Abstract
Based on the CMIP5 simulation and numerical model, the permafrost thermal regimes over Northern Hemisphere land during the early (2016-2035), middle (2046-2065) and late (2080-2099) period of 21st century are projected, and its relationship with climate change is also analyzed. The results show that, relative to the reference period of 1986-2005, the mean annual ground temperature (MAGT) over Northern Hemisphere shows an increasing trend, with a decreasing trend of the depth of zero annual amplitude (DZAA), and the most significant changes occur in Siberia, Tibetan Plateau, Canada arctic and Alaska, and the changes in MAGT and DZAA grow larger with time and emission, especially during the LP for RCP8.5, MAGT will increase by 4 and DZAA decreases by 1.5 m (the relative change exceeds 20%) in most regions. The changes of permafrost in the 21st century mainly depend on the changes of cold permafrost. The relationship between MAGT and air temperature as well as that between DZAA and air temperature suggests that the increase of MAGT and the decrease of DZAA are related to the increase of air temperature in winter, especially in January. However, the rate of change in MAGT and DZAA gradually declines, with the temperature increasing.
Highlights
Permafrost is a product of cold climate
The results show that, relative to the reference period of 1986-2005, the mean annual ground temperature (MAGT) over Northern Hemisphere shows an increasing trend, with a decreasing trend of the depth of zero annual amplitude (DZAA), and the most significant changes occur in Siberia, Tibetan Plateau, Canada arctic and Alaska, and the changes in MAGT and DZAA grow larger with time and emission, especially during the LP for RCP8.5, MAGT will increase by 4 ̊C and DZAA decreases by 1.5 m in most regions
In order to analyze the response of permafrost thermal regime to temperature rising, Table 4 shows the sensitivity of DZAA to air temperature for three Representative Concentration Pathways (RCPs) during the 21st century
Summary
Permafrost thermal regime is an excellent indicator and integrator of climate change (Osterkamp, 2005), recent assessment of the permafrost thermal regime suggests an ongoing warming over most parts of permafrost regions (Romanovsky et al, 2007), the response may be complex and discordances (Wu et al, 2012). We mainly focus on the temporal and spatial changes in permafrost thermal regime and its relation with temperature during the different periods of the 21st century.
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