Observational and laboratory insights into salt finger convection

Improving observational capabilities in the ocean are revealing a substantial body of evidence that the double-diffusive instability known as salt fingers is widely present and plays a significant role in oceanic mixing. This evidence includes unique fine- and microstructure features in particular regions and distinct patterns in the temperature and salinity variations over large areas. Laboratory experiments have also advanced our understanding of salt fingers. The insights gleaned from both laboratory and ocean are reviewed and related to large-scale ocean structure and climate modeling.     

加拿大海盆深层双扩散对流的观测分析

The Canada Basin(CB) is the largest sub-basin in the Arctic, with the deepest abyssal plain of 3 850 m. The double-diffusive process is the possible passage through which the geothermal energy affects the above isolated deep waters. With the temperature-salinity-pressure observations in 2003, 500-m-thick transition layers and lower1 000-m-thick bottom homogenous layers were found below 2 400 m in the central deep CB. Staircases with downward-increasing temperature and salinity are prominent in the transition layers, suggesting the doublediffusive convection in deep CB. The interface of the stairs is about 10 m thick with 0.001–0.002°C temperature difference, while the thicknesses of the homogenous layers in the steps decrease upward from about 60 to 20 m.The density ratio in the deep central CB is generally smaller than 2, indicating stronger double-diffusive convection than that in the upper ocean of 200–400 m. The heat flux through the deepest staircases in the deep CB varies between 0.014 and 0.031 W/m2, which is one-two orders smaller than the upper double-diffusive heat flux,but comparable to the estimates of geothermal heat flux.     

Double-diffusive convection with a nonlinear equation of state: Part II. Laboratory experiments and their interpretation

The term cabbeling describes the convection that can occur when a mixture of two oceanic water masses is more dense than both of the parent water masses. When the two water masses are situated one above the other, the temperature and salinity distributions are in the correct senses for double-diffusive convection to occur and it is found that the prime effects of the nonlinearity of the equation of state are firstly to drive a greater level of double-diffusive convective activity in the lower layer than in the upper layer, and secondly, to make the lower edge of the interfacial region less gravitationally stable. Both of these effects cause the interface to migrate upwards as the lower layer grows at the expense of the upper layer. We introduce a nondimensional parameter $\text{δ}$ (called the cabbeling parameter) which represents the importance of the nonlinearity of the equation of state:—$\text{δ}$ is zero when the equation of state is linear and when cabbeling is normally thought to be possible, $\text{δ}$ is greater than unity. Experiments set up in both the finger and diffuse sense show how the nondimensional measure of the upward interface migration (called the “entrainment” parameter $\text{E}$) varies with the density anomaly ration R_? for various values of $\text{δ}$ between zero and 2.0 and that no abrupt change in this behaviour occurs at $\text{δ}\text{= 1.0}$. It is impossible to explain these observation by neglecting double-diffusive convection and considering only the convection driven by the conventional cabbeling instability. The successful interpretation of the laboratory results relies on considering the effects of a non-linear equation of state on the double-diffusive convection process.     

台风-涡旋相互作用研究进展

台风轨迹和强度的预报一直备受关注,也是大气和海洋学家最为关注的科学问题之一。近些年,随着观测技术和计算机模拟的快速发展,发现海洋中尺度过程和台风有紧密的联系。本文针对该主题进行简要回顾和总结, 主要侧重2个方面：①台风如何影响海洋中尺度过程？强调了地转过程的重要性和高度计观测对台风影响涡旋的低估;②海洋中尺度过程如何影响台风？强调了冷暖涡的不同以及位置不同对台风强度的影响。在此基础上,探讨台风-涡旋相互作用研究中尚未解决的问题：涡旋对台风的三维响应、多涡对台风的综合效应、时间尺度匹配和海气通量等。     

