The volume of water that exists in solid format and below the surface of the earth is called thecryosphere. The cryosphere consists of ice sheets, glaciers, snow cover, permafrost, sea ice, lake ice, riverice, and solid precipitation. Currently, 75% of theearth's fresh water supply is stored in the cryosphere.Approximately 10% of the l and surface is covered byice sheets and glaciers, and 7% of the ocean surface iscovered by sea ice. About half of the l and surface experiences winter snow cover, and the permafrost areais even larger(IPCC, 2007).

The cryosphere plays an important role in theearth's climate system due to high albedo, the latentheat associated with phase changes of snow and ice, and the sheer volume of ice reserves. Rapid changesin the components of the cryosphere have profoundinfluences on the energy balance, atmospheric circulation, ocean circulation, water cycle, changes in sealevel, sources and sinks of carbon, and socio-economicdevelopment(Qin et al., 2006). Changes in ice and snow can alter regional and global climate dynamicsthrough their influences on the energy balance and water cycle. Changes in ice volume can affect theocean circulation by altering distributions of salinity and temperature. Changes in permafrost not only influence the climate system by altering exchanges of water and heat between l and and atmosphere, but alsoinfluence the global carbon cycle via changes in thepermafrost carbon pool. Cryospheric change also contributes significantly to sea level rise(IPCC, 2013):recent increases in sea level can be attributed primarily to melting of the cryosphere and thermal expansionof the ocean(Cazenave et al., 2008, 2009).

China has the largest cryospheric area among the countries in mid and low latitudes. Glaciers, per-mafrost, and snow cover are widespread, with significant effects on climate, the environment, water resources, and ecological processes. The cryosphere isfundamental to maintaining oasis economies in aridareas and ecosystem stability in cold regions, and istherefore of great significance for strategic development in western China(Ding and Qin, 2009; Qin and Ding, 2009).

Cryospheric research has attracted unprecedentedattention in recent years due to high sensitivity of thecryosphere to climate change and its important role inclimate feedbacks. Cryospheric research is now one ofthe most active fields in climate system studies, and an important element of research programs on globalchange and sustainable development(Allison et al., 2001; Xiao, 2008; Qin and Ding, 2009). In this paper, we review recent findings on changes in the global and Chinese cryosphere and summarize recent studies ofthe impacts of cryospheric changes on Chinese climate.We conclude with an outlook for future cryospheric research in China.

The global cryosphere has undergone significantchanges in recent decades. Almost all of the elementsof the cryosphere have lost mass under global warming.The Fifth Assessment Report(AR5)of the Intergovernmental Panel on Climate Change(IPCC)WorkingGroup I(IPCC, 2013)provided a comprehensive assessment of current underst and ing of changes in theglobal cryosphere(Fig. 1).

Fig. 1. Schematic summary of the most prominent changes in the observed cryosphere. [From IPCC, 2013]

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The AR5 reported that the Greenl and and Antarctic ice sheets have lost mass over the last twodecades. The Greenl and ice sheet lost mass at an average rate of 34(-6 to 74)Gt yr^-1 between 1992 and 2001, while the Antarctic ice sheet lost mass at an average rate of 30(-37 to 97)Gt yr^-1 over the sameperiod. These rates have accelerated, with the Greenl and ice sheet losing mass at a rate of 215(157 to 274)Gt yr^-1 and the Antarctic ice sheet losing mass at arate of 147(72 to 221)Gt yr^-1 since 2002. Glaciershave shrunk effectively worldwide. The average rateof global ice loss from glaciers was 226(91 to 361)Gt yr^-1 over the period 1971-2009.

Arctic sea ice extent decreased substantially between 1979 and 2012, at a rate of 3.5%-4.1% perdecade for the annual mean and 9.4%-13.6% perdecade for the summer season. By contrast, the annual mean Antarctic sea ice extent increased at a rateof 1.2%-1.8% per decade over the same period. Thesechanges are regionally heterogeneous, with sea ice extent increasing in some regions and decreasing in others.

