摘要:

AbstractThe Cirque Basin, Tianshan, China is characterized by steep slopes, coarse surficial deposits and a cold climate that maintains permafrost at shallow depths. These conditions exert strong influences on the streamflow processes. In late winter, freezing of the infiltrated meltwater from an uneven snow cover enables ground ice formation. This renders parts of the active layer impervious to seepage, and in the spring both surface and subsurface flows can occur to supply water to the stream. In summer, the coarse materials facilitate rapid infiltration and exfiltration. Where the channel slope is steep, as in the upper basin, infiltration results in a dry stream bed but deep percolation is prevented by a shallow frost table. Exfiltration prevails in the lower basin where the channel gradient is reduced, and streamflow increases rapidly within half a kilometre, from zero to its maximum values at the gauging station. Water balance analysis yields a high runoff ratio of 0.75 for this basin and this is comparable with other tundra areas. The streamflow processes observed in this basin should be applicable to other non‐polar alpine catchment

ISSN:1045-6740    

DOI:10.1002/ppp.3430050202

出版商:John Wiley&Sons, Ltd    

年代:1994

数据来源: WILEY

摘要:

AbstractThe high altitude‐induced permafrost of the Tibet Plateau reflects a geothermal regime characterized by a strong diurnal pattern, high solar radiation inputs at the surface, and a high geothermal gradient. As a result, the permafrost is relatively [warm] and sensitive to thermal disturbance. Typical permafrost‐related processes, such as ice segregation and thermal contraction cracking, are not widespread, and patterned ground phenomena (circles and nets) are restricted to sites of locally high moisture and variable grain size. Ice‐rich sediments on north‐facing slopes occur mainly as silty colluviums derived from local argillaceous bedrock. Mean annual ground temperatures are usually warmer than −3.5°C. Temperatures at 20 m depth have increased by an average of 0.2 to 0.3°C during the past 15 years. If one assumes continued warming, permafrost is likely to become relict within the next 200 years, and an increase in degradation (i.e. thermokarst processes) is to

ISSN:1045-6740    

DOI:10.1002/ppp.3430050203

出版商:John Wiley&Sons, Ltd    

年代:1994

数据来源: WILEY

摘要:

AbstractIn northern Russia, from the time meteorological measurements began in the early nineteenth century to the end of that century, the air temperature was characterized by a general decrease (approximately 1°C). It then rose up to the 1950s (by 0.6°C). A subsequent slight fall in temperature lasted until the mid 1970s. Since then a further rise has been observed (0.6–0.9°C). Temperatures in the upper horizons of permafrost over the last 10–20 years are in good agreement with recent global warming trends. For the European north‐east during the period 1970–90 a rise in temperature at a depth of 3 m amounted to 0.6–0.7°C on average. However, this rise is related not necessarily to a rise in air temperature, but more likely to an increase

ISSN:1045-6740    

DOI:10.1002/ppp.3430050204

出版商:John Wiley&Sons, Ltd    

年代:1994

数据来源: WILEY

摘要:

AbstractAlthough a considerable amount of periglacial work has concentrated on thufur found in polar and subpolar regions, information pertaining to those in other areas, especially the alpine regions of Africa, is extremely limited. Field observations and measurements provide empirical information on their external and internal morphology in an alpine region of Lesotho, southern Africa. Animal activity, wind action, the effects of surface water and/or ice, and the influence of needle ice are factors which cause thufa breakup. Some thufur in the Mohlesi valley are inactive while others are periodically active under present climatic conditions.

ISSN:1045-6740    

DOI:10.1002/ppp.3430050205

出版商:John Wiley&Sons, Ltd    

年代:1994

数据来源: WILEY

摘要:

AbstractSorted stripes have long been recognized in the sub‐Antarctic and the maritime Antarctic. The cold and wet conditions of these regions, when compared with the drier continent, are ideal for their development. In particular, the frequent low‐amplitude, short‐duration freeze‐thaw cycles of the sub‐Antarctic favour the development of miniature sorted forms. The maritime Antarctic, however, with its larger amplitude and longer duration of freeze‐thaw cycles, plus the presence of permafrost, exhibits a more frequent occurrence of the larger forms.The Byers Peninsula has an extensive range of sorted features but, despite being situated in the maritime Antarctic and within a permafrost zone, the majority of these features are of the miniature variety. In addition, the sorted stripes exhibit a distinct spatial preference. Their alignment and spatial distribution are not associated with either the sun or the wind, but are a function of the

ISSN:1045-6740    

DOI:10.1002/ppp.3430050206

出版商:John Wiley&Sons, Ltd    

年代:1994

数据来源: WILEY

ISSN:1045-6740    

DOI:10.1002/ppp.3430050207

出版商:John Wiley&Sons, Ltd    

年代:1994

数据来源: WILEY

ISSN:1045-6740    

DOI:10.1002/ppp.3430050201

出版商:John Wiley&Sons, Ltd    

年代:1994

数据来源: WILEY