Ocean governance in the South Pacific region: Progress and plans for action

The Pacific Island Regional Ocean Policy (PIROP), which was released in 2002, provided the framework for ocean governance in the Pacific region. Since then there have been a myriad of policy documents and institutional arrangements that have been developed to address ocean governance issues, however, little progress has occurred with regard to the actual implementation of PIROP. This paper examines the region's progress in establishing integrated oceans management, and how this fits with the use of marine spatial planning and area based management tools, such as marine protected areas. It argues that policy making in this region encounters the usual difficulties with integrated policy approaches experienced elsewhere but that these difficulties are further accentuated when applied to developing nations that are highly dependent on external support. It suggests a way forward for the future with development of action plans, implementation and the practical application of those plans including a regional contextualisation/analysis of progress against regional objectives.     

Modeling the Global Thermohaline Circulation

This paper reviews recent progress and problems in modeling the thermohaline circulation of the world ocean by use of z-coordinate ocean general circulation models. Discussions focus on four issues: sea surface forcing, mixing in the deep ocean interior, eddy-induced tracer transport, and bottom boundary layer processes. Although some widely used techniques and parameterizations deal with these issues, some aspects are still overlooked and more sophistication is certainly required. This revised version was published online in August 2006 with corrections to the Cover Date.     

海洋三维温盐流数值模拟研究的有关进展和问题

就海洋三维温盐流数值模拟使用的海洋模式和数据同化方法、在中尺度数值预报和再分析中的应用,以及所需支撑条件三方面,简述了国内外研究有关进展和问题。表述了开展大范围分辨中尺度乃至次中尺度涡的高分辨率海洋三维温盐流数值模拟正在研究的有关问题,扼要说明提供相匹配的高性能计算机模拟平台的必要性。初步探讨制约该研究快速发展的有关问题。     

Exploring stakeholder perceptions of marine management in Bermuda

Given competing objectives vying for space in the marine environment, the island of Bermuda may be an ideal candidate for comprehensive marine spatial planning (MSP). However, faced with other pressing issues, ocean management reform has not yet received significant traction from the government, a pattern seen in many locations. Spatial planning processes often struggle during the proposal, planning, or implementation phases due to stakeholder opposition and/or government wariness to change. Conflict among stakeholders about management reform has also proven to be a deterrent to MSP application in many locations. With these obstacles in mind, a detailed stakeholder survey was conducted in Bermuda to determine awareness, attitudes and perceptions regarding ocean health, threats to ocean environments, the effectiveness of current ocean management, and possible future changes to management. How perceptions vary for different types of stakeholders and how attitudes about specific concerns relate to attitudes about management changes were examined. Overall, the results indicate a high degree of support for spatial planning and ocean zoning and a high level of concordance even among stakeholder groups that are typically assumed to have conflicting agendas. However, attitudes were not entirely homogeneous, particularly when delving into details about specific management changes. For example, commercial fishers were generally less in favor, relative to other stakeholder groups, of increasing regulations on ocean uses with the notable exception of regulations for recreational fishing. Given the results of this survey, public support is likely to be high for government action focused on ocean management reform in Bermuda.     

Oceanic double-infusion: introduction

Double-diffusion, the mixing of fluids with two constituents of different molecular diffusivities, was originally discovered in the mid-1800s, forgotten, then rediscovered as an ‘oceanographic curiosity’ a century later. Many oceanographers suspect that double-diffusion has major effects on oceanic water masses and circulation, but direct measurement of the effects has proven difficult. In 1996, a Working Group was formed under the auspices of the Scientific Committee on Ocean Research (SCOR WG108), with the goal to identify progress and barriers to quantifying oceanic double-diffusive fluxes, and make recommendations for further progress. This document gives a brief history of double-diffusion, a review of evidence of its potential effects in the ocean, and gives an overview of the review articles contained in this volume, written by the Working Group members with the above aim in mind.     

