Holocene climate in the subarctic fjord Malangen, northern Norway: a multi-proxy study     

MORTEN HALD  KATRINE HUSUM  TORE O. VORREN  KARI GRØSFJELD  HENNING B. JENSEN  ALLA SHARAPOVA 《Boreas: An International Journal of Quaternary Research》2003,32(4):543-559

A Holocene sedimentary record from the deep-silled Malangen fjord in northern Norway reveals regional changes in sedimentary environment and climate. Down-core analysis of two sediment cores includes multi-core sensor logging, grain size, x-radiography, foraminifera, oxygen isotopes, dinoflagellates, pollen, trace elements and radiocarbon datings. The cores are located just proximal to the submarine Younger Dryas moraine complex, and reveal the deglaciation after Younger Dryas and the postglacial evolution. Five sedimentary units have been identified. The oldest units, V and IV, bracket the Younger Dryas glacial readvance in the fjord between 12 700 cal. years BP and 11 800 cal. years BP. This is followed by deposition of glaciomarine sediments (units IV and III) starting around 12 100 cal. years BP. Glaciomarine sedimentation ceased in the fjord c. 10 300 cal. years BP and was replaced by open marine sedimentation (units II and I). A rapid stepwise warming occurred during the Preboreal. Onset of surface water warming lagged bottom water warming by several hundred years. The δ[Formula: See Text]O record indicates a significant, gradual bottom water cooling (c. 4°C) between 8000 and 2000 cal. years BP, a trend also supported by the other proxy data. Other records in the region, as well as GCM simulations, also support this long-term climatic evolution. Superimposed on this cooling were brief warmings around 6000 cal. years BP and 2000 cal. years BP. The long-term change may be driven by orbitally forced reduction in insolation, whereas the short-term changes may be linked to for example solar forcing, meltwater and NAO changes all causing regional changes in the North Atlantic heat transport.  相似文献   

Improving the representation of radiation interception and photosynthesis for climate model applications     

LINA M. MERCADO  CHRIS HUNTINGFORD  JOHN H. C. GASH  PETER M. COX  VENKATA JOGIREDDY 《Tellus. Series B, Chemical and physical meteorology》2007,59(3):553-565

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Representation of 3-D elevation in terrain databases using hierarchical triangulated irregular networks: a comparative analysis     

MAHDI ABDELGUERFI  CHRIS WYNNE  EDGAR COOPER  LADNER ROY 《International journal of geographical information science》2013,27(8):853-873

3-D terrain representation plays an important role in a number of terrain database applications. Hierarchical Triangulated Irregular Networks (TINs) provide a variable-resolution terrain representation that is based on a nested triangulation of the terrain. This paper compares and analyzes existing hierarchical triangulation techniques. The comparative analysis takes into account how aesthetically appealing and accurate the resulting terrain representation is. Parameters, such as adjacency, slivers, and streaks, are used to provide a measure on how aesthetically appealing the terrain representation is. Slivers occur when the triangulation produces thin and slivery triangles. Streaks appear when there are too many triangulations done at a given vertex. Simple mathematical expressions are derived for these parameters, thereby providing a fairer and a more easily duplicated comparison. In addition to meeting the adjacency requirement, an aesthetically pleasant hierarchical TINs generation algorithm is expected to reduce both slivers and streaks while maintaining accuracy. A comparative analysis of a number of existing approaches shows that a variant of a method originally proposed by Scarlatos exhibits better overall performance.  相似文献   

Climate changes during the last c. 7500 years as recorded by the degree of peat humification in the Lofoten region,Norway     

KARL‐DAG VORREN  CHRISTIN ELDEGARD JENSEN  EILIF NILSSEN 《Boreas: An International Journal of Quaternary Research》2012,41(1):13-30

Vorren, K.‐D., Jensen, C. E. & Nilssen, E. 2012 (January): Climate changes during the last c. 7500 years as recorded by the degree of peat humification in the Lofoten region, Norway. Boreas, Vol. 41, pp. 13–30. 10.1111/j.1502‐3885.2011.00220.x. ISSN 0300‐9483. Two peat cores from two neighbouring bogs in Lofoten, northern Norway were densely AMS dated and analysed for humification. The two cores have been influenced by human agricultural impact, especially c. 1600 cal. a BP, which may have affected the local hydrology of the bogs. From 7400 cal. a BP onwards, 19 distinct wet‐shifts are recorded in the two cores. Eight or nine of these correspond chronologically to periods of low solar activity. This correlation is most convincing during the last 2000 years. Some wet‐shifts are connected with a solar low‐activity period during the Subboreal/Subatlantic transition, which in central Europe is dated at 2750–2565 cal. a BP. For Lofoten, the corresponding Subboreal/Subatlantic transition – or the wet‐shift marking this transition – is dated at c. 2600 cal. a BP. Some wet‐shifts occur just before or just after solar low‐activity periods, but only four of the nineteen wet‐shifts are clearly not temporally connected with periods of low solar activity. Compared with the wet‐shifts in NW European (mainly British Isles) bogs, there are more frequent wet‐shifts in northern Norway. Compared with other peat cores in northern Norway, especially for the interval 6500–5000 cal. a BP, Lofoten deviates by its lack of wet‐shifts. As in England, Scotland and Ireland, there is regional variability in the temporal formation of wet‐shifts in northern Norway.  相似文献   

