Global and Planetary Change 62 (2008) 210–218

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Global and Planetary Change

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Cryospheric change in China

Xin Li ⁎, Guodong Cheng, Huijun Jin, Ersi Kang, Tao Che, Rui Jin, Lizong Wu, Zhuotong Nan,Jian Wang, Yongping ShenCold and Arid Regions Environmental and Engineering Research Institute, Chinese Academy of Sciences, Lanzhou 730000, ChinaWorld Data Center for Glaciology and Geocryology in Lanzhou, Lanzhou 730000, China

a r t i c l e i n f o

⁎ Corresponding author. 320 West Donggang Road, Cmental and Engineering Research Institute, Chinese A730000, Gansu Province, China. Tel.: +86 931 4967249;

E-mail address: lixin@lzb.ac.cn (X. Li).

0921-8181/$ – see front matter © 2008 Elsevier B.V. Aldoi:10.1016/j.gloplacha.2008.02.001

a b s t r a c t

Article history:Received 28 August 2007Accepted 20 February 2008Available online 6 March 2008

This paper provides an overview of the current status of the cryosphere in China and its changes. Up-to-datestatistics of the cryosphere in China are summarized based on the latest available data. There are 46,377glaciers in China, covering an area of 59,425 km2. The glacier ice reserve is estimated to be about 5600 km3

and the annual glacier runoff is about 61.6×109 m3. The continuous snow cover extent (N60 days) in China isabout 3.4×106 km2 and the maximum water equivalent is 95.9×109 m3 yr−1. The permafrost area in China isabout 1.72×106 km2. The total ground ice reserve on the Qinghai–Tibetan Plateau is estimated to be about10,923 km3. Recent investigations indicated that glacier areas in China have shrunk about 2–10% over the past45 yr. Total glacier area has receded by about 5.5%. Snow mass has increased slightly. Permafrost is clearlydegrading, as indicated by shrinking areas of permafrost, increasing depth of the active layer, rising of lowerlimit of permafrost, and thinning of the seasonal frost depth. Some models predict that glacier area shrinkagecould be as high as 26.7% in 2050, with glacier runoff increasing until its maximum in about 2030. Althoughsnowmass shows an increasing trend inwestern China, in eastern China the trend is toward decreasing snowmass, with increasing interannual fluctuations. Permafrost degradation is likely to continue, with one-third toone-half of the permafrost on the Qinghai–Tibetan Plateau anticipated to degrade by 2100. Most of the high-temperature permafrost will disappear by then. The permafrost in northeastern China will retreat furthernorthward.

© 2008 Elsevier B.V. All rights reserved.

Keywords:cryosphereChinaclimate changesnowglacierpermafrost

1. Introduction

As an integral part of the global climate system, the cryosphere playsa significant role in the energy andwater cycle of the Earth's surface. It isusually considered as an indicator of global change because the frozenparts of the Earth's surface, i.e., snow, glaciers, sea/lake/river ice, andpermafrost aremore sensitive to climatic change than other land surfacecomponents. The cryosphere is also an amplifier of climatic warmingbecause temperature rise in cryospheric regions is generally larger thanthat in other regions and the positive feedback of cryosphere to climatesystem can enhance the climatic warming (Cheng 1996; Allison et al.,2001; IPCC, 2001; IPCC, 2007).

China's vast expanse of cryosphere contains a large portion of theworld's middle-altitude and low-latitude mountain glaciers. China'spermafrost area ranks third in the world and is the largest in terms ofmiddle- and high-altitude permafrost areas. In particular, the Qinghai–Tibetan Plateau (QTP) plays a very important role in global change.Recent investigations show the cryosphere in China is experiencing

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rapid changes, such as retreating glaciers, degrading permafrost,destabilizing cryospheric environments and the resulting increase inhazards (Jin et al., 2000; Qin, 2002; Kang et al., 2004; Shen, 2004; Qinet al., 2006b).

Section 2 of this paper introduces basic statistics of majorcryospheric components in China. In Section 3, recent findings ofcryospheric change are reviewed. Section 4 predicts future cryo-spheric changes in China. Section 5 concisely summarizes the paper.

