Recontextualising inshore fisheries: The changing face of British inshore fisheries management

Inshore fisheries are coming under increasing pressure to account for wider environmental impacts and relations with other users of marine space. However approaches to inshore fisheries management across Britain’s devolved governments are becoming even more strikingly divergent. While in England the century old local Sea Fisheries Committees are to be replaced with modernised structures, and in Scotland there are efforts to move to a locally driven management system, in Wales there has been a retreat from local co-management. Not only do the reforms pose ongoing challenges for good governance, not least in the handling of cross-scale interactions and user group participation, but they may also fall short in providing for systematic and full integration of fisheries and marine environmental management.     

Impact of model free parameters and sea-level rise uncertainties on 20-years shoreline hindcast: the case of Truc Vert beach (SW France)

Shoreline change is driven by various complex processes interacting at a large range of temporal and spatial scales, making shoreline reconstructions and predictions challenging and uncertain. Despite recent progress in addressing uncertainties related to the physics of sea-level rise, very little effort is made towards understanding and reducing the uncertainties related to wave-driven shoreline response. To fill this gap, the uncertainties associated with the long-term modelling of shoreline change are analysed at a high-energy cross-shore transport dominated site. Using the state-of-the-art LX-Shore shoreline change model, we produce a probabilistic shoreline reconstruction, based on 3000 simulations over the past 20 years at Truc Vert beach, southwest France, whereby sea-level rise rate, depth of closure and three model free parameters are considered uncertain variables. We further address the relative impact of each source of uncertainty on the model results performing a Global Sensitivity Analysis. This analysis shows that the shoreline changes are mainly sensitive to the three parameters of the wave-driven model, but also that the sensitivity to each of these parameters is strongly modulated seasonally and interannually, in relation with wave energy variability, and depends on the time scale of interest. These results have strong implications on the model skill sensitivity to the calibration period as well as for the predictive skill of the model in a context of future climate change affecting wave climate and extremes. © 2020 John Wiley & Sons, Ltd.     

Issues in Energy Economics Led by Emerging Linkages between the Natural Gas and Power Sectors

Fuel prices in 2006 continued at record levels, with uranium continuing upward unabated and coal, SO₂ emission allowances, and natural gas all softening. This softening did not continue for natural gas, however, whose prices rose, fell and rose again, first following weather influences and, by the second quarter of 2007, continuing at high levels without any support from fundamentals. This article reviews these trends and describes the remarkable increases in fuel expenses for power generation. By the end of 2005, natural gas claimed 55% of annual power sector fuel expenses, even though it was used for only 19% of electric generation. Although natural gas is enormously important to the power sector, the sector also is an important driver of the natural gas market—growing to over 28% of the market even as total use has declined. The article proceeds to discuss globalization, natural gas price risk, and technology developments. Forces of globalization are poised to affect the energy markets in new ways—new in not being only about oil. Of particular interest in the growth of intermodal traffic and its a little-understood impacts on rail traffic patterns and transportation costs, and expected rapidly expanding LNG imports toward the end of the decade. Two aspects of natural gas price risk are discussed: how understanding the use of gas in the power sector helps define price ceilings and floors for natural gas, and how the recent increase in the natural gas production after years of record drilling could alter the supply–demand balance for the better. The article cautions, however, that escalation in natural gas finding and development costs is countering the more positive developments that emerged during 2006. Regarding technology, the exploitation of unconventional natural gas was one highlight. So too was the queuing up of coal-fired power plants for the post-2010 period, a phenomenon that has come under great pressure with many consequences including increased pressures in the natural gas market. The most significant illustration of these forces was the early 2007 suspension of development plans by a large power company, well before the Supreme Court’s ruling on CO₂ as a tailpipe pollutant and President Bush’s call for global goals on CO₂ emissions.

The hypocentral resolution of microearthquake surveys carried out at sea

Summary. The ability to locate the hypocentres of earthquakes occurring along ridge crests and fracture zones accurately is a prerequisite to solving several problems associated with seafloor tectonics and oceanic crustal formation. Such resolution has rarely been achieved in the past, often because the seismic networks deployed were inadequate for the task. We demonstrate that sea surface receivers are not useful in such studies, and that the minimum acceptable size for a seafloor network is five receivers, of which at least one must be capable of detecting shear waves unambiguously.     

