Ammonia Nitrogen at the Water–Sediment Interface in Puck Bay (Baltic Sea)

The magnitude of the exchange flux at the water–sediment interface was determined on the basis of the ammonia concentration gradient at the near-bottom water–interstitial interface and Fick's first law. It was established that in Puck Bay, ammonia almost always passes from the sediment to water. Ammonia flux varied from 5 to 1434 μmol NH₄-N m⁻² day⁻¹. In total,c. 138·2 tonneammonia year⁻¹pass from sediments of Internal Puck Bay to near-bottom water, the equivalent value for External Puck Bay being 686·9 tonne year⁻¹. In total, about 825 tonne ammonia year⁻¹passes from the sediment to near-bottom water of Puck Bay. In interstitial waters, ammonia occurred in concentrations varying over a wide range (3–1084 μmol NH₄-N dm⁻³).The basic factors affecting the magnitude of ammonia concentration in interstitial waters included: oxidation of organic matter, type of sediment, and inflow of fresh underground waters to the region examined.This paper involves preliminary studies only and constitutes a continuation of the studies on ionic macrocomponents and phosphorus in interstitial waters of Puck Bay undertaken previously.     

安达曼海的热收支分析及其水交换研究

The characteristics of the T/S structures, water mass exchange and deep circulation in the Andaman Sea are investigated based on the simulation from a high-resolution general circulation model(MITgcm). The results show that, below 1 000 m, the water mass is saltier, warmer and more homogeneous in the Andaman Sea than that in the Bay of Bengal, attributing to the strong vertical mixing at the depth of ～1 800 m. The water mass exchange between the Andaman Sea and the Bay of Bengal goes through three major channels, which manifests itself as follows: the northern channel(Preparis Channel) is the main passage of water mass transport from the Bay of Bengal to the Andaman Sea, whereas the Middle Channel(the south of Andaman Islands and the north of Nicobar Islands) has an opposite transport; the southern channel(Great Channel) features with a four-layer water exchange which results in the least net transport among the three channels; all the transports through the three channels have an intra-annual variation with a period of half a year. At 1 000-m depth, the entire Andaman Sea is occupied by a cyclonic circulation in January and July while by an anticyclonic one in April and October. The semiannual cycle found in both the deep circulation and water mass exchange is likely associated with the downwelling eastward-propagating Kelvin waves induced by the semiannual westerly component in the equatorial Indian Ocean during intermonsoon seasons.     

潮汐对东海陆架边缘处水交换的影响

为探讨潮汐对东海陆架边缘处水交换通量的影响,本文基于ROMS海洋数值模式,对渤海、黄海、东海的潮汐、环流进行了模拟研究。研究结果显示,在水平方向上,潮汐效应主要影响我国台湾岛东北及日本九州西南的水交换,其中在台湾岛东北区域,潮汐效应通过增加黑潮分支流(KBC)的向岸及离岸速度来加强黑潮水的跨陆架交换。潮汐效应对200 m等深线处跨等深线流速的影响量值约为3～5 cm/s。从垂直方向上来看,潮汐效应能够影响到深度200m处水层的深层交换。进一步研究其作用机制,发现潮汐效应主要通过平流输送项来影响水体交换,而其对水体的水平及垂直扩散项的影响较小。     

冬季大风影响下的渤黄海水交换特征

利用ROMS海洋数值模式对2006年冬季渤黄海的海洋动力环境进行模拟,基于温度、盐度模拟结果,使用谱混合模型进行水团分析,定义了渤海海峡地区的水交换区。并进一步讨论了冬季大风事件对水交换区的影响,给出了冬季大风影响下的渤黄海水交换特征。研究得出,冬季的黄海水团以“舌”形分布于渤海海峡地区,水交换区则表现为沿“舌”形边缘呈带状分布,具有西北——东南的走向趋势,并且在“舌”尖处的水交换面积最大。通过缩小研究范围,发现位于黄海最北部的沿岸海域并不参与渤黄海之间的水体交换。最后研究发现,冬季大风事件对渤海水交换具有促进作用,具体表现为：大风过程使黄海暖流对渤海的入侵更加深入,水交换区向渤海方向伸展,南部的水交换带变宽,河流径流进入渤海后与渤海水的混合区加大,并发生北移。     