National ocean policy—new opportunities for Malaysian ocean development

Being a littoral state, Malaysian maritime sectors provide the basis for the growth and development of marine-related activities. As the country enters the new millennium along with the ‘2020 Vision’ which serves as the basic template against which the economic performance of these sectors should be judged, it poses a new challenge for Malaysia in developing these sectors. This paper attempts to address three basic issues: Firstly, is there any national ocean policy in place? Secondly, are the maritime sectors adequately organized to play an important role in achieving the objectives? Thirdly, what are the opportunities available in developing the ocean?It can be seen that existing policies to develop comprehensive ocean governance have not received the full attention they deserve. Organizational structures governing the ocean for implementing national policies are well in place but in a fragmented and uncoordinated fashion. As a result, sectoral and intersectoral management problems were created such as multiple-use conflicts, overlapping of jurisdiction and duplication of efforts. Environmental problems have also not been properly addressed. A few sectors have been identified as offering opportunities to further develop the Malaysian maritime areas. Among these are marine education and human resources development, marine tourism and the seafood industry.     

A review of the feasibility, costs, and benefits of platform-based open ocean aquaculture in the Gulf of Mexico

Platform-based open ocean aquaculture (or mariculture) is a fledgling industry with a unique set of risks and uncertainties. In the past two decades, several commercial and experimental platform-based mariculture projects have been launched in the United States, however, all these projects failed or were abandoned because of operational problems or legal issues. The oil and gas infrastructure in the Gulf of Mexico is well suited for mariculture systems as these platforms are large, sturdy and long lasting, and designed to operate in the offshore environment. The purpose of this paper is to discuss the costs and benefits of a open ocean aquaculture industry in the Gulf of Mexico with particular focus on platform-based aquaculture. The opportunities for the use of idle oil and gas structures for open ocean aquaculture are limited, but the reuse of previously removed structures may have more promise.     

Conservation values in marine ecosystem-based management

Proactive ecosystem-based management represents a turning point in ocean management, because it formally recognizes the need to balance the potentially competing uses of the ocean, including aquaculture, energy production, conservation, fishing, and recreation. A significant challenge in implementing this balancing act arises from explicitly incorporating conservation in a decision-making framework that embraces assessments of trade-offs between benefits from conservation and conventional commercial uses of marine resources. An economic efficiency-based framework for evaluating trade-offs is utilized, and, for illustration, applied to assess the relative benefits and costs of conservation actions for the endangered western stock of the Steller Sea Lion (wSSL) in Alaska, USA. The example highlights many scientific and political challenges of using empirical estimates of the benefits and costs to evaluate conservation actions in the decision process, particularly given the public's large conservation values for the wSSL. The example also highlights the need to engage in stakeholder discussions on how to incorporate conservation into ecosystem-based management, and more specifically, coastal and marine spatial planning (CMSP). Without explicit consideration of these issues, it is unclear whether CMSP will better conserve and utilize ocean resources than the status quo.     

加拿大海盆东南部锚定观测双扩散阶梯的时间演化研究

加拿大海盆上层,分布着高温高盐的大西洋水和相对低温低盐的盐跃层下部水,两水团之间形成一系列的双扩散阶梯。通过分析2005年8月-2011年8月期间的锚定潜标数据,对双扩散阶梯和这两种水团之间的相互作用进行研究。基于固定盐度范围的方法,在盐度廓线中识别阶梯结构,在盐度34.45~34.83范围内,获取18个阶梯结构,并研究阶梯的参数。发现双扩散阶梯的位温主要受与其接近的水团的影响,同时也受其相邻的阶梯生成或消亡的影响,大西洋水对其上方的双扩散阶梯和盐跃层下部水起到加热作用;而盐跃层下部水的深度变化主导着大西洋水和双扩散阶梯的深度变化。两个相邻的阶梯具有一致的位温和深度变化趋势。通过经验公式,估计大西洋水通过双扩散阶梯向上传输的热通量为0.05~0.6 W/m2,且由下至上呈现逐渐增大的趋势。最后,估算由双扩散造成的垂向涡扩散系数为3×10-6~3.3×10-5 m2/s,且由下至上呈现逐渐减小的趋势。     

