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761.
Christian B. Rodehacke Wolfgang Roether Hartmut H. Hellmer Timothy Hall 《Deep Sea Research Part I: Oceanographic Research Papers》2010,57(2):175-198
The knowledge of chlorofluorocarbon (CFC11, CFC12) concentrations in ocean surface waters is a prerequisite for deriving formation rates of, and water mass ages in, deep and bottom waters on the basis of CFC data. In the Antarctic coastal region, surface-layer data are sparse in time and space, primarily due to the limited accessibility of the region. To help filling this gap, we carried out CFC simulations using a regional ocean general circulation model (OGCM) for the Southern Ocean, which includes the ocean–ice shelf interaction. The simulated surface layer saturations, i.e. the actual surface concentrations relative to solubility-equilibrium values, are verified against available observations. The CFC surface saturations driven by concentration gradients between atmosphere and ocean are controlled mainly by the sea ice cover, sea surface temperature, and salinity. However, no uniform explanation exists for the controlling mechanisms. Here, we present simulated long-term trends and seasonal variations of surface-layer saturation at Southern Ocean deep and bottom water formation sites and other key regions, and we discuss differences between these regions. The amplitudes of the seasonal saturation cycle vary from 22% to 66% and their long-term trends range from 0.1%/year to 0.9%/year. The seasonal surface saturation maximum lags the ice cover minimum by two months. By utilizing observed bottle data the full seasonal CFC saturation cycle can be determined offering the possibility to predict long-term trends in the future. We show that ignoring the trends and using instead the saturations actually observed can lead to systematic errors in deduced inventory-based formation rates by up to 10% and suggest an erroneous decline with time. 相似文献
762.
763.
Maxime Souvignet Patrick Laux Jim Freer Hannah Cloke Dang Quang Thinh Tran Thuc Johannes Cullmann Alexandra Nauditt Wolfgang‐Albert Flügel Harald Kunstmann Lars Ribbe 《水文研究》2014,28(4):1587-1601
In this study, change in rainfall, temperature and river discharge are analysed over the last three decades in Central Vietnam. Trends and rainfall indices are evaluated using non‐parametric tests at different temporal levels. To overcome the sparse locally available network, the high resolution APHRODITE gridded dataset is used in addition to the existing rain gauges. Finally, existing linkages between discharge changes and trends in rainfall and temperature are explored. Results are indicative of an intensification of rainfall (+15%/decade), with more extreme and longer events. A significant increase in winter rainfall and a decrease in consecutive dry days provides strong evidence for a lengthening wet season in Central Vietnam. In addition, trends based on APHRODITE suggest a strong orographic signal in winter and annual trends. These results underline the local variability in the impacts of climatic change at the global scale. Consequently, it is important that change detection investigations are conducted at the local scale. A very weak signal is detected in the trend of minimum temperature (+0.2°C/decade). River discharge trends show an increase in mean discharge (31 to 35%/decade) over the last decades. Between 54 and 74% of this increase is explained by the increase in precipitation. The maximum discharge also responds significantly to precipitation changes leading to a lengthened wet season and an increase in extreme rainfall events. Such trends can be linked with a likely increase in floods in Central Vietnam, which is important for future adaptation planning and management and flood preparedness in the region. Copyright © 2012 John Wiley & Sons, Ltd. 相似文献
764.
Shuang-Qing Li Yan Wang Bo-Wen Fang Jian-Feng He Fukun Chen Wolfgang Siebel 《International Geology Review》2019,61(1):39-55
Following the amalgamation of the Siberian and North China Cratons, NE China, as part of the Central Asian Orogenic Belt (CAOB), underwent Late Mesozoic lithospheric extension that was associated with volcanic activity. The Songliao Basin is the most important rift structure formed during these processes and contains voluminous volcanic rocks interlayered with sedimentary infill. Mafic-to-intermediate lavas are associated with felsic ones. This study focusses on the geochemical compositions of the less-widespread Early Cretaceous mafic-to-intermediate lavas in the Songliao Basin and compares them with the more abundant felsic rocks. Two mafic-to-intermediate magma series, one with alkaline and the other with sub-alkaline affinity, were identified. High MgO and Cr contents, low Th/Nb and La/Nb ratios, and variable but depleted Nd isotope compositions indicate that both magma suites were most likely formed by the melting of enriched upper mantle sources. Sub-alkaline mafic-to-intermediate rocks and I-type rhyolites define a co-genetic magma series. This rock suite was produced by the melting of subduction-modified lithospheric mantle and subsequent magma evolution as well as crustal melting during lithospheric extension. Alkaline mafic-to-intermediate rocks and A-type rhyolites form another co-genetic magma suite that was produced under within-plate conditions from an OIB-type mantle source, supposed to be the heterogeneous shallow asthenosphere and/or the lower lithosphere. Decompression partial melting of this mantle source requires a relatively thin lithosphere. The development of alkaline mafic rocks and A-type rhyolites as typical bimodal volcanic assemblage reflects that lithospheric thinning below the Songliao Basin reached its maximum, whereas basin rifting terminated afterwards. 相似文献
765.
