Land-derived pollutant hydrocarbons     

B.S. Cooper  R.C. Harris  S. Thompson 《Marine pollution bulletin》1974,5(1):15-16

Evidence is given for the derivation of oil pollution from on-shore sources and for a possible relation between its concentration in estuarine sediment and in the lipids of the sediment biomass.  相似文献   

Human and climate forcing of zooplankton populations: Introduction     

Dagg  Michael; Uye  Shin-ichi; Valdes  Luis; Harris  Roger 《ICES Journal of Marine Science》2008,65(3):277-278

Zooplankton play a key role in the pelagic foodweb by controllingphytoplankton production and shaping pelagic ecosystems. Inaddition, because of their critical role as a food source forlarval and juvenile fish, the dynamics of zooplankton populationshave a significant influence on recruitment to fish stocks.In 1961, ICES convened the First Zooplankton Production Symposiumin Charlottenlund, Denmark. ICES also played a leading rolein the Second Zooplankton Production Symposium on "ZooplanktonProduction: measurement and role in global  相似文献   

Non-grey hydrogen burning evolution of subsolar mass Population III stars     

G. J. Harris  A. E. Lynas-Gray  S. Miller  J. Tennyson 《Monthly notices of the Royal Astronomical Society》2007,374(1):337-343

  相似文献   

Lie group variational integrators for the full body problem in orbital mechanics     

Taeyoung Lee  Melvin Leok  N. Harris McClamroch 《Celestial Mechanics and Dynamical Astronomy》2007,98(2):121-144

Equations of motion, referred to as full body models, are developed to describe the dynamics of rigid bodies acting under their mutual gravitational potential. Continuous equations of motion and discrete equations of motion are derived using Hamilton’s principle. These equations are expressed in an inertial frame and in relative coordinates. The discrete equations of motion, referred to as a Lie group variational integrator, provide a geometrically exact and numerically efficient computational method for simulating full body dynamics in orbital mechanics; they are symplectic and momentum preserving, and they exhibit good energy behavior for exponentially long time periods. They are also efficient in only requiring a single evaluation of the gravity forces and moments per time step. The Lie group variational integrator also preserves the group structure without the use of local charts, reprojection, or constraints. Computational results are given for the dynamics of two rigid dumbbell bodies acting under their mutual gravity; these computational results demonstrate the superiority of the Lie group variational integrator compared with integrators that are not symplectic or do not preserve the Lie group structure.  相似文献   

Meteorites at Meridiani Planum provide evidence for significant amounts of surface and near‐surface water on early Mars     

Alberto G. FAIRÉN  James M. DOHM  Victor R. BAKER  Shane D. THOMPSON  William C. MAHANEY  Kenneth E. HERKENHOFF  J. Alexis P. RODRÍGUEZ  Alfonso F. DAVILA  Dirk SCHULZE‐MAKUCH  M. Ramy EL MAARRY  Esther R. UCEDA  Ricardo AMILS  Hirdy MIYAMOTO  Kyeong J. KIM  Robert C. ANDERSON  Christopher P. McKAY 《Meteoritics & planetary science》2011,46(12):1832-1841

Abstract– Six large iron meteorites have been discovered in the Meridiani Planum region of Mars by the Mars Exploration Rover Opportunity in a nearly 25 km‐long traverse. Herein, we review and synthesize the available data to propose that the discovery and characteristics of the six meteorites could be explained as the result of their impact into a soft and wet surface, sometime during the Noachian or the Hesperian, subsequently to be exposed at the Martian surface through differential erosion. As recorded by its sediments and chemical deposits, Meridiani has been interpreted to have undergone a watery past, including a shallow sea, a playa, an environment of fluctuating ground water, and/or an icy landscape. Meteorites could have been encased upon impact and/or subsequently buried, and kept underground for a long time, shielded from the atmosphere. The meteorites apparently underwent significant chemical weathering due to aqueous alteration, as indicated by cavernous features that suggest differential acidic corrosion removing less resistant material and softer inclusions. During the Amazonian, the almost complete disappearance of surface water and desiccation of the landscape, followed by induration of the sediments and subsequent differential erosion and degradation of Meridiani sediments, including at least 10–80 m of deflation in the last 3–3.5 Gy, would have exposed the buried meteorites. We conclude that the iron meteorites support the hypothesis that Mars once had a denser atmosphere and considerable amounts of water and/or water ice at and/or near the surface.  相似文献   