The PROWQM physical–biological model with benthic–pelagic coupling applied to the northern North Sea

PROWQM, a 1-D depth resolving model which couples physical and microbiological processes in the water column with sedimentation/resuspension and benthic mineralisation processes, has been used to simulate seasonal changes of chlorophyll, nutrients and oxygen at the PROVESS north site (59°20′N 1°00′E) in the North Sea. PROWQM is derived from the 3-D model COHERENS, and improves COHEREN's benthic and pelagic biology.The physical sub-model of PROWQM implicitly solves turbulence closure equations forced by climatological, or realistic high-frequency, meteorological and tidal data. The pelagic biological sub-model 2MPPD includes a ‘diatomy’ microplankton (mp1) and a ‘flagellatey’ (or microbial loop) microplankton (mp2), the cycling of silicon and nitrogen, slow-sinking detritus, and fast-sinking phytodetritus. Phytodetritus is formed by shear-driven aggregation of particulate material, using a simple algorithm for bulk processes that is derived by considering the interactions of single cells. The microplankton compartments include heterotrophic bacteria and protozoa as well as phytoplankton, and most microplankton rates are specified with the aid of a ‘heterotroph fraction’ parameter, which was 0.125 for mp1 and 0.6 for mp2. The microbiological system is closed by mesozooplankton grazing pressures imposed as time varying series determined from observed zooplankton abundance. The benthic boundary sub-model includes a superficial fluff layer and a nutrient element reservoir in the consolidated sediment. Particulate material in the fluff layer can be resuspended (in response to bed stress by near-bed flows), mineralised or carried by bioturbation into the underlying, consolidated, sediment, where it is mineralised and its nutrients returned to the water-column at rates mainly dependent on (implicit) macrobenthic pumping. Benthic denitrification can occur when mineralisation rates exceed oxygen supply.Verification of the PROWQM numerical implementation used test cases and checks for nutrient element conservation. Simulations with realistic forcing, for a range of parameter values, were compared with historic observations in the NOWESP data set and during FLEX76, and with those made during the PROVESS cruises in autumn 1998. PROWQM provided a good simulation of the seasonal succession from a diatom-dominated spring bloom to summer dominance by small flagellates. The simulations included sedimentation of organic matter from the spring bloom, and qualitatively realistic behaviour of the fluff layer, but decay rates were too slow and there was almost no denitrification. The simulated surface mixed layer was too shallow during the summer. Simulated annual net microplankton primary production was in between 59 and 91 g C m⁻² y⁻¹. A large proportion of mineralisation, 28–47% of nitrogen and 40–67% of silicon mineralisation, took place as a result of the decay of sinking and resuspended detritus whilst in the water column.PROWQM is discussed in relation to other models that have been used to simulate this part of the North Sea, in particular the simpler ECOHAM1 and the more complex ERSEM, and in relation to PROWQM's evolution from COHERENS.     

乐清湾水交换特征研究

采用EFDC模式模拟研究了乐清湾水交换的三维过程和时空变化特征,并通过计算水示踪剂质量浓度分析水体置换过程。结果表明,乐清湾水交换主要是由鹿西岛两侧流入的外海水体与湾内水体的交换,以及乐清湾口门西侧附近的湾内水体与瓯江北口径流冲淡水之间的交换。从口门到湾顶,水交换能力差别较大。以最窄的连屿至打水山断面为界,以南水体1个月基本可以完全交换,而以北水体2个月后仍然无法交换至湾口水平。连屿至打水山断面以北地形复杂,岛屿较多,污染物主要通过岛屿间的潮汐汊道输运,断面的瓶颈效应也使得断面以北的水体交换能力稍弱。在口门附近90%以上的水体被外海置换所需时间不到5 d,而此时湾顶水质未有太大改变;15 d左右,80%湾内水体被外海水置换;90%湾内水体被置换仅需40 d;70 d时的水体置换率达97%。     

