摘要:

AbstractIn this paper Holocene climatic changes recorded in Lappland, northern Sweden, are described. Recorded changes are dated in three different ways: (1) moraines fronting alpine glaciers are dated licheno- metrically, (2) lacustrine sediments, in which the silt content varies with size fluctuations of a small glacier, are C14dated, and (3) variations in altitude of the pine tree limit are C14dated. The advantages and limitations of the three techniques are discussed and the results of the studies are compared. In general, the results obtained in these three ways are consistent and are interpreted in climatic terms.The area around Vuolep Allakasjaure probably became deglaciated just before 9000 B.P. About 8600 B.P. climate began an improvement which culminated between 7000 and 6000 B.P. Shorter fluctuations are superimposed on this long-term climatic change. The most pronounced periods of relatively cold climate occurred about 7500–7300 B.P., 4500 B.P., 2800–2200 B.P., and during recent centuries. Variations in the composition of sediments in cores from Vuolep Allakasjaure indicate that the glacier in the drainage basin fluctuated frequently in size.

ISSN:0435-3676    

DOI:10.1080/04353676.1976.11879921

出版商:Taylor&Francis    

年代:1976

数据来源: Taylor

摘要:

AbstractFossil tundra fragments consisting chiefly of moss (Rhacomitrium lanuginosum—60%,Dicranum—20 %) were found in the forefield of Werenskioldbreen during the glaciological investigations of the Polish Scientific Spitsbergen Expedition. The vegetation formed a cover about 5 cm thick and occurred between two till layers. The samples taken for radiocarbon analysis in 1973 came from a position 25 m a.s.l., located about 450 m from the glacier front. In 1957 the fossil tundra was still completely covered by ice. The average age of the whole stratum was dated to 1080±105 years B.P. (St-4695). The age of the upper part of this layer was dated to 760±145 years B.P. (Gd-264), and the lower part to 1565±235 (St-5068). Tundra fragments of similar age (1–7578: 1095±85 years B.P.) have also been found between two till layers at the front ofÅrjep Ruotesjekna in Swedish Lapland.The results indicate that during the Viking Age Spitsbergen and northern Scandinavia experienced a warm period with distinct glacier retraction and well-developed tundra on the glacier forefields. This period was preceded by a marked, long-lasting glacier advance and followed by an equally extensive, but shorter advance.

ISSN:0435-3676    

DOI:10.1080/04353676.1976.11879922

出版商:Taylor&Francis    

年代:1976

数据来源: Taylor

摘要:

AbstractArctic regions differ from temperate areas in the extreme seasonality of climatic conditions. In 1971, water samples and bottom sediments were taken from the Colville River system in Arctic Alaska prior to breakup, during breakup, and during summer for nutrient study. Although sediments are primarily sandy, some silt and clay are also present especially in the oceanic portion of the delta. Clay minerals are primarily kaolinite and illite. Montmorillonite and small amounts of a chlorite-like mineral are also present. The organic content in the sediments was higher in the upper river channel than in the ocean, whereas interstitial nitrogen components showed the opposite trend. These interstitial components are the products of organic decomposition in sediments. Through diffusion and animal activity, some of these components may slowly enter the water column beneath the ice cover during winter when exchange of water throughout the river channel is blocked by bottomfast ice. During the flood period in early spring, interstitial components in the basin sediments are also contributed to river water by leaching.Once flooding begins, river water, which consists of snowmelt from mudflats, sand dunes, and the tundra surface, moves under the sea ice as a wedge. It contains more nutrients than does the seawater beneath. This floodwater, rich in inorganic-N (N/P ratio = 23: 1 in 1971), is significant in contributing to the nitrogen-deficient seawater (N/P ratio = 3: 1), and provides a basic ingredient for phytoplankton production. During summer, depletion of nutrients prevails as a result of phytoplankton uptake and dilution by seawater. It was calculated that during spring the nutrient-enriched floodwater of the Colville River contributes 0.875×106kg of inorganic-N to the ocean. Such nutrient input is significant in the primary productivity of this nearshore zone, helping account for the abundance of fish found in the area.