Northern Hemisphere snow cover extent decreased between 1967 and 2012 at mean rates of 1.6%(0.8%-2.4%)per decade for March and April and 11.7%(8.8%-14.6%)per decade for June. Permafrosttemperatures have increased in most regions since theearly 1980s, with observed warming of up to 3‰℃ inparts of northern Alaska(the early 1980s to mid 2000s) and up to 2‰℃ in parts of the Russian European North(1971-2010). This warming has coincided with a considerable reduction in permafrost thickness and arealextent.

As global climate continues to warm in the future, Arctic sea ice will continue to melt, and global glaciervolume, Northern Hemisphere spring snow cover and permafrost extent will continue to decrease. By theend of the 21st century, Arctic sea ice extent is projected to decrease by 43%-94% in September and 8%-34% in February relative to the 1986-2005 mean.Global glacier volume is projected to decrease by 15%-85%, the area of Northern Hemisphere spring snowcover is projected to decrease by 7%-25%, and the extent of near-surface(upper 3.5 m)permafrost at highnorthern latitudes is projected to decrease by 37%-81%.

The Chinese cryosphere consists mainly ofglaciers, frozen ground, and snow cover. China con-tains 46377 glaciers with a total area of 59425 km² and an ice volume of 5600 km³(Shi, 2005). Over70% of the l and area is covered by frozen ground during at least part of the year. Permafrost regions ac-count for 23% of the total l and area, while seasonally frozen regions account for about 50%(Zhou et al., 2000). Snowfall occurs over more than 90% of the Chinese l and surface. The area of China with stable snowcover(more than 60 snow days per year)is 3.4 £ 106km2, while the area with unstable snow cover is 4.8 £106 km2(Che and Li, 2005).

Changes in the Chinese cryosphere are largelyconsistent with changes in the global cryosphere. Mostglaciers in China have receded under global warming.Approximately 82% of Chinese glaciers have recededor disappeared since the 1960s, resulting in the loss ofmore than 10% of the glacier area. Glacier recessionhas accelerated since the 1990s(Committee of the Second National Assessment Report on Climate Change, 2011). For example, the mean recession rate at thetail of the Rongbuk Glacier(Mt. Qomolangma)increased from 5-8 m yr^-1 during 1966-1997 to 7-9 myr^-1 after 1997. Likewise, the mean recession rate ofthe Urumqi Riverhead No. 1 Glacier increased from0.18 m yr^-1 during 1981-2001 to 0.62 m yr^-1 during2001-2006(Fig. 2).

Fig. 2. Changes in the mass balance of selected glaciers over recent decades. [From Qin et al., 2012]

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Permafrost on the Tibetan Plateau has undergonesignificant changes over the past two decades. Thechanges may be summarized in two aspects. First, permafrost temperatures have warmed substantially.For example, the temperature of permafrost areasin the low and middle mountain ranges of the TibetanPlateau has increased from about -3‰℃ to values of -3to 1℃, while the temperature of permafrost in rivervalleys and basins has reached values between -1 and 0.5℃. The temperature of upper-layer permafrost hasincreased at a rate of 0.1‰ yr^-1. Second, a substantialamount of permafrost has experienced direct degradation. Permafrost with temperatures lower than-3‰ has mainly warmed without severe degradation.By contrast, many permafrost areas with temperatures higher than -1℃ have receded. For example, thearea of permafrost near Xidatan has been reduced by12% since 1975, while the area of permafrost within2 km to either side of the Anduo-Liangdaohe Roadhas been reduced by 35.6%. The thickness of seasonally frozen ground has also decreased. The max-imum depth of seasonally frozen ground on the Tibetan Plateau thinned at an average rate of 3.3 mmyr^-1 between 1961 and 2006(Committee of the Second National Assessment Report on Climate Change, 2011).

The depth of snow cover over the Tibetan Plateauincreased steadily over the latter half of the 20th century, but decreased significantly during the early partof the 21st century. The maximum snow depth innorthern Xinjiang has increased at an average rate of0.8% since 1961. The depth of snow cover in NortheastChina|Inner Mongolia shows no obvious long-termtrends, but the amplitude of interannual fluctuationshas increased substantially since the 1990s(Committee of the Second National Assessment Report on Climate Change, 2011).