Role of Kuroshio frontal eddy in exchange between shelf water and Kuroshio water in East China Sea

Basic patterns of the reversal of the Kuroshio water toward the shelf, intrusion of the shelf mixed waterinto the Kuroshio and uplifting of the near-bottom nutrient-rich water into the upper layer by the pumping of the frontal eddy are analyzed on the basis of satellite infrared images and hydrologic, chemical and biological observations. Results show that the Kuroshio frontal eddies play a very important role in the exchange between the shelf water and the Kuroshio water. The estimation of the average volume transports for three frontal eddy events indicates that the shelf mixed water entrained by an eddy into Kuroshio is 0.44×10~6 m3/s and the reversal Kuroshio water onto the shelf region only 0.04×10~6 m3/s. Along the whole shelf edge, the volume transport of the shelf mixed water entrained by the eddies into the Kuroshio is 1.8×10~6 m3/s. The nutrient (NO3-N) flux pumped to the euphotic zone and input to the continental shelf through a column with 1 m wide is 974 μmol/(s·m) when there is frontal eddy and only 79 μmol/(s·m) in the case of no frontal eddy. Yearly nutrient (NO3-N) flux input to the shelf area caused by the frontal eddy is 1.7×10~5 t/a.     

半封闭海湾的水交换数值模拟研究

基于采用不规则三角网格和有限体积方法的FVCOM模式,建立半封闭海湾-湛江湾附近海域的三维潮汐潮流数值模型,通过验证,结果与观测数据符合良好,并在此模型基础上对湛江湾的水交换状况进行了数值模拟,将湛江湾划分成3个区域,针对各区域进行了水交换能力研究,研究结果表明:由于湛江湾内不同区域的地形和地理位置变化较大,使得湛江湾内不同区域交换能力相差较大,其中,靠近湛江湾出口处交换能力最强,特呈岛以北海域交换能力最弱,交换时间与物质的初始浓度无关,与投放时刻和外源强迫密切相关,在治理湛江湾环境时,应分区进行,注意选择污染物排放时间和位置。     

秋季南黄海水文特征及海水的混合与交换

根据1996年10月中韩合作调查获得的CTD资料,分析探讨了南黄海秋季跃层的分布特征及垂直混合状况,同时对黄海冷水团的垂向混合进行了初步探讨.还利用改进后的逐步聚类分析法划分了表、底层水团,确定了各水团的温度、盐度、溶解氧和PH值4要素的平均特征值,并根据各水团的特性和温度、盐度的平面分布特征,重点探讨了黄海水与沿岸水及东海水的混合和交换.     

Impacts of temperature anomalies on mortality of benthic organisms in the Adriatic Sea

Recurrent climate‐induced mass mortality episodes have been recorded in the Mediterranean Sea over the past 15 years, affecting rocky benthic communities. In this study, we provide for the first time a report on the annual mortality events of benthic sessile invertebrates occurring in the eastern part of the Adriatic Sea. Over the course of 14 consecutive years, we studied the sea temperature gradient to a depth of 40 m and found an abnormal summer warming trend and an increased frequency of above‐average temperatures. Mortality events were recorded in the summers of 10 observed years, in particular in 2009, when the highest mortality rates were recorded. Late in summer 2009, extensive mass mortality of sessile invertebrates was observed in the entire Eastern Adriatic Sea. We performed an analysis of selected target benthic species associated with mass mortality events with inter‐regional differences in hydrological and temperature conditions. We were able to characterize the mortality event by studying five areas covering the northern, central and southern regions of the Eastern Adriatic Sea. The degree of impact on each study area was quantified at 28 sites by estimating the proportion of affected target species. According to the obtained data, the northern sites (Cres area) were the least affected, whereas sites in the Central and Southern Adriatic [Tela??ica and Lastovo Nature Parks, Mljet National Park (NP)] displayed the highest impact. In summer 2009, sea surface temperatures reached values of 28 °C in the Cres area and 30 °C in Mljet NP. These thermal conditions were concomitant with moderate to severe mass mortalities of benthic populations. Mass mortality events reached depths of 45 m in most parts of the affected areas. Amongst studied species, the scleractinian coral and gorgonian populations suffered the most extensive damage during the mass mortality events.     

