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91.
The extent to which riverine Os is trapped in a temperate estuary was the aim of this study. The behavior of Os through the Hudson River, East River and the Long Island Sound (LIS) system is addressed using both natural Os and anthropogenically mobilized Os. The Os concentration ([Os]) and isotopic composition (187Os/188Os) of the Mid-Atlantic Bight as inferred from the analysis of a water sample of 31‰ salinity (S) at Vineyard Sound, MA are 46 fM and 1.070, respectively. In comparison, the Hudson River at Newburgh, NY has [Os] = 68 fM and 187Os/188Os = 1.265. The Os concentration of the East River at the Whitestone Bridge is 51 fM and remains essentially constant proceeding eastward in the LIS despite the increase of salinity from 20‰ towards the higher value of the Mid-Atlantic Bight. The 187Os/188Os ratio of water at Whitestone Bridge is 0.945 and increases eastward through the Sound to 0.979 at 7 km and then to 1.019 at 39.6 km. The behavior of Os through LIS appears to be conservative at S > 20‰. On the basis of Os concentration and isotopic composition we infer that anthropogenic Os is being added to the East River through sewers with the likely isotopic ratio of ∼0.13 and that about 24% of riverine Os must be removed at S ? 20‰. There is a net transport of about 0.4-1 mole of anthropogenic Os per year from the East River into the LIS. The residence time of Os in the ocean at present must be about 39,000 years, unless an independent source of supply of Os can be identified. 相似文献
92.
Uwe Mikolajewicz Matthias Gröger Ernst Maier-Reimer Guy Schurgers Miren Vizcaíno Arne M. E. Winguth 《Climate Dynamics》2007,28(6):599-633
A new complex earth system model consisting of an atmospheric general circulation model, an ocean general circulation model,
a three-dimensional ice sheet model, a marine biogeochemistry model, and a dynamic vegetation model was used to study the
long-term response to anthropogenic carbon emissions. The prescribed emissions follow estimates of past emissions for the
period 1751–2000 and standard IPCC emission scenarios up to the year 2100. After 2100, an exponential decrease of the emissions
was assumed. For each of the scenarios, a small ensemble of simulations was carried out. The North Atlantic overturning collapsed
in the high emission scenario (A2) simulations. In the low emission scenario (B1), only a temporary weakening of the deep
water formation in the North Atlantic is predicted. The moderate emission scenario (A1B) brings the system close to its bifurcation
point, with three out of five runs leading to a collapsed North Atlantic overturning circulation. The atmospheric moisture
transport predominantly contributes to the collapse of the deep water formation. In the simulations with collapsed deep water
formation in the North Atlantic a substantial cooling over parts of the North Atlantic is simulated. Anthropogenic climate
change substantially reduces the ability of land and ocean to sequester anthropogenic carbon. The simulated effect of a collapse
of the deep water formation in the North Atlantic on the atmospheric CO2 concentration turned out to be relatively small. The volume of the Greenland ice sheet is reduced, but its contribution to
global mean sea level is almost counterbalanced by the growth of the Antarctic ice sheet due to enhanced snowfall. The modifications
of the high latitude freshwater input due to the simulated changes in mass balance of the ice sheet are one order of magnitude
smaller than the changes due to atmospheric moisture transport. After the year 3000, the global mean surface temperature is
predicted to be almost constant due to the compensating effects of decreasing atmospheric CO2 concentrations due to oceanic uptake and delayed response to increasing atmospheric CO2 concentrations before. 相似文献
93.
94.
We report on dust measurements obtained during the seventh orbit of the Galileo spacecraft about Jupiter. The most prominent
features observed are highly time variable dust streams recorded throughout the Jovian system. The impact rate varied by more
than an order of magnitude with a 5 and 10 hour periodicity, which shows a correlation with Galileo's position relative to
the Jovian magnetic field. This behavior can be qualitatively explained by strong coupling of nanometer-sized dust to the
Jovian magnetic field. In addition to the 5 and 10 h periodicities, a longer period which is compatible with Io's orbital
period is evident in the dust impact rate. This feature indicates that Io most likely is the source of the dust streams. During
a close (3,095 km altitude) flyby at Ganymede on 5 April 1997 an enhanced rate of dust impacts has been observed, which suggests
that Ganymede is a source of ejecta particles. Within a distance of about 25 RJ(Jupiter radius, RJ= 71,492 km) from Jupiter impacts of micrometer-sized particles have been recorded which could be particles on bound orbits
about Jupiter.
This revised version was published online in July 2006 with corrections to the Cover Date. 相似文献
95.
Prof. Dr. Karl Krejci-Graf 《International Journal of Earth Sciences》1981,70(3):1263-1275
Zusammenfassung Die Verfolgung tektonischer Strukturen in die Tiefe ist nur bei kontinuierlicher Verformung einfach. Physikalische oder strukturelle Änderungen innerhalb der sich verformenden Körper, sowie Änderungen in der Richtung der verformenden KrÄfte, bedingungen diskontinuierliche Änderungen in den erzeugten Strukturen, z. B. Scheitelverschiebung, Rückverformung, DurchprÄgung überwÄltigter Strukturen.
To pursue tectonical structures beyond observations is simple only if deformations are continuous. Changes of physical or structural properties of rocks, as well as changes in the direction of transforming forces, create discontinuous alterations within thus generated structures, e. g. displacement of apex, retrograde transformation, penetration of subdued lower structures.
Résumé Le prolongement des structures tectoniques en profondeur n'est simple que dans le cas de déformations continues. Des changements de propriétés physiques ou structurales durant les déformations à l'intérieur des corps tectoniques, ainsi que des modifications dans la direction des forces actives, produisent des transformations discontinues dans les structures engendrées, p. ex. déplacements des sommets des anticlinaux, déformations en retour, rejeu de structures anciennes et leur pénétration dans les structures superposées; etc.
. , : .: , , .相似文献
96.
Prof. Dr. Karl Fuchs 《International Journal of Earth Sciences》1975,64(1):700-716
Specially planned explosion seismic measurements in the oceans provided conclusive evidence that the velocity of Pn-waves depends on the azimuths of the direction of propagation through the upper mantle. The orientation of this azimuthal anisotropy suggests a close connection with the generation of the oceanic lithosphere: in the Pacific the maximum and minimum velocities are measured in a perpendicular and parallel direction to the axis of the oceanic ridges respectively. The observed anisotropy is so strong that a number of models for the generation of anisotropy can be discarded. The most likely cause is a preferred orientation of minerals. The generation of the anisotropy can be simulated in the laboratory under P-T-conditions of the upper mantle. The influence of the rate of deformation can be studied as well. A recent analysis of explosion seismic data in Southern Germany suggests that the continental upper mantle possesses also a velocity anisotropy dependent on azimuth. 相似文献
97.
98.
The fractionation of the oxygen isotopes between water molecules from different sites in CuSO4 · 5H2O has been measured for crystallization temperatures of 25, 40 and 50°C. The temperature dependence found provides a basis for the determination of crystallization temperatures from such intracrystalline oxygen isotope effects; also for hydrated crystals of mineralogical and geological interest. Necessary suppositions for the application of this method are discussed. 相似文献
99.
100.