The Chinese cryosphere is projected to continueto decrease in both area and volume during the following decades. Smaller glaciers and glaciers that contactthe ocean are projected to recede significantly. Thethickness of the active layer of permafrost is expectedto continue increasing, while the area and thicknessof seasonally frozen ground are expected to continuedecreasing. Changes in snow cover are projected tovary substantially among different regions(Qin et al., 2012; Yao et al., 2013).

Snow cover is a product of atmospheric circulationsystems. Variations in snow cover can affect climateby changing the energy balance, the hydrologic cycle, and the atmospheric circulation, and thus play an important role in the earth's climate system. More thana century ago, Blanford(1884) and Walker(1910)proposed that winter snow cover over the Tibetan Plateau and precipitation of the Indian summer monsoon wereout of phase. This hypothesis was later confirmed bymultiple studies(Hahn and Shukla, 1976; Dey and Kumar, 1983; Dickson 1984; Parthasarathy and Yang, 1995).

Chinese scientists have carried out a number ofstudies examining how snow cover over the TibetanPlateau impacts precipitation and the East Asian summer monsoon. Despite isolated discrepancies due todifferences in snow cover data or analysis periods, moststudies show negative correlations between winterspring snow cover over the Tibetan Plateau and theEast Asian summer monsoon(Guo and Wang, 1986;Chen et al., 1996; Fan et al., 1997; Chen et al., 2000a;Zheng et al., 2000; Zhang and Tao, 2001; Qian et al., 2003; Wu and Qian, 2003; Zhao et al., 2007). TheEast Asian summer monsoon tends to be weaker oronset later when the Tibetan Plateau snow cover isabove normal during winter and spring; it tends to bestronger or onset earlier when the snow cover is belownormal. More snow cover over the Tibetan Plateauin winter and spring reduces solar absorption by increasing surface albedo, and decreases the transportof sensible and latent heat from the surface to atmosphere. These effects weaken the plateau heat sourceto the atmosphere. Melting snow absorbs heat and leaves the soil relatively wet. This "wet soil" can retain features of the snow cover anomaly and continueto interact with the atmosphere for a long time.

The most significant climatic effect of snow coverover the Tibetan Plateau is its influence on summer precipitation in China. First, winter-spring snowcover over the plateau is positively correlated withsummer(June-August)precipitation in the YangtzeRiver valley and negatively correlated with summerprecipitation in South China and North China(Chen and Song, 2000a; Chen and Wu, 2000b; Wu and Qian, 2000; Zheng et al., 2000; Wu and Qian, 2003). Second, winter-spring snow cover over the plateau is positivelycorrelated with early summer(May-June)precipitation in South China and negatively correlated withearly summer precipitation over the Yangtze River valley(Chen, 1998; Wei et al., 1998; Cai, 2001; Zhao et al., 2007). Third, interdecadal variations in winter-spring snow cover over the plateau are associated withchanges in the spatial pattern of summer precipita-tion in eastern China. Snow cover over the TibetanPlateau in winter and spring was enhanced betweenthe 1970s and the 1990s(Zhu et al., 2007; Ding et al., 2009; Song et al., 2011), resulting in a weaker summermonsoon(Zhang et al., 2004). This situation induceda "southern flood and northern drought" pattern inChina(Zhao et al., 2007; Zhu et al., 2007; Ding et al., 2009).

Fewer studies have examined the impacts ofEurasian snow cover on Chinese climate, althoughthis has begun to change in recent years. Interannual variations in winter-spring Eurasian snow coverare in phase with summer precipitation in NortheastChina, eastern North China, and Southwest China(Chen and Song, 2000b; Chen and Sun, 2003) and outof phase with summer precipitation in the Yangtze-Huaihe River valley(Liu and Luo, 1990). Yang and Xu(1994)showed significant positive correlations between winter Eurasian snow cover and summer precipitation in South China and North China, and negative correlations with summer precipitation in thewestern, central, and northeastern parts of China. Ye and Bao(2005)indicated that summer precipitationin eastern China is negatively correlated with autumnEurasian snow cover. Interdecadal changes in the spatial pattern of summer precipitation in eastern Chinahave also been linked to interdecadal variations inspring Eurasian snow cover. Summer precipitation insouthern China increased significantly after the late1980s. This change may be associated with a reduction in spring Eurasian snow cover(Zhang et al., 2008, 2013). Wu et al.(2009a)showed that the Eurasiansnow cover distribution between the late 1970s and the 1990s was characterized by a coherent negativeanomaly over most of Eurasia but a positive anomalyover portions of the Tibetan Plateau and East Asia.This distribution can affect high latitude wave activity and stimulate atmospheric teleconnections. As aresult, North China was covered by an anomaloushigh while South China was covered by an anomalous low. This led to positive precipitation anomaliesover South and Southeast China and negative precipitation anomalies over the upper reaches of the Yellow River valley(Fig. 3). This mechanism explainsthe close relationship between the decrease in snowcover over Eurasia, the increase in snow cover over theTibetan Plateau, and the "southern flood and northern drought" pattern that dominated China during thelast 20 years of the 20th century.

