山东半岛东部海域悬浮体分布季节变化及其冬季输送通量研究

山东半岛东部近岸海域流系和水团要素季节变化显著,沉积动力环境特殊,发育有剖面形状独特的泥质沉积体。基于两个年度的夏、冬季山东半岛东部近岸海域水体温度、浊度、悬浮体浓度和海流等调查资料,分析了水团要素分布季节变化特征,并结合研究区域冬季海流和余流分布特征,计算了冬季经山东半岛东部近岸海域向南输送的悬浮体净通量。结果表明:山东半岛东部近岸海域悬浮体分布受沿岸流、黄海冷水团和黄海暖流等流系季节变化的影响存在显著季节变化。夏季,水体垂向层结和黄海冷水团均可抑制悬浮体垂向和东西向扩散。与以往的研究有所不同的是,冬季大量悬浮体可穿越沿岸流与黄海暖流形成的海流切变锋面,进入黄海暖流向北输送,海流切变锋的屏障作用会随着黄海暖流的减弱或东移而削弱。每年冬季经山东半岛东部近岸海域输送的悬浮体占渤海海峡向外海输送的悬浮体年净通量的3.22%~9.10%,冬季的悬浮体输送量较大,占冬季渤海海峡向外海输送的悬浮体年净通量的6.84%~19.38%。     

Inferring bottom circulation based on sediment pattern distribution in the San José Gulf,Patagonia Argentina

The goal of this work was to infer the spatio-temporal patterns of bottom circulation of San José Gulf (SJG), Patagonia, Argentina. The SJG is mainly affected by tidal circulation and presents two hydrographic domains. The Western Hydrographic Domain (WHD) presents vertically mixed waters year-round contrary to the seasonal stratified Eastern Hydrographic Domain (EHD), resulting in the formation of a thermal front between domains. Samples of sediments were collected in spring 2016 and summer 2017 at several locations to analyze the grain-size composition by means of laser diffractometry. A conceptual model of bottom hydrodynamics was inferred based on sediment's grain-size trends. Asymmetric dominant tidal currents affect bottom sediment distribution. A general northward sediment transport is dominant at the WHD, while at the EHD there is a seasonal shift in the transport direction. There, a net northward transport with a counterclockwise gyre dominates bottom hydrodynamics at the end of the thermal front formation, conditioned by residual currents. In contrast, a net southward circulation likely driven by strong westerly winds throughout autumn and winter prevails at the beginning of the water column stratification. The inferred sediment transport suggests a net loss of material that has to be recovered by tidal currents entering through the mouth and coastal sources as runoff, mudslides, and/or aeolian dust.     

近岸强海流切变锋作用下悬浮沉积物的输送和沉积--以山东半岛东端外海为例

利用2007年国家908专项ST02区块（渤海海峡及北黄海）水体专项夏季和冬季两个航次调查的温度、浊度和悬浮体浓度数据,选取了跨越山东半岛东端外海泥质沉积体的B1和B2两个断面,结合该区浅地层剖面资料,辅以研究海域的冬季环流数值模拟,着重分析了山东半岛东端外海强海流切变锋作用下的悬浮体输送和沉积特征。结果表明山东半岛东端外海悬浮体向外海输送存在类似“夏储冬输”的规律:夏季,北黄海海水浊度普遍小,不仅北黄海温跃层抑制了底层悬浮体向中上层水体扩散,而且北黄海冷水团在中底层与山东半岛东部沿岸水也形成了显著的温度和悬浮体锋面,阻碍了悬浮物的纬向输送,故夏季应是悬浮体沉积的主要时节;冬季,温跃层消亡,在强风的作用下,山东半岛东部悬浮体浓度高且垂向混合较好,然而在泥质沉积体顶积层两侧,山东半岛东部沿岸中下层北上的逆风补偿流和北上的黄海暖流与位于顶积层上方表中层南下的沿岸流构成了两道显著的强海流切变锋,使得底积层上大量的再悬浮沉积物不能越过山东半岛东部陆架末梢,从而有助于形成山东半岛东端外海特有的Ω状泥质沉积体。     

Numerical simulation of upwelling off Visakhapatnam on east coast of India during pre-monsoon months

A three-dimensional numerical model of the type described by Johns and coworkers (1992), hereafter referred to as model (J), is applied to study the response of a coastal ocean to pure wind-stress forcing. Conservation equations are applied for mass, momentum, temperature, salinity and turbulence energy. Experiments are performed to investigate the evolution of the thermal structure and upwelling processes along the east coast of India during the pre-monsoon season. A comparison between the computed results and the limited observations on the thermal structure and alongshore currents over the inner-shelf off Visakhapatnam is presented.     

