基于卫星高度计的全球大洋潮汐模式的准确度评估

依据152个深海验潮站与大洋岛屿地面验潮站观测得到的8个主要分潮(M2、S2、K1、O1、N2、K2、P1及Q1)调和常数,对现有7个全球大洋潮汐模式的准确度进行了检验,结果显示各模式在深海大洋区域均达到了比较高的准确度:M2分潮的潮高均方根偏差在1.0～1.3cm之间;8个分潮的和方根偏差在2.1～2.3cm之间,与早期的模式相比,准确度又有了进一步提高。还依据中国近海18个岛屿的调和常数对其中的5个大洋潮汐模式的准确度进行了检验,结果表明,M2分潮均方根偏差在4.4～10cm,明显高于大洋的均方根偏差。其中日本国家天文台的潮汐模式NAO99在中国近海的结果相对较准确。     

中国地壳运动观测网络基准站重力场变化的海潮负荷信号改正问题

利用最新的全球海潮模型（Csr3．0，Fes95．2，Tpxo2和Csr4．0）和原有的Schwiderski海潮模型以及中国近海海潮数据和标准地球模型负荷格林函数，采用直接褶积积分方法研究了中国地壳运动观测网络25个基准站重力固体潮观测中的海潮负荷效应问题，计算了 8个主要潮汐波的负荷振幅和相位，构制了北京和上海等10个台站重力负荷随时间变化函数。     

Effect of tidal fluctuations on transient dispersion of simulated contaminant concentrations in coastal aquifers

Variable-density groundwater models require extensive computational resources, particularly for simulations representing short-term hydrologic variability such as tidal fluctuations. Saltwater-intrusion models usually neglect tidal fluctuations and this may introduce errors in simulated concentrations. The effects of tides on simulated concentrations in a coastal aquifer were assessed. Three analyses are reported: in the first, simulations with and without tides were compared for three different dispersivity values. Tides do not significantly affect the transfer of a hypothetical contaminant into the ocean; however, the concentration difference between tidal and non-tidal simulations could be as much as 15%. In the second analysis, the dispersivity value for the model without tides was increased in a zone near the ocean boundary. By slightly increasing dispersivity in this zone, the maximum concentration difference between the simulations with and without tides was reduced to as low as 7%. In the last analysis, an apparent dispersivity value was calculated for each model cell using the simulated velocity variations from the model with tides. Use of apparent dispersivity values in models with a constant ocean boundary seems to provide a reasonable approach for approximating tidal effects in simulations where explicit representation of tidal fluctuations is not feasible.     

高精度GPS观测中的负荷效应

讨论了高精度GPS观测中的负荷效应问题。根据地表质量负荷理论的Green函数方法,计算了地球表面质量负荷（包括大气、非潮汐海洋和陆地水）对中国部分IGS台站垂直位移的影响。其中,大气负荷对各台站的影响比较一致,变化幅度约为20 mm,非潮汐海洋对沿海台站的负荷影响显著,其变化幅度达到10 mm,水负荷对各台站的影响差异较大,最大的变化幅度约20 mm;总的负荷效应达到厘米量级,与GPS观测结果的比较说明在高精度的GPS观测的时间序列中,存在明显的季节性变化,而该变化与表面负荷有着直接的关系。特别是对于房山和乌鲁木齐2个台站,GPS观测的垂直变化中的季节项基本上就是来自于地球表面的质量负荷;而昆明和拉萨这2个台站尽管位于板块运动活跃区域,垂直季节性变化也主要源于地表负荷。因此扣除这些负荷影响的GPS观测资料将更有利于研究地壳的运动特征。     

Temporal and vertical distribution of crab larvae in a tidal pass

We investigated the vertical and temporal distributions of portunid zoea andCallinectes megalopae in a tidal pass of the Texas coast. Zoea were equally abundant on ebb and flood tide but were more abundant during the day than at night. Megalopae were more abundant during flood tide and at night than during ebb tide or during the day. We examined the evidence for selective tidal stream transport in both life-history stages. Depth of the centers of mass of the larval distributions and the dispersions around those centers were unrelated to temperature, salinity, current velocity, and time of day. Scaling arguments suggest that the absence of pattern in the vertical distributions was not due to turbulent mixing. There was little evidence that either larval stage used these environmental characteristics as cues for changes in behaviour. However, the presence of megalopae in the water column primarily during flood tide does support the tidal transport hypothesis. Megalopae may have difficulty sensing and reacting to environmental cues in wellmixed estuaries with semidiurnal tides.     

