Alpine Permafrost Occurrence at High Mountain Area in Hokkaido

作者报告了位于日本北部北海道中部的大雪山高山永久冻土层的存在。永久冻土层发生的位置是木材线界限（1500米）以上的平坦峰顶，那里的地表没有植被覆盖。对地温剖面的连续监测给出了土层的年平均温度梯度。对冻土层温度梯度的外插值表明，冻土层位于550 cm深度。在平坦的峰顶上观察到地表活跃的霜裂缝。裂缝开口宽度的增加记录为1 cm。裂缝里没有冰。palsas是在泥炭沉积相当深的地区形成的。活动层的冻融循环导致地表形成了分选的圆圈和其他分选特征。

Author reports the existence of alpine permafrost at Mt. Taisetu which locates at the central Hokkaido in northern Japan. The locations of permafrost occurrence are flat summits above timber line limits (1500m) and no vegerations are covered on the ground surgace there. Continuous monitoring of ground temperature profiles give the mean annual temperature gradients in soil layers. The extra-interpolation of temperature gradient to the frozen layers indicates the permafrost table is located at 550 cm depth. Active frost cracks on the ground surface were observed on the flat summits. The increase of the width of open mouth of cracks were recorded as 1 cm. No ice was filled in the cracks. The palsas were formed at the area where considerable depth of peat was deposited. Freeze-thaw cycles in active layers resulted in formations of sorted circles and other sorted features on the ground surface.