Palaeomagnetism and age of mid-Palaeozoic ring complexes in Niger, West Africa, and tectonic implications     

R. B. Hargraves  E. M. Dawson  F. B. Van  Houten 《Geophysical Journal International》1987,90(3):705-729

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B-polarization induction in two thin half-sheets coupled to the mantle by a conducting crust—I. Solution by the Wiener-Hopf technique, with limiting forms     

T. W. Dawson 《Geophysical Journal International》1996,124(2):556-576

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A three-dimensional discontinuous Galerkin model applied to the baroclinic simulation of Corpus Christi Bay     

Vadym Aizinger  Jennifer Proft  Clint Dawson  Dharhas Pothina  Solomon Negusse 《Ocean Dynamics》2013,63(1):89-113

In this work, we present results of a numerical study of Corpus Christi Bay, Texas and surrounding regions and compare simulated model results to recorded data. The validation data for the year 2000 include the water elevation, velocity, and salinity at selected locations. The baroclinic computations were performed using the University of Texas Bays and Estuaries 3D (UTBEST3D) simulator based on a discontinuous Galerkin finite element method for unstructured prismatic meshes. We also detail some recent advances in the modeling capabilities of UTBEST3D, such as a novel turbulence scheme and the support for local vertical discretization on parts of the computational domain. All runs were conducted on parallel clusters; an evaluation of parallel performance of UTBEST3D is included.  相似文献   

Climate–water quality relationships in Texas reservoirs          下载免费PDF全文

Rodica Gelca  Katharine Hayhoe  Ian Scott‐Fleming  Caleb Crow  Dan Dawson  Reynaldo Patiño 《水文研究》2016,30(1):12-29

Water temperature, dissolved oxygen, and concentrations of salts in surface water bodies can be affected by the natural environment and local human activities such as surface and ground water withdrawals, land use and energy extraction, and variability and long‐term trends in atmospheric conditions including temperature and precipitation. Here, we quantify the relationship between 121 indicators of mean and extreme temperature and precipitation and 24 water quality parameters in 57 Texas reservoirs using observational data records covering the period 1960 to 2010. Over time scales ranging from 1 week to 2 years, we find that water temperature, dissolved oxygen, pH, specific conductance, chloride, sulfate, and phosphorus all show consistent correlations with atmospheric predictors, including high and low temperature extremes, dry days, heavy precipitation events, and mean temperature and precipitation. Based on these relationships combined with regional climate projections, we expect climate change to increase water temperatures, decrease dissolved oxygen levels, decrease pH, increase specific conductance, and increase levels of sulfate and chloride in Texas reservoirs. Over decadal time scales, this may affect aquatic ecosystems in the reservoirs, including altering the risk of conditions conducive to algae occurrence, as well as affecting the quality of water available for human consumption and recreation. Copyright © 2015 John Wiley & Sons, Ltd.  相似文献   

Shipboard trials of an ozone-based ballast water treatment system   总被引：1，自引：0，他引：1  

David A. Wright  Robert W. Gensemer  William A. Stubblefield  Rodger Dawson  Jonathon S. Bearr  William J. Cooper 《Marine pollution bulletin》2010,60(9):1571-1583

Legislation introduced by the United Nations International Maritime Organization (IMO) has focused primarily on standards defining successful treatments designed to remove invasive species entrained in ballast water. An earlier shipboard study found that ozone introduced into salt water ballast resulted in the formation of bromine compounds, measured as total residual oxidants (TRO) that were toxic to both bacteria and plankton. However, the diffuser system employed to deliver ozone to the ballast water tanks resulted in patchiness in TRO distribution and toxicity to entrained organisms. In this follow-up study, the shipboard diffuser system was replaced by a single Venturi-type injection system designed to deliver a more homogeneous biocide distribution. Within-tank variability in TRO levels and associated toxicity to zooplankton, phytoplankton and marine bacteria was measured via a matrix of tubes deployed to sample different locations in treated and untreated (control) tanks. Three trials were conducted aboard the oil tanker S/T Prince William Sound in the Strait of Juan de Fuca off Port Angeles, Washington State, USA, between June and December 2007. Mortalities of plankton and bacteria and oxidant concentrations were recorded for treated and untreated ballast water up to 3 days following treatment, and residual toxicity beyond this period was measured by bioassay of standard test organisms. Results indicated uniform compliance with current IMO standards, but only partial compliance with other existing and pending ballast water legislation.  相似文献   

A 21-Event, 4,000-Year History of Surface Ruptures in the Anza Seismic Gap,San Jacinto Fault,and Implications for Long-term Earthquake Production on a Major Plate Boundary Fault     