The importance of estimating the contribution of the oceans to national economies

The oceans are in trouble. Poorly understood and unprecedented environmental and economic changes are underway in our world's oceans that will significantly affect life in the sea as well as on land. Only in the last thirty years has the contribution of the ocean sector to the economy been measured. An examination of these studies has exposed definitional, conceptual and methodological differences in measuring marine-related economic activity in the economy, making comparisons difficult. Both the ocean and the coastal economies face a world of volatile changes. In the ocean economy marine transport faces unpredictable fuel costs. Coastal tourism also faces losses from climate change impacts and sea level rise. Finally, a warming ocean and increasing acidification of the oceans from greenhouse gases is already affecting coral reefs and a range of fish stocks. Economic measures are important to predict these impacts, as are economic measures of the resilience of different areas of the ocean and coastal economies. This article demonstrates how knowledge of both the ocean, coastal and national economies can help governments address the future impacts and demands posed by nature and human populations on our coasts and oceans.     

The economics of the common heritage

It is the thesis of this paper that (a) a very large part of the resources, goods and services in the next century will be ocean-dependent; and (b) that the particular nature of the ocean environment magnifies the issues challenging contemporary economic thinking in general. It is quite possible, therefore, that radical innovation in economic thinking will come from “ocean economics” rather than from land-oriented resource or environmental economics. This becomes quite plausible if one thinks that in other (though obviously related) sectors of new thinking, such as international law and governance, the marine sector has played a leading role, just because the ocean is a medium so different from land that it forces us to think differently. In the future the state of marine environment and health of the ocean will have large economical implications at the regional and global level, as it already has today in a number of places at the local and sub-regional level. Hence this overview within the context of this special issue. The paper will begin with a brief assessment of the oceans resource potential for the next century; it will then describe some of the issues humankind has to face in the use and management of these resources, and, in conclusion, the paper will attempt to distill some guidelines for “ocean economics” in the next century.     

The quality factor of oscillating bubbles as an indication of gas content with particular reference to methane

There has been much interest in detecting the presence of methane gas in the ocean. Although methane exists predominantly as methane hydrate (a buoyant compound) in the deep ocean, recent computer simulations and anecdotal evidence have reported that these hydrates will decompose to produce methane bubbles in shallower waters. This paper describes how the quality factor Q of oscillating bubbles can be used to distinguish methane bubbles (Q=24) from the air bubbles (Q=34) which are ubiquitous near the ocean surface. Values of Q are reported for bubbles in water at atmospheric pressure containing air, carbon dioxide, argon, helium, methane and butane. Possible acoustic techniques for detecting and sizing methane bubbles in the ocean are discussed briefly.     

海底热液活动与海洋科学研究

本文简要介绍了海底热液活动的研究历史 ,以及目前研究的几个主要问题。指出海底热液活动是海洋中永远存在的自然现象。热液区主要分布在大洋中脊、弧后盆地和热点区。在这些区域由于地质构造的不稳定性 ,造成冷海水通过隙缝下渗 ,并在岩浆房作用下形成高温热水。热水在上升通道中与围岩作用 ,并发生复杂的岩 -水反应 ,从而改变了海水的化学成分。流出的热液可以形成多种矿物沉积 ,其中最有价值的是 Zn,Cu,Fe,Pb的硫化物。岩 -水反应可以产生可观的元素通量 ,因此 ,对海水元素恒定性的解释需要重新审视。利用 3 He/热比值可以计算海洋的热通量。热液活动为耐温生物的研究提出了新的课题     