2. The cryosphere in China

The cryosphere in China is composed mainly of mountain glaciers,latitudinal and altitudinal permafrost, seasonally frozen ground, andsnow cover. Sea, lake, and river ice also occurs in northern China andon the QTP, but with relatively insignificant impact on the climatesystem.

2.1. Glaciers

Up-to-date statistics on mountain glaciers were derived from theChinese Glacier Inventory (CGI), which was accomplished in 2002 (Liuet al., 2000; Shi, 2005), and the Chinese Glacier Information System(CGIS), which was established in 2004 (Wu and Li, 2004). The CGIS is a

Fig. 1. Distribution of glaciers in China (The vertical bars denote the magnitudes of glacier numbers, total area and total volume in each drainage system; the table shows the riverbasin code (ID), and statistics of glacier numbers (N), total area (A), total volume (V) and average length (L) of glaciers in each river basin).

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modified CGI, in which strict quality control was conducted. Fig. 1illustrates the distribution of glaciers in China. Glacier distributionfrom the CGI maps and from topographic maps was digitized, andsome editing errors in CGI were corrected. According to the CGISand the Concise Chinese Glacier Inventory1, there are 46,377 glaciersin China that cover an area of 59,425.18 km2, which is 51.2% and10.9–11.6% of the mountain glacier area in Asia (116.18×103 km2)(Dyurgerov and Meier, 2005) and on Earth (excluding the glaciersand ice caps surrounding Greenland and the Antarctic ice sheets)(512×103 – 546×103 km2) (Lemke et al., 2007), respectively. Thetotal ice reserve was estimated using empirical relationships estab-lished by regression analysis of the glacier areas and radar-measuredglacier depths (Liu and Ding, 1986). The total ice reserve of Chinesemountain glaciers is estimated to be about 5600 km3 or 5.04×1012 m3

in water equivalent, which is about five times the annual runoff of theYangtze River (9.6×1011 m3). Annual glacier runoff was about61.6×109 m3 in 1980, when the glaciers were inventoried. The valuewas estimated by using the systematic model, which was based onan empirical equation relating glacier ablation with mean summertemperature (Xie et al., 2002; Xie et al., 2006). Glacier runoff is a veryimportant water resource in the arid regions of northwest China. Inwestern China, glacier melt runoff accounts for 11.9% of total discharge.For inland rivers and outflow rivers, glacier runoff accounts for 24.3%and 8.7% of the annual runoff, respectively (Kang et al., 2004; Xie et al.,2006).

1 The statistics in the Concise Chinese Glacier Inventory are based on CGIS, with newdata from the Bangong Lake area being added (Shi, 2005).

2.2. Snow

A long time series dataset of snow depth and snow water equiv-alent (SWE) from 1978 to 2005 in China was developed using passivemicrowave remote sensing including the Scanning MultichannelMicrowave Radiometer (SMMR) and the Special Sensor Microwave/Imager (SSM/I) (Che and Li, 2005; Che, 2006). The data show thatmaximum annual SWE of about 17.8×109m3 is located in Xinjiang andthe western part of Inner Mongolia, 41.9×109 m3 on the QTP includingthe Pamir Plateau and the QilianMountains, and 36.2×109 m3 in north-eastern China. The maximum areal extent of snow cover occurs inMarch, mid-January, and late February in the three above mentionedzones, respectively. The total maximum SWE of the three major snowcovered regions in China is 95.9×109 m3 yr−1, which is about 10% of thenormal annual discharge of the Yangtze River. Continuous snowcoverexisting for more than 60 days is about 3.4×106 km2 and for more than120 days about 1.5×106 km2 (Che et al., submitted for publication).Fig. 2 shows the distribution of averaged snow depth and continuoussnow cover extent in China. The above statistics are close to thosederived from an earlier study (Kang et al., 2004). The annual snowfallrecharge was estimated to be over 3.45×1011 m3 (Li, 1988). However,this value needs to be reevaluated by using both remote sensing dataand in situ observations.