Turbulence spectra, shear stress and turbulent kinetic energy budgets above two beech forest sites in Denmark   总被引：1，自引：0，他引：1  

IVAN MAMMARELLA  EBBA DELLWIK  NIELS O. JENSEN 《Tellus. Series B, Chemical and physical meteorology》2008,60(2):179-187

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Phase Relations in the Fe-Ni-Cu-PGE-S System at Magmatic Temperature and Application to Massive Sulphide Ores of the Sudbury Igneous Complex     

BALLHAUS  CHRIS; TREDOUX  MARIAN; SPATH  ANDREAS 《Journal of Petrology》2001,42(10):1911-1926

Experiments in the Fe–Ni–Cu–S system wereperformed to identify the role of the metal/S atomic ratio onmonosulphide–melt partition coefficients and closed-systemfractionation paths. In accord with previous work, D_Cu is  相似文献   

Origins of Large Volume Rhyolitic Volcanism in the Antarctic Peninsula and Patagonia by Crustal Melting   总被引：10，自引：1，他引：10  

RILEY  TEAL R.; LEAT  PHILIP T.; PANKHURST  ROBERT J.; HARRIS  CHRIS 《Journal of Petrology》2001,42(6):1043-1065

Voluminous rhyolitic volcanism along the palaeo-Pacific marginof Gondwana was marked by three principal episodes of magmatism.The first of these ( V₁) is essentially coincident with themain episode of Karoo–Ferrar magmatism at  相似文献   

Digital Divides in New South Wales: A research note on socio-spatial inequality using 2001 Census data on computer and Internet technology     

CHRIS GIBSON 《The Australian geographer》2003,34(2):239-257

This paper examines social and spatial inequalities in personal usage of information technologies, drawing on data made available recently as part of Australia's national census, undertaken by the Bureau of Statistics in 2001. Data on both computer and Internet use are analysed in a number of ways: patterns of use and non-use of the technology are examined across New South Wales in relation to a number of variables, including age, place of birth, indigeneity, income and educational status. Selected results are mapped for State-wide trends and within Sydney, revealing spatial inequalities both across and among regions. Correlation and regression analysis are used to demonstrate the strength of association between computer and Internet use and other socio-economic variables. The results suggest that there is a strong class as well as spatial dimension to Australia's digital divides. Educational status and income mediate use of computers and Internet technologies, in addition to factors associated with location, indigeneity and birthplace. Such observations reinforce those made elsewhere regarding the uneven geometries of power apparent in information economies, and suggest interventions in public policy debates, particularly in the areas of telecommunications provision, resourcing of public schools, and regional economic development.  相似文献   

Reconstructing random topography from preserved stratification   总被引：2，自引：1，他引：2  

CHRIS PAOLA  LEON BORGMAN† 《Sedimentology》1991,38(4):553-565

One of the fundamental problems of interpreting the sedimentary record is reconstructing the original heights of palaeotopographical features such as bedforms or river channels. This requires an understanding of the relationship between topography and set thickness, but at present an exact theory exists only for periodic topography of uniform height. The applicability of this simple theory is severely limited by the random variability characteristic of many sedimentary systems. In this paper, we develop an exact theory for the probability-density function (PDF) of sets generated from topography of random height. We focus on the limiting case of zero net deposition in order to provide a lower bound for the set thickness, and derive an analytical set-thickness PDF that is determined by one parameter of the PDF for topographical height. This parameter, β, measures the breadth of the tail of the topographical PDF. The mean set thickness is 0.8225 β for bedforms and 1.645 β for river channels. If the topographical height is gamma distributed, the preservation ratio, defined as (mean thickness of preserved sets)/(mean topographical height), is 0.8225 r² for bedforms and 1.645 r² for river channels, where r is the coefficient of variation (standard deviation/mean) of the generating topography. In a comparison with data from laboratory current ripples, our analytical predictions compare well with observations of both mean set thickness and thickness distribution. The preservation ratio for the ripples is about 0.5, whilst measured dune heights give a preservation ratio of about 0.12. Depth data from two modern braided streams yield preservation ratios ranging from 0.4 to 0.75. As more data on the distributions of topographical height in modern environments become available, calculations such as these should help provide reliable error bounds for quantitative topographical reconstruction.  相似文献   

Effects of land use and fine-scale environmental heterogeneity on net ecosystem production over a temperate coniferous forest landscape   总被引：2，自引：0，他引：2  

DAVID P. TURNER  MICHAEL GUZY  MICHAEL A. LEFSKY  STEVE VAN TUYL  OSBERT SUN  CHRIS DALY  BEVERLY E. LAW 《Tellus. Series B, Chemical and physical meteorology》2003,55(2):657-668

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