Diagnostic tools for 3D unstructured oceanographic data

Most ocean models in current use are built upon structured meshes. It follows that most existing tools for extracting diagnostic quantities (volume and surface integrals, for example) from ocean model output are constructed using techniques and software tools which assume structured meshes. The greater complexity inherent in unstructured meshes (especially fully unstructured grids which are unstructured in the vertical as well as the horizontal direction) has left some oceanographers, accustomed to traditional methods, unclear on how to calculate diagnostics on these meshes. In this paper we show that tools for extracting diagnostic data from the new generation of unstructured ocean models can be constructed with relative ease using open source software. Higher level languages such as Python, in conjunction with packages such as NumPy, SciPy, VTK and MayaVi, provide many of the high-level primitives needed to perform 3D visualisation and evaluate diagnostic quantities, e.g. density fluxes. We demonstrate this in the particular case of calculating flux of vector fields through isosurfaces, using flow data obtained from the unstructured mesh finite element ocean code ICOM, however this tool can be applied to model output from any unstructured grid ocean code.     

Inputs of organic matter to the ocean

The first objective of this introductory paper is to summarize our present understanding of the quantities of total organic carbon produced in the ocean by photosynthesis and non-biotic photochemical reactions, and the amount entering the ocean from rivers, the atmosphere, and the sediments. In this overview it will become apparent that our knowledge of the primary mechanisms and processes involved with the input of organic matter to the ocean via rivers, the atmosphere, sediments, and in situ photochemical reactions is fragmentary and often completely lacking. This becomes critical when we attempt to estimate the input of certain naturally occurring organic compounds and some synthetic organic compounds, since their primary input to the sea is generally via the atmosphere, rivers, and dumping. Thus the second objective of this paper is to emphasize our need to understand the mechanisms involved in these other input processes and the necessity of developing field programs and mathematical models to evaluate the input of specific organic compounds via these pathways. Polychlorinated biphenyls are used as examples of how necessary it is to understand these other input routes in order to evaluate the cycling of pollutant substances in the ocean.     

Biogeochemical and hydrographic controls on chromophoric dissolved organic matter distribution in the Pacific Ocean

Recent in situ observations of chromophoric dissolved organic material (CDOM) in the Pacific Ocean reveal the biogeochemical controls on CDOM and indicate predictive potential for open-ocean CDOM in diagnosing particulate organic matter (POM) remineralization rates within ocean basins. Relationships between CDOM and concentrations of dissolved oxygen, nutrients and inorganic carbon in the subthermocline waters of the Pacific reflect the relative influences of water mass ventilation and water-column oxidative remineralization. Apparent in situ oxygen utilization (AOU) accounts for 86% and 61% of variance in CDOM abundance, respectively, in Antarctic Intermediate Water and North Pacific Intermediate Water. In the deep waters of the Pacific below the zone of remineralization, AOU explains 26% of CDOM variability. The AOU–CDOM relationship results from competing biogeochemical and advective processes within the ocean interior. Dissolved organic carbon (DOC) is not statistically linked to the CDOM or AOU distributions, indicating that the majority of CDOM production occurs during the remineralization of sinking POM and thus potentially provides key information about carbon export. Once formed in the ocean interior, CDOM is relatively stable until it reaches the surface ocean where it is destroyed by solar bleaching. Susceptibility to bleaching confers an additional tracer-like quality for CDOM in water masses with active convection, such as mode waters that appear as subsurface CDOM minima. In the surface ocean, atypically low CDOM abundance highlights a region of unusually extreme oligotrophy: the subtropical South Pacific gyre. For these hyper-oligotrophic waters, the present CDOM observations are consistent with analysis of in situ radiometric observations of light attenuation and reflectance, demonstrating the accuracy of the CDOM spectrophotometric observations. Overall, we illustrate how CDOM abundance in the ocean interior can potentially diagnose rates of thermohaline overturning as they affect regional biogeochemistry and export. We further show how relative surface ocean CDOM abundances are driven in large part by processes occurring in the deep layers of the ocean. This is particularly significant for the interpretation of the global surface distribution of CDOM using satellite remote sensing.