スピッツベルゲン，ニューオールスンにおける地温の観測

Abstract

Ground temperature was continuously measured during 1994-1996 on a debris-mantled slope near Ny Alesund, Spitsbergen. Measurements were taken at one-hour intervals using a digital data logger connected to four platinum thermistor sensors, which were inserted at 0, 10, 40, 80 cm in depth.Diurnal freeze-thaw cycles occurred only five times during the 1994 freezing period and 14 times during the 1995 freezing period. The average frost depth during these diurnal cycles was 4.7 cm. Small daily temperature ranges at the ground surface indicate that the slope was covered with snow from middle September to June or July. The late-lying snow cover was responsible for the absence of diurnal freeze-thaw cycles during the thawing period. Seasonal freezing began in middle to late September, and the freezing front penetrated to a depth of 80cm during these weeks. The seasonal frost began to melt in mid-June, and the thawing front reached a depth of 80 cm in two weeks. The thickness of the active layer was estimated to be about 110 cm on the basis of the distribution of the mean ground temperature profile in July. Seasonal freeze-thaw cycles are considered to be much more selective in producing periglacial landforms in this region than diurnal cycles.