4.2. Permafrost vulnerability
According to Figure 4, the ground temperature of the entire QTP
permafrost is relatively high. In order to analyze the vulnerability of
the QTP permafrost to climate warming, the permafrost region with MAGTs
ranging from -0.5 to 0.5°C was extracted (Figure 10). According to the
permafrost stability classification (Cheng and Wang, 1982), permafrost
in this range is classified as unstable region. It can be observed that
0.49 × 106 km2 of the permafrost
area over the QTP is in danger at present, which accounting for 37.3%
of the maximum permafrost area. This unstable permafrost primarily
distributed in the transition region of permafrost and seasonally frozen
ground.
As a result of the global warming and increased anthropogenic activity,
the QTP has experienced an approximately 3-fold warming increase over
the past 50 years (Wan et al., 2018). Under the influence of this
accelerated warming, the permafrost region adjacent to the seasonally
frozen ground is becoming increasingly fragile (Qin et al., 2017).
This part of the permafrost is
generally in the process of
ice-water phase transformation. A
comparison with Figure 6, reveals that this region is consistent with
the areas in which permafrost will disappear under future RCPs, but it
also greatly affected by the local ground ice content, underlying
surface types, and other related factors (Nelson et al., 2001; Yang et
al., 2010c).
The
Qinghai-Tibet
Engineering Corridor (QTEC, the region that contains the Qinghai-Tibet
Highway and Railway, pipelines, electric transmission lines, and so on)
is an important conduit connecting mainland China and the QTP. Under the
influence of intensifying global climate change and frequent human
activities, the ecological environment along the QTEC is fragile, and
the permafrost in the QTEC has degraded significantly and the alpine
ecosystem is facing new challenges (Niu et al., 2018). Based on Figure
10, the statistical results show that 757 km of the QTEC crosses through
the permafrost region (at its maximum extent), accounting for nearly
40% of its total length (from Xining to Lhasa). Of this,
approximately half of the QTEC faces
the risk of the permafrost disappearing, and the other half may
experience varying degrees of permafrost degradation in the future. This
will result in huge
economic
losses and threaten associated infrastructures along the QTEC.
Recent studies have shown that several cryosphere tipping points
are
dangerously close (IPCC, 2019), and the permafrost in the Arctic has
begun to thaw irreversibly and release carbon dioxide and methane, but
the inevitable effects could still be mitigated by reducing greenhouse
gas emissions (Lenton et al., 2019). The stability and resilience of the
QTP permafrost is in peril. We should take urgent action to reduce
greenhouse gas emissions, and put them as the priority of the present
and future work. In order to effectively mitigate the degradation of
permafrost, all the emission reduction measures should be reflected in
words even in actions.