Modelling the effects and economics of managed realignment on the cycling and storage of nutrients, carbon and sediments in the Blackwater estuary UK     

D. Shepherd  D. Burgess  T. Jickells  J. Andrews  R. Cave  R.K. Turner  J. Aldridge  E.R. Parker  E. Young   《Estuarine, Coastal and Shelf Science》2007,73(3-4):355-367

A hydrodynamic model is developed for the Blackwater estuary (UK) and used to estimate nitrate removal by denitrification. Using the model, sediment analysis and estimates of sedimentation rates, we estimate changes in estuarine denitrification and intertidal carbon and nutrient storage and associated value of habitat created under a scenario of extensive managed realignment. We then use this information, together with engineering and land costs, to conduct a cost benefit analysis of the managed realignment. This demonstrates that over a 50–100 year timescale the value of the habitat created and carbon buried is sufficient to make the large scale managed realignment cost effective. The analysis reveals that carbon and nutrient storage plus habitat creation represent major and quantifiable benefits of realignment. The methodology described here can be readily transferred to other coastal systems.  相似文献   

An assessment of the Western mackerel stock     

Lockwood  S. J.; Shepherd  J. G. 《ICES Journal of Marine Science》1984,41(2):167-180

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New merlin observations of OH/IR stars: OH357.31-1.33 and OH0.9+1.3     

V. Migenes  E. Lüdke  R. J. Cohen  M. Shepherd  P. F. Bowers 《Astrophysics and Space Science》1995,224(1-2):515-516

We present recent radio interferometer measurements of the OH 1612 MHz maser emission from the OH/IR sources OH0.9+1.3 and OH357.31 obtained with the enhanced MERLIN. Some preliminary results are briefly discussed. These results are part of an on-going observational campaign to obtain the best radio maps of bright OH/IR stars with MERLIN, VLA and VLBA, in order to understand the nature and dynamics of their circumstellar matter and evolution.  相似文献   

Electron-Positron Plasmas Created by Ultra-Intense Laser Pulses Interacting with Solid Targets     

S. C. Wilks  H. Chen  E. Liang  P. Patel  D. Price  B. Remington  R. Shepherd  M. Tabak  W. L. Kruer 《Astrophysics and Space Science》2005,298(1-2):347-355

We discuss the necessary requirements to create dense electron-positron plasmas in the laboratory and the possibility of using them to investigate certain aspects of various astrophysical phenomena, such as gamma ray burst engines. Earth-based electron-positron plasmas are created during the interaction of ultra-intense laser pulses impinging on a solid density target. The fact that positrons can be generated during this interaction has already been demonstrated by Cowan et al. (2000). However, several questions concerning the number, energy, and dynamics of these positrons have yet to be answered. Through insight gathered from PIC simulations, we postulate that the e⁺e⁻ plasma leaves the creation region in dense jets, with relativistic energies. In order to estimate the number density of the positrons created, we begin by first experimentally measuring the hot electron temperatures and densities of such interactions using a compact electron spectrometer. Once the electron distribution is known, the positron creation rate, Γ, can be estimated. This same experimental diagnostic can also, with minor modification, measure the energy distribution of positrons. Initial estimates are that, with proper target and laser configurations, we could potentially create one of the densest arraignments of positrons ever assembled on earth. This experimental configuration would only last for a few femtoseconds, but would eventually evolve into astrophysically relevant pure electron-positron jets, possibly relevant to e⁺e⁻ outflow from black holes.  相似文献   

Simple methods for short-term forecasting of catch and biomass     

Shepherd  J. G. 《ICES Journal of Marine Science》1991,48(1):67-78

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An unusual SAR arc observed during ring current development, 4 August 1972     

G.G. Shepherd  L.H. Brace  J.R. Burrows  J.H. Hoffman  H.G. James  D.M. Klumpar  A.F. Nagy  E. Stathopoulos  J.H. Whiteker 《Planetary and Space Science》1980,28(1):69-84

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Storylines: an alternative approach to representing uncertainty in physical aspects of climate change     

Theodore G. Shepherd  Emily Boyd  Raphael A. Calel  Sandra C. Chapman  Suraje Dessai  Ioana M. Dima-West  Hayley J. Fowler  Rachel James  Douglas Maraun  Olivia Martius  Catherine A. Senior  Adam H. Sobel  David A. Stainforth  Simon F. B. Tett  Kevin E. Trenberth  Bart J. J. M. van den Hurk  Nicholas W. Watkins  Dimitri A. Zenghelis 《Climatic change》2018,147(3-4):555-569

Investigating the relationships between climate extremes and crop yield can help us understand how unfavourable climatic conditions affect crop production. In this study, two statistical models, multiple linear regression and random forest, were used to identify rainfall extremes indices affecting wheat yield in three different regions of the New South Wales wheat belt. The results show that the random forest model explained 41–67% of the year-to-year yield variation, whereas the multiple linear regression model explained 34–58%. In the two models, 3-month timescale standardized precipitation index of Jun.–Aug. (SPI_JJA), Sep.–Nov. (SPI_SON), and consecutive dry days (CDDs) were identified as the three most important indices which can explain yield variability for most of the wheat belt. Our results indicated that the inter-annual variability of rainfall in winter and spring was largely responsible for wheat yield variation, and pre-growing season rainfall played a secondary role. Frequent shortages of rainfall posed a greater threat to crop growth than excessive rainfall in eastern Australia. We concluded that the comparison between multiple linear regression and machine learning algorithm proposed in the present study would be useful to provide robust prediction of yields and new insights of the effects of various rainfall extremes, when suitable climate and yield datasets are available.  相似文献   

