Fisheries and failing states: The case of Sierra Leone

Marine fisheries play an important role in the economy of Sierra Leone, supporting livelihoods and contributing significantly to food security. This paper looks in detail at how the performance of fisheries was impacted by the ten year civil war, an event which contributed to the country's reputation for being a “failed state”. The paper focuses mainly on the artisanal fisheries sector, which employs the majority of the country's coastal population, and demonstrates how the conflict caused major social dislocation to fishing communities as well as reducing the productive capacity of the fleet. The paper concludes with a discussion of the policy challenges now facing Sierra Leone, particularly the prevention of resource looting through illegal fishing of the offshore stocks and the development of strategies to enable the potential wealth of these fisheries to be captured.     

The Viking Orbiter cameras' potential for photometric measurement

Although photometry of Mars is not listed as a major mission objective, the Viking Project has provided the Orbiter Imaging Team with cameras exhibiting significant improvement in photometric measurement as compared with past Mariners. Sample calibration data are described, together with predicted performance capabilities.     

Application of discriminant analysis to evaluate compositional controls of stratiform massive sulfide deposits in Canada

Multiple discriminant analysis is used to identify systematic variations of Cu, Pb, Zn, Ag, and Au grade values in the Canadian massive sulfide deposits with the three geological parameters of age, environment, and composition of volcanic lithology. The deposits have been separated into three groups on each of the three parameter scales and discriminant functions that separated the three groups on the basis of metal grades were then obtained. The results of the analysis indicated that Pb and Cu are the most significant in indicating specific trends along the three geological parameter scales. Pb grade increases in younger deposits with an increase in the sedimentary character of their environments, or with a more felsic nature to their volcanic rocks. On the other hand, Cu grade increases in deposits that occur in volcanic environments and with a more mafic nature to the volcanic host rocks. The results could have useful applications in mineral exploration.     

Systematic optimisation and climate simulation of FAMOUS, a fast version of HadCM3

FAMOUS is an unfluxadjusted coupled atmosphere-ocean general circulation model (AOGCM) based on the Met Office Hadley Centre AOGCM HadCM3. Its parametrisations of physical and dynamical processes are almost identical to those of HadCM3, but by virtue of reduced horizontal and vertical resolution and increased timestep it runs about ten times faster. The speed of FAMOUS means that parameter sensitivities can be investigated more thoroughly than in slower higher-resolution models, with the result that it can be tuned closer to its target climatology. We demonstrate a simple method for systematic tuning of parameters, resulting in a configuration of FAMOUS whose climatology is significantly more realistic than would be expected for a model of its resolution and speed. FAMOUS has been tuned to reproduce the behaviour of HadCM3 as nearly as possible, in order that experiments with each model are of maximum relevance to the physical interpretation of the other. Analysis of the control climate and climate change simulation of FAMOUS show that it possesses sufficient skill for its intended purposes in Earth system science as a tool for long-timescale integrations and for large ensembles of integrations, when HadCM3 cannot be afforded. Thus, it can help to bridge the gap between models of intermediate complexity and the higher-resolution AOGCMs used for policy-relevant climate prediction.     

The impact of changes in atmospheric and land surface physics on the thermohaline circulation response to anthropogenic forcing in HadCM2 and HadCM3

We have undertaken a comparative study of the mechanisms which drive the response of the Atlantic thermohaline circulation (THC) to a fourfold increase in CO₂ over 70 years with stabilisation thereafter in HadCM2 and HadCM3. In both models, the THC changes are driven by surface flux forcing, with advection (and diffusion in HadCM2) acting in the opposite sense to limit the circulation change. In both cases, heat fluxes are more important than those of freshwater. We find that different patterns of heat flux forcing in HadCM2 and HadCM3 are the prime determinants of the differing response in the two models. The increased northerly component to the near surface winds (associated with an increase in reflective low level cloud), leads to enhanced heat loss in the west-central North Atlantic, which in turn tends to steepen the steric gradient and strengthen the THC. By contrast, in HadCM3 the winds become more westerly rather than northerly, there is no dynamically-forced enhancement of surface heat loss, and the heat flux in the North Atlantic continues to be strongly positive, relative to the control, leading to a reduction in the meridional steric gradient, and a weaker overturning circulation. Differences in atmospheric response patterns appear to be caused by improvements to atmospheric and land surface physics, and suggest that the THC response in HadCM2 is less credible than in HadCM3.     

An AOGCM simulation of the climate response to a volcanic super-eruption

Volcanic ‘super-eruptions’ have been suggested to have significantly influenced the Earth’s climate, perhaps causing glaciations and impacting on the human population. Climatic changes following a hypothetical ‘super-eruption’ are simulated using a coupled atmosphere ocean general circulation model, incorporating scaled volcanic stratospheric aerosols. Assumptions are made about the stratospheric sulphate aerosol loading, size distribution, lifetime, chemical make up and spatial distribution. As this study is concentrating on the physical climatological impacts over long timescales, microphysics and chemical interactive processes are not simulated. Near-surface temperatures fall by as much as 10 K globally for a few months and a considerable deviation from normal temperatures continues for several decades. A warming pattern is evident over northern land masses during the winter due to increased longwave forcing and a positive AO mode. The overturning rate of the North Atlantic thermohaline circulation doubles in intensity. Snow and ice increases in extent to a maximum coverage of 35% of the Earth. Despite these and other impacts longer term climatic changes that could lead to a transition to a glaciation do not occur, for present day boundary conditions and one possible plausible aerosol loading.     

Observations of bedforms on a dissipative macrotidal beach

Field measurements of wave ripples and megaripples were made with a Sand Ripple Profiler in the surf and shoaling zones of a sandy macrotidal dissipative beach at Perranporth, UK in depths 1–6 m and significant wave heights up to 2.2 m. A frequency domain partitioning approach allowed quantification of height (η), length (λ) and migration rate of ripples and megaripples. Wave ripples with heights up to 2 cm and wavelengths ～20 cm developed in low orbital velocity conditions (u _m?<?0.65 m/s) with mobility number ψ?<?25. Wave ripple heights decreased with increasing orbital velocity and were flattened when mean currents were >0.1 m/s. Wave ripples were superimposed on top of megaripples (η?=?10 cm, λ?=?1 m) and contributed up to 35 % of the total bed roughness. Large megaripples with heights up to 30 cm and lengths 1–1.8 m developed when the orbital velocity was 0.5–0.8 m/s, corresponding to mobility numbers 25–50. Megaripple heights and wavelengths increased with orbital velocity but reduced when mean current strengths were >0.15 m/s. Wave ripple and megaripple migrations were generally onshore directed in the shoaling and surf zones. Onshore ripple migration rates increased with onshore-directed (+ve) incident wave skewness. The onshore migration rate reduced as offshore-directed mean flows (undertow) increased in strength and reached zero when the offshore-directed mean flow was >0.15 m/s. The migration pattern was therefore linked to cross-shore position relative to the surf zone, controlled by competition between onshore-directed velocity skewness and offshore-directed mean flow.     

Mariner 9 photometric observations of Mars from November 1971 through March 1972

The large quantity of Mariner 9 television pictures taken at phase angles ranging up to twice those accessible from Earth has been used to describe intergrated photometric properties of Mars. Although frame-to-frame variations emphasize the shortcomings of vidicon cameras when used in a photometric mode, statistical trends have yielded data comparable with Earth-based observations.Analysis of atmospheric parameters over a period of changing opacity, November 1971 through March 1972, has provided time-varying optical depths and light-scattering information. Linear function characterization of the Mars reflectance is clearly discrepant at large incidence or emission angles and at phase angles greater than 40°.