Low δ¹⁸O eclogites from the Kokchetav massif, northern Kazakhstan     

H. Masago  D. Rumble  W. G. Ernst  C. D. Parkinson  S. Maruyama 《Journal of Metamorphic Geology》2003,21(6):579-587

Oxygen isotopic compositions of silicates in eclogites and whiteschists from the Kokchetav massif were analyzed by whole‐grain CO₂‐laser fluorination methods. Systematic analyses yield extremely low δ¹⁸O for eclogites, as low as ?3.9‰ for garnet; these values are comparable with those reported for the Dabie‐Sulu UHP eclogites. Oxygen isotopic compositions are heterogeneous in samples of eclogite, even on an outcrop scale. Schists have rather uniform oxygen isotope values compared to eclogites, and low δ¹⁸O is not observed. Isotope thermometry indicates that both eclogites and schists achieved high‐temperature isotopic equilibration at 500–800 °C. This implies that retrograde metamorphic recrystallization barely modified the peak‐metamorphic oxygen isotopic signatures. A possible geological environment to account for the low‐δ¹⁸O basaltic protolith is a continental rift, most likely subjected to the conditions of a cold climate. After the basalt interacted with low δ¹⁸O meteoric water, it was tectonically inserted into the surrounding sedimentary units prior to, or during subduction and UHP metamorphism.  相似文献   

A preliminary application GIS in glaciological research along the traverse route from Zhongshan Station to Dome A, Antarctica   总被引：1，自引：0，他引：1  

温家洪  孙波  康建成  李院生 《极地研究(英文版)》2003,14(1)

1　IntroductionGeographicalinformationsystem (GIS)isanefficientwayandimportanttechniquetomanage,displayandanalyzeAntarcticspatialdata.GIScanbeusedtomakeandre newmapproductsquickly ,evaluateenvironment,supportlogisticmanagementandfieldoperation,providechancetoextractnewknowledge,andtopromoteinformationex changeamongnationsunderthedemandoftheMadridProtocol(AADC 2 0 0 1 ;MAGIC1 998;1 999) .WorkingGroupofGeodesyandGeographicInformation (WG GGI)ofScientificCommitteeonAntarcticResearch (…  相似文献   

The mass of the neutron star in the low-mass X-ray binary 2A 1822 − 371     

P. G. Jonker  M. van der Klis  P. J. Groot 《Monthly notices of the Royal Astronomical Society》2003,339(3):663-668

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An algorithm for clustering profile data and its application to near-surface ice content data from wet coastal tundra soils near Barrow, Alaska     

G. F. Estabrook  S. Outcalt 《Mathematical Geology》1984,16(2):193-205

An algorithm to cluster profile data into groups that minimize the sum of the intra-group variances was applied to near-surface soil ice content data collected near Barrow, Alaska, in wet tundra terrain. When the algorithm was requested to produce 2–5 groups and group mean profiles, the results were consistant with the modern theory of ice segregation. This process produces much of the variability of near surface soil ice stratigraphy in nature. These results strengthen the case for employing the algorithm on other profile data sets as an aid in hypothesis formulation.  相似文献   

Analysis of a podded propulsion system of a polar icebreaker and simulation of its control performance          下载免费PDF全文

Huang Rong  Li Wenming  Yuan Dongfang 《极地研究》1988,31(4):441

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Late devensian ice sheet in the western Grampians,Scotland     

Peter W. Thorp 《第四纪科学杂志》1987,2(2):103-112

A radial pattern of ice flow of the last ice sheet in the largest source area of ice (c. 5000 km²) in the British Isles in western Scotland is demonstrated by the dispersal of indicator erratics and by patterns of striae, friction cracks and ice-moulded landforms. Three major ice domes and the principal ice divide are identified in the western Grampians. The ice domes coincided with the highest mountain blocks while it is inferred that the alignment of many of the pre-existing valleys controlled much of the outflow of ice, forming ice streams within the ice sheet. The importance of the Rannoch Moor basin as a radial provider of ice to surrounding areas was apparently less significant than has hitherto been considered. Ice flowed into and across the southern part of the basin from the principal ice divide located to the west and south. No evidence has yet been found that would support a model of an eastward-migrating ice divide either during the build-up or during the deglaciation of the Late Devensian ice sheet.  相似文献   

Linking the northern hemisphere sea-ice reduction trend and the quasi-decadal arctic sea-ice oscillation     