Dr. Wolfgang Hofmann 《Aquatic Sciences - Research Across Boundaries》1984,46(1):139-146
A late glacial population ofBosmina longispina Leydig from the Lobsigensee (Swiss Plateau) showed significant morphological variation, particularly in the number of antennule
segments, in the period from the Oldest Dryas to the Preboreal. As there was no indication of introgressive hybridisation
it is presumed that the variation is a result of environmental changes. The subfossilBosmina longispina resembles recent fennoscandian and late glacial north German forms rather than recent alpine populations. 相似文献
766.
The reported systemic velocities of the low-mass X-ray binaries (=LMXBs) are found to be unreliable, because of intrinsic Doppler shifts. We argue that the non-globular-cluster LMXBs form a disk population, whose typicalz-velocities are unlikely to exceed 30 km s–1. They are moderately old and rare (among neutron-star sources) and have oscillated through the disk a number of times. 相似文献
767.
Wolfgang Kundt 《Astrophysics and Space Science》1973,21(2):487-493
The true orbit of a spacecraft differs from its reference orbit by small deviations due to erros in planetary and initial data, radiation and impact accelerations, and correction terms to Newton's theory of gravitation. These distortions are usually small enough to haveadditive effects on range, at the 10 m accuracy level, throughout the mission. Closed form expressions are derived (in cylindrical coordinates) for thedeviation inrange due to any given perturbing acceleration. 相似文献
768.
Based on maps of the extragalactic radio sources Cyg A, Her A, Cen A, 3C 277.3 and others, arguments are given that the twin-jets
from the respective active galactic nucleus ram their channels repeatedly through thin, massive shells. The jets are thereby
temporarily choked and blow radio bubbles. Warm shell matter in the cocoon shows up radio-dark through electron-scattering. 相似文献
769.
Michel?CaraEmail author Wolfgang?Brüstle Monika?Gisler Philipp?K?stli Christophe?Sira Claire?Weihermüller Jér?me?Lambert 《Journal of Seismology》2005,9(3):317-328
The 2003 Ml = 5.4 Rambervillers earthquake, north-east of France, is the largest seismic event recorded north of the Alps
since the 1992 Ms = 5.3, I0 = VII, Roermond earthquake, Netherlands. With a maximum macroseismic intensity of VI-VII EMS-98, the 2003 event was broadly
felt to a distance of 300 km from the epicentre. It provides a unique opportunity to test and compare the different procedures
used in France, Germany and Switzerland when evaluating macroseismic intensities. The main purpose of this paper is to present
a common transfrontier macroseismic map based on the EMS-98 intensity scale. Maximum horizontal accelerations recorded in
the area are compared to the intensity values, and we propose to use a differential technique to re-estimate the magnitude
of the 1682 Remiremont, I0 = VIII, earthquake, which occurred 40 km south of Rambervillers. 相似文献
770.
The provenance of Cenomanian to Eocene flysch deposits accreted along the northern margin of the Eastern Alps has been investigated by means of zircon fission-track (FT) geochronology and zircon morphology. The Rhenodanubian flysch and Ybbsitz klippen zone comprise several nappes representing the Main flysch and Laab basins. The Laab basin received sediments of stable European provenance, indicated by pre-Variscan, Variscan, and Permian–Triassic zircon FT ages, and was thus located in the immediate south of the European margin. The Main flysch basin was supplied mainly from the evolving Eastern Alps and was therefore situated south of the Laab basin. Zircon populations with Permian to Jurassic cooling ages in the Main flysch basin are related to increased heat fluxes during the break-up of Pangaea and are probably derived from the northwestern part of the Eastern Alps. The dominant Cretaceous zircon FT cooling ages reflect Eoalpine metamorphism in the Austroalpine realm. 相似文献