Determing the effects of El Niño-Southern Oscillation events on coastal water quality

The importance of the El Niño-Southern Oscillation (ENSO) on regional-scale climate variability is well recognized although the associated effects on local weather patterns are poorly understood. Little work has addressed the ancillary impacts of climate variability at the community level, which require analysis at a local scale. In coastal communities water quality and public health effects are of particular interest. Here we describe the historical influence of ENSO events on coastal water quality in Tampa Bay, Florida (USA) as a test case. Using approximate randomized statistics, we show significant ENSO influences on water quality particularly during winter months, with significantly greater fecal pollution levels during strong El Niño winters and significantly lower levels during strong La Niña winters as compared to neutral conditions. Similar significant patterns were also noted for El Niño and La Niña fall periods. The success of the analysis demonstrates the feasibility of assessing local effects associated with large-scale climate variability. It also highlights the possibility of using ENSO forecasts to predict periods of poor coastal water quality in urban region which local agencies may use to make appropriate prepations.     

Impact of a Tropical Cyclone on Coastal Upwelling Processes

A three-dimensional numerical model is described to study theresponse of a coastal ocean excited by a tropical cyclone in the Bay of Bengal. The numericalexperiments have been carried out using the model to understand the dynamics and thermodynamics ofthe ocean due to different cyclonic systems approaching in different directions. In the firstexperiment, the model is used to simulate the vertical thermal structure of the ocean as a response ofpassage of the less intensified 1997 cyclone, which was skirting the east coast of India before crossingthe Bangladesh coast. The simulations are compared with the buoy data available during the storm period.In the next experiment, it is considered an idealized cyclone with hurricane winds movingnormal to the east coast of India crossing between Visakhapatnam and Kakinada to evolve thermalstructure and currents of the ocean. A net decrease of the SST of 6–7 °C is simulated whenthe severe cyclonic storm moved over the coastal ocean.     

Circulation and water masses of the Arabian Sea

The dynamics and thermodynamics of the surface layer of the Arabian Sea, north of about 10N, are dominated by the monsoon-related annual cycle of air-sea fluxes of momentum and heat. The currents in open-sea regime of this layer can be largely accounted for by Ekman drift and the thermal field is dominated by local heat fluxes. The geostrophic currents in open-sea subsurface regime also show a seasonal cycle and there is some evidence that signatures of this cycle appear as deep as 1000 m. The forcing due to Ekman suction is an important mechanism for the geostrophic currents in the central and western parts of the Sea. Recent studies suggest that the eastern part is strongly influenced by the Rossby waves radiated by the Kelvin waves propagating along the west coast of India. The circulation in the coastal region off Oman is driven mainly by local winds and there is no remotely driven western boundary current. Local wind-driving is also important to the coastal circulation off western India during the southwest monsoon but not during the northeast monsoon when a strong (approximately 7 × 10⁶m³/sec) current moves poleward against weak winds. This current is driven by a pressure gradient which forms along this coast during the northeast monsoon due to either thermohaline-forcing or due to the arrival of Kelvin waves from the Bay of Bengal. The present speculation about flow of bottom water (deeper than about 3500 m) in the Arabian Sea is that it moves northward and upwells into the layer of North Indian Deep Water (approximately 1500–3500m). It is further speculated that the flow in this layer consists of a poleward western boundary current and a weak equatorward flow in the interior. It is not known if there is an annual cycle associated with the deep and the bottom water circulation.     

波生流垂向结构研究综述

波生流是海岸工程和海岸演变非常重要的动力因素之一,水深平均的平面二维波生流目前已有大量的研究成果,且广泛应用于工程实践中,其垂向变化往往对建筑物的稳定和海岸地貌的变化造成显著影响,例如堤前冲刷和岸滩蚀退.回顾了国内外对波生流垂向结构的研究与进展,从实验室与现场观测、理论分析以及数值模拟3个方面概述了该领域的研究现状与发展趋势,总结了已有研究存在的不足,提出需要进一步研究的课题.     