J Wang  M Ikeda  S Zhang  R Gerdes 《Climate Dynamics》2005,24(2-3):115-130

The nature of the reduction trend and quasi-decadal oscillation in Northern Hemisphere sea-ice extent is investigated. The trend and oscillation that seem to be two separate phenomena have been found in data. This study examines a hypothesis that the Arctic sea-ice reduction trend in the last three decades amplified the quasi-decadal Arctic sea-ice oscillation (ASIO) due to a positive ice/ocean-albedo feedback, based on data analysis and a conceptual model proposed by Ikeda et al. The theoretical, conceptual model predicts that the quasi-decadal oscillation is amplified by the thinning sea-ice, leading to the ASIO, which is driven by the strong positive feedback between the atmosphere and ice-ocean systems. Such oscillation is predicted to be out-of-phase between the Arctic Basin and the Nordic Seas with a phase difference of 3/4, with the Nordic Seas leading the Arctic. The wavelet analysis of the sea ice data reveals that the quasi-decadal ASIO occurred actively since the 1970s following the trend starting in the 1960s (i.e., as sea-ice became thinner and thinner), as the atmosphere experienced quasi-decadal oscillations during the last century. The wavelet analysis also confirms the prediction of such out-of-phase feature between these two basins, which varied from 0.62 in 1960 to 0.25 in 1995. Furthermore, a coupled ice-ocean general circulation model (GCM) was used to simulate two scenarios, one without the greenhouse gas warming and the other having realistic atmospheric forcing along with the warming that leads to sea-ice reduction trend. The quasi-decadal ASIO is excited in the latter case compared to the no-warming case. The wavelet analyses of the simulated ice volume were also conducted to derive decadal ASIO and similar phase relationship between the Arctic Ocean and the Nordic Seas. An independent data source was used to confirm such decadal oscillation in the upper layer (or freshwater) thickness, which is consistent with the model simulation. A modified feedback loop for the sea-ice trend and ASIO was proposed based on the previous one by Mysak and Venegas and the ice/albedo and cloud/albedo feedabcks, which are responsible for the sea ice reduction trend.  相似文献   

Ab initio study of the high-pressure behavior of CaSiO3 perovskite     

Daniel Y. Jung  Artem R. Oganov 《Physics and Chemistry of Minerals》2005,32(2):146-153

Using density functional simulations, within the generalized gradient approximation and projector-augmented wave method, we study structures and energetics of CaSiO₃ perovskite in the pressure range of the Earths lower mantle (0–150 GPa). At zero Kelvin temperature the cubic CaSiO₃ perovskite structure is unstable in the whole pressure range, at low pressures the orthorhombic (Pnam) structure is preferred. At 14.2 GPa there is a phase transition to the tetragonal (I4/mcm) phase. The CaIrO₃-type structure is not stable for CaSiO₃. Our results also rule out the possibility of decomposition into oxides.

Daniel Y. JungEmail: Phone: +41-44-6323744Fax: +41-44-6321133

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Modelling and Mapping Damage to Forests from an Ice Storm Using Remote Sensing and Environmental Data     

D.?J.?KingEmail author  I.?Olthof  P.?K.?E.?Pellikka  E.?D.?Seed  C.?Butson 《Natural Hazards》2005,35(3):321-342

An extreme ice storm in January 1998 deposited up to 100 mm of ice and resulted in significant forest damage across eastern North America. Average crown loss of over 75% was recorded in large areas of eastern Ontario and southern Quebec. A primary question that arose following the storm was: can forest damage be effectively assessed using remote sensing and other available environmental data? This paper presents two contrasting studies to address this question. The first involves damage modelling at a local scale in an unmanaged forest using spectral and spatial information in high-resolution airborne imagery. Results of field data analyses are also given that show relations between damage and forest structure and composition as well as changes in forest structure that occurred in the years following the storm. The second study involves regional scale damage mapping in managed and unmanaged forests of eastern Ontario using medium resolution satellite imagery and other environmental data. In comparison of several image classification and data interpolation methods, the best damage map was produced using a neural network classifier and a mix of Landsat and environmental data. The methods and results presented in this paper form the basis for ongoing long-term temporal study of damage impacts on forest condition.  相似文献   

δ34S isotope values of dissolved sulfate (SO4 2−) as a tracer for battery acid (H2SO4) contamination in groundwater     

Thomas Pichler 《Environmental Geology》2005,47(2):215-224

The application of sulfur isotope (³⁴S) values of sulfate in groundwater provided the information necessary to evaluate the source, transport and fate of battery acid and associated contaminants at the Gulf Coast Recycling (GCR) facility. The chemical and isotopic composition of groundwater beneath the (GCR) property, a battery recycling facility in east Tampa, Florida, varies more than expected for an area of comparable size. Sulfate (SO₄^2–) values, for example, range from 1.2 to 11,500 mg/L and oxygen and hydrogen isotopes do not attenuate towards the weighted annual mean. Those samples that are high in sulfate generally have a low pH, which immediately indicates battery acid (H₂SO₄) contamination as a potential source for the sulfate. The low pH and high reactivity of the sulfuric acid groundwater cause the formation of hydrogeological microenvironments due to preferential dissolution of carbonate minerals, which in turn causes enhanced recharge and groundwater flow in certain areas; thus, the extreme scatter in the data set. Because of the difficult hydrogeology it is not straightforward to delineate the point-sources of contamination and up to five potential scenarios have to be evaluated: (1) seawater intrusion, (2) upwelling of high-sulfate groundwater, (3) local dissolution of gypsum, (4) an up-gradient contaminant source to the northeast of the GCR property and (5) battery acid contamination.  相似文献