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51.
Bruce E. Marti 《Geoforum》1986,17(3-4)
The marketing of port forelands will become increasingly more important in an era of load center development resulting from container technologies. In this paper, we have provided a mechanism for identifying overseas port marketing areas where trade development and port promotion should be exercised. The Port of Miami's trade relationships were the foci of this study. Location quotients served to highlight the competitive aspect of port facilities. 相似文献
52.
The Gd isotopic composition in 19 lunar rock and soil samples from three Apollo sites is reported. The analytical techniques and the high precision mass spectrometric measurements are discussed. Enrichments in158GdO/157GdO due to neutron capture range up to 0.75%. Integrated ‘thermal’ neutron fluxes derived from the isotopic anomalies of Gd are compared with spallation Kr data from aliquot samples to construct a model which gives both average cosmic-ray irradiation depths and effective neutron exposure ages (Tn) for some rocks. In the case of rock 12053, this yields an average sample location of ∼300 g/cm2 below the lunar surface and an effective irradiation age of ∼230 my, compared to 99 my obtained by the81Kr-Kr method. Rock 14310 is the first lunar sample where Kr anomalies due to resonance neutron capture in Br are observed. A81Kr-Kr exposure age of 262 ± 7 my is calculated for this rock. 相似文献
53.
M. Wilding Sharon Webb D. Dingwell Giray Ablay Joan Marti 《Contributions to Mineralogy and Petrology》1996,125(2-3):151-160
Silicate melts form glasses in a variety of geological environments. The relaxation (equilibration) of the frozen glass structure
provides a means of investigating the quench rates of natural glasses, and this cooling history provides an important constraint
for models of melt dynamics. Phonolite glasses from the central volcanic edifice of Tenerife, Canary Islands indicate a range
of five orders of magnitude cooling rate, determined by modeling the relaxation of the structure-dependent property, enthalpy
(H) across the glass transition. The relaxation of enthalpy is determined by heat capacity (c
p
= ΔH/ΔT) measurement of natural glass samples by differential scanning calorimetry (DSC). Upon heating, the heat capacity curve in
the vicinity of the glass transition has a geometry characteristic of the previous cooling rate. A series of thermal treatments
applied to each individual sample results in a set of sample-specific parameters which are used to model the heat capacity
curve of the naturally cooled glass. The cooling rate is then derived. The equivalence of shear and enthalpic relaxation enables
the relaxation of enthalpy for these volcanic samples to be described by a general term for the evolution of fictive temperature.
Quench rates for thirty-one glasses are calculated to be within the range 10°C s–1 to 7°C per day. The cooling rates quoted are linear approximations across the glass transition. Within different volcanic
facies cooling rates depend on several factors. The most rapidly cooled glasses occur where samples lose heat by radiation
from the surface. Our analyses indicate that in certain environments, a natural annealing process results in slow quench rates.
This is interpreted as either a slow initial cooling process or the reheating of a glass to an annealing temperature within
the glass transition interval. The latter results in relaxation to a lower temperature structure. Controls on these processes
include the initial temperature and dissipation of thermal energy from the volcanic body. Our results are consistent with
an influence of volatiles on quench rates in volcanic bombs where glass adjacent to vesicular layers is relatively rapidly
quenched. We interpret this as a rapid quench rate frozen into the glass resulting from a change in viscosity due to volatile
degassing. In lava flows, the conduction of heat from the hot flow interior controls the cooling process and diminishes the
effect of volatile exsolution. Relaxation geospeedometry can be applied to glass samples from a variety of geological environments
where cooling rates cannot be measured directly. Such measurements provide a means of determining cooling rates for a variety
of volcanic processes, an independent calibration for existing temperature and time data and a means for testing cooling-rate-dependent
models.
Received: 9 January 1996 / Accepted: 13 May 1996 相似文献
54.
Zenobi R Philippoz JM Zare RN Wing MR Bada JL Marti K 《Geochimica et cosmochimica acta》1992,56(7):2899-2905
We have analyzed the H4 ordinary chondrite Forest Vale for polycyclic aromatic hydrocarbons (PAHs) using two-step laser mass spectrometry (L2MS) and for amino acids using a standard chromatographic method. Indigenous PAHs were identified in the matrices of freshly cleaved interior faces but could not be detected in pulverized silicates and chondrules. No depth dependence of the PAHs was found in a chipped interior piece. Amino acids, taken from the entire sample, consisted of protein amino acids that were nonracemic, indicating that they are terrestrial contaminants. The presence of indigenous PAHs and absence of indigenous amino acids provides support for the contention that different processes and environments contributed to the synthesis of the organic matter in the solar system. 相似文献
55.
56.
