Temporal variations and trends of CFC11 and CFC12 surface-water saturations in Antarctic marginal seas: Results of a regional ocean circulation model     

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   

Spectral measurements of aerosol particle extinction in the 0.4–3.7 μm wavelength range, performed at Sagres with the IR‐RAD sun‐radiometer     

Vito Vitale  Claudio Tomasi  Wolfgang Von Hoyningen&#;huene  Ubaldo Bonafe  Stefano Marani  Angelo Lupi  Alessandra Cacciari  Pietro Ruggeri 《Tellus. Series B, Chemical and physical meteorology》2000,52(2):716-733

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Sclerochronology: editorial     

Wolfgang Oschmann 《International Journal of Earth Sciences》2009,98(1):1-2

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东西特提斯晚白垩世深水底栖有孔虫生物相和岩相     

WolfgangKUHNT AnnHOLBOURN 《地学前缘》2005,12(2):81-103

白垩纪深水古海洋学研究仍处于早期发展阶段,一方面是由于来自钙质底栖有孔虫的稳定同位素和地球化学数据的缺乏,其原因在于白垩纪高碳酸盐补偿深度;另一方面在于深水有机质胶结有孔虫示踪古海洋还没有充分发展起来。深海环境深水胶结有孔虫的分布主要取决于碳酸盐可利用状况、原始生产的输入通量、深水交换、环境波动(深海洋流、浊流和快速沉积事件)和底层沉积类型,因此对于重建深海环境具有非常巨大的潜力。东、西特提斯Campanian Maastrichtian深水底栖有孔虫组合的统计分析揭示出6个生物相,代表着明显不同的沉积环境。包括:深海红色泥岩与矮小深海生物组合(生物相1);红色深海泥灰岩(“Couches Rouges”相),含钙质胶结有孔虫组合(生物相3);深水远洋灰岩(“Scaglia Rossa”相),含易碎的Rhizammina组合(生物相2);绿色灰色半远洋泥灰岩,含适应高输出通量生物组合(生物相4);半远洋泥岩和粉砂岩,含Aschemocella Nothia 组合(生物相5);陆源浊积层序,含“复理石型”Rhabdammina组合(生物相6)。Campanian Maastrichtian红色氧化深水环境动物组合与现今深海类似,而白垩纪贫氧深海环境胶结组合在现今无法找到相类似物。随着古生态信息的增加和数据库的扩展,深水胶结有孔虫有望成为揭示古海洋条件的重要工具,尤?  相似文献   

Early Cretaceous rift-related volcanism in the Songliao Basin,NE China – A geochemical study     

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   

Scaling Issues in Forest Succession Modelling   总被引：5，自引：0，他引：5  

Harald Bugmann  Marcus Lindner  Petra Lasch  Michael Flechsig  Beatrix Ebert  Wolfgang Cramer 《Climatic change》2000,44(3):265-289

This paper reviews scaling issues in forest succession modelling, focusing on forest gap models. Two modes of scaling are distinguished: (1) implicit scaling, i.e. taking scale-dependent features into account while developing model equations, and (2) explicit scaling, i.e. using procedures that typically involve numerical simulation to scale up the response of a local model in space and/or time. Special attention is paid to spatial upscaling methods, and downscaling is covered with respect to deriving scenarios of climatic change to drive gap models in impact assessments. When examining the equations used to represent ecological processes in forest gap models, it becomes evident that implicit scaling is relevant, but has not always been fully taken into consideration. A categorization from the literature is used to distinguish four methods for explicit upscaling of ecological models in space: (1) Lumping, (2) Direct extrapolation, (3) Extrapolation by expected value, and (4) Explicit integration. Examples from gap model studies are used to elaborate the potential and limitations of these methods, showing that upscaling to areas as large as 3000 km² is possible, given that there are no significant disturbances such as fires or insect outbreaks at the landscape scale. Regarding temporal upscaling, we find that it is important to consider migrational lags, i.e. limited availability of propagules, if one wants to assess the transient behaviour of forests in a changing climate, specifically with respect to carbon storage and the associated feedbacks to the atmospheric CO₂ content. Regarding downscaling, the ecological effects of different climate scenarios for the year 2100 were compared at a range of sites in central Europe. The derivation of the scenarios is based on (1) imposing GCM grid-cell average changes of temperature and precipitation on the local weather records; (2) a qualitative downscaling technique applied by the IPCC for central and southern Europe; and (3) statistical downscaling relating large-scale circulation patterns to local weather records. Widely different forest compositions may be obtained depending on the local climate scenario, suggesting that the downscaling issue is quite important for assessments of the ecological impacts of climatic change on forests.  相似文献   

Recent climatic trends and linkages to river discharge in Central Vietnam   总被引：1，自引：0，他引：1       下载免费PDF全文

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   

Sources of polyfluoroalkyl compounds in the North Sea, Baltic Sea and Norwegian Sea: Evidence from their spatial distribution in surface water   总被引：2，自引：0，他引：2  

Lutz Ahrens  Wolfgang Gerwinski  Ralf Ebinghaus 《Marine pollution bulletin》2010,60(2):255-5700

The spatial distribution of 15 polyfluoroalkyl compounds (PFCs) in surface water was investigated in the North Sea, Baltic Sea and Norwegian Sea. In addition, an interlaboratory comparison of the sampling techniques and analysis was conducted. Highest concentration in the North Sea was found near the coast, whereas the ∑PFC concentration decreased rapidly from 18.4 to 0.07 ng l⁻¹ towards the open North Sea. The river Elbe could identify as a local input source for PFCs into the North Sea, whereas perfluorobutanoic acid (PFBA) was transported into the sampling area with the easterly current. In contrast to the North Sea, the distribution of PFCs in the Baltic Sea was relatively homogenous, where diffuse sources dominated. In general, the composition profile was influenced from local sources caused by human activities, whereas atmospheric depositions of here analysed PFCs were negligible, but it could have possibly an influence on low contaminated sites like the open North Sea or Norwegian Sea.  相似文献   

High Zn and Cd accumulation in the oyster Crassostrea rhizophorae, and its relevance as a sentinel species     

de Freitas Rebelo M  do Amaral MC  Pfeiffer WC 《Marine pollution bulletin》2003,46(10):1354-1358

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Morphological variation in a late glacial population ofBosmina longispina Leydig (Crustacea,Cladocera) from the Lobsigensee (Swiss Plateau). Studies in the Late-Quaternary of Lobsigensee 9   总被引：2，自引：0，他引：2  

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