Sea‐ice dynamics and CO2 sensitivity in a global climate model     

David Pollard  Starley L. Thompson 《大气与海洋》2013,51(2):449-467

Abstract

Present‐day results and CO₂ sensitivity are described for two versions of a global climate model (genesis) with and without sea‐ice dynamics. Sea‐ice dynamics is modelled using the cavitating‐fluid method of Flato and Hibler (1990, 1992). The atmospheric general circulation model originated from the NCAR Community Climate Model version 1, but is heavily modified to include new treatments of clouds, penetrative convection, planetary boundary‐layer mixing, solar radiation, the diurnal cycle and the semi‐Lagrangian transport of water vapour. The surface models include an explicit model of vegetation (similar to BATS and SiB), multilayer models of soil, snow and sea ice, and a slab ocean mixed layer.

When sea‐ice dynamics is turned off, the CO₂‐induced warming increases drastically around ～60–80°S in winter and spring. This is due to the much greater (and unrealistic) compactness of the Antarctic ice cover without dynamics, which is reduced considerably when CO₂ is doubled and exposes more open ocean to the atmosphere. With dynamics, the winter ice is already quite dispersed for 1 × CO₂ so that its compactness does not decrease as much when CO₂ is doubled.  相似文献   

Fluid-absent (dehydration) melting of biotite in metapelites in the early stages of crustal anatexis   总被引：48，自引：1，他引：48  

Nicole Le Breton  Alan Bruce Thompson 《Contributions to Mineralogy and Petrology》1988,99(2):226-237

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A MEG study of the olivine and spinel forms of Mg2SiO4     

Mark D. Jackson  Roy G. Gordon 《Physics and Chemistry of Minerals》1988,15(6):514-520

In this paper we present a theoretical investigation of the structures and relative stability of the olivine and spinel phases of Mg₂SiO₄. We use both a purely ionic model, based on the Modified Electron Gas (MEG) model of intermolecular forces, and a bond polarization model, developed for low pressure silica phases, to investigate the role of covalency in these compounds. The standard MEG ionic model gives adequate structural results for the two phases but incorrectly predicts the spinel phase to be more stable at zero pressure. This is mainly because the ionic modeling of Mg₂SiO₄ only accounts for 95 percent of the lattice energy. The remainder can be attributed to covalency and many-body effects. An extension of the MEG ionic model using “many-body” pair potentials corrects the phase stability error, but predicts structures which are in poorer agreement with experiment than the standard ionic approach. In addition, calculations using these many-body pair potentials can only account for 10 percent of the missing lattice energy. This model predicts an olivine-spinel phase transition of 8 GPa, below the experimental value of 20 GPa. Therefore, in order to understand more fully the stability of these structures we must consider polarization. A two-shell bond polarization model enhances the stability of both structures, with the olivine structure being stabilized more. This model predicts a phase transition at about 80 GPa, well above the observed value. Also, the olivine and spinel structures calculated with this approach are in poorer agreement with experiment than the ionic model. Therefore, based on our investigations, to properly model covalency in Mg₂SiO₄, a treatment more sophisticated than the two-shell model is needed.  相似文献   

Limitations and feasibility of the land disposal of organic solvent-contaminated wastes     

W. R. Roy  R. A. Griffin  J. K. Mitchell  R. A. Mitchell 《Environmental Geology》1989,13(3):225-231

The limitations and feasibility of the land disposal of solid wastes containing organic solvents and refrigerants (chlorinated fluorocarbons) were investigated by evaluating the attenuation capacity of a hypothetical waste-disposal site by numerical modeling. The basic theorem of this approach was that the land disposal of wastes would be environmentally acceptable if subsurface attenuation reduced groundwater concentrations of organic compounds to concentrations that were less than health-based, water-quality criteria. Computer simulations indicated that the predicted concentrations of 13 of 33 organic compounds in groundwater would be less than their health-based criteria. Hence, solid wastes containing these compounds could be safely disposed at the site. The attenuation capacity of the site was insufficient to reduce concentrations of four compounds to safe levels without limiting the amount of mass available to leach into groundwater. Threshold masses based on time-dependent migration simulations were estimated for these compounds. The remaining 16 compounds, which consisted mainly of chlorinated hydrocarbons and fluorocarbons could not be safely landfilled without severe restrictions on the amounts disposed. These organic compounds were candidates to ban from land disposal.  相似文献   

Cumulate gabbros from the Southwest Indian Ridge, 54°S-7° 16′ E: implications for magmatic processes at a slow spreading ridge     

Peter S. Meyer  Henry J. B. Dick  Geoffrey Thompson 《Contributions to Mineralogy and Petrology》1989,103(1):44-63

