European climate of the past 500 years: new challenges for historical climatology

Temperature reconstructions from Europe for the past 500 years based on documentary and instrumental data are analysed. First, the basic documentary data sources, including information about climate and weather-related extremes, are described. Then, the standard palaeoclimatological reconstruction method adopted here is discussed with a particular application to temperature reconstructions from documentary-based proxy data. The focus is on two new reconstructions; January–April mean temperatures for Stockholm (1502–2008), based on a combination of data for the sailing season in the Stockholm harbour and instrumental temperature measurements, and monthly Central European temperature (CEuT) series (1500–2007) based on documentary-derived temperature indices of the Czech Republic, Germany and Switzerland combined with instrumental records from the same countries. The two series, both of which are individually discussed in greater detail in subsequent papers in this special edition, are here compared and analysed using running correlations and wavelet analysis. While the Stockholm series shows a pronounced low-frequency component, the CEuT series indicates much weaker low-frequency variations. Both series are analysed with respect to three different long-period reconstructions of the North Atlantic Oscillation (NAO) and are compared with other European temperature reconstructions based on tree-rings, wine-harvest data and various climate multiproxies. Correlation coefficients between individual proxy-based series show weaker correlations compared to the instrumental data. There are also indications of temporally varying temperature cross-correlations between different areas of Europe. The two temperature reconstructions have also been compared to geographically corresponding temperature output from simulations with global and regional climate models for the past few centuries. The findings are twofold: on the one hand, the analysis reinforces the hypothesis that the index-data based CEuT reconstruction may not appropriately reflect the centennial scale variations. On the other hand, it is possible that climate models may underestimate regional decadal variability. By way of a conclusion, the results are discussed from a broader point of view and attention is drawn to some new challenges for future investigations in the historical climatology in Europe.     

近千年全球气候变化的长积分模拟试验

近千年全球气候变化的长积分模拟试验是全球气候模拟研究的新领域,它不仅将现代器测资料与过去代用指标序列进行了有机的衔接,而且对过去百年和年代际尺度的气候变化可进行动力学解释,探讨其主要控制因素及其导致的区域响应差异。由于这类长积分模拟对计算机技术和气候模式本身的要求较高,目前能进行这类研究的国家为数不多。重点介绍了德国马普气象研究所的全球海气耦合气候模式ECHO G,以及利用该模式进行的千年长积分模拟试验结果。首先,应用全球120年的器测资料对模拟结果进行了检验,论证了该模型较强的气候模拟能力;其次,根据全球地表2 m气温的千年模拟结果,揭示了中世纪暖期—小冰期—20世纪暖期三段式气候变化时段,然后讨论了中世纪暖期和小冰期鼎盛期全球及中国的温度分布特点;最后根据对各控制因子的拟合分析与比较,初步揭示了近千年来的温度变化主要受太阳有效辐射的变化控制,而温室气体含量的增加对100年来温度的快速上升起着主导作用。      

A geochemical approach to distinguishing competing tectono-magmatic processes preserved in small eruptive centres

Small eruptive centres (SECs) representing short-lived, isolated eruptions are effective samples of mantle heterogeneity over a given area, as they are generally of basaltic composition and show evidence of little magmatic processing. This is particularly powerful in volcanic arcs where the original melting process generating stratovolcanoes is often obscured by additions from the down-going slab (fluids and sediments) and the overlying crust. The Pucón area of southern Chile contains active and dormant stratovolcanoes, Holocene, basaltic SECs and an arc-scale strike-slip fault (the Liquiñe Ofqui Fault System: LOFS). The SECs show unexpected compositional heterogeneity considering their spatial proximity. We present a detailed study of these SECs combining whole rock major and trace element concentrations, U-Th isotopes and olivine-hosted melt inclusion major element and volatile contents to highlight the complex inter-relations in this small but active area. We show that heterogeneity preserved at individual SECs relates to different processes: some start in the melting region with the input of slab-derived fluids, whilst others occur later in a centre’s magmatic history with the influence of crustal contamination prior to olivine crystallisation. These signals are deduced through the combination of the different geochemical tools used in this study. We show that there is no correlation between composition and distance from the arc front, whilst the local tectonic regime has an effect on melt composition: SECs aligned along the LOFS have either equilibrium U-Th ratios or small Th-excesses instead of the large—fluid influenced—U-excesses displayed by SECs situated away from this feature. One of the SECs is modelled as being generated from fluid-enriched depleted mantle, a source which it may share with the stratovolcano Villarrica, whilst another SEC with abundant evidence of crustal contamination may share its plumbing system with its neighbouring stratovolcano Quetrupillán, showing that polygenetic–monogenetic connections are unpredictable. Such marked preservation of individual magmatic histories highlights the isolation of individual melting events even in complex and highly volcanically active areas.     