2.3. Frozen soil

Statistics on extent of permafrost area vary in the published lit-erature (Jin et al., 2000; Qiu et al., 2000; Zhou et al., 2000). According

Fig. 2. Distribution of snow in China.

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to an up-to-date frozen soil map of China, the Map of the Glaciers,Frozen Ground and Desert in China (Wang et al., 2006), the permafrostarea in China is about 1.72×106 km2 (glaciers and lakes in the perma-frost area are excluded) and the seasonal frozen ground area (exclud-ing intermittently frozen ground) is about 5.21×106 km2 (Fig. 3).Together, they occupy 72% of China's land territory. Most permafrost inChina is altitudinal and distributed on the QTP, in northeastern Chinaand in other mountainous areas. The area of altitudinal permafrost isapproximately 1.36×106 km2. The ice reserve in permafrost is huge.Nan (2003) estimated the ice volume in permafrost on the QTP to beabout 10,923 km3, assuming an average thickness of 61.5 m. Thisestimated ice reserve is approximately two times the total glacier icereserve in China.

3. Cryospheric change

3.1. Glacier trends

Glacier change in the last few decades in China has been in-vestigated by many Chinese glaciologists. Results show that glacierretreat is common but varies spatiotemporally. Area shrinkage issignificant in the Himalayas (Qin et al., 2000; Ren et al., 2004; Jin et al.,2005), Qilian Mountains (Liu et al., 2002), and Tianshan Mountains(He et al., 1999; Shi, 2000; Liu et al., 2006), with area shrinkage about5–10% over the last 30 yr. Glaciers in the interior of the Tibetan Plateauare relatively stable (Li et al., 1998; Lu et al., 2002; Liu et al., 2004).However, in recent years, glacier shrinkage in mountainous areas isaccelerating (Shi, 2001).

Table 1 summarizes recent investigations on changes of glacierareal extents. Most data were derived from remote sensing data. Fig. 4shows the locations of the investigations in Table 1, with area changesand number of glaciers investigated. Kang et al. (2004) extracted thearea change of all glaciers in China (Table 2). As a total, to date China'sglaciers have shrunk 5.5% since 1960s.

3.2. Snow cover change

The variability of snow cover in China and its response to climaticchange is more complex than glacier change. Analysis of snow covervariability and change is difficult; very little work has been carriedout.

Chen and Wu (2000) used data from ground stations to analyzesnow cover variability on the QTP and showed that in the 1970s snowcover increased from light to heavy. Li (1999) revealed that in north-western China, the snow cover experienced no significant decreasefrom 1987 to 1999. Li's data included SMMR snow charts, NOAAweekly snow cover chart, and snow data from selected metrologicalstations inwestern China. Li's findings are further verified by Qin et al.(2006a). Their results show that long-term variability of snow cover inwestern China is characterized by large interannual variations super-imposed on a small increasing trend for the period 1951–1997. Noabrupt change in snow cover was found. But over the QTP, a largeinterannual oscillation is the most striking feature, and annual am-plitude has increased since 1980s.

These conclusions are consistent with the results of Ke and Li(1998), Che and Li (2005), and Che (2006). However, Che (2006)

Fig. 3. Distribution of permafrost and seasonally frozen ground in China.

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recommends that analysis of a long time series of snow data derivedfrom remote sensing data is needed to analyze change in snow coverin China.

Another important factor to consider is seasonal changes in thebeginning and ending dates of recorded snowfall and duration ofsnow cover. However, we did not find any published literature thataddressed this issue.

3.3. Frozen soil trends

China's permafrost, especially the altitudinal permafrost whichis mainly distributed on the QTP, is sensitive to climatic warming.Significant permafrost degradation has occurred and continues tooccur in most permafrost regions of China. Areal extent of seasonallyfrozen ground is shrinking and the frozen layer is decreasing in depth.In this section, we introduce evidence for shrinkage of permafrostareas, elevation of the lower limit of mountain permafrost, increasingground temperatures, deepening of the active layer, and thinning ofthe seasonal frost depth.

