渤海夏季底层环流的观测与模拟

通过分析用人工水母在渤海夏季进行的首次底层环流的 L agrange观测 ,发现在渤海底层 Lagrange余流只有几 cm/s,在海峡处基本是北进南出的情况 ,在辽东湾有 1个逆时针的环流 ,在渤海湾有 1个顺时针的环流。但是进一步分析发现 ,底层人工水母的运移 (代表了物质输运 )并不完全反映环流的方向 ,在有些站位甚至出现相反的趋势。通过数值模拟知道瞬时的扩散及沉降等过程是产生这种结果的原因 ,而根源在于环流场的不均匀性。     

山东荣成湾月湖口门落潮干道的推移质输运

改进了Gao等 ( 1 994)方法 ,并用以计算潮汐汊道口门落潮干道的垂线平均流速。利用月湖潮汐汊道系统冬、夏季各一个月的潮位资料 ,计算落潮干道的潮流流速和推移质输运率。结果表明 ,流速的计算值和实测值呈良好的相关性 ,落潮干道内落潮流的输沙能力高于涨潮流输沙能力     

渤海盐度年代际变异对环流结构的影响

收集并利用1950年代~1990年代后共5个年代的渤海盐度统计资料,诊断计算了不同时期的渤海密度流分布及其变化。通过对比分析,揭示了冬、夏两季渤海盐度的年代际变异特征及其对环流结构的影响。结果显示,自1980年代以来,渤海的盐度格局发生了显著的变化,盐度的水平梯度减小,渤海内部盐度由明显低于海峡区向普遍高于海峡区转变。渤海密度流在冬季较弱,对总环流的贡献较小,而在夏季较强,并在总环流中占优。夏季,渤海密度流随盐度变异有所改变,在1990年代后环流系统在海区中部、渤海湾以及莱州湾呈现出局部的差异,原有流动明显减弱。夏季渤海重要断面的密度流流量和盐通量值整体上呈减小趋势,渤海与外海间的平均水及盐交换量由1950年代的7.85×104 m3/s、2.49×106kg/s降至1990年代后的7.09×104 m3/s、2.27×106 kg/s。     

北黄海北部海域潮余流的模拟研究

基于二维水动力模型,在仅考虑潮流作用条件下,通过计算欧拉余流和拉格朗日余流并结合粒子追踪方法研究了辽宁大连—朝鲜龙渊郡连线北侧的北黄海北部海域的潮余流结构和粒子运移的趋势。结果表明:欧拉余流和拉格朗日余流流速整体较小,呈现由南向北的流向,但在獐子岛及长山群岛的附近岛屿和朝鲜半岛沿岸的海域欧拉余流和拉格朗日余流流速较大。对比粒子追踪计算的结果与欧拉余流和拉格朗日余流的结果表明,流向与粒子运移路径基本一致。该海湾的余流及粒子运动规律特点对辽东半岛东岸及朝鲜半岛西侧海域的排污及污染控制有重要的借鉴意义。     

江苏海岸中部近岸冬季潮汐和潮流特征

南黄海西侧的江苏海岸近岸区域,素以地形复杂、潮流强劲、悬沙输运剧烈著称,但是较长期的同步潮位和潮流观测数据仍然缺乏,尤其是在近岸(20 km)浅水(20 m)区域。2014年1月在大丰港附近开展了连续潮位和潮流观测,获得的数据揭示了一系列特征。此地潮汐潮流为正规半日潮,浅水分潮显著。平均潮差为3.05 m,最显著的两个分潮为M2和S2分潮,振幅分别为1.45 m和0.52 m。潮流最显著的半日分潮M2分潮和最显著的浅水分潮M4分潮在沿岸方向上振幅分别为0.84m/s和0.12m/s,在跨岸方向上振幅分别为0.24 m/s和0.01 m/s,沿岸方向占绝对优势。潮波的沿岸传播介于前进波和驻波之间,驻波的特征稍强。M2分潮潮流椭圆最大流(长轴)方向为南偏东7.4°。存在冬季沿岸向北的余流,垂向平均值的大小为2.2 cm/s。以上潮汐潮流特征为该区域海洋物质输运研究提供了基础资料。     

Effect of atmospheric CO2 and solar activity on wind regime and water column stability in the major global upwelling areas

It is not clear whether global warming will favour or reduce global ocean phytoplankton productivity in coastal areas. Moreover, the relative contributions made by natural and/or anthropogenic factors to possible changes in phytoplankton productivity are not clear. As the relationship between primary production and alongshore wind forcing is well established for the Eastern Boundary Current (EBC) ecosystems, our aim is to determine whether the changes experienced over the last five decades (1958–2007) in atmospheric CO₂ and solar activity have been able to affect the wind regime and water column stability in the most biologically productive upwelling areas of California, Canary, Humboldt and Benguela. We approached the work by statistically studying the effect of solar activity and atmospheric CO₂ on surface alongshore wind stress and on water column stability. There was an increasing trend in wind stress and water column stability in all the upwelling areas over the period studied (with the single exception of stability in the California EBC system). The analysis of detrended series evidenced significant relationships between atmospheric CO₂ concentration and wind stress and water column stability in the coastal upwelling areas investigated. In addition, wind stress and stability data were found to be consistent, with negative linear relationships between wind stress and CO₂ in most of the sites in the Benguela, Canary and Humboldt regions associated, as expected, to positive relationships when water column stability is used as regressand. The results of the present study suggest that greenhouse gas forcing, independent of its well known general increasing trend, was able to decrease wind stress intensity and increase water column stability for the period 1958 to present in most of the sites of the four Eastern Boundary Ecosystems studied, with the one exception of the California region. Conversely, the impact of solar activity appeared to be quite low compared to the greenhouse gas forcing.     