Magnetorotational instability in a rotating liquid metal annulus

Although the magnetorotational instability (MRI) has been widely accepted as a powerful accretion mechanism in magnetized accretion discs, it has not been realized in the laboratory. The possibility of studying MRI in a rotating liquid metal annulus (Couette flow) is explored by local and global stability analysis. Stability diagrams are drawn in dimensionless parameters, and also in terms of the angular velocities at the inner and outer cylinders. It is shown that MRI can be triggered in a moderately rapidly rotating table-top apparatus, using easy-to-handle metals such as gallium. Practical issues of this proposed experiment are discussed.     

A sensitivity analysis for universal kriging

Universal kriging is an interpolation method for producing contour maps from irregularly spaced sample points, taking into account the trend (or polynomial drift), which is of known form. It assumes a known covariance model to express correlation of points a short distance apart. A sensitivity analysis examines how the fitted surface will change for given perturbations in the covariance model. We develop a simple approximate analysis in preference to exact analysis and show that it is adequate for small perturbations. For large data sets, a dramatic reduction in computer time is possible using approximate analysis. Possible extensions of this work are noted.     

Geomagnetic field analysis—IV. Testing the frozen-flux hypothesis

Summary. We present a model of the magnetic field at the core–mantle boundary, for epoch 1959.5, based on a large set of observatory and survey measurements. Formal error estimates for the radial field at the core are 50 μT, compared with 30 and 40 μT for our previous MAGSAT (1980) and POGO (1970) models.
Current work on the determination of the velocity of the core fluid relies on the assumption that the core behaves as a perfect conductor, so that the field lines remain frozen to the fluid at the core surface. This frozen-flux condition requires that the integrated flux over patches of the core surface bounded by contours of zero radial field remain constant in time. A new method is presented for constructing core fields that satisfy these frozen-flux constraints. The constraints are non-linear when applied to main field data, unlike the case of secular variation which was considered in an earlier paper. The method is applied to datasets from epochs 1969.5 and 1959.5 to produce fields with the same flux integrals as the 1980 model.
The frozen-flux hypothesis is tested by comparing the changes in the flux integrals between 1980/1969.5, 1969.5/1959.5 and 1980/1959.5 with their errors. We find that the hypothesis can be rejected with 95 per cent confidence. The main evidence for flux diffusion is in the South Atlantic region, where a new null flux curve appears between 1960 and 1970, and continues to grow at a rapid rate from 1970 to 1980. However, the statistical result depends critically on our error estimates for the field at the core surface, which are difficult to assess with any certainty; indeed, doubling the error estimates negates the statistical argument. The conclusion is therefore, at this stage, tentative, and requires further evidence, either from older data, if good enough, or from future satellite measurements.     

Devensian glacigenic sedimentation and landscape evolution in the Cardigan area of southwest Wales

The depositional processes associated with late Devensian ice in areas bordering the Irish Sea basin have been the subject of considerable debate. Among the key areas around the Irish Sea, southwest Wales occupies a particularly crucial position because it is here that ice flowing from the north impinged upon the coast orthogonally and encroached inland. Two main hypotheses have emerged concerning deglaciation of the Irish Sea basin. The traditional hypothesis holds that sedimentation was ice‐marginal or subglacial, whereas an alternative hypothesis that emerged in the 1980s argued that sedimentation was glaciomarine. Southwest Wales is well‐placed to contribute to this debate. However, few detailed sedimentological studies, linked to topography, have been made previously in order to reconstruct glacial environments in this area. In this paper, evidence is presented from four boreholes drilled recently in the Cardigan area, combined with data from coastal and inland exposures in the lower Teifi valley and adjacent areas. A complex history of glaciation has emerged: (i) subglacial drainage channel formation in pre‐Devensian time, (ii) deposition of iron‐cemented breccias and conglomerates possibly during the last interglacial (or in the early/mid‐Devensian interstadial), (iii) late Devensian ice advance across the region, during which a glaciolacustrine sequence over 75 m thick accumulated, within a glacial lake known as Llyn Teifi, (iv) a second high‐level glaciolacustrine succession formed near Llandudoch, (v) outside the Teifi valley, ice‐marginal, subglacial and glaciofluvial sediments were also laid down, providing a near‐continuous cover of drift throughout the area. Glacial advance was characterized by reworking, deformation and sometimes erosion of the underlying sediments. The glaciomarine hypothesis is thus rejected for southwest Wales. Copyright © 2001 John Wiley & Sons, Ltd.