Inspirations from IODP Expedition 361

International Ocean Discovery Program, or present IODP that has been evolved from the early Deep Sea Drilling Project (DSDP), Ocean Drilling Program (ODP) and Integrated Ocean Drilling Program (IODP) is one of the international ocean drilling and exploration programs originated from USA. IODP 361 cruse supported by JOIDES Resolution is characterized of high maneuverability, high tectonic integrity, high comprehensive disciplinary, information aggregation, international researcher gathering, global study targeting, quantity study production, isolated close working environments and huge investment, which is one of the most important international cooperation platforms of the geosciences, especially global changes. It is also one of the super powerful engines not only guiding but also pushing the study on global change via exploring the records of ocean evolution, and also the fountainhead to understand the processes and mechanism of the global changes. As one the main members of the IODP, China is not only participating the activities and scientific researches of IODP, but also needs to improve the capabilities to monitor the ocean and establish our own facilities, laboratories and research centers. These are not only very important for the global research and the future development, but also crucial for the preservation of the ocean environment. Leaning and mastering mature operation models from the JOIDES Resolution, using the experience of IODP management for reference may benefit our research work and yield twice the result with half the effort.     

琉球群岛附近海域中尺度涡的初步研究

采用1977年1月至2006年12月高分辨率全球大洋环流模型OFES输出结果对琉球群岛附近海域的中尺度涡进行了研究分析。结果表明:(1)尺度较大的涡旋的分布密集区主要有台湾以东海域、琉球海沟上层海域和四国以南海域。(2)琉球海流流经海域的反气旋涡旋占优势,有利于琉球海流的发展。(3)琉球海流受中尺度涡的影响十分显著,纬度越低,其受中尺度涡的影响越明显,而黑潮相对比较稳定,受中尺度涡的影响并不显著。(4)四国以南海域暖涡从黑潮脱落之后向西南移动,该涡旋的移动对琉球海流和黑潮产生特别显著的影响。文章的最后还讨论了中尺度涡与黑潮弯曲以及琉球海流可能存在的联系。     

A system-level modelling perspective of the KwaZulu-Natal Bight ecosystem,eastern South Africa

The KwaZulu-Natal Bight comprises the only sizeable shelf region on the eastern coast of South Africa, and is influenced by both the Agulhas Current on its seaward side and rivers and estuaries on its landward side. Established knowledge of the effect of the Agulhas Current includes the influence on nutrient concentrations in the bight of a semi-permanent upwelling cell at its northern border (St Lucia) and, to a much lesser extent, of a semi-permanent eddy feature at its southern extremity. Current modelling efforts, however, point to a very important role of land-derived nutrients, which supplement the productivity of food webs of the bight. This connectivity of the bight to its adjacent ecosystems has various implications. First, its productivity has traditionally been viewed via phytoplankton growth, whereas ecosystem modelling efforts point to a very high reliance on imported detritus (mainly land-derived) in order to sustain especially the rich benthic food web. The benthos in the bight dominates the food web, and is in marked contrast to the upwelling system of the west coast of South Africa (Atlantic Ocean) where water-column productivity dominates. Second, the importance of the connectivity of the Thukela Bank prawn-trawling ground to estuarine nursery areas, which has been modelled quantitatively, highlights the significance of this particular ecosystem connectivity for fisheries and also for the Thukela Bank food web. Heterogeneity across the bight is apparent for nutrient turnover rates (carbon, nitrogen, phosphorus), CNP content and stoichiometry, whereas nitrogen is a limiting nutrient across the entire bight. The food web near the Thukela River is richer in nutrient content and more active (higher turnover rates) compared to the northern and southern parts of the bight. This environmental heterogeneity was also apparent from the CNP content and stoichiometry of the various species and species groups in the bight. Requirements to take the hydrodynamic, biogeochemical and first ecosystem modelling efforts towards a meaningful predictive capability are discussed. The importance of adopting a system-level view of the bight and its connected systems for realistic exploration of global change scenarios is highlighted.     