3.3.1. Shrinkage of permafrost areal extent and elevation of the lowerlimit of mountain permafrost

A preliminary estimate for the reduction of permafrost areal ex-tent on the QTP is 0.1×106 km2 from 1970s tomid-1990s (Wang,1997;Jin et al., 1999). Observations show that along the Qinghai–TibetHighway (QTH), the southern lower limit of permafrost has moved12 km northward, whereas the northern lower limit has moved3 km southward (Wang and Mi, 1993; Jin et al., 2006). According to

the 1:100,000 map of island permafrost compiled in 1975, for theLiangdaohe area of the southern QTH (with a width of 2 km on eachside), the permafrost area was 64.8 km2 within the measured area of320 km2, or about 20%. The permafrost areas were divided into fourgroups according to geomorphic locations. Recent comprehensiveinvestigations indicate that the permafrost area has decreased to41.7 km2, suggesting a reduction of 35.6% in the island permafrost area(Wang et al., 1996; Wang, 1997; Wang et al., 2000; Jin et al., 2000,2006).

Investigations using ground penetration radar (GPR) provide moredetailed evidence. Nan et al. (2003) conducted a GPR survey in theXidatan, QTP in 2002. They found that the permafrost area in theregion had diminished to 141.0 km2 from 160.5 km2 surveyed in 1975,displaying a shrinkage of about 12%.

Observations on the QTP since the 1970s have shown that thelower limit of permafrost had risen 25 to 80 m (Wang et al., 2000). OnXidatan, the north part of the QTP, it experienced an increase inelevation of 25 m from 1975 to 2002 (Nan et al., 2003). In thehinterland of the QTP, such as Amdo and Mado, the lower boundaryhas risen about 40–50m. In the boundary areas of the QTP, such as theQilian Mountains, the rise of the lower boundary of permafrost hasreached up to 80 m.

In northeast China, the degradation of warm, isolated patches ofpermafrost is more severe than on the QTP because of dramatic cli-mate warming and strong influences from human activities such asdeforestation. The patchy permafrost has disappeared in the south-ern Da and Xiao Xing'anling Mountains, where mean annual groundtemperatures (MAGTs) range from −0.5 to +0.5 °C, and permafrost

Table 1Changes of glacier areal extents in China

Study area and location Data used Period Glaciernumber

Area at thestart of record (km2)

Area at endof record (km2)

Areachange(%)

Reference

Pumqu River basin, Himalayas Topographic map (1970, 80s), ASTERand CBERS (2001)

1970s–2001 999 1462±9 1330±8 −9.0 Jin et al. (2005)

Poiqu River basin, Himalayas Topographic map (1970, 80s), IRS1D-LISS 3 (2000, 2001)

1970s–2000 153 236.8 231.6 −2.2 Wu et al. (2004)

Rongxer River basin, Himalayas Same as above 1970s–2000 200 334.3 324.1 −3.1 Wu et al. (2004)Glacier Reqiang, XixiapamaMt., Himalayas MSS (1977 and 1984), TM (1990 and

1996), ETM+ (2000), ASTER (2003)1977–2003 1 6.92 5.34 −22.9 Che et al., 2005

Glacier Jicongpu, Xixiapama Mt.,Himalayas

Same as above 1977–2003 1 20.28 18.81 −7.3 Che et al. (2005)

Naimona'nyi region, western Himalayas MSS (1976), ASTER (2003) 1976–2003 N/A 84.41 77.29 −8.4 Ye et al. (2006a)Gangrigabu range, southeast QTP Topographic map (1980), CBERS (2001) 1980–2001 88 797.78 795.76 −0.25 Liu et al. (2005)Xinqingfeng ice cap, Northern QTP Aerial photograph (1971), ETM+ (2000) 1971–2000 64 442.7 435.3 −1.7 Liu et al. (2004)Malan ice cap, Northern QTP Same as above 1971–2000 65 247.08 248.14 +0.43 Liu et al. (2004)Mountainous areas of Tarim basin Topographic map (1960, 70s), TM/ETM+

(1999–2001)1963–1999 3081 9998.5 9542.3 −4.6 Liu et al. (2006)