Observations of currents and density structure across a buoyant plume front

Observations of the Mobile Bay, Alabama, plume during a flood event in April 1991 reveal significant differences in the current field on either side of a front associated with the buoyant plume. During a strong southeasterly wind, turbid, low salinity water from Mobile Bay was pushed through an opening in the west side of the ebb-tidal delta and moved parallel to the coast. A stable front developed between the low salinity water of the buoyant plume (11‰) and the high salinity coastal water (>23‰) that was being forced landward by the prevailing winds. Despite the shallow water depth of 6 m, measurements of currents, temperature, and salinity show large shears and density gradients in both the vertical and the horizontal directions. At a station outside of the buoyant plume, currents at 0.5 m and 1.5 m below the surface were in the same direction as the wind. Inside the plume, however, currents at 0.5 m below the surface were parallel to the coast, 45°, off the direction of the wind and the magnitude was 45% larger than the magnitude of the surface currents outside the plume. Beneath the level of the plume, the currents were identical to the wind-driven currents in the ambient water south of the front. Our observations suggest that the wind-driven surface currents of the ambient water converged with the buoyant plume at the front and were subducted beneath the plume. The motion of the ambient coastal surface water was in the direction of the local wind stress, however, the motion of the plume had no northerly component of motion. The plume also did not show any flow toward the front, suggesting a balance between the northerly component of wind stress and the southerly component of buoyant spreading. In addition, the motion of the plume did not appear to affect the motion of the underlying ambient water, suggesting a lack of mixing between the two waters.     

Assessment of bioclimatic comfort conditions based on Physiologically Equivalent Temperature (PET) using the RayMan Model in Iran

In this study thermal comfort conditions are analyzed to determine possible thermal perceptions during different months in Iran through the Physiologically Equivalent Temperature (PET). The monthly PET values produced using the RayMan Model ranged from ?7.6°C to 46.8°C. Over the winter months the thermal comfort condition (18–23°C) were concentrated in southern coastal areas along the Persian Gulf and Oman Sea. Most of the country experienced comfort conditions during the spring months, in particular in April, while during the summer months of July and August no thermal comfort conditions were observed. In November coastal areas of the Caspian Sea had the same physiological stress level of thermal comfort as April. The map produced showing mean annual PET conditions demonstrated the greatest spatial distribution of comfortable levels in the elevation range from 1000 to 2000 meter a.s.l., with annual temperatures of 12–20°C and annual precipitation of under 200 mm. The statistical relationship between PET conditions and each controlling parameter revealed a significant correlation in areas above 2000 meter, annual temperature over 20°C and annual precipitation of 200–400 mm with a correlation coefficient (R ²) of 0.91, 0.97 and 0.96, respectively.     

Recent observations of meteotsunamis on the Finnish coast

We present four case studies of exceptional wave events of meteorological origin, observed on the Finnish coast in the summers of 2010 and 2011. Eyewitnesses report unusually rapid and strong sea-level variations (up to 1 m in 5–15 min) and strong oscillating currents during these events. High-resolution sea-level measurements confirm the eyewitness observations, but the oscillations recorded by tide gauges mostly have a considerably smaller amplitude. The oscillations coincide with sudden jumps in surface air pressure at coastal observation stations, related to the passage of squall lines or gust fronts. These fronts propagate above the sea at a resonant speed, allowing efficient energy transfer between the atmospheric disturbance and the sea wave that it generates. Thus, we interpret the observed sea-level oscillations as small meteotsunamis, long tsunami-like waves generated by meteorological processes and resonance effects.     

Quantification of the Attenuation of Storm Surge Components by a Coastal Wetland of the US Mid Atlantic

Coastal wetlands are receiving increased consideration as natural defenses for coastal communities from storm surge. However, there are gaps in storm surge measurements collected in marsh areas during extreme events as well as understanding of storm surge processes. The present study evaluates the importance and variation of different processes (i.e., wave, current, and water level dynamics with respect of the marsh topography and vegetation characteristics) involved in a storm surge over a marsh, assesses how these processes contribute to storm surge attenuation, and quantifies the storm surge attenuation in field conditions. During the Fall of 2015, morphology and vegetation surveys were conducted along a marsh transect in a coastal marsh located at the mouth of the Chesapeake Bay, mainly composed of Spartina alterniflora and Spartina patens. Hydrodynamic surveys were conducted during two storm events. Collected data included wave characteristics, current velocity and direction, and water levels. Data analysis focused on the understanding of the cross-shore evolution of waves, currents and water level, and their influence on the overall storm surge attenuation. Results indicate that the marsh area, despite its short length, attenuates waves and reduces current velocity and water level. Tides have a dominant influence on current direction and velocity, but the presence of vegetation and the marsh morphology contribute to a strong reduction of current velocity over the marsh platform relative to the currents at the marsh front. Wave attenuation varies across the tide cycle which implies a link between wave attenuation and water level and, consequently, storm surge height. Storm surge reduction, here assessed through high water level (HWL) attenuation, is linked to wave attenuation across the front edge of the marsh; this positive trend highlights the reduction of water level height induced by wave setup reduction during wave propagation across the marsh front edge. Water level attenuation rates observed here have a greater range than the rates observed or modeled by other authors, and our results suggest that this is linked to the strong influence of waves in storm surge attenuation over coastal areas.     