Impact of the LMDZ atmospheric grid configuration on the climate and sensitivity of the IPSL-CM5A coupled model 总被引:3,自引:3,他引:0
Frédéric Hourdin Marie-Alice Foujols Francis Codron Virginie Guemas Jean-Louis Dufresne Sandrine Bony Sébastien Denvil Lionel Guez François Lott Josefine Ghattas Pascale Braconnot Olivier Marti Yann Meurdesoif Laurent Bopp 《Climate Dynamics》2013,40(9-10):2167-2192
The IPSL-CM5A climate model was used to perform a large number of control, historical and climate change simulations in the frame of CMIP5. The refined horizontal and vertical grid of the atmospheric component, LMDZ, constitutes a major difference compared to the previous IPSL-CM4 version used for CMIP3. From imposed-SST (Sea Surface Temperature) and coupled numerical experiments, we systematically analyze the impact of the horizontal and vertical grid resolution on the simulated climate. The refinement of the horizontal grid results in a systematic reduction of major biases in the mean tropospheric structures and SST. The mid-latitude jets, located too close to the equator with the coarsest grids, move poleward. This robust feature, is accompanied by a drying at mid-latitudes and a reduction of cold biases in mid-latitudes relative to the equator. The model was also extended to the stratosphere by increasing the number of layers on the vertical from 19 to 39 (15 in the stratosphere) and adding relevant parameterizations. The 39-layer version captures the dominant modes of the stratospheric variability and exhibits stratospheric sudden warmings. Changing either the vertical or horizontal resolution modifies the global energy balance in imposed-SST simulations by typically several W/m2 which translates in the coupled atmosphere-ocean simulations into a different global-mean SST. The sensitivity is of about 1.2 K per 1 W/m2 when varying the horizontal grid. A re-tuning of model parameters was thus required to restore this energy balance in the imposed-SST simulations and reduce the biases in the simulated mean surface temperature and, to some extent, latitudinal SST variations in the coupled experiments for the modern climate. The tuning hardly compensates, however, for robust biases of the coupled model. Despite the wide range of grid configurations explored and their significant impact on the present-day climate, the climate sensitivity remains essentially unchanged. 相似文献
57.
M. Latif K. Sperber J. Arblaster P. Braconnot D. Chen A. Colman U. Cubasch C. Cooper P. Delecluse D. Dewitt L. Fairhead G. Flato T. Hogan M. Ji M. Kimoto A. Kitoh T. Knutson H. Le Treut T. Li S. Manabe O. Marti C. Mechoso G. Meehl S. Power E. Roeckner J. Sirven L. Terray A. Vintzileos R. Voß B. Wang W. Washington I. Yoshikawa J. Yu S. Zebiak 《Climate Dynamics》2001,18(3-4):255-276
An ensemble of twenty four coupled ocean-atmosphere models has been compared with respect to their performance in the tropical Pacific. The coupled models span a large portion of the parameter space and differ in many respects. The intercomparison includes TOGA (Tropical Ocean Global Atmosphere)-type models consisting of high-resolution tropical ocean models and coarse-resolution global atmosphere models, coarse-resolution global coupled models, and a few global coupled models with high resolution in the equatorial region in their ocean components. The performance of the annual mean state, the seasonal cycle and the interannual variability are investigated. The primary quantity analysed is sea surface temperature (SST). Additionally, the evolution of interannual heat content variations in the tropical Pacific and the relationship between the interannual SST variations in the equatorial Pacific to fluctuations in the strength of the Indian summer monsoon are investigated. The results can be summarised as follows: almost all models (even those employing flux corrections) still have problems in simulating the SST climatology, although some improvements are found relative to earlier intercomparison studies. Only a few of the coupled models simulate the El Niño/Southern Oscillation (ENSO) in terms of gross equatorial SST anomalies realistically. In particular, many models overestimate the variability in the western equatorial Pacific and underestimate the SST variability in the east. The evolution of interannual heat content variations is similar to that observed in almost all models. Finally, the majority of the models show a strong connection between ENSO and the strength of the Indian summer monsoon. 相似文献
58.
Analysis of the Temporal Occurrence of Seismicity at Deception Island (Antarctica). A Nonlinear Approach 总被引:1,自引:0,他引:1
—Deception Island is characterized by small magnitude local events with constant energy flux and very low stress drop. To obtain information about its origin, an interevent time series of 546 events, corresponding to an observational period of two month, has been analyzed. From a statistical point of view, data satisfies a Weibull distribution and presents clustering. A rescaled range analysis reveals that data are not independent, i.e. have memory, and the correlation dimension saturates at 2.2; as a consequence, the system can be modeled as a nonlinear iterative equation with three degrees of freedom that presents chaotic behavior. Taking into account that the average interevent time is of the order of 130 minutes, too short to be only due to tectonic activity, the above results indicate that some other mechanism may coexist with the regional tectonic one. According to several geological and geophysical observations, we suggest that most of the local events may be originated by pressure waves generated by a sudden change of phase, of sea and fresh water infiltrated into the main fractures and faults and also from shallow and confined water-saturated layers. 相似文献
59.