Fig. 3. Spatial distributions of the leading singular value decomposition modes of(a)springtime Eurasian snow water equivalent(SWE) and (b)summertime rainfall at stations in China.(c)Normalized time series of spring Eurasian SWE(solid line) and summer rainfall in China(dashed line). [From Wu et al., 2009a]

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Changes in Eurasian snow cover also significantlyinfluence springtime precipitation over China. Wu and Kirtman(2007)showed that snow cover over westernSiberia is positively correlated with precipitation insouthern China during spring. Zuo et al.(2012a, b)showed that increases in springtime snow coverover Eurasia are associated with more precipitationin southeastern China and less precipitation in southwestern China, while decreases in springtime snowcover over Eurasia are associated with the oppositepattern. They argued that the significant decreasesin springtime Eurasian snow cover since the 1980s arean important reason for the simultaneous decreases inprecipitation over southeastern China and increases inprecipitation over southwestern China.

Mu and Zhou(2010, 2012)analyzed the impactsof changes in newly increased winter snow cover onsummer temperature in China. They showed thatwinters with significantly increased snow cover overnorthern Eurasia are generally associated with anomalous low pressure over midlatitudes of East Asia during the following summer. This anomalous low causescool summers over the eastern part of Inner Mongolia and western part of Northeast China. These summersare also characterized by a more intense East Asianwesterly jet, while the western Pacific subtropical highstrengthens and shifts northward and westward. Thissituation results in droughts and high temperaturessouth of the Yangtze River. The opposite changesare observed following the winters with marginally increased Eurasian snow cover.

Polar regions play important roles in global and regional climate. They have therefore been identifiedas key regions in many international scientific programs on global climate change. Chinese scientistshave conducted a variety of studies examining howchanges in polar environments(especially changes intemperature and ice)influence the atmospheric circulation over East Asia and the climate in China.

Recent warming in the Arctic has resulted in reductions of ice and snow, which have caused rapidchanges in both ecosystem and climate(Committeeon Emerging Research Questions in Arctic, 2014).Changes in Arctic sea ice can impact atmospheric and oceanic heat transport, as well as fluxes of heatbetween the ocean and atmosphere. Strong warming over the Arctic Ocean in autumn and winter isclearly associated with reduced sea ice extent duringthe past decades(Serreze and Barry, 2011). Studieshave shown close relationships between sea ice changesin the Kara, Barents seas, and Greenl and seas duringwinter and the Northern Hemisphere subtropical high, El Ni~no-Southern Oscillation(ENSO), and the EastAsian winter monsoon(Fang, 1987; Huang et al., 1992;Fang and Wallace, 1994; Yang et al., 1994; Wu et al., 1997, 1999, 2001, 2004; Wu and Qian, 2000). Interannual and interdecadal changes in Chinese climatealso appear to be closely related to Arctic sea ice extent.