Several characteristics of water exchange in the Luzon Strait

1IntroductionTheLuzonChannelissituatedonthewest-ernsideofthenorthernPacificandbetweenTaiwanandLuzonIslands.ItisthemainpassageofthePacificwaterenteringtheSCS.Therearenumerousdifferent-sizedislandsformingmanynarrowwaterpassagesinthischannel,sotheLuzonChannelisthegeneralnameofthesepas-sages(includingBabuyan,BalintangandBashiChannels,etc.).Customarily,theLuzonStraitiscalledtheBashiChannel.Itswidthis386kmandhasameandepthof1400m. Toagreatextent,thehydro-meteorologi-calconditionso…     

象山港水交换特性研究

在验证良好的三维斜压潮流数学模型的基础上,以溶解态的保守性物质为示踪剂,建立对流-扩散型的海湾水交换数值模型,计算了象山港水体半交换时间和平均滞留时间,并研究了斜压动力对湾内外水交换的贡献.研究结果表明,象山港水交换速度的区域性变化较大,水体半交换时间和平均滞留时间由象山港口门向湾顶逐渐增加,口门附近半交换时间在5d以内,平均滞留时间为5～10 d;湾顶水交换速度缓慢,水体半交换时间为30～35 d,平均滞留时间为35～40 d.斜压动力对狭湾外段水交换影响较弱,对狭湾内段有较大的影响.     

天津海域围填海工程对渤海湾水交换的影响研究

利用三维海洋数值模型FVCOM,进行渤海湾三维水动力和水交换数值模拟,经实测潮汐和潮流资料验证,模型模拟结果较好。然后采用该模型对渤海湾内的水体水交换能力进行定量研究。研究结果表明,在天津海域进行围填海工程之前渤海湾水体的半交换周期为300 d左右,围填海之后,水体半交换周期延长25 d,渤海湾西部水体的水交换率下降可达10%,半交换周期延长92 d。尤其是天津沿海南部海域的水交换能力下降严重,围填海之后其水体半交换周期延长可达200 d。渤海湾北部也有部分海域水交换周期延长达200 d。建议在进行围填海工程建设时,应将工程对水体交换能力的影响纳入考虑,避免因围填海工程因素造成的恶劣环境影响。     

Flow regimes and long-term water exchange of the Himmerfjärden estuary

A numerical model of processes determining the water exchange encountered in Baltic coastal archipelagos is calibrated and validated against salinity and temperature field data spanning two decades with approximately bi-weekly resolution assessed in the Himmerfjärden estuary. This area is resolved into 17 basins interconnected by 38 individual straits of varying geometrical properties using GIS-based methods. All formulations of the strait exchange flows are free from parameters that need calibration and permit computations of the flow through a strait contraction with or without a coincident sill under a flow classification scheme, of which the first one (a) consists of two groups of multiple layers including aspirated layers from levels beneath the sill crest. The other regimes are as follows. (b) Pure barotropic flow; (c) rotationally controlled flow and (d) plug-flow, which serves as resort solution for flow situations that cannot be solved with (a) and also for computation of the barotropic part of the total flow. For long canals where friction effects act to reduce the flow, a fifth exchange regime is used. The vertical mixing formulation is based on energy balances between supplied wind energy and its work against buoyancy forces. The values of semi-empirical parameters involved in the mixing scheme have been established by calibration against measured data of the first decade period. A statistical evaluation is performed comparing the model results with the measurements of the second decade.     