Operational wave prediction of extreme storms in Northern Europe

The disastrous effects of numerous winter storms on the marine environment in the North Sea and the Baltic Sea during the last decade show that wind waves generated by strong winds actually represent natural hazards and require high quality wave forecast systems as warning tools to avoid losses due to the impact of rough seas. Hence, the operational wave forecast system running at the German Weather Service including a regional wave model for the North Sea and the Baltic Sea is checked extensively whether it provides reasonable wave forecasts, especially for periods of extraordinary high sea states during winter storms. For two selected extreme storm events that induced serious damage in the area of interest, comprehensive comparisons between wave measurements and wave model forecast data are accomplished. Spectral data as well as integrated parameters are considered, and the final outcome of the corresponding comparisons and statistical analysis is encouraging. Over and above the capability to provide good short-term forecast results, the regional wave model is able to predict extreme events as severe winter storms connected with extraordinary high waves already about 2 days in advance. Therefore, it represents an appropriate warning tool for offshore activities and coastal environment.     

Climatic and sea level controls on Late Quaternary eolian activity on the Agulhas Plain, South Africa

Located at the interface between the temperate westerly and sub-tropical climate systems, South Africa's winter rainfall zone (WRZ) is a key location in understanding Late Quaternary atmospheric circulation dynamics. Inactive eolian deposits in the WRZ, comprising pan-fringing lunette and coastal dunes, were investigated to establish their depositional ages and utility as paleoenvironmental indicators. The resulting optical luminescence chronology reveals episodic lunette accretion at 60,000-45,000 yr, 12,000-13,000 yr, 2800-2600 yr, 1200 yr, and <1000 yr, with coastal dune ages clustering at 4100-4700 yr.Episodes of lunette and coastal dune accretion on the Agulhas Plain are temporally distinct, reflecting differing fundamental controls on their activity. Comparisons to previously published data also reveal that the lunettes differ in age from more ancient coastal eolianites. Lunette deposition is asynchronous between locations, reflecting the topographic and hydrological setting of the individual pans. In near-coastal settings, with limited surface recharge, lunette accretion appears to be at least partially controlled by sea level induced changes in groundwater levels. Those pans with more significant surface recharge (particularly from fluvial systems) may produce less ambiguous paleoenvironmental records, with pan status more strongly reflecting regional hydrological conditions. Lunette orientation is indicative of strong westerly winds during both the Pleistocene and Holocene. Lunette accretion would have been promoted by reduced on-shore moisture transport during the summer months, enhancing rainfall seasonality. Such conditions would have been promoted by increased continentality as the Agulhas Bank was exposed during low sea level stands.     

波浪作用下砂质滩坝的沉积过程与沉积模式

受波浪及沿岸流影响,在滨岸地区形成的滩坝砂体是滨海（湖）带发育的主要砂体类型。目前国内外学者对滩坝沉积砂体的认识多来自于现代沉积和油气地质特征,对滩坝砂体的沉积机制和内部结构研究相对较弱。基于沉积水槽实验,采用规则波浪对沙质斜坡滨岸带进行模拟实验,观测波浪作用下滨岸带滩坝形成过程和波浪运动特征,记录波浪作用下滨岸带沙质滩坝在不同浪带平面时空演化规律。实验结果显示:波浪是改造湖岸原有沉积物的关键驱动力,波浪作用下沙质岸滩床面泥砂将发生输移运动,而滩坝是陆湖（海）泥沙在水动力驱动下搬运沉积的结果,水动力的强弱及水流结构引起泥沙在空间上的不均匀输运和分布,进而塑造不同的滩坝形态。与强波浪相关的高水位可以加速滩坝系统的形成并最终形成大规模的滩坝砂;相比之下,与较弱波浪相关的低水位只能略微改变初始沉积物形态。根据不同的沉积物特征可将实验中的滩坝系统分为三类:冲浪带和碎浪带滩坝系统近端部分的大规模厚层坝砂,破浪带和升浪带滩坝系统中部分布广泛的薄滩砂,以及位于滩坝系统中远端的弧形或平行排列的脊状、砂纹坝砂。建立了水槽实验模式下滩坝沉积模式,可用于指导油气勘探开发。     