Observations and mechanisms of upwelling in the northern KwaZulu-Natal Bight,South Africa

New in situ time-series data were acquired by two ADCP moorings placed on the shelf off Richards Bay on the east coast of South Africa at depths of 25 m and 582 m between October 2009 and August 2010. The 11-month inshore bottom-temperature record revealed five substantial upwelling events lasting 5–10 days each where temperatures decreased by about 7 °C to 17–18 °C. Satellite sea surface temperature data showed these events to coincide with cold-water plumes occupying the northern wedge of the KwaZulu-Natal (KZN) Bight. Numerous shorter duration (1–2 days) upwelling events with less vivid surface expressions were also observed throughout the entire record where bottom temperature dropped by 2–3 °C. The last four months of the record were characterised by a protracted cool period lacking a seasonal trend but punctuated with oscillations of warm and cooler bottom water. In contrast to earlier studies that suggested upwelling was topographically and dynamically driven by the juxtaposition of the Cape St Lucia offset and the Agulhas Current (a solitary mechanism), our analysis showed almost all major and minor cold-water intrusions to coincide with upwelling-favourable north-easterly winds that simultaneously force a south-westerly coastal current. Ekman veering in the bottom boundary layer of the Agulhas Current, and the concomitant movement of cold water up the slope, was found to coexist at times with coastal upwelling, but its absence did not impede inshore cold-water intrusions, calling into question its role as a primary driver of upwelling. Both major and minor upwelling events were observed to promote phytoplankton blooms in the northern KZN Bight which commonly extended to the Thukela River. Wind-driven upwelling was also observed in the inner bight between Richards Bay and Port Durnford, explaining the ribbon of coastal chlorophyll continuously observed on ocean colour images between Cape St Lucia and the Thukela River. Similarities in upwelling character and mechanisms are observed between the northern KZN Bight and the Florida Current shelf systems.     

多平台MC-SBAS长时序建模与形变提取方法

卫星时序差分雷达干涉已在区域地表形变监测中展现出极好的应用潜力,但因受卫星寿命及重访周期等因素的限制,单一卫星平台很难为长时间跨度(如5~10年)的时序形变计算与分析提供数据源。为扩展区域地表形变监测的时间跨度,本文提出了基于模型约束的短基线集(MC-SBAS)时序干涉方法,即使用非线性形变模型约束SBAS分析与处理,达到不同卫星平台数据融合和形变监测效率提高的目的。研究选取美国南加州地区为试验区域,使用2002—2005年获取的10幅ERS SAR影像和2004—2008年获取的20幅EnviSat ASAR影像,基于MC-SBAS提取该区域时序形变信息,时间跨度扩展为6.5年;以6个GPS站时序观测数据为参考,对MC-SBAS结果和常规SBAS结果进行了对比验证。分析表明,MC-SBAS、SBAS与GPS形变结果的均方根误差分别为8.7和11.7mm,MC-SBAS形变序列的连续性得到有效改善,而且形变监测精度得到提高。     

长江口邻近海域夏、冬季水文特征分析

长江冲淡水和台湾流是我国陆架海上两个重要的海洋现象。二者在长江口邻近海域交汇并相互制约，其分布和变化控制着该地区的温盐、环流结构，也影响着长江径流所携带的泥沙、营养盐等物质向外海的扩散和输运，以及舟山渔场的形成和变化。 长江每年以巨量径流注入东海，在长江口外形成一股很强的冲淡水，以低盐、高营养盐、高悬浮体含量为特征。毛汉礼等(1963)首先对长江冲淡水的扩散与混合特征作了系统的描述，并指出，冬季长江冲淡水沿岸南下，其范围仅限于贴岸的一狭带内；夏则在径流入海后不久转向东北，直指济州岛方向，到达对马海峡。众多学者通过资料分析、理论研究和数值模拟等探讨了长江冲淡水转向的原因，认为主要影响因素有长江径流量、地形效应、海面风应力、斜压效应、台湾曖流的顶托，以及黄海冷水团的诱导作用等(乐肯堂，1984；崔茂常，1984；顾玉荷，1985；王从敏，1986；赵保仁，1991；朱建荣，1998)，但至今对其转向机制的认识尚不一致。 台湾暖流水起源于台湾海峡和黑潮，是具有高盐、低悬浮体含量特征的大洋水体。翁学传等(1983，1984)研究认为，具有高温和次高盐特征的台湾暖流表层水同时起源于台湾海峡水和黑潮表层水，而具有高盐特征的深层水只来源于由台湾东北部入侵陆架的黑潮次表层水；翁学传(1983)还根据历史资料分析指出，夏季台湾暖流表层水的前锋大体沿着123°E可以伸展到31°N，深层水进一步延伸至31°N以北；且深层水在28°N和30°N断面并不终年存在，仅存于夏半年。王凡等(2001)的分析结果则显示，台湾暖流表层水和深层水在夏季可以在次表层北侵至30°N以北海域，而以深层水特点为主的台湾暖流水在冬季和晚秋甚至可在整个深度上伸展至30°N以北。总之，对台湾暖流水在不同季节、不同层次的北侵程度方面还存在着不同看法。 为深入研究长江口邻近海域的物质通量、扩散、传输和输运规律，中国科学院知识创新工程重要方向项目“中国主要河口及邻近陆架海域陆海相互作用”于2001年7-8月和2002年1月在长江口外28°~32°N、124°E以西海域组织了两次多学科综合考察。作者首先根据这两次考察获得的温盐深观测仪(CTD)观测到的温盐资料和声学多普勒流速剖面仪(ADP、ADCP)流速资料,分析该年夏、冬季长江口邻近海域的水文特征。考虑到调查海域有较强的年际变动，从年际变化的角度来更深刻地认识夏、冬季长江口邻近海域的水文特征，以及长江冲淡水与台湾暖流水的关系是很有必要的。为此，作者收集了1987~2001年其他项目3个夏季航次和2个冬季航次的温盐资料，以及1958~1982年标准断面历史资料，与最近2次观测资料相结合，综合分析研究了长江口邻近海域夏、冬季水文特征和变化情况，为今后更进一步开展此项研究提供了科学依据。     

