Evaluation of time series of soil moisture and soil temperature and computation of apparent thermal diffusivity of active layer in the Barton Peninsula, Antarctica

Abstract

We have examined soil moisture and soil temperature of three sites in the Barton Peninsula, Antarctica. Auto-correlation, spectral analysis, and cross-correlation analysis were conducted using time series data. In addition, apparent thermal diffusivity was computed and active layer thickness was calculated. Soil moisture and soil temperature meters were installed at depths of 5, 10, 15, 20 cm, and measured every five minutes during summer 2019-2020. The soil moisture content was the largest at 20 cm depth at all sites. Rainfall below 0.5 mm/day could not affect the soil moisture content. The soil temperature in deeper depth was low. The soil temperature was above zero except for one day (December 20, 2019). The auto-correlation of soil moisture indicated shorter lag time at gradual slope and that of soil temperature indicated shorter lag time at shallower depth. The cycle of soil moisture was between 2.5 and 4.7 days, and the cycle of soil temperature was between 1.0 and 1.1 days. The cross-correlation of air temperature-soil temperature showed shorter lag time and larger correlation coefficient than that of solar radiation-soil temperature. The apparent thermal diffusivity (ATD) ranged from 0.01 to 121.94 mm2/sec (median=0.34-0.59 mm2/sec). The median values were close to that of minimum of previous study (0.4-3.3 mm2/sec) using same methods. The active layer thickness ranged from 23.6 to 38.6 cm. The ATD is smaller and active layer thickness is thinner than that near the coast (within 0.2 km) because the study area is located 1.5 km from the sea.