Influence of snow cover and grain size on the ground thermal regime in the discontinuous permafrost zone, Swiss Alps
Influence of snow cover and grain size on the ground thermal regime in the discontinuous permafrost zone, Swiss Alps
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DOI：
10.1016/j.geomorph.2012.07.008
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发表时间：
2012-11
期刊：
影响因子：
3.9
通讯作者：
Tobias Rödder;C. Kneisel
中科院分区：
文献类型：
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作者：
Tobias Rödder;C. Kneisel
不连续山地多年冻土带中冻土的存在与否在很大程度上取决于当地场地特征。积雪在空间上因地形起伏而在短距离内发生变化，在时间上也逐年发生变化。基质颗粒大小影响空气与地表之间的热交换过程，导致地表热物性差异。基于四个浅钻孔和25个温度记录仪的数据，这些因素对地面热状况的影响，在最近的冰消前田在恩加丁，瑞士阿尔卑斯山进行了研究。每年寒潮的深度取决于积雪的特点，在积雪高度低于0.8米的冬季，寒潮的深度可能是积雪深度的两倍。相反，即使无雪期的持续时间每年都有很大变化，活动层的厚度也是恒定的。在50米的距离上，年平均地表温度相差4.3°C。我们的观测结果证实了块状地表负热异常的假设。然而，永久冻土条件也记录在一个网站与细粒碎片（砂/砾石），这是由于其地貌位置和强烈的耦合空气和地面温度在初冬。因此，地面热制度显示出很大的空间和时间的变化作为雪盖演变，积雪高度，表面基板，和救济的功能。短的数据记录还没有使我们能够检测到任何气候信号的不连续的永久冻土。
The presence or absence of frozen ground within the discontinuous mountain permafrost zone is on a small scale largely determined by local site characteristics. Snow cover changes spatially at short distances caused by relief and temporally from year to year. Substrate grain size influences the heat exchange processes between air and surface and causes differences in the ground thermal properties. Based on data of four shallow boreholes and 25 temperature loggers, the effect of these factors on the ground thermal regime in two recently deglaciated forefields in the Engadin, Swiss Alps is investigated. The annual depth of the cold wave is dependent on the characteristics of the snow cover and can be twice as deep in winters with a snow height below 0.8m. In contrast, the active layer thickness is constant even though the duration of the snow-free period changes substantially from year to year. A difference in mean annual ground surface temperatures of 4.3°C is registered over distances of 50m. The postulated negative thermal anomaly in blocky surfaces is confirmed by our data. However, permafrost conditions are also recorded at one site with fine-grained debris (sand/gravel) that is attributed to its geomorphological position and a strong coupling between air and ground surface temperatures in early winter. Thus, the ground thermal regime shows a large spatial and temporal variability as a function of snow cover evolution, snow height, surface substrate, and relief. The short data record does not yet enable us to detect any climatic signal within the discontinuous permafrost.