Effects of atmospheric dynamics and ocean resolution on bi-stability of the thermohaline circulation examined using the Grid ENabled Integrated Earth system modelling (GENIE) framework     

T. M. Lenton  R. Marsh  A. R. Price  D. J. Lunt  Y. Aksenov  J. D. Annan  T. Cooper-Chadwick  S. J. Cox  N. R. Edwards  S. Goswami  J. C. Hargreaves  P. P. Harris  Z. Jiao  V. N. Livina  A. J. Payne  I. C. Rutt  J. G. Shepherd  P. J. Valdes  G. Williams  M. S. Williamson  A. Yool 《Climate Dynamics》2007,29(6):591-613

We have used the Grid ENabled Integrated Earth system modelling (GENIE) framework to undertake a systematic search for bi-stability of the ocean thermohaline circulation (THC) for different surface grids and resolutions of 3-D ocean (GOLDSTEIN) under a 3-D dynamical atmosphere model (IGCM). A total of 407,000 years were simulated over a three month period using Grid computing. We find bi-stability of the THC despite significant, quasi-periodic variability in its strength driven by variability in the dynamical atmosphere. The position and width of the hysteresis loop depends on the choice of surface grid (longitude-latitude or equal area), but is less sensitive to changes in ocean resolution. For the same ocean resolution, the region of bi-stability is broader with the IGCM than with a simple energy-moisture balance atmosphere model (EMBM). Feedbacks involving both ocean and atmospheric dynamics are found to promote THC bi-stability. THC switch-off leads to increased import of freshwater at the southern boundary of the Atlantic associated with meridional overturning circulation. This is counteracted by decreased freshwater import associated with gyre and diffusive transports. However, these are localised such that the density gradient between North and South is reduced tending to maintain the THC off state. THC switch-off can also generate net atmospheric freshwater input to the Atlantic that tends to maintain the off state. The ocean feedbacks are present in all resolutions, across most of the bi-stable region, whereas the atmosphere feedback is strongest in the longitude–latitude grid and around the transition where the THC off state is disappearing. Here the net oceanic freshwater import due to the overturning mode weakens, promoting THC switch-on, but the atmosphere counteracts this by increasing net freshwater input. This increases the extent of THC bi-stability in this version of the model. Electronic supplementary material The online version of this article (doi:) contains supplementary material, which is available to authorized users.  相似文献   

Quantifying strain birefringence halos around inclusions in diamond   总被引：1，自引：0，他引：1  

D. Howell  I. G. Wood  D. P. Dobson  A. P. Jones  L. Nasdala  J. W. Harris 《Contributions to Mineralogy and Petrology》2010,160(5):705-717