Quantifying the AMOC feedbacks during a 2×CO2 stabilization experiment with land-ice melting 总被引:1,自引:0,他引:1
The response of the Atlantic Meridional Overturning Circulation (AMOC) to an increase in atmospheric CO2 concentration is analyzed using the IPSL-CM4 coupled ocean–atmosphere model. Two simulations are integrated for 70 years
with 1%/year increase in CO2 concentration until 2×CO2, and are then stabilized for further 430 years. The first simulation takes land-ice melting into account, via a simple parameterization,
which results in a strong freshwater input of about 0.13 Sv at high latitudes in a warmer climate. During this scenario, the
AMOC shuts down. A second simulation does not include this land-ice melting and herein, the AMOC recovers after 200 years.
This behavior shows that this model is close to an AMOC shutdown threshold under global warming conditions, due to continuous
input of land-ice melting. The analysis of the origin of density changes in the Northern Hemisphere convection sites allows
an identification as to the origin of the changes in the AMOC. The processes that decrease the AMOC are the reduction of surface
cooling due to the reduction in the air–sea temperature gradient as the atmosphere warms and the local freshening of convection
sites that results from the increase in local freshwater forcing. Two processes also control the recovery of the AMOC: the
northward advection of positive salinity anomalies from the tropics and the decrease in sea-ice transport through the Fram
Strait toward the convection sites. The quantification of the AMOC related feedbacks shows that the salinity related processes
contribute to a strong positive feedback, while feedback related to temperature processes is negative but remains small as
there is a compensation between heat transport and surface heat flux in ocean–atmosphere coupled model. We conclude that in
our model, AMOC feedbacks amplify land-ice melting perturbation by 2.5. 相似文献
60.
Past and future polar amplification of climate change: climate model intercomparisons and ice-core constraints 总被引:2,自引:2,他引:2
V. Masson-Delmotte M. Kageyama P. Braconnot S. Charbit G. Krinner C. Ritz E. Guilyardi J. Jouzel A. Abe-Ouchi M. Crucifix R. M. Gladstone C. D. Hewitt A. Kitoh A. N. LeGrande O. Marti U. Merkel T. Motoi R. Ohgaito B. Otto-Bliesner W. R. Peltier I. Ross P. J. Valdes G. Vettoretti S. L. Weber F. Wolk Y. YU 《Climate Dynamics》2006,26(5):513-529
Climate model simulations available from the PMIP1, PMIP2 and CMIP (IPCC-AR4) intercomparison projects for past and future
climate change simulations are examined in terms of polar temperature changes in comparison to global temperature changes
and with respect to pre-industrial reference simulations. For the mid-Holocene (MH, 6,000 years ago), the models are forced
by changes in the Earth’s orbital parameters. The MH PMIP1 atmosphere-only simulations conducted with sea surface temperatures
fixed to modern conditions show no MH consistent response for the poles, whereas the new PMIP2 coupled atmosphere–ocean climate
models systematically simulate a significant MH warming both for Greenland (but smaller than ice-core based estimates) and
Antarctica (consistent with the range of ice-core based range). In both PMIP1 and PMIP2, the MH annual mean changes in global
temperature are negligible, consistent with the MH orbital forcing. The simulated last glacial maximum (LGM, 21,000 years
ago) to pre-industrial change in global mean temperature ranges between 3 and 7°C in PMIP1 and PMIP2 model runs, similar to
the range of temperature change expected from a quadrupling of atmospheric CO2 concentrations in the CMIP simulations. Both LGM and future climate simulations are associated with a polar amplification
of climate change. The range of glacial polar amplification in Greenland is strongly dependent on the ice sheet elevation
changes prescribed to the climate models. All PMIP2 simulations systematically underestimate the reconstructed glacial–interglacial
Greenland temperature change, while some of the simulations do capture the reconstructed glacial–interglacial Antarctic temperature
change. Uncertainties in the prescribed central ice cap elevation cannot account for the temperature change underestimation
by climate models. The variety of climate model sensitivities enables the exploration of the relative changes in polar temperature
with respect to changes in global temperatures. Simulated changes of polar temperatures are strongly related to changes in
simulated global temperatures for both future and LGM climates, confirming that ice-core-based reconstructions provide quantitative
insights on global climate changes.
An erratum to this article can be found at 相似文献