摘要:

ABSTRACTThis paper examines the radiation balance and heat transfers over undisturbed subarctic tundra. The data varied considerably with the three synoptic periods observed at the site; viz. anticyclonic, changeable/transitional and cyclonic. For example, the incoming shortwave radiation averaged 25.8 Megajoules per square metre per day (MJm-2day-1) with clear anticyclonic weather compared with 19.3 MJm-2day-1in the changeable period (with alternating cloudy and sunny spells) and 11.3 MJm-2day-1in the cloudy cyclonic period. The remaining shortwave and longwave components displayed similar decreases. Albedo changes were related to variations in surface moisture, ranging from 22.5 percent at the end of the dry spell to 15.5 percent when standing water occupied all surface depressions.The Bowen ratio and heat transfer data emphasise the dominance of latent heat fluxes over the freely evaporating and transpiring terrain. However, the transfers were controlled by the synoptic variations which influenced the supply of net radiation and surface moisture levels. Obviously, the latent heat flux was at its greatest when snow ablation maintained the field capacity of the soil and especially in wet cyclonic weather, when surface water was evident. During this rainy period, the lowest Bowen ratio values were recorded (0.22) despite the limited supply of net radiation. Conversely, when the soil was at its driest, the Bowen ratio averaged 0.51 with frequent surges over 1.00 when sensible heat fluxes become temporarily dominant.Latent heat fluxes exceeded the available net radiation for most of the period and the supplementary energy was provided by ground heat flux, which was characterised by large negative values. The exception was the period 13–16 July, when the driest soil conditions recorded were associated with minimum latent heat flux demands. At this time, the available net radiation was adequate for all heat transfers and a perfect energy balance resulted. The paper concludes with a discussion of Bowen ratio and heat transfers at the study area vis-a-vis other snow-free tundra environments.

ISSN:0435-3676    

DOI:10.1080/04353676.1982.11880051

出版商:Taylor&Francis    

年代:1982

数据来源: Taylor

摘要:

ABSTRACTTwo main points of dispute are discussed: first, the potential error in the14C dating of end moraines using buried soils; second, the date of the‘Little Ice Age’glacier maximum and associated moraines in southern Norway. Because of the‘age/depth effect’in well-developed soils, it is concluded that overestimates of moraine age in excess of 1000 years are possible. It is emphasized that there is no reliable evidence for any‘Little Ice Age’moraine ridges older than about A. D. 1750 in southern Norway. Whilst in northern Scandinavia the evidence suggests the presence of older Neoglacial moraine ridges, more sophisticated14C dating appears necessary to date them precisely.

ISSN:0435-3676    

DOI:10.1080/04353676.1982.11880052

出版商:Taylor&Francis    

年代:1982

数据来源: Taylor

摘要:

ABSTRACTSmall pockets of stones, in which a one grain thick layer of coarser material overlies finer particles, occur near the margin of the Norwegian glacierØsterdalsisen, on the lower slopes of Burfjell. The stones in the upper layer are closely packed and their long axes near-horizontal. In some pockets, size sorting of the upper layer has occurred, the grains fining downslope. Sorting is considered to result from a combination of meltwater saturation, frost heaving, needle ice formation and turning and compaction of stones under a snow cover.

ISSN:0435-3676    

DOI:10.1080/04353676.1982.11880053

出版商:Taylor&Francis    

年代:1982

数据来源: Taylor

摘要:

ABSTRACTClast fabrics in the coarse borders of sorted patterned-ground features have been descriptively characterized in a variety of ways, but have rarely been measured or analyzed statistically. Three-dimensional analyses of rock fragments in the borders of a large sorted stripe reveal significant departures from uniformity. Most a-axes are oriented subparallel to the axis of the stripe and dip gently, but have no discernable tendency for up- or downslope imbrication. In contrast, b-axes are steeply inclined, indicating compression due to expansion of fine centers as autumn freezeback proceeds. Particle orientation at the stripe's downslope margin does not differ significantly from uniformity.

ISSN:0435-3676    

DOI:10.1080/04353676.1982.11880054

出版商:Taylor&Francis    

年代:1982

数据来源: Taylor

摘要:

ABSTRACTThe Svea Lowland, located in eastern van Mijenfjorden, central Spitsbergen, is composed of both marine clay and glacial till. These deposits have been divided into three geologic units based on their differing lithology and topographic expression: (1) the Geikie Moraine, (2) the Dames Moraine, and (3) an organic-rich marine clay. The sediments were deposited during two surges of the Paula Glacier in Holocene time.The first surge of the Paula Glacier is suggested by the limited C-14 age range of marine mollusk shells, between 7800 and 8500 years old, incorporated in all three deposits. This surge provides a mechanism to kill the molluscs at this time while producing a deposit of limited-age material available for redeposition and incorporation with younger material by a later surge of the Paula Glacier.A second surge of the Paula Glacier is suggested by (1) the ice-cored nature of the moraine deposits on the lowland, (2) the semi-arcuate distribution of the moraine deposits traceable to the current glacial front, (3) young radiometric dates of driftwood and whalebone incorporated within and on the surface of the marine clay, and (4) the presence of a datable turf horizon underlying the glacially pushed marine clay. These features suggest this surge occurred between 600 and 250 years ago. As the Paula Glacier surged across the fjord, the fjordbottom clay, possibly deposited in the past by a previous surge, was both pushed before the advancing glacier and incorporated into its till. Some of the ice-shoved marine clay was pushed as a slab before the ice-cored Dames Moraine, over the existing tundra-covered lowland. Recent strandlines present up to 20 m above sea level surrounding Braganza Bay suggest that the Paula Glacier dammed Braganza Bay producing a lake at this time.Subsequent to the last surge, partial melting of the ice in the Dames Moraine has resulted in the striking knob and kettle terrain and associated small lakes over much of the area. A recent surge of the Sabbarp Glacier deformed moraine material (Dames Moraine) produced by the second surge of the Paula Glacier. Intense frost action has created frost-split debris on the moraine surfaces.