海潮引起滨海含水层地下水位变化的初步研究

依据短序列和长序列的潮汐效应观测数据,分析了北海地区海潮引起滨海含水层地下水位变化的动态特征.结果表明,受海潮影响的滨海含水层地下水位与海潮有相似的波动特征,但变幅减小,受海潮的影响程度与观测点离海岸的距离有关,随着离海岸距离的增加地下水位的变幅和潮汐系数大致呈负指数减小.在南、北海岸距离海岸分别达3756m和2276m以远时地下水位不受海潮变化的影响.长序列的观测资料显示,海潮和岸边地下水位有15天的长周期和1天的短周期的波动.     

Effects of tides on a sloping shore: groundwater dynamics and propagation of the tidal wave

The influences of tides on a coastal environment with a sloping shore are investigated by means of field observations and groundwater flow modelling. The Belgian western coastal plain consists of a wide shore, dunes and polders where diurnal tides with large amplitude occur. The effects of tides on the groundwater flow are studied using the MOCDENS3D code. First, MOCDENS3D is validated to accurately simulate the propagation, attenuation and lag of a tidal wave in an aquifer. Then groundwater flow and influences of tides are modelled for a cross-section along the French–Belgian border. This gives an exhaustive insight into the spatial and temporal varying groundwater flow and propagation of the tidal wave in the aquifer. Simulation shows that there are two interfering flow cycles. The first is a shallow tidally fluctuating flow cycle on the shore due to the interaction of the gently sloping shore and the tidally oscillating sea level. The second is a deeper flow cycle from the dunes towards the sea. Further, it is indicated that the propagation and attenuation of the tidal wave follows a complex pattern with lateral as well as vertical components. The interaction between tides and shore topography also influences the salinity distribution.     

Estimation and removal of non-tectonic effects from gravity survey data

When gravity survey accuracies of a few microgals are sought, many correction factors must be accounted for, including meter calibration constants, water-table level fluctations, solid-earth tides, ocean tides and in some cases rapid atmospheric fluctuations. Calculation of most of these correction factors is relatively straightforward. However, the effects of ocean tide loading are not as easily estimated, partly due to the lack of knowledge of the ocean tides themselves. Amplitude and phase factors for the better-known ocean tide components O₁ and M₂ have been theoretically computed for a grid in southern California in order to correct gravity survey data at arbitrary locations for these ocean tidal-loading components. The gravity data from a three-month period were recorded on a tidal gravimeter at the station PAS and then hand-digitized in order to test the ocean tide estimation program. The O₁ and M₂ ocean tidal components were effectively reduced to less than 0.5 μGal. The remaining high-frequency tidal components appear to be K₁ and S₂. If the ocean tides are not taken into account, as much as 16–20 μGal of error can occur solely due to the effect of ocean loading on the gravitational tides when comparing two surveys near Pasadena. The effect increases towards the coastline and decreases inland. Examples of reduced data from the CIT gravity survey network, which has been observed on an approximately monthly basis since 1974, will be shown.     

Diurnal and semidiurnal tidal currents in the deep mid-Arabian Sea

Current meter records from two depths, approximately 1000 and 3000 m, at three moorings in the deep mid-Arabian Sea were used to study tidal components. Tidal ellipses for the semi-diurnal (M₂, S₂ and K₂) and the diurnal (K₁, and P₁) tidal constituents have been determined using the currents recorded at hourly intervals during May 1986–May 1987. The clockwise rotating M₂ tidal currents were the strongest. The maximum horizontal velocities due to M₂,₂ and K₁ tides were 2.2 cm/s, l.0cm/s and 0.89 cm/s respectively. The amplitudes of the other two constituents (P₁, and K₂) were much smaller. The barotropic M₂ ellipses have been estimated by averaging the M₂ tidal currents at the upper and lower levels. Although the amplitudes of computed ellipses are lower than those that have been predicted using numerical models of global tidal model, their orientations are the same.     

