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The polythcrmal valley glacier Erikbreen (79°40'N 12°30'E), northern Spitsbergen, was investigated in 1970 and 1990 using digital photogrammetry and digital elevation model (DEM) techniques. The bottom topography was derived from radio-echo soundings. Based on the DEM, mass balance and changes of surface slope, crevasse and flow pattern were evaluated, and internal ice deformation velocities were calculated. Calculations of the total mass balance show that Erikbreen has not been in equilibrium for the last 20 years. The average surface lowering was 0.38 m/a and the volume had decreased by 5% to 6% from 1970 to 1990 or on the average by 3.5 × 10−1 water. The glacier surface subsided over the whole glacier area except in minor areas with northfacing slopes in the accumulation area. The surface slope and the crevasse pattern, however, did not change significantly during the 20-year-period, except in areas below 100 ma.s.l. 相似文献
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Sensitive diffusive samplers for concentration measurements in ambient airhave been used successfully in Sweden for several years. The samplers have theadvantage of being stable at room temperature before, as well as after,sampling, easy to handle, and cost-efficient. Furthermore, they do not requireelectricity or field calibration. In order to test their use in tropical andsubtropical environments and to obtain a preliminary set of data to validateatmospheric chemistry transport models in this part of the world, duplicatesamples were collected at 11 sites every second month during one year. Eightof the sites were background sites in Asia. It was not possible within theproject to compare the measured concentrations with other measurementtechniques. However, the reproducibility of the duplicates was satisfactoryover the whole measuring range (almost three orders of magnitude of theconcentration for SO2) and reasonable agreement with modelcalculations was obtained at least for SO2 andNH3. Further testing of the measuring technique in tropicalareas is, however, warranted. 相似文献
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Influence of temperature conditions in formation of end moraines in Fennoscandia and Svalbard 总被引:2,自引:0,他引:2
JOHAN LUDVIG SOLLID LEIEF SØRBEL 《Boreas: An International Journal of Quaternary Research》1988,17(4):553-558
In the Finnmark region of northern Norway, end from Younger Drays and earlier periods appear as irregular mounds and ridges in a broad zone with a distinct distal margin. These moraines are similar in shape to end moraines formed in Svalbard today by melting of ice-cored moraines in front of subpolar glaciers under permafrost conditions. The end moraines in Finnmark were mkost likely formed in the same way in a permafrost climate during deglaciation. This might also be the case for moraines in the southernmost parts of Fennoscandia, in Denmark and southernmost Sweden. Cold-based ice during deglaciation in central parts of Fennoscandia is due to climatic conditions tens of thousands of years earlier. The period with climatic improvement after the Weicheselian maximum was too short to have any influence on the thermal conditions at the base of the ice-cap in the central areas. 相似文献
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Numerous studies show that the environmental concentrations of PCBs have been decreasing since the production and use of PCBs in most industrialised countries was banned in the 1970s. However, most of these studies have been conducted close to historical sources. The few studies conducted in remote locations detect no trend of decreasing concentrations over the past 20–30 years. These observations suggest that PCBs may be removed more slowly from the environment, when viewed from a global or hemispheric perspective. The present study estimates the mass fluxes of individual PCB congeners in the Northern Hemisphere in order to elucidate the most important removal processes and the rate of decrease one may expect with complete cessation of emissions. Atmospheric reaction lifetimes, open‐ocean settling fluxes and the pools and mobility of PCBs in the terrestrial environment are shown to be crucial parameters. However, the calculations identify important gaps of knowledge regarding predictions of environmental half‐lives of PCBs. The results suggest that highly chlorinated congeners such as PCB 153 and 180 may be persistent in the global environment with annual rates of decrease of less than 1%. The compiled environmental data also highlight large differences between the different PCB congeners. Although this paper is based on more than 800 PCB measurements it should be considered a starting point for further research aiming to quantify the global fate of toxic and persistent organic substances such as the PCBs. 相似文献
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LARS RODHE 《Boreas: An International Journal of Quaternary Research》1988,17(4):511-516
At four localities in area east of the Sarek and Kebnekajse massifs in Swedish Lapland, glaciofluvial channels seem to have been overhidden by glaciers without having extensively modified. It is suggested that the channels were formed during an Early Weichselian stade. The last glaical advance had little effect on the pre-exiting landforms at these localities and probably also at many other places in the area. Earlier theories about glacial development and deglaciation patterns in this area are based on morphology and the assumption that the landforms were formed during the last deglaciation. These theories need to be revised. 相似文献
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JOHAN STRIBERGER SVANTE BJÖRCK ÓLAFUR INGÓLFSSON KURT H. KJÆR IAN SNOWBALL CINTIA B. UVO 《Boreas: An International Journal of Quaternary Research》2011,40(1):28-45
Striberger, J., Björck, S., Ingólfsson, Ó., Kjær, K. H., Snowball, I. & Uvo, C. B. 2010: Climate variability and glacial processes in eastern Iceland during the past 700 years based on varved lake sediments. Boreas, 10.1111/j.1502‐3885.2010.00153.x. ISSN 0300‐9483. Properties of varved sediments from Lake Lögurinn in eastern Iceland and their link to climate and glacial processes of Eyjabakkajökull, an outlet glacier of the Vatnajökull icecap, were examined. A varve chronology, which covers the period AD 1262–2005, was constructed from visual observations, high‐resolution images, X‐ray density and geochemical properties determined from X‐radiography and X‐ray fluorescence scanning. Independent dating provided by 137Cs analysis and eight historical tephras verify the varve chronology. The thickness of dark‐coloured seasonal laminae, formed mainly of coarser suspended matter from the non‐glacial river Grímsá, is positively correlated (r=0.70) with winter precipitation, and our 743‐year‐long varve series indicates that precipitation was higher and more varied during the later part of the Little Ice Age. Light‐coloured laminae thickness, controlled mainly by the amount of finer suspended matter from the glacial river Jökulsáí Fljótsdal, increased significantly during the AD 1972 surge of Eyjabakkajökull. As a consequence of the surge, the ice‐dammed Lake Háöldulón formed and recurrently drained and delivered significant amounts of rock flour to Lake Lögurinn. Based on these observations, and the recurring cyclic pattern of periods of thicker light‐coloured laminae in the sediment record, we suggest that Eyjabakkajökull has surged repeatedly during the past 743 years, but with an increased frequency during the later part of the Little Ice Age. 相似文献
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HENNING RODHE 《地球,A辑:动力气象学与海洋学》1999,51(1):110-122
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KRISTER N. JANSSON ARJEN P. STROEVEN JOHAN KLEMAN 《Boreas: An International Journal of Quaternary Research》2003,32(1):256-262
The prominent Ungava Bay landform swarm (UBLS), covering an area of ˜260000 km2 south of Ungava Bay, Canada, is defined by drumlins, crag-and-tails, horned crag-and-tails and flutes indicating convergent ice flow towards Ungava Bay. The UBLS has been difficult to interpret in terms of ice-sheet configuration, dynamics and age. Aerial photograph and satellite image interpretations of the Labrador-Ungava region reveal a previously unrecognized level of complexity within the UBLS consisting of several well-defined segments, most interpreted as representing discrete stream-flow events. Each of the segments is characterized by one or more of the criteria (convergent flow patterns at their heads, attenuated till lineations and abrupt lateral margins) previously suggested as diagnostic for formation by fast-flowing ice (ice streams). The UBLS reflects the most direct and probably fastest contact (in terms of sediment transport) between the Laurentide Ice Sheet interior and the ocean. It is therefore a prime candidate for abrupt changes in glacial-age northwest Atlantic seafloor sedimentation. 相似文献