The pressure and temperature conditions of formation of natural diamond can be estimated by measuring the residual stress that an inclusion remains under within a diamond. Raman spectroscopy has been the most commonly used technique for determining this stress by utilising pressure-sensitive peak shifts in the Raman spectrum of both the inclusion and the diamond host. Here, we present a new approach to measure the residual stress using quantitative analysis of the birefringence induced in the diamond. As the analysis of stress-induced birefringence is very different from that of normal birefringence, an analytical model is developed that relates the spherical inclusion size, R _i, host diamond thickness, L, and measured value of birefringence at the edge of the inclusion, \Updelta n(R_\texti )_\textav \Updelta n(R_{\text{i}} )_{\text{av}} , to the peak value of birefringence that has been encountered; to first order \Updelta n_\textpk = (3/4)(L/R_\texti )  \Updelta n(R_\texti )_\textav \Updelta n_{\text{pk}} = (3/4)(L/R_{\text{i}} ) \, \Updelta n(R_{\text{i}} )_{\text{av}} . From this birefringence, the remnant pressure (P _i) can be calculated using the photoelastic relationship \Updelta n_\textpk = - (3/4)n³ q_\textiso P_\texti \Updelta n_{\text{pk}} = - (3/4)n^{3} q_{\text{iso}} P_{\text{i}} , where q _iso is a piezo-optical coefficient, which can be assumed to be independent of crystallographic orientation, and n is the refractive index of the diamond. This model has been used in combination with quantitative birefringence analysis with a MetriPol system and compared to the results from both Raman point and 2D mapping analysis for a garnet inclusion in a diamond from the Udachnaya mine (Russia) and coesite inclusions in a diamond from the Finsch mine (South Africa). The birefringence model and analysis gave a remnant pressure of 0.53 ± 0.01 GPa for the garnet inclusion, from which a source pressure was calculated as 5.7 GPa at 1,175°C (temperature obtained from IR analysis of the diamond host). The Raman techniques could not be applied quantitatively to this sample to support the birefringence model; they were, however, applied to the largest coesite inclusion in the Finsch sample. The remnant pressure values obtained were 2.5 ± 0.1 GPa (birefringence), 2.5 ± 0.3 GPa (2D Raman map), and 2.5–2.6 GPa (Raman point analysis from all four inclusions). However, although the remnant pressures from the three methods were self-consistent, they led to anomalously low source pressure of 2.9 GPa at 1,150°C (temperature obtained from IR analysis) raising serious concerns about the use of the coesite-in-diamond geobarometer.  相似文献   

Thick sections of layered ultramafic cumulates in the Oman ophiolite revealed by an airborne hyperspectral survey: Petrogenesis and relationship to mantle diapirism     

Harold Clénet  Georges Ceuleneer  Patrick Pinet  Bénédicte Abily  Yves Daydou  Esther Harris  Isma Amri  Céline Dantas 《Lithos》2010,114(3-4):265-281

Using the HyMap instrument, we have acquired visible and near infrared hyperspectral data over the Maqsad area of the Oman ophiolite (~ 15 × 60 km). This survey allowed us to identify and map the distribution of clinopyroxene-rich cumulates (inter-layered clinopyroxenites and wehrlites) whose occurrence was previously undocumented in this area. The cumulates reach several hundred meters in thickness and crop out at distances exceeding 15 km on both sides of the Maqsad former spreading centre. They occur either in mantle harzburgites, as km-sized layered intrusions surrounded by fields of pegmatitic dykes consisting of orthopyroxene-rich pyroxenite and gabbronorites, or at the base of the crustal section where they are conformably overlain by cumulate gabbros. These ultramafic cumulates crystallized from silica- and Mg-rich melts derived from a refractory mantle source (e.g. high Cr#, low [Al₂O₃], low [TiO₂]). These melts are close to high-Ca boninites, although, strictly speaking, not perfect equivalents of present-day, supra-subduction zone, boninites. Chemical stratigraphy reveals cycles of replenishment, mixing and fractional crystallization from primitive (high Mg#) melts, typical of open magma chambers and migration of inter-cumulus melts. The TiO₂ content of clinopyroxene is always low (≤ 0.2 wt.%) but quite variable compared to the associated pegmatites that are all derived from a source ultra-depleted in high field strength elements (HFSE). This variability is not caused by fractional crystallization alone, and is best explained by hybridization between the ultra-depleted melts (parent melts of the pegmatites) and the less depleted mid-ocean ridge basalts (MORB) parent of the dunitic–troctolitic–gabbroic cumulates making up the crustal section above the Maqsad diapir.We propose that, following a period of magma-starved spreading, the Maqsad mantle diapir, impregnated with tholeiitic melts of MORB affinity, reached shallow depths beneath the ocean ridge. This diapir induced melting of the formerly accreted and hydrothermally altered lithosphere. At this stage, these boninitic-like lithospheric melts crystallized as pegmatitic dykes. As the diapir continued to rise, the amount of MORB reaching shallow depths increased, together with the surrounding temperature, leading to the formation of magma chambers where the crystallization of layered cumulates became possible. These cumulates remained rich in pyroxene and devoid of plagioclase as long as the contribution of MORB-derived melts was moderate relative to the lithospheric-derived melts. As the contribution of MORB to the refilling of the magma chamber increased, gabbroic cumulates started to crystallize.  相似文献   