Apogean–perigean signals encoded in tidal flats at the fluvio–estuarine transition of Glacier Creek,Turnagain Arm,Alaska; implications for ancient tidal rhythmites

Turnagain Arm is a macrotidal fjord‐style estuary. Glacier Creek is a small, glacially fed stream which enters the estuary tangentially near Girdwood, Alaska. Trenches and daily sedimentation measurements were made in a mudflat along the fluvio–estuarine transition of Glacier Creek during several summers since 2003. Each year, the flats appear to erode during the winter and then accrete vertically in the spring and summer. In each of the years studied, tidal laminae in vertically thickening and thinning laminae bundles were deposited by twice daily tides in neap–spring tidal cycles. In 2004, bundles of thickening and thinning laminae couplets were noted in trenches cut into the flats. Five laminae bundles alternated between thicker and thinner bundles, corresponding to the perigean (high spring) and apogean (low spring) tides. Well‐preserved apogean–perigean cycles have rarely been documented in modern tidal flat sediments. At this location, vertical accretion of tidal rhythmites with well‐developed neap–spring cyclicity is possible because of the near‐complete removal of the flat from the previous year, which creates accommodation space for vertical accretion without significant reworking. Macrotidal conditions, no reworking by infaunal invertebrates, protection from the main tidal channel by a gravel bar and protection from storm waves and fluvial erosion by a recess in the sedge marsh that surrounds the flats all aid in preservation of rhythmites during aggradation. The position of the flats relative to tidal range allows for accumulation of complete spring cycles and incomplete neap cycles. In the summer of 2004, apogee and perigee were closely aligned with the new and full moons, resulting in successive strong perigee and apogee tides which probably aided in the accumulation of successive thick–thin spring cycles encoding the apogean and perigean tidal cycle. The apogean–perigean signal was not observed in subsequent years.     

无人机技术在潮滩地貌演变研究中的应用

随着海平面上升和人类活动加剧,潮滩正面临着严重威胁,掌握其形态变化规律是研究潮滩系统对外在条件响应的直接手段。以江苏斗龙港潮滩为研究对象,利用无人机倾斜摄影测量技术,结合运动恢复结构(Structure from Motion,SfM)算法,重建潮滩三维点云,生成数字高程模型和正射影像,分析潮滩滩面及潮沟系统年内变化规律。研究结果表明:潮滩高程测量精度优于9 cm,水平精度优于2 cm;高程年内变化较大,变幅高达±0.5 m;潮沟短历时变化剧烈,无明显季节性变化特征;潮沟发育过程中,宽深比范围为10~25。无人机技术不仅可以监测粉砂淤泥质潮滩滩面变化趋势,还可以观测到卫星难以捕获的中小型潮沟短历时发育过程,可为监测河口海岸短周期动力地貌过程提供有力的技术支持。     

Circulation and mixing due to tidal forcing in the Bertioga Channel, São Paulo, Brazil

Bertioga Channel is a partially mixed (type 2) tidal estuary on the coastal plain of São Paulo, Brazil. Hourly current and salinity measurements during neap and spring tides in July 1991 yielded information about the physical structure of the system. Peak along-channel velocities varied from 40 cm s^?1 to 60 cm s^?1 during flood tides and from 70 cm s^?1 to 100 cm s^?1 during ebb tides. Net vertical velocity profiles indicate that the net current reverses directions at a depth of 2.5–3.0 m in the halocline. Due to appreciable fortnightly tidal modulation, the estuary alternates from being highly stratified (type 2b) during neap tides, with advection and diffusion contributing equally to the net upstream salt flux, to being moderately stratified (type 2a) during spring tides, when 90% of the net upstream salt transport is the result of effective tidal diffusion. Decomposition of the salt flux indicates that the relative contribution to the upstream salt transport by gravitational circulation shear is greater than the oscillatory tidal flux by a factor of 2.6 during neap tides. The oscillatory tidal flux is generated by the correlation of the tidal components of the u-velocity and salinity and is responsible for approximately the same amount of upstream salt transport, during neap and spring tides. However, during spring tides, this oscillatory term is greater than the other salt flux terms by a factor of 1.4. The total salt transport, through a unit width of the section perpendicular to the flow, was within 2% of the sum of the seven major decomposed, advective and dispersive terms. On the assumption that the Bertioga Channel is laterally homogeneous, the results also indicate that the estuary is not in steady state with respect to salt flux.     