Impact of hydrographic parameters and seasonal variation in sediment fluxes on coral status at Chumbe and Bawe reefs,Zanzibar, Tanzania

Coral reefs which are an important resource to coastal communities and nation at large are adversely affected by rate of sediment flux to the reefs. However, there is little information on seasonal trend in sediment flux and its impact at the reefs off Zanzibar. Two years’ monthly data on sedimentation at Chumbe and Bawe reefs were used to assess seasonal variability in sediment flux and its implication on the coral status. Sediment flux to the Bawe reefs for the duration of the study ranged from 0.2 to 41.5 mg cm⁻² d⁻¹, while it ranged from 0.8 to 65.8 mg cm⁻² d⁻¹ at the Chumbe reefs. Sediment fluxes at Bawe reefs were highest between November and March, while they were highest between April and September at Chumbe reefs. Generally, sediment fluxes at Bawe reefs were low compared to those at Chumbe. The total sediment input to the reefs ranged from 4615 to 123,403 kg d⁻¹ for Bawe reefs and 2750 to 79,636 kg d⁻¹ for Chumbe reefs. High sediment fluxes at Bawe reefs between November and March; and the Chumbe reefs between April and September can be attributed to water currents and wind pattern in the east African region which are under the influence of the monsoons. The observed trend suggests that the period for coral transplant as a management option for the two sites should be different. Coral transplant can be undertaken in such a way that stress of the corals due to sedimentation can be felt after they have overcome stress from transplant process and temperature. The results from this study contribute to the much needed information for coral transplant, restoration, and management.     

The mid-depth circulation of the northwestern tropical Atlantic observed by floats

A comprehensive analysis of velocity data from subsurface floats in the northwestern tropical Atlantic at two depth layers is presented: one representing the Antarctic Intermediate Water (AAIW, pressure range 600–1050 dbar), the other the upper North Atlantic Deep Water (uNADW, pressure range 1200–2050 dbar). New data from three independent research programs are combined with previously available data to achieve blanket coverage in space for the AAIW layer, while coverage in the uNADW remains more intermittent. Results from the AAIW mainly confirm previous studies on the mean flow, namely the equatorial zonal and the boundary currents, but clarify details on pathways, mostly by virtue of the spatial data coverage that sets float observations apart from e.g. shipborne or mooring observations. Mean transports in each of five zonal equatorial current bands is found to be between 2.7 and 4.5 Sv. Pathways carrying AAIW northward beyond the North Brazil Undercurrent are clearly visible in the mean velocity field, in particular a northward transport of 3.7 Sv across 16°N between the Antilles islands and the Mid-Atlantic Ridge. New maps of Lagrangian eddy kinetic energy and integral time scales are presented to quantify mesoscale activity. For the uNADW, mean flow and mesoscale properties are discussed as data availability allows. Trajectories in the uNADW east of the Lesser Antilles reveal interactions between the Deep Western Boundary Current (DWBC) and the basin interior, which can explain recent hydrographic observations of changes in composition of DWBC water along its southward flow.     

船载ADCP资料的潮流分离方法在厦门港断面重复走航中的应用

本文运用Candela等提出的潮流分离方法,选用高斯函数作为基函数,采用Matlab程序,首次对厦门港嵩鼓水道的船载ADCP断面重复走航资料进行潮流分离计算．通过对14个计算点的Candela方法计算结果与引进差比关系准调和分析方法计算结果的分析比较可见：（1）两种方法计算所得余流在大、小潮的相关系数分别为0．9882和0．8521,余流相对误差在大、小潮分别为0．065和0．150,而所得余流方向在大、小潮的相关系数分别为0．9982和0．9865,余流方向相对误差在大、小潮分别为0．023和0．027．两种方法计算的余流及其方向的相关性很高（在样本数为14,置信度为α=1％时,相关系数大于0．6610,结果是可信的）,而平均相对误差也很小．（2）对14个计算点的M2、S2、K1、O1、M4和MS4等6个分潮的计算结果（共有84个样本数据）进行分析比较,两种方法计算所得6个分潮的长轴、长轴方向和短轴在大潮的相关系数分别为0．9838、0．8960和0．2335,而在小潮的相关系数分别为0．9656、0．7555和0．2209．这两种方法计算所得6个分潮的长轴、长轴方向和短轴在大潮的平均相对误差分别为0．375、0．071和0．753,而在小潮的平均相对误差分别为0．287、0．254和0．845．两种方法计算的分潮长轴及其方向的相关性很高（在样本数为84,置信度为α=1％时,相关系数大于0．283,结果是可信的）．相应的分潮长轴的相关性略低,但是在样本数为84,置信度为α=5％时,相关系数均大于0．217．可认为在置信度为α=5％时,计算结果是可信的,而平均相对误差则略显较大．综上所述,我们认为采用Candela等的方法对船载ADCP断面重复走航资料进行潮流分离计算是可行的．