Beach erosion and acceretion—An example from Kerala,Southwest Coast of India

The thickly populated coastal zone of Kerala, India is facing severe problems due to attack of high waves during the southwest monsoon. Systematic beach profiling at 5-km intervals was carried out along the 560-km stretch of the Kerala coast during the pre-and postmonsoon seasons in 1984. Beach volume changes were calculated at each profile station, and the erosional and accretional trends for the entire coastal tract were demarcated in a map. Total erosion along 55 stations is 1276 m³/m. The general erosional and acceretional trends were also found to coincide with diverging and converging littoral currents deduced from the wave refraction diagrams. Such study at periodic intervals will be highly useful for proper management of the coastal zone.     

Plumes and coastal currents near large river mouths

Theory and observations of river plumes are reviewed. The importance of the Kelvin number in characterizing anticipated plume behavior is stressed. In the absence of strong external forcing, a northern hemisphere plume will turn anticyclonically and attach to the coast, where it then merges into a coastal current. Observations and theory of such coastal currents are also reviewed, with emphasis on flows over shallow continental shelves. Major unresolved questions involve the processes controlling mixing of coastal current waters with ambient shelf waters and the dynamics of the plume in the region where it attaches to the coast.     

Recent climatic tendencies in the Barents Sea

Based on the results of multiannual oceanographic research at the Murmansk Marine Biological Institute in the “Kola Meridian” secular section, the recent tendencies of cyclic climate changes in the Barents Sea are discussed on the basis of the data on ice coverage and coastal meteorological conditions. It has been shown that a return from the extremely warm and warm state to the normal one was observed in the period of winter 2005/06–winter 2010/11. Further, this may be changed both to cooling and warming, which verifies the hypothesis about predominance of cyclic natural variability in the thermal and ice characteristics of the Arctic Region.     

Sedimentation on a wave-dominated, open-coast tidal flat, south-western Korea: summer tidal flat – winter shoreface

Sedimentation on the open-coast tidal flats of south-western Korea is controlled by seasonal variation in the intensity of onshore-directed winds and waves. As a result, an environmental oscillation takes place between tide-dominated conditions in summer and wave-dominated conditions in winter. In summer, thick muddy deposits, including sporadic storm deposits, accumulate in response to low wave energy, weak currents, and intense solar insolation that promotes consolidation of the mud at low tide. Bioturbation is minimal because of rapid sedimentation and soft substrate. During the autumn, the summer mud deposits experience erosion due to increasingly strong onshore winds and waves, until only small mud patches and mud pebbles remain. The concentration of ebb runoff between the mud patches produces small, ephemeral tidal creeks. In winter, storm waves occur frequently (ca 10 days a month) and dominate sedimentation in the intertidal zone, producing extensive wave-generated parallel lamination and short-wavelength (0·3–2 m) hummocky cross-stratification. The prevalence of strong onshore winds decreases in spring, allowing longer and more frequent intervals of calm weather, during which time muddy sediments are deposited by tidal processes. Over the long term, winter storm waves dominate sedimentation and the preserved deposits consist of amalgamated storm beds that resemble those generally associated with shorefaces. This raises the question of how many ancient ‘shorefaces’ are, in fact, open-coast tidal flats.     

碰撞造山带地壳上地幔热结构研究——以东南沿海地区石城—惠安剖面为例

由于碰撞造山带具有的地壳结构的复杂性,必须采用新的研究方法来分析其热结构。本文以东南沿海地区为例,根据地震波速与生热率之间的相关性,分析了碰撞造山带的地壳上地幔热结构特征。取得了地壳中的生热率分布状态。在此基础上,讨论了岩石圈热状态与构造发展历史的关系,并进一步揭示了东南沿海地区碰撞造山带的构造热演化历史。