Muztahgata Mountains Aerial photograph (1965), ASTER (2001) 1965–2001 128 377.21 373.04 −1.1 Cai et al. (2006)Karamilan–Keriya River, Tarim basin Topographic map (1970s), TM/ETM+

(1999–2001)1970–2000 895 1374.18 1334.91 −2.9 Xu et al. (2006)

Kaidu River basin, Middle TianshanMountains

Topographic map (1963), ETM+ (2000) 1963–2000 70 55 48 −13 Li et al. (2006)

Glacier No. 1, Urumqi River, TianshanMountains

Large-scale topographic map (1963 and2003)

1962–2003 1 1.95 1.71 −12.4 Li et al. (2003b);Ye et al. (2005)

DaxueshanMt.,Western QilianMountains Aerial photograph (1956), TM (1990) 1956–1990 175 162.8 155.1 −4.7 Liu et al. (2002)A'nyêmaqên Range, the upper YellowRiver

Aerial photograph (1966), TM (2000) 1966–2000 57 125.50 103.80 −17.3 Lu et al. (2005)

GeladandongMt., the upper Yangtze River Aerial photograph (1969), ETM+ (2002) 1969–2002 N/A 889.31±0.02 846.81±0.0007 −4.8 Ye et al. (2006b)YurungkaxRiver,westernKunlunMountains TM (1989), ETM+ (2001) 1989–2001 42 1372.39 1366.06 −0.5 Shangguan et al.

(2004)MuztagAta-KongurTagh, thePamirPlateau Aerial photograph (1962–66), ASTER

(2001)1962/1966–2001

379 1092.7 1025.8 −6.2 Shangguan et al.(2005)

Note:(1) In the column “data used”, the original data used instead of the CGI are indicated. The glacier parameters in CGI are usually derived from the aerial photographs from the 1960sto 1980s.(2) There is some overlap of glacier change data in the mountainous areas of Tarim basin, Muztahgata Mountains, and Karamilan–Keriya River of Tarim basin.(3) ASTER: Advanced Spaceborne Thermal Emission and Reflection Radiometer. CBERS: China–Brazil Earth Resource Satellite. ETM+: Enhanced Thematic Mapper Plus. IRS 1D-LISS:Indian Remote Sensing satellite series 1D, Linear Imaging and Self-scanning Sensor. MSS: Multispectral Scanner. TM: Thematic Mapper.

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thicknesses vary from 5 to 15m. Investigations show that in one of theforestry bureaus in the Xiao Xing'anling Mountains, the areal per-centage of permafrost has decreased from 10.5% in 1957 to 0.05% in1980 and the degradation is believed to be closely related to defores-tation. With this rate of deforestation and subsequent permafrostdegradation, permafrost may have completely thawed in this forestrybureau area by now. The distribution of island permafrost in othersites has also degraded substantially over the past 30 to 40 yr (Jin et al.,2007).

3.3.2. Borehole monitoringMonitoring along the QTH from Golmud to Lhasa indicates that

mean annual ground temperatures (MAGTs) are experiencing in-creases of about 0.3–0.5 °C in seasonal frozen ground, taliks, andisland permafrost zones, and about 0.1–0.3 °C in the continuous per-mafrost zones (Jin et al., 2000; Wang et al., 2000). Table 3 containsmonitoring results from some representative stations.

Wu et al. (2005) recently found that the temperature of permafrost(at 6 m depth) is increasing at a rate of 0.05 °C/yr and 0.02 °C/yr in thelow- and high-temperature permafrost areas on the QTP, respectively.

3.3.3. Active layer thickeningCold region engineering, i.e., maintenance of the QTH and con-

struction of the Qinghai–Tibet Railroad (QTR), has provided good op-portunities to observe changes in permafrost and many monitoringsystems have been established. A remarkable thickening of the activelayer has been observed on the QTP. Wu and Liu (2004) and Wu et al.(2005) analyzed temperature data collected from 1995 to 2004 at 11sites in the permafrost area along the QTH and QTR and found that the

active layer had clearly thickened, particularly in the warm (≥−1 °C)permafrost area. They concluded that in cold (b−1 °C) permafrostareas, the thaw penetration deepened by 3.1 cm/yr on average, where-as in warm permafrost areas, it deepened 8.4 cm/yr on average.

