Discussion of the new kinematic mantle convection theory     

Uwe Walzer 《Pure and Applied Geophysics》1973,105(1):696-712

Summary First of all it is shown that the nine fundamental suppositions of the kinematic theory of the mantle convection fit well into the image which is obtained from the mantle by other geophysical results. The question of episodicity of the orogenesis is dealt with in connection with the questions of steadiness and unsteadiness of the convection. Moreover it is shown that the ocean-spreading theory and the kinematic mantle convection theory are compatible with each other in their main aspects and that they complement each other.  相似文献   

The infrared spectrum of asteroid 433 Eros     

Harold P. Larson  Uwe Fink  Richard R. Treffers  Thomas N. Gautier 《Icarus》1976,28(1):95-103

The mineralogical composition of asteroid Eros has been determined from its infrared spectrum (0.9–2.7μm; 28cm^?1 resolution). Major minerals include metallic NiFe and pyroxene; no spectroscopic evidence for olivine or plagioclase feldspar was found. The IR spectrum of Eros is most consistent with a stony-iron composition.  相似文献   

Lithium isotope fractionation in the southern Cascadia subduction zone   总被引：2，自引：0，他引：2  

Tom&#x; Magna  Uwe Wiechert  Timothy L. Grove  Alex N. Halliday 《Earth and Planetary Science Letters》2006,250(3-4):428-443

We present lithium (Li) abundances and isotope compositions for a suite of anhydrous olivine tholeiites (HAOTs) and hydrous basalt-andesitic (BA) lavas from the Mt. Shasta and Medicine Lake regions, California. The values of δ⁷Li vary from + 0.9‰ to + 6.4‰ and correlate inversely with distance from the trench. These data are consistent with continuous isotope fractionation of Li during dehydration of the subducted oceanic lithosphere, an interpretation corroborated by uniformly high pre-eruptive H₂O contents in basaltic andesites accompanied by high Li, Rb, Sr, Ba and Pb abundances. The subduction-derived component that was added to these hydrous magmas is shown to be very similar beneath both Mt. Shasta and Medicine Lake volcanoes despite characteristically distinct Li isotope compositions in the magmas themselves. More evolved andesites and dacites from Mt. Shasta have δ⁷Li from + 2.8 to + 6.9‰ which is identical with the range obtained for HAOTs and BA lavas from Mt. Shasta. Therefore, Li isotopes do not provide evidence for any other crustal component admixed to Mt. Shasta andesites or dacites during magmatic differentiation and magma mixing in the crust.  相似文献   

Variability of Fram Strait sea ice export: causes, impacts and feedbacks in a coupled climate model   总被引：1，自引：2，他引：1  

Torben Koenigk  Uwe Mikolajewicz  Helmuth Haak  Johann Jungclaus 《Climate Dynamics》2006,26(1):17-34

Analyses of a 500-year control integration of the global coupled atmosphere–sea ice–ocean model ECHAM5.0/MPI-OM show a high variability in the ice export through Fram Strait on interannual to decadal timescales. This variability is mainly determined by variations in the sea level pressure gradient across Fram Strait and thus geostrophic wind stress. Ice thickness anomalies, formed at the Siberian coast and in the Chukchi Sea, propagate across the Arctic to Fram Strait and contribute to the variability of the ice export on a timescale of about 9 years. Large anomalies of the ice export through Fram Strait cause fresh water signals, which reach the Labrador Sea after 1–2 years and lead to significant changes in the deep convection. The associated anomalies in ice cover and ocean heat release have a significant impact on air temperature in the Labrador Sea and on the large-scale atmospheric circulation. This affects the sea ice transport and distribution in the Arctic again. Sensitivity studies, simulating the effect of large ice exports through Fram Strait, show that the isolated effect of a prescribed ice/fresh water anomaly is very important for the climate variability in the Labrador Sea. Thus, the ice export through Fram Strait can be used for predictability of Labrador Sea climate up to 2 years in advance.  相似文献   

Long-term effects of anthropogenic CO<Subscript>2</Subscript> emissions simulated with a complex earth system model     

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   

The tidal stream in the German Bight     

Christoph Brockmann  Wolfgang Lange  Dr. Ekkehard Mittelstaedt  Kai C. Soetje 《Ocean Dynamics》1981,34(2):56-60

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Investigation of groundwater residence times during bank filtration in Berlin: a multi‐tracer approach     

Gudrun Massmann  Jürgen Sültenfuß  Uwe Dünnbier  Andrea Knappe  Thomas Taute  Asaf Pekdeger 《水文研究》2008,22(6):788-801

Berlin relies on induced bank filtration from a broad‐scale, lake‐type surface water system. Because the surface water contains treated sewage, wastewater residues are present in surface water and groundwater. Multiple environmental tracers, including tritium and helium isotopes (³H, ³He, ⁴He), stable isotopes (δ¹⁸O and δ²H) and a number of persistent sewage indicators, such as chloride, boron and a selection of pharmaceutical residues (phenazone‐type analgesics and their metabolites, carbamazepine and anthropogenic gadolinium, Gd_excess), were used to estimate travel times from the surface water to individual production and observation wells at two sites. The study revealed a strong vertical age stratification throughout the upper aquifer, with travel times varying from a few months to several decades in greater depth. Whereas the shallow bank filtrate is characterized by the reflection of the time‐variant tracer input concentrations and young ³H/³He ages, the deeper, older bank filtrate displays no tracer seasonality, ³H/³He ages of a few years to decades and strongly deviating concentrations of several pharmaceutical residues, reflecting concentrations of the source surface water over time. The phenazone‐type pharmaceuticals persist in the aquatic environments for decades. Bank filtration in Berlin is only possible at the sandy lakeshores. In greater water depth, impermeable lacustrine sapropels inhibit infiltration. The young bank filtrate originates from the nearest shore, whereas the older bank filtrate infiltrates at more distant shores. This paper illustrates the importance of using multiple tracer methods, capable of resolving a broad range of residence times, to gain a comprehensive understanding of time‐scales and infiltration characteristics in a bank filtration system. Copyright © 2007 John Wiley & Sons, Ltd.  相似文献   

