ISSN:0435-3676    

DOI:10.1080/04353676.1996.11880455

出版商:Taylor&Francis    

年代:1996

数据来源: Taylor

摘要:

ABSTRACTIn 1945 Storglaciären located in the Kebnekaise massif, northern Sweden, was selected for a long term study of the climatic impact on glaciers and an annual mass balance programme was initiated. Since the mass balance year 1945–1946 the average annual winter precipitation has increased by 0.53 m water equivalent (w. eq.), the annual average ablation has decreased by 0.58 m w. eq., and the annual average net balance has increased from -0.80 m w. eq./year to +0.30 m w. eq./year. The decrease in ablation is caused by a decrease in summer temperature of about 1°C. In addition, frontal retreat has decreased the low altitude area of the glacier and hence contributed to this decrease in ablation. A comparison with results from mass balance studies at three additional glaciers in the Kebnekaise area show that Storglaciären is representative for the area. The mass balance of Storglaciären is also positively correlated with each of four Norwegian glaciers, although accumulation and net balance are better correlated than ablation. Correlations become less positive with increasing distance between sites. Glacier front measurements provide filtered and delayed indications of climatic changes. Small glaciers are at present in balance with the climate. However, retreating fronts of large glaciers show that they are still adjusting to the major warming of the first half of the 1900s.

ISSN:0435-3676    

DOI:10.1080/04353676.1996.11880456

出版商:Taylor&Francis    

年代:1996

数据来源: Taylor

摘要:

ABSTRACTAir temperatures at Tarfala Research Station have been measured during the summers of 1946 to 1995. Since 1965 several different types of automatic systems have been used for measurements throughout the entire year. Mean annual temperature for the period 1965 to 1995 was -3.9°C. Mean summer (June-August) and mean winter temperatures (October-April) were +5.5°C and -8.9°C respectively. The mean annual temperature shows a weak warming trend which is caused by increasing winter temperatures and slightly decreasing summer temperatures. The amplitude between the temperature of the coldest winter month and that of the warmest month of the following summer decreased by 0.8°C per decade during the period from 1965 to 1995, indicating a change towards a more maritime climate in the Tarfala Valley.

ISSN:0435-3676    

DOI:10.1080/04353676.1996.11880457

出版商:Taylor&Francis    

年代:1996

数据来源: Taylor

摘要:

ABSTRACTA comprehensive glacio-meteorological experiment was conducted on Storglaciaren in both the second half of the 1970s and in the 1990s. For a 40 day period in July and August 1994, the surface energy balance was calculated from measurements obtained by a meteorological station on the glacier. Melt rates obtained as residuals in the heat balance equation were compared to measurements with ablatographs and ablation stakes in the vicinity of the climate station. On average, the contributions of the net radiation and the turbulent fluxes were roughly two thirds and one third, respectively. Calculated melt energy was considerably underestimated on days characterized by dense fog or precipitation. The energy balance was extremely sensitive to the choice of surface roughness. The roughness length for the logarithmic profile of wind speed was higher than the roughness length for temperature by two orders of magnitude.

ISSN:0435-3676    

DOI:10.1080/04353676.1996.11880458

出版商:Taylor&Francis    

年代:1996

数据来源: Taylor

摘要:

ABSTRACTThe robustness of a simple flow-line model has been tested against new data from Storglaciären. The model appears robust for given subglacial geometry. A realistic longitudinal profile and acceptable ice surface velocities were generated. The model has been tested in a series of sensitivity experiments, and was found to react strongly to changes in climatic parameters (ΔELA of 25 m,∼0.25 meters water equivalent). Due to the uneven subglacial topography underlying Storglaciären, its behavior is non-linear and prone to considerable hysteresis. From these experiments it appears that Storglaciären was not in balance with its climate when it reached its maximum historic extent in 1915.

ISSN:0435-3676    

DOI:10.1080/04353676.1996.11880459

出版商:Taylor&Francis    

年代:1996

数据来源: Taylor

摘要:

ABSTRACTIce cores obtained from cold glaciers are known to contain detailed archives on past climates. So far, no such data-set has been retrieved from Scandinavia, in part because most Scandinavian glaciers are largely of a temperate type, thus having a less well preserved climatic signal. However, within the more continental parts of the Scandinavian mountain range, glaciers often have a substantial cold surface layer in the ablation area. Past climate variations may be reconstructed from studies of crystallography and stratigraphy of ice from the cold surface layer. The thicknesses of such cold layers at two closely situated sites in northern Sweden have been mapped by a ground based high resolution radar. The best results were obtained by using the frequency interval 700–900 MHz. The two investigated glaciers Storglaciären and Mårmaglaciären are situated 20 km from each other in an area with a strong east-west climatic gradient. The annual average air temperature is similar at the two sites, whilst the precipitation rate on Storglaciären is almost double that of Mårmaglaciären. The radar soundings show that Mårmaglaciären has a significantly thicker cold surface layer, 65 m on average compared with 30 m on Storglaciären. The difference is caused by less snow cover insulation from winter cold and less net ablation on Mårmaglaciären. The measured thicknesses of the cold surface layer therefore seem to correlate well with the degree of continentality at the sites. Radar sounding is a highly useful tool for locating glaciers containing a potential relatively well preserved climatic signal. Such glaciers may be found within the more continental parts of the Scandinavian mountain range.