Active layer thickening is even more dramatic in northeasternChina. Maximum thaw penetration depth at a wetland site in theDaxing'anling Mountains was 50–70 cm during the 1960s–1970s.However, it increased to 90–120 cm or greater during the 1990s. AtYitulihe Permafrost Observatory, maximum thaw penetrationincreased by 16 cm during the three year period from 1996 to 1999,with an average rate of 5.3 cm per year (Jin et al., 2007).

3.3.4. Seasonal freezingZhao et al. (2004) investigated the freezing depth change at 50

meteorological stations on the QTP from 1967 to 1997. They foundthat the depth of seasonal frozen ground thinned about 22 cm in theinterior QTP, with an averaged annual decreasing rate of 0.71 cm. Innortheastern QTP, the depth of seasonally frozen ground thinned21 cm, with amean annual decreasing rate of 0.7 cm. In northwest andsoutheast QTP, the decrease of seasonally frozen ground depth is notso significant, with thinning of 6 cm in the interior QTP and 5 cm innortheastern QTP over a 30 yr period.

Wang et al. (2005a) also summarized the change of seasonally fro-zen ground depth at 16 meteorological stations in Qinghai Province.The mean value of frozen depth was 144 cm from 1961 to 1970, butdecreased to 124 cm in the period 1990 to 2001.

Wang et al. (2005b) used data from 19 stations in Xinjiang toanalyze the variation of seasonal freezing from1961 to 2002. Themeanand maximum frost penetration depths have thinned significantly

Fig. 4. Glacier change in China (The dot denotes themagnitude of change of glacier areal extent, the number with the dot shows the percentage of area change and number of glaciersthat have been investigated).

Table 2Glacier change from the 1960s to 2000 in China (Kang et al., 2004)

Glacier type Area (km2) Decreasearea (km2)

Areachange (%)

1960s 2000

Extreme continental type 19,137.73 18,685.54 452.19 2.4Sub-continental type 27,008.18 25,390.53 1617.65 6.0Maritime type 13,254.16 12,076.28 1177.88 8.9Total 59,400.07 56,152.35 3247.72 5.5

Note: The total areas listed in this table differ slightly from the areas described inSection 2 because different data sources are used (Kang et al., 2004).

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with decreased values ranging from 7 to 37 cm. The freezing–thawingperiod has also shortened. The freezing date is four days earlier andthawing date is five days later in the season.

4. Predictions of future cryospheric change

4.1. Glaciers

It is predicted that China's mountain glaciers will experience rapidretreat under a warming climate scenario. According to Shi (2001),most glaciers with area less than 1 km2 will disappear before 2050.Table 4 summarizes detailed predictions of glacier change for differ-ent glacier types (Shi and Liu, 2000; Qin, 2002; Kang et al., 2004). Thescenarios of temperature rise are based on predictions from theHadCM2 (Second Hadley Centre Coupled Model). It should be notedthat precipitation change was not taken into account. However, pre-cipitation is very likely to increase in west China and the QTP (Qin,2002; IPCC, 2007, pp 879∼887). More precipitationwill result in moreice accumulation on glaciers. Therefore, the predicted values in Table 4can be considered as maximum decreases.

Glacier runoff will increase because glacier melting will accelerate(Shi, 2001; Xie et al., 2006). Xie et al. (2002, 2006) used a systematicmodel to simulate future changes in glacier runoff. According to theirmodel, total glacier runoff in China was 61.6×109 m3 in the 1980s andwas estimated to be 66.0×109 m3–68.2×109 m3 in 2000. If air tem-perature rises at a rate of 0.02 k/yr or 0.03 k/yr, glacier runoff willincrease continuously from 2000 to 2030, and will reach its maximum

value of 67.5×109 m3–70.8×109 m3 in about 2030. Thereafter, glacierrunoff potentially will show a decreasing trend. Until 2050, however,runoff will be greater than in 2000.