Time-series of surface water CO2 and oxygen measurements on a platform in the central Arkona Sea (Baltic Sea): Seasonality of uptake and release

High resolution measurements of carbon dioxide and oxygen were made in surface waters of the central Arkona Sea (Baltic Sea) from May 2003 to September 2004. Sensors for CO₂ partial pressure (pCO₂^w) and oxygen (O₂) concentration were mounted in 7 m depth on a moored platform which is used for hydrographic and meteorological monitoring. The pCO₂^w data were obtained in half hour intervals and O₂ was measured each hour as an average of a 10 min measurement. To check the performance of the sensors, pCO₂^w and O₂ were determined by shipboard measurements on a research vessel which visited the site in 1–2 month intervals. In addition, pCO₂^w was measured on a “volunteer observing ship” (VOS) passing the platform each second day at a distance of about 25 km. Minima of 220 to 250 μatm of pCO₂^w were observed at the time of the spring bloom and a cyanobacteria bloom in mid-summer. During winter the pCO₂^w was mostly close to equilibrium with the atmosphere but maxima of 430 to 530 μatm were also observed. The seasonality of oxygen and pCO₂^w showed an opposing pattern. From a multiple regression analysis, we concluded that two processes primarily controlled pCO₂^w during our study: biological turnover and mixing. A parameterization, based on apparent oxygen utilisation (AOU) and salinity (S) only (pCO₂^w = 1.23 AOU + 43 S), reproduced the seasonality of pCO₂^w in surface water reasonably well. Based on our pCO₂, salinity, and temperature data set, we attempted to separate processes changing total inorganic carbon concentrations (C_T) by using an alkalinity–salinity relation for the area. The contribution of CO₂ gas exchange and mixing were calculated and from this the biological turnover was deduced to reveal the calculated C_T changes.The net annual uptake of CO₂ in the central Arkona Sea was estimated to be about 1.5 Tg (1.5·10¹² g) which was approximately balanced by a net oxygen release considering the uncertainties of the flux calculations. Near-coast CO₂ emission due to episodic upwelling partly compensated the uptake of the central part of the Arkona Sea reducing the overall magnitude of the CO₂ uptake.     

Tidal time-scale variation in nutrient flux across the sediment–water interface of an estuarine tidal flat

We determined the range of the tidal variations in nutrient flux across the sediment–water interface and elucidated mechanisms of the flux variation in two estuarine intertidal flats (one sand, one mud) in northeastern Japan. Nutrient flux was measured using in situ light and dark chambers, which were incubated for 2 h, 2–6 times per day. Results showed that nutrient concentration in overlying water varied by tide and was also affected by sewage-treated water inflow. The nutrient fluxes responded quickly to the tidal variation in overlying water chemistry and the range of the variation in flux was as large as the seasonal-scale variation reported in previous studies. In the sand flat, salinity increase likely enhanced benthos respiration and led to increases in both O₂ consumption and PO₄³⁻ regeneration under low illumination, while benthic microalgae were likely to actively generate O₂, uptake PO₄³⁻ and suppress PO₄³⁻ release under high illumination (>900 μmol photons m⁻² s⁻¹). Also in the mud flat, PO₄³⁻ flux was related with O₂ flux, although the range of temporal variation in PO₄³⁻ flux was small. In both the flats, NH₄⁺ flux was always governed by NH₄⁺ concentration in the overlying water; either an increase in NH₄⁺ uptake or a decrease in NH₄⁺ release was observed as the NH₄⁺ concentration rose due to inflow of river water or input of sewage-treated water. Although NO₃⁻ tended to be released in both tidal flats when low NO₃⁻ concentration seawater dominated, their relationship was likely to be weakened under conditions of low oxygen consumption and suppressed denitrification. It is likely that tidal variation in nutrient flux is governed more by the nutrient concentration than other factors, such as benthic biological processes, particularly in the case where nutrient concentration in the overlying water is relatively high and with wide amplitude.     