A diverse volcanic and plutonic rock suite was recovered from the center of the 80 km long ridge segment of the Southwest Indian Ridge (54°S, 7°16 E) between the Islas Orcadas and Shaka Fracture Zones. The cumulus nature of the gabbroic rocks in the suite is indicated by phase, modal and cryptic layering, igneous lamination, and low incompatible element abundances. We present a mass-balance model for calculating the proportions and compositions of cumulus phases and crystallized intercumulus liquid from bulk-rock major element compositions. The model is based on the ability to define a compositional array of basaltic liquids and on the assumption that cumulus minerals are initially in equilibrium with trapped liquid. Calculated proportions of trapped liquid range from 3%–15%; values that are characteristic of adcumulates to mesocumulates. Models of postcumulus crystallization indicate significant enrichments of incompatible elements and buffering of compatible elements in residual trapped liquids, thus explaining the high TiO₂ contents observed in magnesian clinopyroxenes. Cumulus phase assemblages and compositions suggest solidification in shallow level magma chambers, but disequilibrium plagioclase compositions suggest some crystallization at greater depth. Furthermore, basalt compositions projected onto the olivine-clinopyroxenequartz pseudoternary suggest magma generation over a range of pressures (from less than 10 to greater than 20 kb) as well as polybaric fractional crystallization. We suggest that the Southwest Indian Ridge is characterized by low magma supply with small batches of melt that either ascend directly to the surface having undergone limited polybaric crystallization or are trapped in shallow crustal magma chambers where they evolve and solidify to form cumulate gabbros. The adcumulus nature of the gabbros investigated here suggests slow cooling rates typical of large intrusions implying relatively large, but ephemeral magma chambers below segments of the Southwest Indian Ridge.  相似文献   

IGU Commission on Health and Developement     

Helen Roy  Eric Wajnberg 《GeoJournal》1989,18(4):451-451

The International Geographical Union Reports

IGU Commission on Population Geography  相似文献   

Occurrence of thorite and radioactive zircon in syenite pegmatite,North of Ashwaraopet,Khammam district,Andhra Pradesh,India     

K. Surya Prakash Rao  R. S. N. Sastry  Gautam Roy 《Journal of Earth System Science》1989,98(2):183-187

This paper reports the occurrence of thorite and confirms the earlier find of radioactive zircon by Subbarao, Murali and others from syenite pegmatite in the Vinayakapuram-Kunavaram alkaline belt in the Khammam district of Andhra Pradesh, India. Thorite has also been found as residual concentrations in soil overlying the pegmatite.  相似文献   

A simplified computational approach for prediction of transient climatic conditions in underground mine airways     

T. R. Roy 《Geotechnical and Geological Engineering》1993,11(1):15-23

Summary A simplified approach for prediction of transient climatic conditions in an underground airway os presented. The dry surface temperature of the airway is calculated using a finite difference scheme, whereas the wet surface temperature is determined following the concept of pseudo-base-temperature of air and using the value of thermal gradient at the dry surface as obtained from the finite difference solution of the temperature profile in the dry rock. The air-current temperatures are regularly evaluated after a suitable time span so as to simulate a real-case situation, and the re-evaluated air-current temperatures are used for further calculations. For increasing age of the airway the wet surface temperature obtained by the finite difference scheme, with an appropriate value of thermal diffusivity, is compared with its value determined by the pseudo-base-temperature approach.  相似文献   

Characterisation of ecological parameters in tropical forest community—A remote sensing approach     

P S Roy  Sarnam Singh  M C Porwal 《Journal of the Indian Society of Remote Sensing》1993,21(3):127-149

Satellite Remote Sensing data has been used for vegetation mapping, initial stratification, distribution of sample plots and for calculating the area under different vegetation types. Primary and secondary analyses of vegetation has been done using phytosociological ground data collected from sample piots to assess the ecological importance of different species. Interrelationships among different communities have been evaluated through various available indices. The spatial distribution and vegetation analysis indicate that commercial extraction of natural forests of Andaman has set in retrogression. The evergreen forests subjected to shorter rotation of commercial exploitation are being invaded with seral deciduous species. The study highlights the status of forests (spatial and community) and stresses the need to conserve germplasm present in the natural evergreen forests.  相似文献   

Comparison of methods used in the measurement of precipitation and evaporation     

R. D. Thompson  F. M. Shaw 《Theoretical and Applied Climatology》1990,42(1):27-32

Summary The measurement of evaporation and precipitation continues to be most problematic, particularly in terms of the accuracy of the instruments used and their standardization world-wide. This paper analyzes daily data from three rain gauges and two evaporimeters over a five-year period and correlates observed differences with the prevailing meteorological conditions. It was determined that ground-level gauges and large evaporation tanks provide the most acceptable and representative measurements from instruments currently in use. However, new developments are necessary for improved accuracy and world-wide adoption.With 2 Figures  相似文献