Abstract
ABSTRACTSoil moisture (SM), snow depth (SND), and air temperature are crucial factors for the soil thermal and hydraulic regimes in the permafrost regions. This paper analyzes the contribution of these factors to active layer thickness (ALT) under different climate change scenarios in northern hemisphere permafrost regions, using simulations from the Coupled Model Intercomparison Project Phase 5 (CMIP5) for the early (2016–2035, EP), middle (2046–2065, MP), and late (2080–2099, LP) periods of the 21st century. The results indicate that, with the temperature increasing, the relation between ALT and SM, SND, and mean annual air temperature (MAAT) will change in different permafrost regions. During 1986–2005 (reference period), ALT correlates significantly with SND in Europe only, the contribution of MAAT and SM to ALT are significant over the Tibetan Plateau (TP) and in North America (NA). MAAT is the only significant contribution factor to ALT deepening for all regions. In the 21st century, for the high Representative Concentration Pathways (RCP8.5), MAAT plays a dominant role in ALT over the TP and NA; however, snow effect is enhanced under RCP2.6 and RCP4.5 in Europe and NA. With temperature increasing, the importance of SM and SND alternates for low and middle emission, and gradually declines for high emission. In general, MAAT is the main contributor to ALT during the 21st century, while the impact of SM and SND declines with increasing temperature. Contribution of SM, SND, and MAAT to ALT varies, which illustrates the differences in regional thermal and hydraulic regimes from warming in permafrost regions.
Highlights
Permafrost occupies much of Earth’s land area, that is, the area of permafrost underlying the exposed land surface is estimated to be 16–21 × 106 km2 (Gruber, 2012), and it is sensitive to climate change, especially in high-latitude and high-altitude regions (Walter et al, 2006; Li et al, 2008)
We investigated the changes of soil thermal and hydraulic regimes with temperature increasing in the 21st century over permafrost regions
The relationship between active layer thickness (ALT) and Soil moisture (SM), mean annual air temperature (MAAT), and snow depth (SND) shows that soil thermal and hydraulic regimes varied with the increasing temperature rate and regions
Summary
Permafrost occupies much of Earth’s land area, that is, the area of permafrost underlying the exposed land surface is estimated to be 16–21 × 106 km (Gruber, 2012), and it is sensitive to climate change, especially in high-latitude and high-altitude regions (Walter et al, 2006; Li et al, 2008). A number of recent studies have suggested that permafrost is warming and degrading, and active layer thickness (ALT) is increasing (Jafarov et al, 2013; Park et al, 2013; Guglielmin et al, 2014; Sobota and Nowak, 2014;Wang et al, 2014; Peng et al, 2015; Pogliotti et al, 2015;Yu et al, 2015).Widespread warming in permafrost regions will result in substantial changes in terrestrial hydrology, vegetation composition, and ecosystem function, as well as carbon dioxide and methane fluxes (Nelson and Anisimov, 1993; McNamara et al.,1998; Jorgenson et al, 2001; Christensen et al, 2004; Hinzman et al, 2005; Smith et al, 2005). There are many uncertainties associated with estimates of the magnitude of these effects, there is an urgent need to resolve questions regarding the fate of permafrost and changes in the ALT (Walker, 2007)
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