The Use of Geographically Weighted Regression for Spatial Prediction: An Evaluation of Models Using Simulated Data Sets   总被引：5，自引：0，他引：5  

P. Harris  A. S. Fotheringham  R. Crespo  M. Charlton 《Mathematical Geosciences》2010,42(6):657-680

Increasingly, the geographically weighted regression (GWR) model is being used for spatial prediction rather than for inference. Our study compares GWR as a predictor to (a) its global counterpart of multiple linear regression (MLR); (b) traditional geostatistical models such as ordinary kriging (OK) and universal kriging (UK), with MLR as a mean component; and (c) hybrids, where kriging models are specified with GWR as a mean component. For this purpose, we test the performance of each model on data simulated with differing levels of spatial heterogeneity (with respect to data relationships in the mean process) and spatial autocorrelation (in the residual process). Our results demonstrate that kriging (in a UK form) should be the preferred predictor, reflecting its optimal statistical properties. However the GWR-kriging hybrids perform with merit and, as such, a predictor of this form may provide a worthy alternative to UK for particular (non-stationary relationship) situations when UK models cannot be reliably calibrated. GWR predictors tend to perform more poorly than their more complex GWR-kriging counterparts, but both GWR-based models are useful in that they provide extra information on the spatial processes generating the data that are being predicted.  相似文献   

Transient climate changes in a perturbed parameter ensemble of emissions-driven earth system model simulations     

James M. Murphy  Ben B. B. Booth  Chris A. Boulton  Robin T. Clark  Glen R. Harris  Jason A. Lowe  David M. H. Sexton 《Climate Dynamics》2014,43(9-10):2855-2885

We describe results from a 57-member ensemble of transient climate change simulations, featuring simultaneous perturbations to 54 parameters in the atmosphere, ocean, sulphur cycle and terrestrial ecosystem components of an earth system model (ESM). These emissions-driven simulations are compared against the CMIP3 multi-model ensemble of physical climate system models, used extensively to inform previous assessments of regional climate change, and also against emissions-driven simulations from ESMs contributed to the CMIP5 archive. Members of our earth system perturbed parameter ensemble (ESPPE) are competitive with CMIP3 and CMIP5 models in their simulations of historical climate. In particular, they perform reasonably well in comparison with HadGEM2-ES, a more sophisticated and expensive earth system model contributed to CMIP5. The ESPPE therefore provides a computationally cost-effective tool to explore interactions between earth system processes. In response to a non-intervention emissions scenario, the ESPPE simulates distributions of future regional temperature change characterised by wide ranges, and warm shifts, compared to those of CMIP3 models. These differences partly reflect the uncertain influence of global carbon cycle feedbacks in the ESPPE. In addition, the regional effects of interactions between different earth system feedbacks, particularly involving physical and ecosystem processes, shift and widen the ESPPE spread in normalised patterns of surface temperature and precipitation change in many regions. Significant differences from CMIP3 also arise from the use of parametric perturbations (rather than a multimodel ensemble) to represent model uncertainties, and this is also the case when ESPPE results are compared against parallel emissions-driven simulations from CMIP5 ESMs. When driven by an aggressive mitigation scenario, the ESPPE and HadGEM2-ES reveal significant but uncertain impacts in limiting temperature increases during the second half of the twenty-first century. Emissions-driven simulations create scope for development of errors in properties that were previously prescribed in coupled ocean–atmosphere models, such as historical CO₂ concentrations and vegetation distributions. In this context, historical intra-ensemble variations in the airborne fraction of CO₂ emissions, and in summer soil moisture in northern hemisphere continental regions, are shown to be potentially useful constraints, subject to uncertainties in the relevant observations. Our results suggest that future climate-related risks can be assessed more comprehensively by updating projection methodologies to support formal combination of emissions-driven perturbed parameter and multi-model earth system model simulations with suitable observational constraints. This would provide scenarios underpinned by a more complete representation of the chain of uncertainties from anthropogenic emissions to future climate outcomes.  相似文献