrupting its geostrophic flow. We also discuss in detail the (partial) evidence of dramatic interactions of the dense water with bottom particulate, of geological or biological origin, thus generating impulsive or quasi-steady density-turbidity currents. This complex interaction allows one to consider bottom particular and dense water as a unique self-interacting system. In synthesis, this is a first tentative analysis of the effect of bottom particulate on the dense water dynamics in the Ross Sea.     

A box model for North-East Atlantic coastal waters compared with radioactive tracers

A box model for the estimation of doses to members of the public from discharges of radioactivity into North-East Atlantic coastal waters has been used to predict annual means of radionuclide seawater concentrations which have been compared with measured data of tracer radionuclides, ¹³⁷Cs, ⁹⁹Tc and ¹²⁵Sb. Discharges of these radionuclides into the sea from the nuclear reprocessing plants Sellafield in the UK and La Hague in France have been used as input to the model. Fallout of ¹³⁷Cs from atmospheric nuclear weapons tests and fallout of ¹³⁷Cs from the Chernobyl accident into the Baltic Sea have been taken into account. A large proportion of the measured data was collected during the CEC MAST-900052 project which is concerned with the utilization of radionuclides as tracers for water movements. The data cover the time period 1972–1992. A comparison between predicted and measured concentrations of radionuclides in seawater indicated the need to improve the model with respect to mixing conditions in the English Channel and water transport from the North Sea to the Baltic Sea via the Skagerrak, the Kattegat and the Belt Sea. Improvements were made using the data for ¹³⁷Cs and ⁹⁹Tc and involved adjustments of the mixing conditions (water exchange rates) between adjacent water boxes while keeping the net advective water fluxes of the model unaltered. The results of the modified version of the model have been compared with observed values. The comparison shows a somewhat better agreement for ¹³⁷Cs and ¹²⁵Sb than for ⁹⁹Tc which is believed to be due to the lower reliability of the ⁹⁹Tc discharge data from Sellafield in 1978. An analysis of the predicted-to-observed seawater concentrations indicates an overall predictive accuracy of the model of 0.9 corresponding to a 10% underestimation and a predictive precision of about a factor of 2.5 at a confidence level of 95%. The ¹²⁵Sb data, which are independent of the tuning of the model, support the general conclusions about the model predictions of radionuclide concentrations in seawater.     

On the fresh balance of the Adriatic Sea

The long-term mean fresh water balance of the Adriatic Sea is studied by ananalysing evaporation, precipitation and river runoff. Evaporation is computed from May latent heat flux and by means of bulk formula. In the latter case two wind speed data sets are used, namely those from the NMC and May. The sea surface temperature is taken from a historical Adriatic data set, and the air temperature and relative humidity come from the NMC data set. Two precipitation data sets are considered, namely the Legates and Willmott climatology and a data set consisting of data measured at 62 rain-gauge stations located on the Adriatic coasts. Runoff contribution to the fresh water balance is estimated from the long-term average flow rates of 39 rivers and the horizontal distribution of salinity in the upper mixed layer.The spatial distribution of the fresh water balance, as well as of its components, is analysed by means of monthly objective maps, from which averages and standard deviations are computed. The results obtained from the different computations are not always univocal, particularly in the evaluation of Summer evaporation, and are affected by relatively large statistical errors. Significant spatial and seasonal variability occurs, with a noticeable fresh water gain along the coastline of the northern and middle basins, while small areas of fresh water loss are found in the middle and southern basins. Nevertheless, on an annual basis, the difference between the fresh water losses by evaporation and the gains by precipitation and runoff is clearly negative, indicating that, unlike the whole Mediterranean, the Adriatic Sea is generally a dilution basin.     

长江上游涪陵至丰都段航道水运量分析预测

涪陵至丰都河段是联系长江上游与中下游的重要运输通道,水运量分析预测对该段航道的建设规划具有重要意义。提出采用长江干线主要港口进出港货运数据,基于港口和航道的位置关系来统计航道水运量及流向等。结果表明该河段水运量从2000年的1 241万t增长到2016年的1. 604 4亿t,上下行水运量占比分别为66%和34%,贡献了三峡过闸货运量的94%,矿建材料、矿石、钢材、煤炭、石油和集装箱等主要货种占水运量的73%。提出采用回归分析法、弹性系数法、指数平滑法和投入产出法分别考虑腹地GDP、产业结构、运输结构等多因素对水运量的影响。预测表明:工程河段水运量呈持续增长趋势,但增长速度逐步减缓,2045年水运量达到3. 233 3亿t,主要货物水运量占总水运量的86%。水运量分析预测方法和结果可为航道的建设规划提供支撑。     