ISSN:0435-3676    

DOI:10.1080/04353676.1976.11879923

出版商:Taylor&Francis    

年代:1976

数据来源: Taylor

摘要:

AbstractA fossil brown podzolic (Typic Cryochrept) soil covers the two outermost moraine ridges at Engabreen. This soil is buried by a sediment which is considered to be of aeolian origin and is thought to have been derived from an adjacent sandur which had been reactivated by a later glacial advance. The subsequent advance built a major moraine ridge just proximal to the two older ridges. A comparison of the palaeosol with the modern soils on the three ridges reveals similar development. It is suggested that these soils each indicate some 250 years of soil formation so consequently the two outer ridges were created by a glacial advance prior to 1450 A.D. This latter event was the maximal Neoglacial advance. The historically recorded early eighteenth century advance which destroyed a farm terminated at the major moraine ridge and thus was not the largest advance.

ISSN:0435-3676    

DOI:10.1080/04353676.1976.11879924

出版商:Taylor&Francis    

年代:1976

数据来源: Taylor

摘要:

AbstractExtensive areas of the eastern Canadian Arctic are light grey/white on both conventional black and white air photography and on multi-spectral LANDSAT-1 satellite imagery. These areas stand out in marked contrast to the darker toned surrounding terrain. Field investigations indicate that the light grey areas possess few lichens or plants; in contrast, their margins abut terrain with a mature lichen cover. Areas within the lichen trimlines are interpretcd as the sites of former permanent snowbeds and snowfields. Radiometric and lichenometric dates indicate that the episode of permanent snowfields occurred about 500 to 300 years ago with retreat starting between 300 and 70 years ago. The LANDSAT-1 satellite imagery at a scale of 1: 1000000 has proven ideal for mapping the regional extent of this former snow-cover and this is illustraled by two frames from north-central Baffin Island. Interpretation problems can arise from a number of sources, such as: light early summer or fall snowcover, limestene bedrock, recent outwash plains, and low clouds. However, ambiguities can be eliminated by inspection of LANDSAT-1 frames from different passes, by the examination of 1: 60 000 air photographs, by the use of 1: 250 000 scale contour maps, and by comparison with maps of the bedrock geology.A comparison of Little Ice Age glaciation levels with those based on the present distribution of permanent ice/snow bodies indicates that during the Little Ice Age the regional snowline fell between 100 and 400 m: thus extensive areas of the upland plateaus of Baffin Island above 600 m were mantled by a thin but extensive permanent snowcover. This study serves to provide a realistic modet for the inception of a North American ice sheet.

ISSN:0435-3676    

DOI:10.1080/04353676.1976.11879925

出版商:Taylor&Francis    

年代:1976

数据来源: Taylor

摘要:

ZusammenfassungIn Rondane/Norwegen wurde der periglaziale Formenschatz auf Luftbildern kartiert und im Gelände kontrolliert. Wir unterscheiden dabei die folgenden Formen:1.Erd- und Rasenhügel2.Rasenzungen3.Schuttzungen4.Polygonböden5.Steinstreifen6.Blockgletscher.Die wahre Verteilung der einzelnen Formen ist in der Karte (Abb. 1) wiedergegeben, die modellhafte Anordnung der Formen in einem idealisierten Relief findet sich auf Abb. 8. Trotz der Tatsache, daßlokale Faktoren (wie Korngröße, Hangneigung usw.) und die statistisch gesehen geringe Anzahl der Formen den Expositionsunterschied maskieren, läßt sich deutlich erkennen, daßdie Solifluktionsformen (Rasenzungen) in die alpine Höhenstufe gehören. Dagegen nehmen die Polygonböden, die Steinstreifen und die Blockgletscher die obere periglaziale Höhenstufe in Rondane ein. Die aktiven Blockgletscher entsprechen denen der Alpen. Auch in Rondane können sie als Indikatoren für Permafrost angesehen werden.