4.2. Snow

Qin (2002) and Kang et al. (2004) delineated possible changes ofsnow by extrapolating current trends and analyzing the relationshipbetween snowfall, air temperature and precipitation. They suggestthat snow mass will increase slightly on the QTP and in Xinjiang andsnow variability will increase, implying an increase of snow blizzardsand other associated hazards. For example, the possibility for springdrought will tend to increase due to snow melt earlier in the season.However, in northeastern China and Inner Mongolia, snow mass maydecrease.

Table 3Changes in mean annual ground temperatures along the Qinghai–Tibet Highway (Jin et al., 2000; Wang et al., 2000)

Borehole JXG CK114 CK124-4 Ck123-4 CK-7 K2956 No.1 CK123-7

Location Xidantan Taoerjiu Valley Basin Tongtian Cumar FHS BasinPermafrost zone Northern lower limit Continuous/island

permafrost boundarySouthern lower limit Seasonally frozen

groundRiver taliks Continuous

permafrostContinuouspermafrost

Islandpermafrost

Present MAGT (°C) 0.3 0.8 0.8 0.8 0.8 −0.9 −2.8 −1.0Rise from 1970–1990s (°C) 0.5 0.3 0.3 0.3 0.4 0.1 0.2 0.2

Note: The MAGT here is defined as the mean annual ground temperature at about 15 m.

216 X. Li et al. / Global and Planetary Change 62 (2008) 210–218

Different model simulations show that snow melt runoff in theinland river basins of northwestern China will definitely increase(Kang et al., 2002). Wang and Li (2006) chose the upper Heihe RiverBasin as a case study area and used a degree-day factor based snow-melt runoff model to simulate possible changes of snowmelt runoffin response to a warming scenario of 4 °C air temperature rise. Sim-ulation results show an earlier snow melting period, an increase inwater flows in this earlier melting season, and a decline in flows inlater melting seasons.

4.3. Frozen soil

Due to the combined influence of climatic warming and increasinganthropogenic activities, substantial retreat of permafrost is expectedon the QTP and in northeastern China during the 21st century. Dif-ferent modeling approaches including empirical and more physically-based models were used to predict the permafrost change. Li andCheng (1999) used the altitude model, an empirical model that relatesthe lower limit of altitudinal permafrost with latitude (Cheng, 1984),to predict the occurrence of permafrost. The results show that theareal extent of permafrost degradation is about 8% when air tem-perature rises about 0.5 °C by 2019. When air temperature rises about1.1 °C by 2049, permafrost on the QTP will change significantly withthe degraded area reaching about 18%. More drastically, by the year2099, if air temperature increases by an average of 2.9 °C on the QTP,the degraded permafrost area will exceed 58%. Almost all the perma-frost in the southern QTP and in the eastern QTPwill be in degradation(Li and Cheng, 1999; Li et al., 2003a). However, it should be noted thatthere will be a lag time for the response of permafrost in deep groundto climatic warming.

Nan et al. (2005) also simulated future permafrost change on theQTP using a physically-based model (Li et al., 1996). Simulation resultsshowed that in the case of 0.02 °C/yr air–temperature rise, thepermafrost area on the QTP will shrink about 8.8% in the next 50 yr,and high-temperature permafrost with MAGT higher than −0.11 °Cmay be converted into seasonally frozen ground. In the next 100 yr,permafrost with MAGT higher than −0.5 °C will disappear and thepermafrost area will shrink by 13.4%. In the case of 0.052 °C/yr air–temperature rise, the permafrost area on the QTP will shrink by about13.5% after 50 yr. More remarkable degradation will take place after100 yr, and permafrost area will be reduced about 46%. Permafrostareas warmer than −2 °C will thaw.