The mid-depth circulation of the northwestern tropical Atlantic observed by floats     

Matthias Lankhorst  David Fratantoni  Michel Ollitrault  Philip Richardson  Uwe Send  Walter Zenk 《Deep Sea Research Part I: Oceanographic Research Papers》2009,56(10):1615-1632

A comprehensive analysis of velocity data from subsurface floats in the northwestern tropical Atlantic at two depth layers is presented: one representing the Antarctic Intermediate Water (AAIW, pressure range 600–1050 dbar), the other the upper North Atlantic Deep Water (uNADW, pressure range 1200–2050 dbar). New data from three independent research programs are combined with previously available data to achieve blanket coverage in space for the AAIW layer, while coverage in the uNADW remains more intermittent. Results from the AAIW mainly confirm previous studies on the mean flow, namely the equatorial zonal and the boundary currents, but clarify details on pathways, mostly by virtue of the spatial data coverage that sets float observations apart from e.g. shipborne or mooring observations. Mean transports in each of five zonal equatorial current bands is found to be between 2.7 and 4.5 Sv. Pathways carrying AAIW northward beyond the North Brazil Undercurrent are clearly visible in the mean velocity field, in particular a northward transport of 3.7 Sv across 16°N between the Antilles islands and the Mid-Atlantic Ridge. New maps of Lagrangian eddy kinetic energy and integral time scales are presented to quantify mesoscale activity. For the uNADW, mean flow and mesoscale properties are discussed as data availability allows. Trajectories in the uNADW east of the Lesser Antilles reveal interactions between the Deep Western Boundary Current (DWBC) and the basin interior, which can explain recent hydrographic observations of changes in composition of DWBC water along its southward flow.  相似文献   

Brownish inclusions and dark streaks in Libyan Desert Glass: Evidence for high‐temperature melting of the target rock     

Ansgar GRESHAKE  Christian KOEBERL  Jrg FRITZ  W. Uwe REIMOLD 《Meteoritics & planetary science》2010,45(6):973-989

Abstract– Dark streaks and different types of inclusions in Libyan Desert Glass (LDG) collected from the LDG strewn field in Egypt were investigated. Rare transparent spherules enclosed in the glassy matrix are characterized by concentric cracks, irregular internal cracks, intense twinning, and considerable amounts of Ti and Al. Raman spectra show that the spherules are α‐cristobalite. Their occurrence together with lechatelierite indicates quick heating of the source rock to at least 1550 °C, followed by rapid quenching leading to crystallization of β‐cristobalite, which upon cooling inverted into α‐cristobalite. Brownish inclusions are irregularly shaped, elongated objects with smooth contacts to the surrounding glass. They contain small roundish to elliptical droplets, and a few larger angular grains, which compositionally and according to their Raman spectra most closely resemble low‐Ca, Al‐rich orthopyroxene. Composition and texture of the orthopyroxene suggest that the brownish inclusions formed by incomplete melting of an Al‐rich orthopyroxene bearing precursor, e.g., mafic phases present in desert surface sands or also of orthopyroxene‐bearing granulite dykes in the LDG target. Experimental data on Ca‐poor enstatite also support that the inclusions were heated to about 1550 °C. Analyses of dark streaks in LDG reveal high abundances of Al, Ti, Mn, Cr, Fe, and Ni and a pronounced correlation between the abundances of Cr, Mn, Fe, and Ni. As the Fe/Ni, Mn/Ni, and Cr/Ni ratios are all clearly nonchondritic, the source of this material is most likely terrestrial and the dark streaks studied here represent a different type of schlieren compared to those which contain a meteoritic component. These findings suggest LDG formation during a short high‐temperature event. Melting of Al‐rich orthopyroxene bearing target material seems to suggest an asteroid impact rather than a near‐surface airburst.  相似文献   

A New Fossil Termite(Isoptera,Stolotermitidae,Stolotermes)from the Early Miocene of Otago,New Zealand   总被引：1，自引：1，他引：0  

Uwe Kaulfuss  Anthony C. Harris  Daphne E. Lee 《《地质学报》英文版》2010,84(4):705-709

<正>The forewing of a termite from Early Miocene lake sediments in Otago,southern New Zealand is figured and described.It exhibits the generic characters of the damp-wood termite Stolotermes Hagen,but differs from forewings of the known species in size and venation pattern and is described as Stolotermes kupe sp.nov.S.kupe represents the first confident record of fossil Stolotermitidae and extends the fossil record of the family back to the Early Miocene.It also is the first direct evidence of fossil Isoptera from New Zealand,though silicified termite faecal pellets,referable to Kalotermes brauni,have been previously described.S.kupe indicates that Stolotermitidae has been present in the Australasian region since at least the Early Miocene.  相似文献