Degradation of permafrost in the Xing'anling Mountains, northeastern China

Abstract

Permafrost in the Da and Xiao Xing'anling Mountains in northeastern China is warm, thin and sensitive to climatic warming. In the 1970s, the southern limit of permafrost (SLP) was empirically correlated to the −1 to 0°C isotherms of mean annual air temperature (MAAT) in the western part of the Da Xing'anling Mountains, to about 0°C in the northern part of the Songnen Plain, and to 0 to +1°C in the eastern part of the Xiao Xing'anling Mountains. Climate warming and deforestation have led to permafrost degradation as shown by deepening of the active layer, thinning permafrost, rising ground temperatures, expanding taliks and the disappearance of permafrost patches. The present position of the SLP was estimated using the −1.0 to +1.0°C MAAT isotherms for 1991–2000. Compared to the SLP in the 1970s, areas of sporadic discontinuous and isolated patchy permafrost have decreased by 90,000–100,000 km2, or 35–37% of their total areal extent (260,000–270,000 km2) in the 1970s. Recent field observations along the Hei'he to Bei'an Highway, the proposed Mo'he to Daqing Crude Oil Pipeline route and the Hai'lar to Daqing Highway confirm these changes. Continuing northward shifting of the SLP is likely to occur during the next 40–50 years under a warming of 1.0–1.5 °C, reducing the permafrost areal extent to an estimated 35% of that in the 1970s and 1980s. Copyright © 2007 John Wiley & Sons, Ltd.

Increasing Winter Baseflow in Response to Permafrost Thaw and Precipitation Regime Shifts in Northeastern China

“…Northeastern China has experienced a pronounced warming trend over the past half a century [59], which has resulted in rapid warming and thawing of permafrost as shown by active layer thickening, thinning permafrost, increasing ground temperatures, expanding taliks, and disappearing permafrost islands in northeastern China [33]. Such changes have specifically been documented in the region of the study watersheds.…”

“…The thickness of permafrost ranges from 0 to 30 m with a supra-permafrost thawed zone (active layer plus potential taliks) ranging from 1.0 to 3.0 m [39]. Although the forest vegetation and organic soil can thermally insulate the ground [38], the permafrost in the study regions has been experiencing rapid thaw in the past several decades [33]. Both watersheds are characterized by a typical continental monsoon climate with a wet, hot summer and a cold, dry winter.…”

“…Such climate warming can result in significant permafrost degradation, and changes in the precipitation regimes [31], and permafrost warming or degradation has already been observed in this region [32][33][34]. For instance, the active layer thickness increased from 1.2 m in the 1990s to more than 1.8 m in 2004 in the Yituli'he Permafrost Observatory (121 • 20 E, 50 • 56 N) [33].…”

“…Such climate warming can result in significant permafrost degradation, and changes in the precipitation regimes [31], and permafrost warming or degradation has already been observed in this region [32][33][34]. For instance, the active layer thickness increased from 1.2 m in the 1990s to more than 1.8 m in 2004 in the Yituli'he Permafrost Observatory (121 • 20 E, 50 • 56 N) [33]. The results of direct observations from boreholes (CK38, CK3, 123 • 11 E, 52 • 50 N) showed that the permafrost thickness decreased from 7 m in 1979 to 2 m in 1991, resulting in an average thinning rate of 0.4 m/year during this period [33].…”

“…For instance, the active layer thickness increased from 1.2 m in the 1990s to more than 1.8 m in 2004 in the Yituli'he Permafrost Observatory (121 • 20 E, 50 • 56 N) [33]. The results of direct observations from boreholes (CK38, CK3, 123 • 11 E, 52 • 50 N) showed that the permafrost thickness decreased from 7 m in 1979 to 2 m in 1991, resulting in an average thinning rate of 0.4 m/year during this period [33]. Also, inactive ice wedges that were observed in the Wuma River basin (121 • 45 E, 52 • 58 N) in 1987 [34] had disappeared by 2007 due to recent climate warming [32].…”