连续18年“暖冬”终结的原因

季林的气候潮汐循环说和郭增建的海震调温说,阐明了冷气候、强潮汐和强震相互对应的物理机制,对2000年地球进入拉马德雷冷位相后的气候预测有重大科学意义。中国连续18年暖冬的终结是2000年地球进入拉马德雷冷位相和2004年12月26日印尼发生了地震海啸的合理结果。     

A depositional model for a wave‐dominated open‐coast tidal flat,based on analyses of the Cambrian–Ordovician Lagarto and Palmares formations,north‐eastern Brazil

Open‐coast tidal flats are hybrid depositional systems resulting from the interaction of waves and tides. Modern examples have been recognized, but few cases have been described in ancient rock successions. An example of an ancient open‐coast tidal flat, the depositional architecture of the Lagarto and Palmares formations (Cambrian–Ordovician of the Sergipano Belt, north‐eastern Brazil) is presented here. Detailed field analyses of outcrops allowed the development of a conceptual architectural model for a coastal depositional environment that is substantially different from classical wave‐dominated or tide‐dominated coastal models. This architectural model is dominated by storm wave, low orbital velocity wave and tidal current beds, which vary in their characteristics and distribution. In a landward direction, the storm deposits decrease in abundance, dimension (thickness and spacing) and grain size, and vary from accretionary through scour and drape to anisotropic hummocky cross‐stratification beds. Low orbital wave deposits are more common in the medium and upper portion of the tidal flat. Tidal deposits, which are characterized by mudstone interbedded with sandstone strata, are dominant in the landward portion of the tidal flat. Hummocky cross‐stratification beds in the rock record are believed, in general, to represent storm deposits in palaeoenvironments below the fair‐weather wave base. However, in this model of an open‐coast tidal flat, hummocky cross‐stratification beds were found in very shallow waters above the fair‐weather wave base. Indeed, this depositional environment was characterized by: (i) fair‐weather waves and tides that lacked sufficient energy to rework the storm deposits; (ii) an absence of biological communities that could disrupt the storm deposits; and (iii) high aggradation rates linked to an active foreland basin, which contributed definitively to the rapid burial and preservation of these hummocky cross‐stratification deposits.     

利用GPS提取南极Amery冰架海潮信号

潮汐运动是冰架短期垂直运动的来源, 对冰架影响十分显著. 选取2003/2004年度南极夏季期间中国在Amery冰架上连续5 d的GPS数据, 利用GAMIT/GLOBK进行数据处理, 获取了由海潮引起的冰架垂向运动时间序列;垂直方向精度优于0.18 m, 并且和中国南极中山验潮站的潮汐变化曲线进行了对比, 获得了一致的结论. 利用GPS测量海潮可为精化南极地区的海潮模型提供可靠的现场数据, 对南极冰盖物质平衡研究及冰海交互动力学模型研究有着重要的作用.     

Multi-technique monitoring of ocean tide loading in northern France

We have organised afield study of ocean tide loading in the northwestern part of France, where tidal amplitudes are known to be among the highest in the world. GPS and gravimetric techniques have already proved their capability to measure such weak and high-frequency signals. In this study, these classical observations are complemented with less usual techniques, such as tiltmeter and Satellite Laser Ranging (SLR) measurements. We present here the preliminary results for a common period of observations spanning from 12–19 May 2004. Additional measurements from the French Transportable Laser Ranging Station (FTLRS) were available during September and October 2004. Observation residuals are computed as the difference between the observed and the predicted time signals. We obtain small RMS residuals for GPS measurements (2.5/3.1/4.5 mm for the eastward, northward and upward components), for absolute and relative gravimetry (9 nm/s² and 13 nm/s²) and for tiltmeters (0.05 μrad for EW component). We also fit the amplitude of the main M2 tidal constituent to FTLRS observations and we find a value of 3.731 cm, which is comparable to the theoretical value.     