Wu et al.(2011)showed strong negative correlations between the intensity of the Siberian high during winter and sea ice concentrations in the easternArctic and along the northern coast of Eurasia during autumn and winter. They proposed that increasesin sea ice near the eastern Arctic and the Greenl and Barents-Kara seas and negative SST anomalies(especially in the northern North Atlantic)during autumn and winter can cause a decrease in winter sea level pressure over northern Eurasia and the northernNorth Atlantic. This acts to weaken the Siberian high and enhance westerly winds in the mid-high latitudesof Eurasia. Increases in autumn-winter sea ice extentare also associated with negative temperature anomalies in the Arctic that enhance the atmospheric temperature gradient between the Arctic and the mid-highlatitudes of Eurasia. This enhances westerly winds innorthern Eurasia. These enhanced westerlies preventcold air at high latitudes from breaking out towardthe south, and therefore result in warmer surface temperatures over the high latitudes of Eurasia and EastAsia. Decreased sea ice extent results in the oppositechanges, so that the high frequency of severe winterweather over Eurasia in recent years may be closelylinked to reductions in autumn-winter Arctic sea iceextent(Honda et al., 2009; Petoukhov and Semenov, 2010; Liu N. et al., 2012).

Changes in Arctic sea ice extent affect not only climate variability in winter, but also the prevailing meteorological regime and the intensity and frequency ofextreme weather over Eurasia(Wu et al., 2013a). Thedecline in autumn Arctic sea ice extent since the late1980s favors the frequent occurrence of blocking highsover northern Eurasia. Blocking highs over northernEurasia are associated with colder temperatures overthe middle and northern parts of the Asian continentduring winter(Fig. 4). Liu J. P. et al.(2012)showedthat the decrease in autumn Arctic sea ice extent isrelated to the occurrence of extreme temperature and snowfall events during winter in the mid-high latitudesof the Northern Hemisphere. Wide reductions in summer Arctic sea ice extent and delays in the autumn-winter recovery of Arctic sea ice may cause anomalouswinter atmospheric circulations that include more frequent blocking events in mid-high latitudes. Thesechanges increase the extent of open water in the Arctic, which can increase the flux of water vapor fromthe ocean to the atmosphere. Arctic warming also increases the amount of water vapor that the atmospherecan hold.

Fig. 4. Schematic diagram illustrating how reduced Arctic sea ice a®ects winter surface air temperature(SAT) and precipitation in Eurasia. Arrows show the typical locations of anomalous anticyclonic and cyclonic circulations in thelower troposphere associated with the negative phase of the tripole wind pattern. The brown line represents an isoline ofgeopotential height at 500 hPa. The yellow and green areas indicate decreases and increases in precipitation, respectively, while the red and purple areas indicate positive and negative SAT anomalies. [From Wu et al., 2013a]

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The effects of changes in winter Arctic sea ice extent on the atmospheric circulation and climate overEurasia can persist into the following summer viaSST anomalies in North Atlantic(Wu et al., 2013b).Changes in spring Arctic sea ice are also linked tosummer precipitation in China. Reductions in springArctic sea ice extent are associated with increases insummer precipitation over Northeast China and theYangtze-Huaihe River valley, and decreases in summerprecipitation over South China. Wu et al.(2009b, c)suggested that the Arctic dipole might act as a bridgelinking spring Arctic sea ice and summer precipitationover China. Zhao et al.(2004)showed that decreasesin spring sea ice extent in the Bering and Okhotskseas inhibit the northward movement of the East Asian summer monsoon, thereby resulting in increases insummer precipitation over southeastern China. Seaice changes in the Bering and Okhotsk seas can also affect the frequency of typhoons over the western NorthPacific through their influences on the tropical atmospheric circulation(Fan, 2007; Zhou and Cui, 2008;Zhou and Wang, 2008). A larger winter-spring sea iceextent in North Pacific corresponds to fewer typhoonsin the western North Pacific.

Climatic influences of changes in Antarctic seaice are observed not only in the Southern Hemisphere(e.g., the Antarctic Oscillation, the Mascarene high, and the Australian high)(Gao et al., 2003; Xue et al., 2004), but also over East Asia(Fu, 1981; Yang and Huang, 1992; Xue et al., 2003; Ma et al., 2006, 2007).Changes in Antarctic sea ice extent are negatively correlated with Meiyu rainfall in the Yangtze River valley(Fu, 1981). Decreases in sea ice extent are associatedwith a later end of the following Meiyu season, whileincreases in sea ice extent are associated with an earlier end. Xue et al.(2003)showed that increases inAntarctic sea ice during boreal spring and summer areassociated with increases in summer precipitation overNorth China and decreases in summer precipitationover South China and Northeast China. This pattern of precipitation changes reflects a change in theEast Asian summer monsoon circulation. Changes inAntarctic sea ice also affect the polar vortex, equatorial SST, the western Pacific subtropical high, and typhoon activities(Peng and Wang, 1989; Zhao and Ji, 1989; Bian et al., 1996).

