A legal regime for the Arctic?: Interplay with the Law of the Sea Convention

The Law of the Sea Convention constrains regional environmental regimes, especially with respect to navigation beyond the territorial sea. Existing soft-law institutions, notably the Arctic Council, have already strengthened environmental governance in the region by (1) improving the knowledge base; (2) preparing practical guidance on risk reduction; (3) highlighting in broader regulatory fora the Arctic dimension of problems like long-range transported hazardous compounds; and (4) supporting the capacity of Arctic states to implement existing commitments. None of those functions would be much enhanced by a legally binding Arctic environmental regime. The political impediments to reaching circumpolar agreement on a single comprehensive legal regime would suggest a flexible approach to norm building that seeks productive interplay with existing institutions.     

Scaling,analysis and new instrumentation for dynamic bed tests: The SANDS-Hydralab III papers

This special issue presents the main research results from the SANDS project in Hydralab-III, a research project of the European Union. The papers review the scaling and design of mobile bed tests, the role and limits of conventional and new instrumentation and the extrapolation to full scale. The project has focused on innovative systems of opto-acoustic instrumentation, able to recover water and sediments fluxes at an unprecedented level of accuracy and resolution. The research also included large scale experiments at different scales and a critical comparison of experimental and numerical results to improve the state of the art in Coastal Engineering.     

Prediction and assimilation of surf-zone processes using a Bayesian network: Part I: Forward models

Prediction of coastal processes, including waves, currents, and sediment transport, can be obtained from a variety of detailed geophysical-process models with many simulations showing significant skill. This capability supports a wide range of research and applied efforts that can benefit from accurate numerical predictions. However, the predictions are only as accurate as the data used to drive the models and, given the large temporal and spatial variability of the surf zone, inaccuracies in data are unavoidable such that useful predictions require corresponding estimates of uncertainty. We demonstrate how a Bayesian-network model can be used to provide accurate predictions of wave-height evolution in the surf zone given very sparse and/or inaccurate boundary-condition data. The approach is based on a formal treatment of a data-assimilation problem that takes advantage of significant reduction of the dimensionality of the model system. We demonstrate that predictions of a detailed geophysical model of the wave evolution are reproduced accurately using a Bayesian approach. In this surf-zone application, forward prediction skill was 83%, and uncertainties in the model inputs were accurately transferred to uncertainty in output variables. We also demonstrate that if modeling uncertainties were not conveyed to the Bayesian network (i.e., perfect data or model were assumed), then overly optimistic prediction uncertainties were computed. More consistent predictions and uncertainties were obtained by including model-parameter errors as a source of input uncertainty. Improved predictions (skill of 90%) were achieved because the Bayesian network simultaneously estimated optimal parameters while predicting wave heights.     

Prediction and assimilation of surf-zone processes using a Bayesian network: Part II: Inverse models

A Bayesian network model has been developed to simulate a relatively simple problem of wave propagation in the surf zone (detailed in Part I). Here, we demonstrate that this Bayesian model can provide both inverse modeling and data-assimilation solutions for predicting offshore wave heights and depth estimates given limited wave-height and depth information from an onshore location. The inverse method is extended to allow data assimilation using observational inputs that are not compatible with deterministic solutions of the problem. These inputs include sand bar positions (instead of bathymetry) and estimates of the intensity of wave breaking (instead of wave-height observations). Our results indicate that wave breaking information is essential to reduce prediction errors. In many practical situations, this information could be provided from a shore-based observer or from remote-sensing systems. We show that various combinations of the assimilated inputs significantly reduce the uncertainty in the estimates of water depths and wave heights in the model domain. Application of the Bayesian network model to new field data demonstrated significant predictive skill (R² = 0.7) for the inverse estimate of a month-long time series of offshore wave heights. The Bayesian inverse results include uncertainty estimates that were shown to be most accurate when given uncertainty in the inputs (e.g., depth and tuning parameters). Furthermore, the inverse modeling was extended to directly estimate tuning parameters associated with the underlying wave-process model. The inverse estimates of the model parameters not only showed an offshore wave height dependence consistent with results of previous studies but the uncertainty estimates of the tuning parameters also explain previously reported variations in the model parameters.     

