ABSTRACT
Slope direction affects permafrost
degradation because of its
influence on the surface energy balance. The ground thermal difference
between slopes of differing aspect is known, however there are few
detailed reports on differences in soil temperature, humidity, and
radiation from slopes in permafrost areas that caused permafrost
degradation. In this study variations in air and ground thermal regime
were compared at two sloping sites with opposing aspect in a permafrost
region of the Qinghai-Tibetan Plateau (QTP). The results indicate that
air temperatures (Ta) were similar at both sites in September 2016-19.
However, ground temperatures, including the ground surface temperature
(Ts), the temperature near the permafrost surface (Tps),
and the permafrost temperature at 5.0 m depth (Tg), and soil moisture
content within the active layer differed greatly between sites. The mean
annual Ts, Tps, and Tg over three years (2016-19) were 1.3-1.4 ℃ higher
at the sunny slope than at the shady slope. The near-surface soil
moisture content during the thawing season was 10-13% lower at the
sunny slope (~22-27%) than the shady slope
(~35-38%), and was significantly and negatively
correlated with ground temperature. Shortwave downward radiation (DR) at
the sunny slope was higher than at the shady slope. However, net
radiation (Rn) was lower at the sunny slope due to the greater surface
albedo at the site. The results
highlight a complex spatial pattern of ground thermal conditions in
mountainous permafrost regions, help define the climate-permafrost
relation in the region, and for understanding permafrost degradation on
a local scale.