Epithermal gold mineralisation in the active Aegean Volcanic Arc: the Profitis Ilias deposit, Milos Island, Greece     

Stephanos P. Kilias  Jon Naden  Ioannis Cheliotis  Thomas J. Shepherd  Heleni Constandinidou  John Crossing  Ioannis Simos 《Mineralium Deposita》2001,36(1):32-44

The Profitis Ilias gold deposit, located on the western part of Milos Island, Greece, is the first epithermal gold deposit discovered in the Pliocene–Pleistocene Aegean volcanic arc. Estimated ore reserves are 5 million tonnes grading 4.4 g/tonne Au and 43 g/tonne Ag. The deposit is closely associated with a horst and graben structure, and occurs in a series of steep interconnected crustiform-banded quartz veins up to 3 m wide, extending to depths of at least 300 m. The mineralisation occurs in three stages and is hosted by 3.5–2.5 Ma old silicified and sericitised rhyolitic lapilli-tuffs and ignimbrites. It consists of pyrite, galena, chalcopyrite, electrum and native gold. Additionally, adularia occurs with quartz mainly in veins. Homogenisation temperatures of primary liquid-rich inclusions vary from 145 to 399 °C for the ore stage, and 112 to 263 °C for the post-ore stage. Salinities range between 0.1 and 11.4 wt% NaCl equiv. and 0.93 to 8.5 wt% NaCl equiv. for the ore stage and the post-ore stage, respectively. Rare vapour-rich inclusions in ore stage quartz homogenise between 368 and 399 °C and estimates of eutectic melting (−25 to −38 °C) indicate the presence of Ca and Mg in the ore fluids. Sample elevation versus fluid inclusion T_h–salinity relationships show (1) a high-salinity trend, where moderate-temperature (300–250 °C) and moderate-salinity brines (∼3 wt% NaCl equiv.) trend to high-salinity (up to 15 wt% NaCl equiv.) fluids with lower (∼25–50 °C) homogenisation temperatures, and (2) a high-T_h trend where moderate-salinity and moderate-temperature brines (200–250 °C; 3 wt% NaCl equiv.) develop into low-salinity (<1 wt% NaCl equiv.), high-temperature (>350 °C) fluids. These trends are best explained by extreme boiling and vapourisation phenomena between 200 and 250 °C. The 430–450 m asl (metres above sea level) level marks the transition between a lower liquid-dominated segment of the system where only the steep high-salinity trend is seen, and an upper vapour-dominated segment where the high-T_h trend or a combination of both are seen. There is a close spatial association between mineable gold grades and the upper segment of the system. Depth-to-boiling curves suggest that the paleo-surface was ∼200 m above the present summit of Profitis Ilias. Comparison of the mineralisation and fluid geochemistry at Profitis Ilias with that of the nearby modern geothermal system indicates that the processes of metal mineralisation have probably been continuous since the Late Pliocene. Received: 24 February 2000 / Accepted: 15 July 2000  相似文献   

Bifurcations of the thermohaline circulation in a simplified three-dimensional model of the world ocean and the effects of inter-basin connectivity     

N. Edwards  J. Shepherd 《Climate Dynamics》2002,19(1):31-42

A coarse-resolution, global, three-dimensional, idealised model of the world ocean, based on the thermocline equations, is described. It is demonstrated that, at suitable resolution, such a model can be integrated for hundreds or thousands of millenia, and could therefore form a component of an earth system model designed to investigate climate change on these time scales. As in other ocean models, the thermohaline circulation is found to exhibit multiple stable states. The bifurcation structure of the model has been explored, as a function of surface saline forcing, and is found to depend on the inter-basin connectivity, the topography, and the form of the imposed wind forcing.  相似文献   

Impacts of the Jessica oil spill on intertidal and shallow subtidal plants and animals     

Edgar GJ  Kerrison L  Shepherd SA  Veronica Toral-Granda M 《Marine pollution bulletin》2003,47(7-8):276-283

Densities of fishes, invertebrates and plants at rocky intertidal and shallow subtidal sites were censused 1-2 days prior to the Jessica oil spill and compared with information obtained for the same sites one month after the spill, both for sites impacted by oil and unaffected reference sites. While the availability of pre-spill data made this analysis one of the most powerful to date for testing impacts of oil on shoreline environments, no clear changes attributable to oiling could be identified. Discharged oil appeared to cause very little impact in the intertidal and shallow subtidal zones, with such impacts lying within the range of natural spatial and temporal variation at sites investigated. Factors considered to minimize impact in Galápagos included paucity of fully sheltered shores in spill path, moderate wave action, warm temperature, high levels of sunlight, and mixing of bunker oil with diesel.  相似文献