ISSN:0435-3676    

DOI:10.1080/04353676.1976.11879926

出版商:Taylor&Francis    

年代:1976

数据来源: Taylor

摘要:

AbstractIn April—May, 1971 and 1972, temperatures measured in Quito, Ecuador, at a height of 1.4 m were characterised by horizontal differences which contrasted strongly with the generally accepted patterns for mid-latitude cities. The separated heat islands over the old and modern sections of the city achieved their greatest magnitudes between 1200 and 1300 hours solar time, and these were frequently 5–10 times greater than the mid-day values reported from mid-latitude locations. On the other hand, in the three-hour period preceeding midnight, when heat islands in mid-latitude cities generally achieve their greatest magnitudes, those in Quito were obliterated by the drainage of cooler air from the very steep slopes to the west. By day, the horizontal temperature gradients between Quito's parks and open spaces on the one hand and its modern section on the other were much steeper than any which have been previously reported from other locations. A previous analysis of those critical wind velocities which, in seven mid-latitude cities, caused the destruction of heat islands, indicated that, if no additional factor was involved, such features in Quito should have been obliterated when the wind speed reached 7.9 m/sec. However, there were several occasions on which winds of 9–11 m/sec. permitted well-developed heat islands to remain as dominant features of the daytime temperature pattern. An examination of the possible reasons for the differences in magnitude between the two separated parts of Quito's heat island indicated that albedo was the dominant factor. Finally, it is suggested that the results of an urban climatic study should only be extrapolated within the same macroclimatic region and to areas where the local topography is essentially similar.

ISSN:0435-3676    

DOI:10.1080/04353676.1976.11879927

出版商:Taylor&Francis    

年代:1976

数据来源: Taylor

摘要:

RésuméL'ampleur de la météorisation postglaciaire de diverses surfaces rocheuses aétédéterminée par mesures du déchaussement de filons de quartz dans les Appalaches québécoises (région de Sherbrooke, Cantons de l'Est, Canada) entre 200 et 400 m d'altitude. La méthode employée aétécelle développée par R. Dahl (1967). La mise en relief est en moyenne de 6à15 mm, soit une intensitémoyenne de 0,5à1,2 mm par millénaire. Les matériaux encaissant les moins sensibles sont des roches sédimentaires détritiques fines (schistes ardoisiers et grès quartzites) et volcaniques détritiques grossières (tufs). Le déchaussement est favorisépar la largeur et la puretédu filon, l'intensitédu réseau de fissuration de la roche encaissante, l'entretien de l'humiditépar de faibles pentes et l'existence d'une couche de végétation sur les filons.

ISSN:0435-3676    

DOI:10.1080/04353676.1976.11879928

出版商:Taylor&Francis    

年代:1976

数据来源: Taylor

摘要:

AbstractThe excavation of material by burrowing mammals (voles and moles) was investigated on experimental plots on a wooded slope in the Luxembourg Ardennes. Monthly records of the amount of material excavated by animals, the area they disturbed and of the total area of the bare ground enabled the significance of the downslope displacement of material and the consequences of burrowing for splash erosion to be evaluated. Markedly seasonally variable burrowing was related to soil and slope conditions. Although the rate of displacement of material down- slope during excavation is low, it would seem that burrowing animals were directly or indirectly responsible for most of the transport of material on the investigated slope and that they therefore play an important role in colluviation and sediment supply. As burrowing by animals is possibly a more important slope process under forest than hitherto recognised, it deserves further investigation.

ISSN:0435-3676    

DOI:10.1080/04353676.1976.11879929

出版商:Taylor&Francis    

年代:1976

数据来源: Taylor

ISSN:0435-3676    

DOI:10.1080/04353676.1976.11879920

出版商:Taylor&Francis    

年代:1976

数据来源: Taylor