ISSN:0435-3676    

DOI:10.1080/04353676.1995.11880438

出版商:Taylor&Francis    

年代:1995

数据来源: Taylor

摘要:

ABSTRACTThis paper on selected case studies makes comparisons with climate parameters, slope erosion caused by rapid snow melt and slushflows (slush avalanches, slushers), and slope erosion due to debris flows or slides, triggered by heavy rainfalls. The slushers and debris flows are viewed in a 100-year time perspective and compared with observations at other sites and with records from railway and highway. Other papers in this volume are progress reports based on more detailed international projects in Kärkevagge.

ISSN:0435-3676    

DOI:10.1080/04353676.1995.11880439

出版商:Taylor&Francis    

年代:1995

数据来源: Taylor

摘要:

ABSTRACTIn May and June 1995, the snowmelt period in general and the release conditions of slush torrents in particular were studied within a joint Swiss-German project during a field campaign in Kärkevagge, Swedish Lappland. Measurements and observations comprised all energy balance components and meteorological conditions in the course of the snowmelt period, as well as intra- and subnival meltwater flows and the formation of a saturation zone within the snow cover during the initial period of snowmelt-runoff. In addition, release and movement of a high magnitude—low frequency slush torrent was documented on video and photographs. The results verify that the initiation of slush streams is confined to meltwater accumulation areas in drainage basins. Moreover, it can be demonstrated that both variants of slush streams are released by a hydraulic pressure gradient that is evolving from an inclined water table within the saturated snow cover. This release mechanism allows the initiation of major events without any external triggering. Neither permafrost nor extreme meteorological conditions are prerequisite to slush torrents.

ISSN:0435-3676    

DOI:10.1080/04353676.1995.11880440

出版商:Taylor&Francis    

年代:1995

数据来源: Taylor

摘要:

ABSTRACTGreen Lakes Valley is a high (3500 m elevation), mid-continental drainage at relatively low latitude (40°N) which appears to have been influenced by a variety of environmental changes in the past half-century. Important among these have been increased rates of deposition of strong acid anions from the atmosphere and a corresponding tendency toward acidification of surface waters. In response, a declining trend in acid neutralizing capacity (ANC) and in the pH of streamwater in the basin has occurred in the past 25 years. This trend is most marked at the highest (most alpine) elevations in the basin where there is little soil and vegetation cover but remains detectable, if less marked, at all elevations down to treeline (3250 m). It suggests that acidification (defined as a loss of ANC) of surface water will be widespread in the basin within a decade.

ISSN:0435-3676    

DOI:10.1080/04353676.1995.11880441

出版商:Taylor&Francis    

年代:1995

数据来源: Taylor

摘要:

ABSTRACTThe hydraulic geometry, runoff and sediment transport processes were studied during the 1991 summer season in two small pyroclastic drainage basins on Deception Island, South Shetland Islands. Daily discharge measurements were conducted in two channels draining 0.65 km2and 0.12 km2.The empirical relationship between the depth, velocity and width exponents- f>m>b in channels with non-cohesive material is valid for the studied area. Width is relatively conservative during increase of water discharge. Runoff was almost continuous for about 40 days, showing a strong association between streamflow and temperature. Two main periods are distinguished in the annual hydrological regime: 1. Runoff during a short melting period of snow and glaciers. 2. Snow cover and frozen period of the entire drainage area. Temperature is the main factor affecting the hydrological regime of the rivers and snow availability during the summer season determines discharge water volumes in the non-glaciated basin. The specific discharge value was 3.42 1/sec/km2.Fluvial sediment transport for the 1991 season was 46 ton/ km2yr, one order of magnitude less than values for Arctic rivers, but similar to average yearly sediment yield values of pyroclastic basins in middle latitude areas.

ISSN:0435-3676    

DOI:10.1080/04353676.1995.11880442

出版商:Taylor&Francis    

年代:1995

数据来源: Taylor

摘要:

ABSTRACTSizes of isolated and fully exposed largest lichens on 950 blocks of schistose rock record the times and extents of slush avalanches derived from a stream channel and cirque upstream from the 300 m long Kärkerieppe fan in Kärkevagge, northern Sweden. Small slush avalanches are so frequent that few blocks older than 50 years remain on the fanhead. At least 13 smaller and larger slush avalanches occurred between 1950 and 1995; a production rate of about 30 per century. At least 24 slush avalanches extended to the mid-fan area between about 1790 and 1950; a mean production rate of large slush avalanches of about 15 per century.“Little Ice Age”advances of the Kärkerieppe cirque glacier ended at about 1870 and may have supplied blocks to slush avalanches. Subsequent glacier retreat has changed the source-area hydrologic and topographic characteristics affecting generation of slush avalanches, and has exposed new bedrock sources of blocks for slush avalanches.