ISSN:0435-3676    

DOI:10.1080/04353676.1982.11880055

出版商:Taylor&Francis    

年代:1982

数据来源: Taylor

摘要:

ABSTRACTStoröyjökulen is a low-lying ice cap of about 28 km2that covers the southern half of Storöya in eastern Svalbard. Between July 8 and August 12, 1980, a reconnaissance study of the present glaciation of Storöya was carried out by 4 physical geographers from the University of Stockholm.Ice temperature measurements on many spots all over the glacier showed that Storöyjökulen is a cold glacier of the subpolar type. Core drilling on the summit showed that glacier ice is formed inoneseason, as no firn was found. This process of infiltration-congelation has in part been followed by stake and snow depth measurements.The winter season 1979–80 ended around June 30, 1980, and then the winter balance of Storöyjökulen was 12 cm of water equivalent. This winter balance was unequally distributed over the ice cap. A primary maximum was located at low elevation along the cliffed, southeastern margin, while a secondary maximum existed on the plateau.The ablation season was not ended when we had to depart from Storöya, but it seems as if the net balance of Storöyjökulen might have been positive in 1979–80; at any rate in its southeastern sector.The reason for the existence of Storöyjökulen, although its highest point is only 239 m a.s.l. and its winter balance very small, seems to be a combination of cold ice and a cloud-covered summit plateau with frequent summer snowfalls and summer air temperatures most often below zero degrees.

ISSN:0435-3676    

DOI:10.1080/04353676.1982.11880056

出版商:Taylor&Francis    

年代:1982

数据来源: Taylor

摘要:

ABSTRACTThe amount and type of driftwood logs on raised beaches in Svalbard probably indicate variations in sea ice conditions through time in the Arctic Ocean. This idea is based on the fact that wood floating in water has a limited buoyancy. The maximum period of buoyancy for coniferous wood (Picea/spruce, Larix/larch, Pinus/pine) is between 10 and 17 months: for broadleaves (Betula/birch, Salix/willow, Populus/aspen) from 6 to 10 months. The buoyancy depends on many circumstances but foremost on the properties and basic density of wood when the drift starts.Two dominant drift features are evident in the Arctic Ocean. The Pacific Gyral has a clockwise circulation in the Beaufort Sea. There are large variations in the rate of drift of this circulation, but the average speed is probably 700–800 km/year. The Transpolar Drift Stream runs from the Siberian coast to Svalbard and north Greenland and the average drift rate 600 km/year may be close to the actual net speed of an ice floe or a log of driftwood.The passage from the Siberian coast to the Svalbard area takes, roughly, five years. A trunk with the best possible buoyancy sinks after a third of that time. However, because of rafting on or in the sea ice, driftwood logs land on the islands of Svalbard. Most of the wood on the eastern islands of the archipelago is coniferous wood of Siberian origin. There are at least two easily noticeable zones on the shores with raised beaches where the amount of driftwood is small. These zones probably represent climatic conditions with periods of“long summers”; a high percentage of open water and a northerly position of the ice limit.

ISSN:0435-3676    

DOI:10.1080/04353676.1982.11880057

出版商:Taylor&Francis    

年代:1982

数据来源: Taylor

摘要:

ABSTRACTDuring the latter half of the 18th century quite a large number of Swedish maps was constructed. The question, whether this map material can be used for a study of shoredis-placement is illuminated by a case study from the Hållnäs peninsula in northern Uppland. It was found that, in this case, the old shoreline was not very well mapped. However, a careful analysis of the altitude of areas that were mapped as rocks or skerries on the old maps might provide valuable information about the maximum shore displacement since the map was constructed. Also, levelling of areas that were mapped as sounds or narrow channels on the old maps but are now dry land might provide valuable information about the minimum shore displacement since the map was constructed. An examination of the lowest maximum values and the highest minimum values leaves, in this case, a very small gap which leads to the assumption of a shore displacement in the area of 1.50 m during the last 230 years. This value is well in accordance with observations from the old water mark at Lövgrundet, and extrapolated values from tide-gauge observations.

ISSN:0435-3676    

DOI:10.1080/04353676.1982.11880058

出版商:Taylor&Francis    

年代:1982

数据来源: Taylor