闽台水产加工业的发展现状与合作前景

本文分析了闽台水产加工业的发展现状、面临的主要问题以及加入世贸组织后对产业的影响，预测未来两岸水产加工业的发展前景。认为如两地能采取优势互补、合作开发、谋求共同发展，将有利于推动闽台两地水产加工业，乃至渔业生产的持续、健康、稳定地发展。     

Probability distribution of random wave–current forces

Based on the second-order solutions obtained for the three-dimensional weakly nonlinear random waves propagating over a steady uniform current in finite water depth, the joint statistical distribution of the velocity and acceleration of the fluid particle in the current direction is derived using the characteristic function expansion method. From the joint distribution and the Morison equation, the theoretical distributions of drag forces, inertia forces and total random forces caused by waves propagating over a steady uniform current are determined. The distribution of inertia forces is Gaussian as that derived using the linear wave model, whereas the distributions of drag forces and total random forces deviate slightly from those derived utilizing the linear wave model. The distributions presented can be determined by the wave number spectrum of ocean waves, current speed and the second order wave–wave and wave–current interactions. As an illustrative example, for fully developed deep ocean waves, the parameters appeared in the distributions near still water level are calculated for various wind speeds and current speeds by using Donelan–Pierson–Banner spectrum and the effects of the current and the nonlinearity of ocean waves on the distribution are studied.     

Abundance and distribution of pelagic piscivorous fishes in the Columbia River plume during spring/early summer 1998-2003: Relationship to oceanographic conditions, forage fishes, and juvenile salmonids

From 1998 to 2003, we observed large fluctuations in the abundance and distribution of four pelagic predatory (piscivorous) fishes off northern Oregon and southern Washington, USA. Fluctuations in predatory fish species composition and abundance were strongly linked to the date of the spring transition and to ocean temperatures. Predatory fishes, forage fishes, and juvenile salmonids had distinct spatial distributions, with predators distributed primarily offshore and forage fish and salmonids onshore, but this varied depending on ocean conditions. We suggest that predatory and forage fish distributions respond to ocean temperatures, predator/prey interactions, and possibly turbidity. A shift in ocean conditions in 1999 decreased overall predator fish abundance in the Columbia River plume, particularly for Pacific hake. Marine survival of juvenile salmon started to increase in 1999, and forage fish densities increased in 2000, lagging by one year.     

Branching of the Tsushima Current by an Abrupt Increase of Bottom Depth

An analytical model of the branching of an inertial current partly afloat incident upon a step fall in bottom topography is considered to account for the branching of the Tsushima Current induced by an abrupt increase of the bottom depth near the northern end of the Korea-Tsushima Strait. The grounded portion of the incident current is constraint by bottom topography and eventually runs along the depth discontinuity over the shallow region. Due to the inertia of the incident current, however, the ungrounded portion crosses the depth discontinuity and forms a free inertial jet, giving rise to the branching. The deflection angle of this free inertial jet is determined through an integrated momentum balance. The branching is more restricted as the grounded portion of the incident current becomes relatively more important, in terms of the momentum transport, than the ungrounded portion. For typical values of the bottom depth, the transport of the Tsushima Current through the Korea-Tsushima Strait, and for acceptable values of other physical parameters, it appears that branching is possible. Hence, the abrupt increase of the bottom depth near the northern end of the Korea-Tsushima Strait, combined with the inertia of current, may indeed be an important factor in the branching of the Tsushima Current.