Interactions between permafrost and global climate have attracted increased attention in recent years(Zhang et al., 1999; Qin and Ding, 2009). Early studies of these interactions were mainly limited to the effects of climate change on permafrost due to the complexity of permafrost hydrothermal processes(Jin et al., 2000; Cheng and Wu, 2007; Wu and Zhang, 2008;Zhao et al., 2010; Guo and Wang, 2013). Relativelyfew studies have focused on how changes in permafrostaffect regional climate, especially in China.

The available studies(Li et al., 2002; Tanaka et al., 2003; Guo et al., 2011a, b)have demonstratedthat the Tibetan Plateau permafrost plays an important role in surface heat flux changes. The freezing and thawing of plateau soils can enhance the exchangeof heat between the l and atmosphere, and significantly influence atmospheric circulation patterns(including the South Asian high, the western Pacificsubtropical high, and the Indian low). Hydrothermalchanges resulting from freeze-thaw processes over theTibetan Plateau appear to have important influenceson East Asian climate(Wang et al., 2003), with significant implications for precipitation in eastern China(particularly during the flood season). Gao et al.(2005)showed that the thaw date over the plateau ispositively correlated with summer precipitation overthe mid-lower reaches of the Yangtze River valley.

L and -atmosphere coupled models are importanttools for studying interactions between the l and surface and atmosphere. These models provide a meansof quantifying the impacts of permafrost changes onglobal and regional climate. Although permafrost simulations are still in their infancy, some progress hasbeen made. Several studies have investigated the influence of freeze-thaw processes in the Tibetan Plateaupermafrost on atmospheric circulation and regional climate of East Asia(Wang et al., 2002; Zhang et al., 2003; Wang et al., 2008; Li et al., 2011; Xin et al., 2012). For example, Wang et al.(2008)showed anincrease in the consistency between simulated and observed summer precipitation over the Yangtze Rivervalley after incorporating a new permafrost parameterization into CCM3(Community Climate Model 3).The model's ability to simulate the East Asian atmospheric circulation is also greatly improved. Li et al.(2011)indicated that improving the permafrost parameterization scheme in CAM3(Community Atmosphere Model 3)significantly enhanced the simulatedheating of the atmosphere above the Tibetan Plateau.Surface temperatures in East Asia during winter and summer have also changed substantially. Xin et al.(2012)analyzed the response of East Asian climate tochanges in permafrost by introducing non-frozen water processes into CAM3. Their simulations indicateda weakening of the East Asian winter monsoon and a strengthening of the East Asian summer monsoon.Summer precipitation increased over the southern Tibetan Plateau, the middle part of the Yangtze Rivervalley, and Northeast China, and decreased over SouthChina and Hainan Isl and. The results of these studieshighlight the important role that permafrost plays innumerical simulations of East Asian climate.

Glaciers are an important water resource for thearid regions in Northwest China. Variations in runofffrom mountainous watersheds are tightly related tothe evolution of glacier area within the basin. Glaciershave two main impacts on water resources in China:to supply water, and to regulate river runoff by reducing peak flows and supplementing insu±cient flows.Glaciers regulate river flow according to the followingmechanism. Enhanced precipitation during high flowyears reduces temperatures in the glacial areas of highmountains. Lower temperatures decrease glacial ablation, so that less glacial melt water enters the rivers.This mechanism limits the increase in runoff that results from the increase in precipitation. Conversely, when precipitation in the basin decreases, the relatively high temperatures in the glacier area cause anincrease in glacial melt that supplements the river flow(Ding and Qin, 2009; Committee on the Second National Assessment Report on Climate Change, 2011).