International fisheries agreement: Review of the International Commission for the Conservation of Atlantic Tunas: Case study—Shark management

To properly manage world fisheries, especially highly migratory species, there are numerous treaties that have been implemented by specialized international fishery commissions. One of the oldest organizations is the International Commission for the Conservation of Atlantic Tunas (ICCAT). The main focus of this review was to summarize the history, roles and responsibilities of ICCAT, and to evaluate ICCAT's management of sharks in general and specifically for shortfin mako (Isurus oxyrinchus) shark. This review found that the Convention was established 40 years ago, but it was not until 2004 that the commission conducted its first population assessment on pelagic sharks.     

Sea Grant in Latin America?: Adapting the US Sea Grant model of linked applied research,extension, and education to a Latin American Context—Is there a fit?

This paper explores the application of the US Sea Grant model of applied research, extension, and education to two case studies in Latin America: Coastal Ecuador and the Gulf of Fonseca. The analysis is based on a series of meetings and roundtables with in-country partners and leaders of the US Sea Grant program. We conclude that the Sea Grant model provides an institutional structure that Latin America lacks and the model's features would improve governance of marine and coastal resources through more effective linkages between coastal communities, universities, and policy/decision makers at local, national, and international levels.     

Large-scale turbulence under a solitary wave: Part 2: Forms and evolution of coherent structures

The instantaneous turbulent velocity field produced by a broken solitary wave propagating on a 1 in 50 plane slope was measured in the longitudinal transverse plane in the middle part of the water column and near the bottom using a stereoscopic particle image velocimetry system. These measurements showed that large-scale turbulence first arrived in the form of a downburst of turbulent fluid. In the middle of the water column, the downbursts arrived shortly after the wave crest had passed. Each downburst was accompanied by two counter-rotating vortices. The latter grew rapidly in size to become a prominent feature of the flow field. Each vortex had a typical length scale of 1/2 to 1 water depth, and carried most of the turbulent kinetic energy in the region between the vortices. Near the bottom, the counter-rotating vortices were not as well defined and covered only a small plane area compared to the entire flow structure. The turbulent fluid descending from above diverged at the bed and the resulting flow structure developed an elongated shape as the source of down-flow travelled onshore with the broken wave. It was found that the transverse spacing between adjacent downbursts ranged from 2 to 5 times the local still water depth. Since vortices cannot end in the interior of the fluid, the counter-rotating vortices must extend to the free surface in the form of a vortex loop. It was suggested that these vortex loops were produced by bending and stretching of primary vorticity generated in the wave breaking process, possibly as a result of three-dimensional water surface deformation. The vortex loops were then carried downward by the falling water from the broken wave.     

Adaptive fisheries management in Vietnam: The use of indicators and the introduction of a multi-disciplinary Marine Fisheries Specialist Team to support implementation

Vietnam is in the process of introducing adaptive management based on indicators and time-series to manage its marine fisheries. The development of indicator-based frameworks for fisheries management has accelerated in recent years. This article describes the suite of indicators being suggested or used in Vietnam including the data-collection system. The Vietnamese approach is supported by an institutional structure consisting of a multi-disciplinary advisory system to facilitate the process of using indicators and to introduce knowledge-based management. The article concludes by identifying current problems and weaknesses and by providing suggestions for future improvement of the system.     

Impact of mega-scale sand extraction on tidal dynamics in semi-enclosed basins: An idealized model study with application to the Southern North Sea

Long-term considerations of repeated and increasing sand extraction on the Netherlands Continental Shelf (North Sea) may lead to the creation of a mega-scale extraction trench in front of the Dutch coast (length hundreds of km, width over 10 km, depth several m). We investigate the impact of such a huge topographic intervention on tidal dynamics, which is a key aspect in hydrodynamics, and indirectly also affecting morphodynamics and ecology.     

Econometric analysis on the effect of port state control inspections on the probability of casualty: Can targeting of substandard ships for inspections be improved?

This article is based on 183,819 port state control inspections from various port state control regimes and casualties from three different data sources for a time period of 6 years. It is the first time an analysis on a combined dataset of this magnitude has been performed. Binary logistic regression is used to measure the effect of inspections on the probability of casualty, which can be measured for very serious casualties but not for serious or less serious casualties. In addition, the magnitude of improvement areas for targeting substandard vessels is determined and the models further show how targeting of substandard ships on a combined dataset can be improved. In addition, the analysis also compares the fishing fleet with the commercial fleet.