Nonlinear wave profiles of wave–wave interaction in a finite water depth by fixed point approach

In this paper, a superposition of two periodic wave profiles in a finite water depth was investigated. This paper is focused on the improvement of a wave profile on the linear superposition of two waves. This improvement was realized by introducing an iterative method, which was based on a fixed point approach. Application of the fixed point approach to the wave superposition made it possible to obtain a wave profile of wave–wave interaction. The improved result of the wave profile was in good agreement with that of the nonlinear perturbation solution of the second order. It was interesting that the improved result revealed the higher-order nonlinear frequencies for two interacting Stokes waves while Dalzell's solution by a perturbation method could not predict them.     

Unsteady ship waves in shallow water of varying depth based on Green–Naghdi equation

Based on Green–Naghdi equation this work studies unsteady ship waves in shallow water of varying depth. A moving ship is regarded as a moving pressure disturbance on free surface. The moving pressure is incorporated into the Green–Naghdi equation to formulate forcing of ship waves in shallow water. The frequency dispersion term of the Green–Naghdi equation accounts for the effects of finite water depth on ship waves. A wave equation model and the finite element method (WE/FEM) are adopted to solve the Green–Naghdi equation. The numerical examples of a Series 60 (C_B=0.6) ship moving in shallow water are presented. Three-dimensional ship wave profiles and wave resistance are given when the ship moves in shallow water with a bed bump (or a trench). The numerical results indicate that the wave resistance increases first, then decreases, and finally returns to normal value as the ship passes a bed bump. A comparison between the numerical results predicted by the Green–Naghdi equation and the shallow water equations is made. It is found that the wave resistance predicted by the Green–Naghdi equation is larger than that predicted by the shallow water equations in subcritical flow , and the Green–Naghdi equation and the shallow water equations predict almost the same wave resistance when , the frequency dispersion can be neglected in supercritical flows.     

象山港分区水交换数值研究

在验证良好的三维斜压潮流数学模型的基础上,将象山港划分成7个海区,以7种不同的溶解态保守性物质为示踪剂,建立对流-扩散型的海湾水交换数值模型,采用关联矩阵法来描述各区之间以及各区与外海之间的水交换特性。通过不同示踪剂的浓度分布,计算了15、30、45、60和80d的水交换矩阵。由各时刻水交换矩阵可知,在象山港的7个子区中与湾外水的水交换速度最快的为Ⅰ区,最慢的为Ⅶ区。Ⅲ区(西沪港)、Ⅵ区(黄墩港)和Ⅶ区(铁港)内水体与湾外海水之间的水交换速度缓慢,但与区域外水体之间的交换速度要明显快于其他几个海区。从水交换矩阵可以看出西沪港、黄墩港和3个内港之间相互交换的海水量很小。     

Numerical analysis on water exchange and its response to the coastal engineering in the Yueqing Bay in China

On the basis of a numerical model of tidal current using Delft3D, the distribution of the semi - exchange time of water was simula- ted in the Yueqing Bay here. The result showed that the semi - exchange time was about more than 6 d in the bay end, and about 1～2 d in the bay mouth. Besides, based on the calculation of the semi - exchange time before and after the Xuanmen Dam pro- ject, a comparison between them was further carried out. And the same work was also done with the recent reclamation projects in the Yueqing Bay as well. The results showed that the change in semi - exchange time caused by the Xuanmen Dam project was a- bout 6 d increase near the dam and 4.5 d increase at the bay end. And it was about 5 d increase at the bay end and 1 d increase at the mouth of the bay caused by the recent reclamation projects.