Thermokarst lakes and alasses in ice-rich permafrost of the Lena Delta region

Abstract

The retrogression and thermal regime of a thaw slump affecting the stability of a slope along the Qinghai–Tibet Highway in China were studied over the last twenty years. The thaw slump was initiated in 1992 and the retrogression rate at the headwall slowed down somewhat in the recent years following the thermal stabilization of the affected area. According to field observation and monitoring, while the ground temperature was still not stabilized after the occurrence of the thaw slump, the depth of the permafrost table was usually shallower in the recently disturbed area than in the undisturbed area away from the thaw slump. However, due to a positive heat budget in the disturbed area, the ground temperature was increasing and the permafrost table was deepening. Moreover, since the ground temperature is higher close to the headwall than in the undisturbed area, lateral heat flux occurs in the thaw slump area inducing more retrogression at the headwall. However, as soon as the vegetation invaded the bare ground surface of the disturbed area, the ground temperature was decreasing in the disturbed area over the past two years and stabilization of the disturbed area was occurring. Following the stopping of the headwall retrogression and the decrease of the lateral heat flux, the ground temperature near the headwall is also decreasing.