ISSN:0435-3676    

DOI:10.1080/04353676.1996.11880460

出版商:Taylor&Francis    

年代:1996

数据来源: Taylor

摘要:

ABSTRACTThe mean annual suspended sediment load in the Storglaciären drainage basin is estimated to be 5.74×106kg yr-1. Assuming, that erosion and sedimentation in the proglacial area is in balance, the specific suspended sediment transport from Storglaciären amounts to 1.85×106kg km-2yr-1, which corresponds to an annual erosion of 0.7 mm. Adding estimated contributions by bedload, total annual erosion becomes 0.9-1.3 mm. The transport of suspended sediment in the proglacial stream is characterised by a time lag between peaks in suspended sediment concentration and peaks in water discharge and the flushing of material during flood events, followed by periods of low sediment transport. These patterns were found at diurnal, seasonal and annual time scales, A linear regression analysis of logarithmically transformed suspended sediment concentration and water discharge data yields good results, despite systematic underestimation of real suspended load. This underestimation most probably occurs because mobilisation of fine-grained material by rainstorms is ignored.

ISSN:0435-3676    

DOI:10.1080/04353676.1996.11880461

出版商:Taylor&Francis    

年代:1996

数据来源: Taylor

摘要:

ABSTRACTIn the Scandinavian mountains several land-surfaces of different ages can be discerned. The youngest one is the Quaternary, glacially eroded surface still under formation. Sediment transport data, recorded downstream from the glacier Storglaciären, Swedish Lapland, and deep-sea records of benthicδ18O were used to calculate the time required for the formation of the glacial trough of this glacier and to discuss the climatic conditions under which subglacial erosion could have taken place. It was found that 300 000 years of glacial erosion were sufficient, but the process has been going on intermittently during 2.5 million years as relatively brief events, separated by extended periods of cold-based, non-erosive conditions. The erosional events were characterized by a climate ranging between the present one and a somewhat cooler, but still interglacial climate, similar to what was prevailing during isotopic substage 7c (about 235 000 years BP).

ISSN:0435-3676    

DOI:10.1080/04353676.1996.11880462

出版商:Taylor&Francis    

年代:1996

数据来源: Taylor

摘要:

ABSTRACTStorglaciären is a small valley glacier in northern Sweden. Detailed studies of surface velocity, glacier hydrology and ice dynamics between 1981 and 1995 have revealed unexpected details of dynamic behaviour of the glacier. The glacier accelerates and decelerates, frequently on a diurnal basis, in direct response to subglacial water pressure variations. Furthermore longitudinal coupling effects are evident where the glacier flows across irregularities on the bed. This coupling is caused by a change in the hydraulic system underneath the glacier as the glacier flows across a bedrock ridge. Since the properties of the drainage system can change over small distance, the dynamics of the glacier is also spatially highly variable. Thus, small glaciers, such as Storglaciären, are not as sluggish as may be expected but exhibit behaviour similar to that of larger glaciers. This means that features of large glaciers and ice sheets can be studied on smaller glaciers where logistics and experimental set-ups are easier to establish.

ISSN:0435-3676    

DOI:10.1080/04353676.1996.11880463

出版商:Taylor&Francis    

年代:1996

数据来源: Taylor

摘要:

ABSTRACTPaths, travel times and deformation of particles are simulated with a flow model in order to study two questions regarding the ice flow in Storglaciären. This model suggest that blue-ice structures observed on the ice surface did not originate as crevasses. The two applications of the model are: 1. To investigate advection and deformation of extensional crevasses in the upper accumulation area, too see whether they are the source of extensive arcuate blue-ice structures found at a lower altitude on the glacier surface. 2. To determine whether traces from crevasses originated in different areas would mix into each other during the transportation through the glacier.The simulations of the particle paths and their deformation shows that: 1. Crevasses visible today in the accumulation area will emerge upglacier from the zone where the arcuate structures are found. Consequently, the model does not support explanation of the blue-ice arcs as closed or frozen water-filled crevasses. 2. Traces of crevasses from different crevassed areas will mix into each other when emerging at the surface. A discussion if changes in geometry of the glacier will affect the results gives that the dynamics in the glacier have not changed much in the uppermost 3/4 of the glacier since the mid-19th century.

ISSN:0435-3676    

DOI:10.1080/04353676.1996.11880464

出版商:Taylor&Francis    

年代:1996

数据来源: Taylor