10,000 years of climate control over carbon accumulation in an Iberian bog(southwestern Europe)

The northwest region of the Iberian Peninsula is home to a unique ecosystem of bogs,which are particularly sensitive to projected climate cha nge.In this context,the rate of carbon(C)accumulation in Chao de Veiga Mol.an intact raised bog,was analysed.Changes in the accumulation rate over the past10 millennia were determined in a peat core of 847 cm in depth,with a high mean rate of peat growth(11 yr cm^-1,0.09 cm yr^-1).An age-depth model was generated from 22 14C dates and fallout radionuclides.Chronological,stratigraphical and physico-chemical data confirmed the existence of a single cycle of peat formation throughout the Holocene and the formation of ombrotrophic peat 9500 years ago.The total mean C content was 50.2%,and over 10 millennia 583 kg C m^-2 accumulated at a mean rate of 35.3 g C m^-2 yr^-1,with a long-term(apparent)rate of carbon accumulation in the catotelm of59.9 g C m^-2 yr^-1.These values are much higher than reported for other Iberian peatlands and are amongst the highest documented for peatlands in the northern hemisphere.The dynamics of C accumulation and other measured parameters reveals important variations throughout the Holocene.They could be associated with the main climatic events described in the northern hemisphere and are highly consistent with models established for northern latitudes.The Chao de Veiga Mol raised bog is unique and of great potential value for carrying out high resolution palaeoenvironmental studies,especially in relation to regional and Iocal modulations in southern Europe.     

Geostatistical case studies of the advantages of lognormal-de Wijsian kriging with mean for a base metal mine and a gold mine

Parallel variogram analyses, block kriging, and follow-up studies were effected for the lead content of part of the Prieska copper-zinc ore body and for the gold content of the highly variable Breef in a section of the Loraine gold mine, based first on untransformed values and second on logarithmically transformed values using the lognormal-de Wijsian model. For both models the effect was also analyzed of using the population mean or ignoring it. Practical follow-up comparisons confirm theoretical considerations and show that on these mines conditional biases can be eliminated conveniently by kriging with mean; also that the lognormal-de Wijsian model with mean gives the best results.     

The role of the Río de la Plata bottom salinity front in accumulating debris

The Río de la Plata, one of the most important South American estuarine environments, is characterized by a bottom salinity front that generates an ecotone between the river and the estuary. Based on bottom trawls and costal sampling we describe the distribution, types, and amount of debris found in the bottom and shoreline across this front. Plastics and plastic bags were the main debris types in both areas. Concentrations of total debris upriver the front were always significantly higher than downriver the front showing that the front acts as a barrier accumulating debris. Moreover, a large part of debris end ups accumulated in the coastal area upriver the frontal position. This area is particularly sensitive because the coastline encompasses an UNESCO Man and the Biosphere Reserve and a Ramsar site, and due to the ecological significance of the front for many valuable species.     

Scattering of waves by subterranean structures via the boundary element method

The boundary element method (BEM) is used to study the two-dimensional wave field generated when buried structures of arbitrary shape (i.e. inclusions) in an elastic medium are illuminated (or insonified) by dynamic line sources. Both steady-state responses and time-domain transients are presented. The problem is formulated in the frequency domain by means of appropriate Green's functions. The evaluation of the singular integrals is achieved (and to the best of the writers' knowledge, for the first time in the technical literature) in analytical form, which results in improvements in computational efficiency and accuracy. Closed-form solutions for regular geometries are then used to validate the method. The interaction of two cavities, the formation of shadow zones by inclusions and the complexity of the scattered field from bodies with irregular shapes are used as examples to demonstrate the versatility of the method. The responses computed in the time domain were invariably found to be causal, even for non-convex domains, which belies a recent assertion by some researchers that the application of boundary element methods to concave domains is associated with non-causal effects.     

Studies in selected fragilarioid diatoms of potential indicator value from Florida (USA) with notes on the genus Opephora Petit (Bacillariophyceae)

Four araphid diatom taxa were collected from Florida streams and studied with both light microscopy (LM) and scanning electron microscopy (SEM). Three taxa, formerly in the genus Fragilaria Lyngbye, are here placed in the genus Pseudostaurosira Williams et Round. On the basis of ultrastructure observed by SEM, the remaining taxon is placed in a new genus, Sarcophagodes. At least two of the species referred to Pseudostaurosira may have been confused with species of the genus Opephora Petit, which may have led to misinterpretation of the ecological characteristics of the latter genus.All the taxa treated here belong to the Family Fragilariaceae Greville as delimited in current classification schemes. Two new combinations Pseudostaurosiropsis geocollegarum (=Fragilaria geocollegarum Witkowski et Lange-Bertalot), Pseudostaurosira neoelliptica (=Fragilaria neoelliptica Witkowski) and the new species Pseudostaurosira clavatum are presented herein. Additionally, a new genus, Sarcophagodes, is erected to accommodate the new species S. delicatula. LM and SEM details, as well as criteria delimiting these taxa are discussed. More collections and further analyses are needed to assess the distribution of both Opephora and Sarcophagodes.