Interannual and interdecadal variations in the volume and extent of glaciers in the basin control themagnitude of glacier runoff. Glacial melt water canhave a significant impact on river runoff if the glaciercoverage in the basin exceeds 5%(Ye et al., 2003). Approximately 70% of the increase in runoff in the headwaters of the Urumqi River in recent years has beensupplied by increases in glacial melt. About one thirdof the increase in runoff in Akesu can be attributed toincreases in glacier runoff(Liu et al., 2006). Glaciermelt water in the basin above Zhimenda hydrologicalstation in the headwaters of the Yangtze River has increased by 15% over the past 40 years, even as riverrunoff has decreased by 14%(Liu et al., 2009). Theseincreases in river flow due to glacial melt are beneficial at present, but it is worth noting that the associated loss of glacier mass will eventually result in rapiddecreases in river runoff. Changes in snow and permafrost also have important effects on river flow. Theinfluence of snow and permafrost on runoff processescan even lead to changes in the allocation of river water(Committee on the Second National AssessmentReport on Climate Change, 2011).

The cryosphere plays an important role in theearth's climate system and is one of the most sensitive indicators of climate change. In this paper, we review recent scientific studies of changes in theglobal cryosphere, with particular focus on the Chinesecryosphere. We have summarized advances in underst and ing how snow cover over the Tibetan Plateau and Eurasia, Arctic sea ice, Antarctic sea ice, permafrost, and glaciers influence the atmospheric circulation overEast Asia and the climate in China.

Changes in the cryosphere also have significanteffects on ecological health, environmental systems, and resource availability, among others. The effects ofcryospheric change in China have become increasinglypronounced under global warming, with significantimpacts on regional climate, water resources, ecology, environment, and sustainable development. The regions directly affected by the cryosphere in China areboth ecologically vulnerable and economically underdeveloped. The influences of cryospheric changes inthese regions will increase the ecological and environmental pressures associated with economic development.

From the international perspective, cryosphericresearch is shifting from mechanistic and process studies focusing on single elements to holistic studies ofthe cryospheric system. The Climate and Cryosphere(CliC)Project developed by the World Climate Research Program focuses on the integrated interactionof the elements of the cryosphere with climate, hydrology, ecology, and environment, among others. Theaim of the CliC project is threefold: 1)to improveunderst and ing of the physical processes and feedbackmechanisms that control the interactions between the cryosphere and other elements of the climate system, 2)to improve the representation of cryosphericprocesses in climate models and thereby reduce uncertainties in climate simulations and climate changeprojections, and 3)to assess and quantify changes ineach component of the cryosphere during past and future climate change. Future cryospheric researchwill accordingly focus on physical mechanisms and impacts.

Both the international scientific direction and thenational dem and require that cryospheric studies inChina should focus on the mechanisms of cryosphericchange, the interactions between the cryosphere and climate, the impacts of cryospheric change, and strategies for adapting to current and future cryosphericchange. We should conduct comprehensive interdisciplinary studies that build underst and ing of thecomplete cryospheric system. The mechanisms ofcryospheric change are the foundation of cryosphericscience. The interaction between the cryosphere and climate is a focus of current studies, which still needsto be strengthened. More and more attention is beingpaid to explore the impacts of cryospheric change, butthe research base remains relatively weak. Examination of possible strategies for adapting to the impactsof cryospheric change is still in its infancy(Ding and Xiao, 2013).

Future cryospheric research should therefore address three m and ates. First, we must continue basic research that deepens scientific underst and ing ofcryospheric processes and their response to climatechange. Important elements of this m and ate includequantifying the relationships between glacial change and climate change and improving underst and ing ofthe responses of permafrost and snow cover to climatechange. A deeper exploration of the physical processes and feedback mechanisms in the interaction betweenthe cryosphere and climate will help to improve ourability to realistically simulate cryospheric processesin climate system models and quantitatively assess therole of the cryosphere in global and regional climatechange. Second, we must strengthen studies that examine the impacts of cryospheric change. Particularattention should be paid to the influences and physical mechanisms of changes in different components ofthe cryosphere on climate, water resources, and ecology. Third, we must increase the resources allocatedto studies of adaptation strategies. We should propose and develop scientific evaluation indices that aresuitable for the Chinese cryosphere and are based onboth the characteristics of cryospheric change and acomprehensive consideration of social, economic, and cultural factors. This could include the constructionof a system for evaluating vulnerability to cryosphericchange, proposing adaption pathways and strategiesthat address changes in the Chinese cryosphere and their impacts, and providing scientific support for sustainable economic development.