渤海湾全新世贝壳堤:时空分布和海面变化标志点

以他人和本研究小组对渤海湾西岸贝壳堤平原的全新世贝壳堤研究为基础,重新考订了贝壳堤的底板形态,发现底板多向海倾斜,经多处水准测量获得的前、后缘底板平均高差为1m。堤底板的前、后缘位于形成时的平均大潮潮差的垂直范围内。底板的高差,或依实测值、或依高差平均值补足至1m,由此确定底板的高度误差范围。当对应当时的平均大潮差时,再进一步补足至±1.5m的垂直范围,堤底板遂成为海面变化标志点。经过对96个14C数据的考订,补正了贝壳堤的时空分布,重新肯定了Ⅱ堤的2道支堤和隋唐堤的存在,提出Ⅰ堤二分的可能,揭示了风暴潮再搬运造成的Ⅰ堤中部老于下部—底部的年龄倒置原因。该研究是重建贝壳堤平原全新世相对海面变化曲线、探讨贝壳堤与气候变化关系的基础。     

Tidal influence on high frequency harbor oscillations in a narrow entrance bay

High frequency sea level oscillations at Wells Harbor (Maine, Northeastern US), with periods in the range of several tens of minutes, display a tidally modulated response. During low tides, these sea level oscillations reach amplitudes of 10–20 cm, while during high tides they are significantly smaller. Wells Harbor is located in a low lying area with a tidal range of about 2 m and is connected to the open ocean through a narrow channel. Thus, the extent and depth of the bay significantly vary over a tidal cycle. This changing geometry determines both the resonant periods and the amplification factor of the bay. Numerical results confirm the link between observed variability and these specific topographic features. Results imply that when exceptionally energetic long waves reach the Wells Harbor entrance (as in the case of a tsunami or meteotsunami) the expected response will be significantly stronger during low tide than during high tide. Although mean sea level would be lower in the former case, the currents inside the bay would be stronger and potentially more dangerous. This tidally modulated response could be extrapolated to other sites with similar topographic characteristics.     

River tributaries as sediment sinks: Processes operating where the Tapajós and Xingu rivers meet the Amazon tidal river

The Amazon River is the largest fluvial source of fresh water and sediment to the global ocean and has the longest tidally influenced reach in the world. Two major rivers, the Tapajós and Xingu, enter the Amazon along its tidal reach. However, unlike most fluvial confluences, these are not one‐way conduits through which water and sediment flow downstream towards the sea. The drowned‐river valleys (rias) at the confluences of the Tapajós and Xingu with the Amazon River experience water‐level fluctuations associated not only with the seasonal rise and fall of the river network, but also with semidiurnal tides that propagate as far as 800 km up the Amazon River. Superimposed seasonal and tidal forcing, distinct sediment and temperature signatures of Amazon and tributary waters, and antecedent geomorphology combine to create mainstem–tributary confluences that act as sediment traps rather than sources of sediment. Hydrodynamic measurements are combined with data from sediment cores to determine the distribution of tributary‐derived and Amazon‐derived sediment within the ria basins, characterize the sediment‐transport mechanisms within the confluence areas and estimate rates of sediment accumulation within both rias. The Tapajós and Xingu ria basins trap the majority of the sediment carried by the tributaries themselves in addition to ca 20 Mt year^?1 of sediment sourced from the Amazon River. These findings have implications for the interpretation of stratigraphy associated with incised‐valley systems, such as those that dominated the transfer of sediment to the oceans during lowstands in sea level.     

A description of the tides and effect of Qeshm canal on that in the Persian Gulf using two-dimensional numerical model

The main semidiurnal (M2 and S2) and diurnal (K1 and O1) tidal constituents are simulated in the Persian Gulf (PG). The topography is discretized on a spherical grid with a resolution of 30 s in both latitude and longitude. It includes coastal areas prone to flooding. The model permits flooding of drying banks up to 5 m above mean sea level. At the open boundary, it is forced by 13 harmonic constituents extracted from a global tidal model. The model results are in good agreement with tide gauge observations. Co-tidal charts and flow extremes are presented for each tidal constituent. The co-tidal charts show two amphidromic points for semidiurnal and one for diurnal tidal constituents. Maximum amplitudes of sea level are obtained for the north-western part of the PG, where coastal flooding prevails in wide areas. Strong tidal currents occur in different parts of the PG for different types of constituents. Maximum velocities are found in shallow regions. Particularly, high amplitudes of elevations and high speed currents are founded in the canal between Qeshm Island and the mainland. Rectification of tides around Qeshm Island affects the propagation of tides in the PG as far as the coast of Saudi Arabia and the northern part of the PG.