Thomas K. Rockwell  Timothy E. Dawson  Jeri Young Ben-Horin  Gordon Seitz 《Pure and Applied Geophysics》2015,172(5):1143-1165

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Integrated analysis of risks of coastal flooding and cliff erosion under scenarios of long term change   总被引：2，自引：1，他引：1  

R. J. Dawson  M. E. Dickson  R. J. Nicholls  J. W. Hall  M. J. A. Walkden  P. K. Stansby  M. Mokrech  J. Richards  J. Zhou  J. Milligan  A. Jordan  S. Pearson  J. Rees  P. D. Bates  S. Koukoulas  A. R. Watkinson 《Climatic change》2009,95(1-2):249-288

The risks to human populations in coastal areas are changing due to climate and socio-economic changes, and these trends are predicted to accelerate during the twenty-first century. To understand these changing risks, and the resulting choices and pathways to successful management and adaptation, broad-scale integrated assessment is essential. Due to their complexity the two risks of flooding and erosion are usually managed independently, yet frequently they are interconnected by longshore exchange of sediments and the resulting broad scale morphological system behaviour. In order to generate new insights into the effects of climate change and coastal management practises on coastal erosion and flood risk, we present an integrated assessment of 72 km of shoreline over the twenty-first century on the East Anglian coast of England which is a site of significant controversy about how to manage coastal flood and erosion risks over the twenty-first century. A coupled system of hydrodynamic, morphological, reliability and socio-economic models has been developed for the analysis, implemented under scenarios of coastal management, climate and socio-economic change. The study is unique in coastal management terms because of the large spatial scale and extended temporal scale over which the analysis is quantified. This study for the first time quantifies what has for some years been argued qualitatively: the role of sediments released from cliff erosion in protecting neighbouring low-lying land from flooding. The losses and benefits are expressed using the common currency of economic risk. The analysis demonstrates that over the twenty-first century, flood risk in the study area is expected to be an order of magnitude greater than erosion risk. Climate and socio-economic change and coastal management policy have a significant influence on flood risk. This study demonstrates that the choices concerning coastal management are profound, and there are clear tradeoffs between erosion and flood impacts.  相似文献   

Antarctic icebergs near New Zealand     

J. W. Brodie  E. W. Dawson 《新西兰海洋与淡水研究杂志》2013,47(1):80-85

Records of icebergs near New Zealand are noted, and their implications on the interpretation of ice‐rafted sediments are discussed.  相似文献   

Early Flandrian tidal surges in the Tay estuary,Scotland     

A. G. Dawson  D. E. Smith  D. Long  Robin A. Cullingford  Christopher J. Caseldine  Paul E. Gotts 《第四纪科学杂志》1989,4(3):273-274

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The brevity of carbonatite sources in the mantle: evidence from Hf isotopes   总被引：5，自引：0，他引：5  

Michael?BizimisEmail author  Vincent?J.?M.?Salters  J.?Barry?Dawson 《Contributions to Mineralogy and Petrology》2003,145(3):281-300

Hf, Zr and Ti in carbonatites primarily reside in their non-carbonate fraction while the carbonate fraction dominates the Nd and Sr elemental budget of the whole rock. A detailed investigation of the Hf, Nd and Sr isotopic compositions shows frequent isotopic disequilibrium between the carbonate and non-carbonate fractions. We suggest that the trace element and isotopic composition of the carbonate fraction better represents that of the carbonatite magma, which in turn better reflects the composition of the carbonatitic source. Experimental partitioning data between carbonatite melt and peridotitic mineralogy suggest that the Lu/Hf ratio of the carbonatite source will be equal to or greater than the Lu/Hf ratio of the carbonatite. This, combined with the Hf isotope systematics of carbonatites, suggests that, if carbonatites are primary mantle melts, then their sources must be short-lived features in the mantle (maximum age of 10–30 Ma), otherwise they would develop extremely radiogenic Hf compositions. Alternatively, if carbonatites are products of extreme crystal fractionation or liquid immiscibility then the lack of radiogenic initial Hf isotope compositions also suggests that their sources do not have long-lived Hf depletions. We present a model in which the carbonatite source is created in the sublithospheric mantle by the crystallization of earlier carbonatitic melts from a mantle plume. This new source melts shortly after its formation by the excess heat provided by the approaching hotter center of the plume and/or the subsequent ascending silicate melts. This model explains the HIMU-EMI isotope characteristics of the East African carbonatites, their high LREE/HREE ratios as well as the rarity of carbonatites in the oceanic lithosphere.  相似文献