ISSN:0435-3676    

DOI:10.1080/04353676.1995.11880443

出版商:Taylor&Francis    

年代:1995

数据来源: Taylor

摘要:

ABSTRACTGeomorphological investigations, detailed mapping and lichenometrical surveys carried out at 27 sites located in northwest and central Spitsbergen provide new insight into the history of major slush stream and debris flow events. Recurrence intervals are estimated at 80–500 yr for debris flows andca.500 yr for slush avalanches, which is consistent with previous estimates from other Scandinavian mountains. The life-expectancy of resulting landforms is estimated to be 2000 yr for avalanche boulder tongues which are protected from active slope processes by their distance from adjacent rockwalls. In contrast, except for some restricted sites, the fragile debris flow levées are rarely preserved for more than 30–40 years and the terminal lobes do not survive for much more than 100 years. The short lifespan of these features is due to their small size (limited by the thinness of the active layer), by the erosive effects of spring snow avalanches and by reworking by subsequent debris flow events. Correlating extreme events and climate fluctuations in the Scandinavian mountains is difficult because of the low frequency of major slush stream events and of the brief lifetime of debris flow features. Even if the increase of debris flow episodes after 1950 reported in the literature may partly result from improved observations, field evidence suggests that debris flows, combined with slope wash and active throughflow, have replaced pressure release and frost related mechanisms as the most prominent component of contemporary morphogenesis in arctic environments.

ISSN:0435-3676    

DOI:10.1080/04353676.1995.11880444

出版商:Taylor&Francis    

年代:1995

数据来源: Taylor

摘要:

ABSTRACTThe aim of the paper is to show the geomorphological role of processes operating around snow patches on the alpine slopes of the High Tatras, using the quantitative data. There are different aspects of nivation which influence on its geomorphological effects, for example topography, snow patches distribution, meteorological conditions in particular years, etc. The geomorphological effects of snow patches on debris mantled slopes and on debris slopes were analyzed. Type of weathering covers, aspect, lithology, vegetation cover were taken into consideration. On the debris mantled slopes the erosional effects could be noticed on these fragments which are devoid of vegetation cover. This is due mainly to frost action and rill erosion. On debris slopes“accumulation niches”are developing in places occupied by snow patches, most often in the apex part of the slope. This is the most important impact of snow patches on the present day development of the slopes of the High Tatras. The rates of accretion in various niches vary from 0.004 to 0.64 cm/ year. At present, the role of nivation is limited to reshaping the forms occupied by snow patches. These forms are often produced by high energy geomorphological processes.

ISSN:0435-3676    

DOI:10.1080/04353676.1995.11880445

出版商:Taylor&Francis    

年代:1995

数据来源: Taylor

摘要:

ABSTRACTGeochemical responses to potential global environmental change predicted by Global Circulation Models (GCM's) for high altitude/latitude environments are being assessed for Kärkevagge (literally translated as“boulder valley”), Swedish Lappland on the basis of a series of static and dynamic field and laboratory studies. Static studies provide baseline information on the geochemical process system, essential for understanding process responses to environmental change. Preliminary studies involve the determination of the nature and origin of lime crusts, rock varnish, and weathering rinds occurring extensively on coarse debris in Kärkevagge.

ISSN:0435-3676    

DOI:10.1080/04353676.1995.11880446

出版商:Taylor&Francis    

年代:1995

数据来源: Taylor

摘要:

ABSTRACTA model is proposed for gelifluction rates, in terms of active layer depths and sub-surface runoff. It is concluded that the flow of soil during melting can generally be assumed to be under saturated conditions, so that active layer depth is the dominant driver. Erosional slope profiles produced by gelifluction should be convex, with no tendency for small hollows to enlarge into valleys at any scale. This model has been applied, using a global database of monthly climate, to estimate regional variations in gelifluction rates under current conditions, and with both increases and decreases in mean temperatures. It is concluded that wide bands, roughly between 40–65°N and S, should have experienced a period of very intense gelifluction during the postglacial warming.

ISSN:0435-3676    

DOI:10.1080/04353676.1995.11880447

出版商:Taylor&Francis    

年代:1995

数据来源: Taylor