Climatic warming will also have a significant impact on the en-gineering properties of permafrost. Wu et al. (2000) predicted the

Table 4Prediction of future glacier change in China (Shi and Liu, 2000; Qin, 2002; Kang et al., 2004

Glacier type Current Area (km2) 2030

Air temperature risein summer (°C)

Reduced area (km

Extreme continental type 22,497 0.56 1237Sub-continental type 23,649 0.46 3027Maritime type 13,254 0.38 4095Total 59,400 0.47 8359

permafrost stability along the QTH using the altitude model and athermal stability based permafrost classification system (Cheng andWang, 1982). Results show that permafrost stability will change sig-nificantly under climatic warming. Areal extent of permafrost alongthe highway will decrease and the permafrost zone will move upwardand degrade. Areas of extreme stable zone, stable zone and sub-stablezone will decrease, while the areas of transit zone, unstable zone andextreme unstable zone will increase.

The probabilistic prediction of active layer depth according to awarming climate along the QTR was also attempted recently. First, airtemperatures from the IPCC A2 scenario, which are used as the forc-ing data to run the frozen soil model, were perturbed to generate 100ensemble members using the Monte Carlo method. Then, using a landsurface model (Dai et al., 2003), the active layer depth and itsprobability distribution in the next 100 yr were calculated by theensemble prediction. Results show that thaw penetration along theQTR will deepen 10–40 cm by 2050 and 20–70 cm by 2100 (Yang,2007). The uncertainties of the prediction, in terms of standard de-viation, were also quantified.

In northeastern China, with a warming of 1.0–1.5 °C during thenext 40–50 yr, the southern limit of permafrost would shift north-wards. Present patchy permafrost would largely disappear, thesouthern limit of permafrost would approach the present southernboundary of discontinuous permafrost zone with island taliks, whichwill be converted to isolated patches of permafrost. Current wide-spread continuous permafrost would become discontinuous. In 40–50 yr, the area of residual permafrost in the Da and Xiao Xing'anlingMountains would be 35% of today's total permafrost area (Jin et al.,2007).

5. Summary

China has vast areas of cryosphere within the QTP and its nu-merous mountain areas. This paper provides an overview of the cur-rent status of the cryosphere in China and its changes based on thelatest available data. The up-to-date statistics of glaciers, perma-frost, seasonally frozen ground, perennial and seasonal snow cover aresummarized. Recent observations from both remote sensing and insitu showed that the cryosphere in China is experiencing a rapidchange: China's glaciers have shrunk by 5.5% from the 1960s to date;snowfall variation fluctuates interannually with a slight increasingtrend; significant permafrost degradation is occurring in most perma-frost regions in China. Future trends are predicted by models, whichindicate that the glacier recession could be very rapid, the trend of

)

2050

2) Decrease rate (%) Air temperature risein summer (°C)

Reduced area (km2) Decrease rate (%)

5.5 1.40 3105 13.812.8 0.97 5770 24.430.9 0.65 6958 52.514.1 1.00 15,833 26.7

217X. Li et al. / Global and Planetary Change 62 (2008) 210–218

snowfall increase will continue in western China until 2050 but ineastern China snowfall shows a decreasing trend, and the permafrostwill continue to degrade.

The published data on lake/river/sea ice are insufficient, whichhampers an analysis of changing trends. The monitoring and researchof these very important components of the cryosphere in China ob-viously need to be strengthened. This is of critical importance notonly for fully understanding cryospheric change in China but also forpreventing hazards caused by lake/river/sea ice, such as river ice jams.

The scenarios for future climate change are fraught with highlevels of uncertainty, both globally and in China (IPCC, 2007; Qin,2002). Accordingly, although the shrinkage of the cryosphere in Chinais underway, predicting future change is uncertain and difficult andneeds to be quantified more precisely.

According to the data presented in this paper, it appears that thefragility of cryospheric environments of Chinawill increase. Therefore,it is critical to improve the understanding and predictability of thecryosphere and be prepared for future changes, which will helpalleviate the problems caused by cryospheric change.

Acknowledgments

Thiswork is supported by the CAS International Partnership Project“The Basic Research for Water Issues of Inland River Basin in AridRegion” (CXTD-Z2005-2) and the NSFC (National Science Foundationof China) project (grant number: 90502010). The authors thankMs. GeChunmei for her assistance in preparing the figures in the paper.Generous help for revising the paper was provided by the Editor,Professor Thomas M. Cronin and by Mrs. Betsy Armstrong and twoanonymous reviewers.

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