Upwelling mechanisms in the northwestern Alboran Sea

From April 1996 to July 1997, a series of hydrographic surveys were carried out in the Northwestern part of the Alboran Sea to investigate the upwelling that is an almost permanent feature in this area. Simultaneously a mooring line was deployed in the north part of the eastern section of the Strait of Gibraltar to monitor the variability of the Atlantic Jet (AJ). Two mechanisms are shown to be relevant for the upwelling dynamic in the region: the southward drifting of the AJ and wind stress. A linear relation between the angle under which the Jet enters the Alboran Sea and the distance from the coastline to the front associated with the Jet has been found. This angle that has been estimated from the low passed time series of current velocity measured by the uppermost instrument of the moored line has been then used to identify the onshore–offshore excursions of the Jet. Both upwelling mechanisms are identified from hydrographic data, because each of them has associated a different type of water mass, and they take place in different locations. Wind-driven upwelling dominates in coastal zones, on the shelf, while upwelling associated with southward drifting of the AJ prevails further offshore. The amount of sub-surface water brought up to the surface by each one is of the same order. However, wind-driven upwelling contributes to the fertilization of this region in a major extent because water upwelled by wind is richer in nutrient concentration.     

Mass balance of trace metals in the Adriatic Sea

A first order mass balance of six different trace metals (Mn, Fe, Pb, Zn, Cu, Ni) was presented for a 1-year period for the different compartments of the Adriatic Sea: compartment 1 (northern Adriatic Sea), compartment 2 (central Adriatic Sea and surface layer of the southern Adriatic Sea) and compartment 3 (deep water of the southern Adriatic Sea). The Adriatic Sea appeared to be a source of dissolved Cu, Mn and Fe for the Mediterranean Sea through the Strait of Otranto whereas for dissolved Zn and Pb the Adriatic Sea appeared to be a net sink. For dissolved Ni, inputs and outputs through the Strait of Otranto balanced each other. The residence times of all metals in compartment 1 were significantly shorter than that of water indicating significant removal. In compartments 2 and 3, residence times of Mn and Fe were relatively short suggesting removal from the water column whereas for the other metals their residence times were similar to that of water. Calculations of turnover times of metals with respect to different processes showed that in compartments 1 and 2, sedimentation was the main process that affected the content of the reservoirs whereas in compartment 3, the water flux exchanges played an important role for Zn, Cu and Ni.Most of the metals clearly undergo a very dynamic cycle of sedimentation/remobilization particularly in the Northern Adriatic Sea. In the northern Adriatic Sea, most of the Mn and Fe in deposited sediment were remobilized. This was related to diagenetic processes involving the utilisation and solubilisation of Mn and Fe oxides, which occur in the surface of the sediment in the northern Adriatic Sea. In the central Adriatic Sea, remobilization of Mn and Fe was less than in the northern Adriatic Sea, suggesting that diagenesis processes appear deeper in the sediment. Advective transport of sediment was a major source of metals for the deep basin. As much as 80% of the sediments in the South Adriatic Pit might be advected from the shelf. Remobilization fluxes in the South Adriatic Pit were significantly less than in the Northern and Central Adriatic Sea reflecting hemi-pelagic sediments.     

Variability of the Bohai Sea circulation based on model calculations

The circulation and the hydrography of the Bohai Sea are simulated with the Hamburg Shelf Ocean Model (HAMSOM). The model is three-dimensional, prognostic baroclinic and has a resolution of 5 min in latitude and longitude and 10 layers in the vertical. It is initialised and forced with the five main tidal constituents, temperature and salinity distributions taken from the Levitus database, monthly mean river run-off values and European Centre for Medium Range Weather Forecast (ECMWF) re-analysed data of air pressure, wind stress and of those parameters relevant for the calculation of heat fluxes. The simulation period covers 14 years from 1980 to 1993 due to the availability of the time-dependent ECMWF forcing.The results are analysed by means of time series and EOFs focussing on the interpretation of fluctuations with periods above the tidal cycle. Furthermore, tracer simulations are carried out and turnover times are calculated in order to evaluate the importance of these fluctuations on the renewal and transport of water masses in the Bohai Sea.One of the major outcomes of the investigation is the overall dominance of the annual cycle in all hydrographic parameters and the importance of stochastic weather fluctuations on the transport of water masses in the Bohai Sea.