Distribution and activity of ice wedges across the forest‐tundra transition, western Arctic Canada
Distribution and activity of ice wedges across the forest‐tundra transition, western Arctic Canada
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DOI：
10.1002/2014jf003085
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发表时间：
2014-09
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影响因子：
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通讯作者：
S. Kokelj;T. Lantz;S. A. Wolfe;J. Kanigan;P. Morse;R. Coutts;N. Molina-Giraldo;C. Burn
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文献类型：
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作者：
S. Kokelj;T. Lantz;S. A. Wolfe;J. Kanigan;P. Morse;R. Coutts;N. Molina-Giraldo;C. Burn
遥感，区域地面温度和地面冰观测，和数值模拟被用来调查的大小，分布和冰楔在细粒矿物和有机土壤在森林苔原过渡的麦肯齐三角洲东部高地的活动。在最北部的矮灌木苔原，冰楔多边形覆盖了40%的地表，楔形通常超过3米宽。最大的冰楔位于泥炭地，那里的热收缩开裂比附近的细粒土丘陵地形更频繁。在南部的高地上，冰楔较少，宽度很少超过2米，在高灌木苔原的矿物质土壤中也没有发现，尽管在泥炭地中发现了活跃的冰楔。在云杉林地带，小的残留冰楔仅限于泥炭地。在苔原地区，有机土壤中的永久冻土层顶部冬季温度低于矿物土壤，因为永久冻土层较浅，在0°C时发生相变，冰泥炭的导热性相对较高。由于这些因素和冻结饱和泥炭的高热收缩系数，冰楔开裂和生长在泥炭地比在矿质土壤中更常见。然而，饱和有机活性层土壤的高潜热含量可能会抑制回冻，特别是在厚雪堆积的地方，使永久冻土和云杉林多边形泥炭地的冰楔容易在排水或气候变暖改变后退化。
Remote sensing, regional ground temperature and ground ice observations, and numerical simulation were used to investigate the size, distribution, and activity of ice wedges in fine‐grained mineral and organic soils across the forest‐tundra transition in uplands east of the Mackenzie Delta. In the northernmost dwarf‐shrub tundra, ice wedge polygons cover up to 40% of the ground surface, with the wedges commonly exceeding 3 m in width. The largest ice wedges are in peatlands where thermal contraction cracking occurs more frequently than in nearby hummocky terrain with fine‐grained soils. There are fewer ice wedges, rarely exceeding 2 m in width, in uplands to the south and none have been found in mineral soils of the tall‐shrub tundra, although active ice wedges are found there throughout peatlands. In the spruce forest zone, small, relict ice wedges are restricted to peatlands. At tundra sites, winter temperatures at the top of permafrost are lower in organic than mineral soils because of the shallow permafrost table, occurrence of phase change at 0°C, and the relatively high thermal conductivity of icy peat. Due to these factors and the high coefficient of thermal contraction of frozen saturated peat, ice wedge cracking and growth is more common in peatlands than in mineral soil. However, the high latent heat content of saturated organic active layer soils may inhibit freezeback, particularly where thick snow accumulates, making the permafrost and the ice wedges in spruce forest polygonal peatlands susceptible to degradation following alteration of drainage or climate warming.