acknowledgement references sir, introduction

Ding and Haeberli: Correspondence in snow precip a ti on a nd th erm a l in so la ti o n , whi ch ex plains th e recentl y observed g lacier-m ass loss (Arenillas a nd o th er s, 1992 ). Furth erm o re, Nla rtinez d e Pison and Arenill as Pa rra ( 1988 ) includ ed some glaciere ts in th eir ca ta logue. As th ese glacier e ts d o not h ave crevasse, th ey do not consid er th em as g laciers, a lth o ug h th ey are remn a nts of previous ones (e.g. Punta Z a rra glacieret). Lik ewi se, a report of th e Nlini stero d e Obras Pllbli cas y Tra nsportes ( 1992 ) on th e snow in th e Spa nish cordill eras in cl ud es some glaciers in th e Spa ni sh P yrenees with dime nsions simil a r to Gl acia r J ou N egro, such as th ose of Punta Za rra, Balaitu s a nd T aillon. All of th em, loca ted in th e western part of th e glac ieri zed area, are sma ll-size g lac iers wi Lh an a rea o f 2 x 10" m 2 . R ega rdin g thi ckn ess, Glacia r J ou Negro is thi cker th an th ose in that rep o rt, the rea l valu es reachin g 14 m a t some points. Th e presen ce of isol a ted g lacier ice in th e Pi cos de Europa is pro ba bly du e to its slower res ponse to recent clim a te cha nges du e to th e specifi c charac teristi cs of its loca ti on, a bove 2200 m and with a north eas t as pec t a nd a shad y topogr a ph y, as it occ upi es an impo rta nt karsti c d epress ion. Future research co nce rning th e stage of evo luti on is pl a nn ed and this includ es th e m eas urem ents of poss ible va ri a ti ons in ice thi c kn ess and in g lacie r ex tent, as well as m odifi ca ti ons to th e wa ter-condui t sys tem.

ACKNOWLEDGEMENT Fi eld assista nce a nd to pogra phi c wo rk, carri ed o ut by J. Al onso PCl'i a, is g ra tefull y ac kn ow ledged by th e a u th ors.

Federacioll Asturiana de r..speleologlo, 33080 Olliedo, Spaill DejJartmenlo de Geologt'a, Universidad de Oviedo, 33005 Oviedo, Spain

J UAN J OSf'. G OKZc\LE Z S U,\RE Z

SIR , Compi/alion oJ long-Lerm glacier-jlucllIaLion data in China and a comparison with corresponding records }i'om Swilzeriand

INTRODUCTION D a ta on world-wid e glac ier flu c tu a ti o ns a re b ein g compa red a nd inte rpreted in a n in c reas ing numbe r of pu blica ti ons (Pa tze l t, 1985; Ki slov a nd K orya kin , 1986; M a ka revi ch a nd Rototayeva, 1986 ; V a llon a nd oth e rs, 1986; H ae berli a nd oth ers, 1989a; Ki c k, 1989; O erl em a ns a nd oth ers, 1993; Willi a llls and F erri g no, 1993; O erl em a ns, 1994). Th e surface a reas of glaciers in C hin a acco un t for abo u t 10 % of th e tota l surface area cove red b y ice caps a nd mounta in glac iers o n Ea rth , existin g o u [sid e th e la rge pola r ice shee ts (H ae berli a nd o th e rs, 1989b ) . With th e exce pti on of a few indi \'idu al glac ie rs, ho w ever , 111 0 t C hin ese g lac ie rs h ave bee n r a r e ly m o nitored a nd m cas ured . Consequ entl y, data on glacie r flu ctu a ti ons in C hin a a re limited. Th e C hin ese glacie r m o nitored a ndlll cas ured in mos t d etail is U rlimqi Glac ie r N o. 1 within th e U rLimqi Ri ve r so urce region in th e ce ntral Ti en Sha n . Sin ce 1980, va ri a ti o ns in th e positi o ns o f glacier fronts (len g th cha nge ) durin g va ri ous tim e period s have bee n re po n edlor abo ut 200 glaciers (Zh a ng, 1980a, b: K a ra ko ra m ; Zh a ng a nd Mi , 198 1: Qilia nsh a n , Kunlunshan a nd Ti e n Shan: \Vu a nd o th ers, 1983: Ti en Sh a n ; Xi e and o th e rs, 1985: Qili a nsh a n , Kunlunsha n a nd Ti en Sh a n; \Vu a nd o th ers, 1983: Ti en Sha n; Xi e a nd oth ers, 1985: Qili a nsha n; R cn, 198 7: Kunlun shan; er. a lso Shi a nd oth ers, 1988, cr. Fi g. I). Gl acie rs in th e Swiss Alps were chosen fo r a m a in compa riso n, beca use th ey h ave

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REFERENCES Arcl1 ill as, 111. , I. CanLaril1o, R. \Ia n in cz. E. \ Iartinez de Pi so n a nd A. Pedrcro. 1992. El cOl1trol de los g lac iares ac tu a les en cl progra m3 EH RI[\' . III La lIie/'e ell las cordilleraJ CS/Hlliolas. Programa E RI-/!.A', /ilio 1990/91. i\la drid , i\finisterio de O b ras publ icas. T ransponcs y M edi o Ambicnte. Direcc ion Genera l d e Obras Hidrau li cas, 2 15 227. frochoso. 111. a nd J .C. C35 t311 011 . 1995. Co rres pondence. COlll ments on " G laciers in Pi cos de Eu ropa. Cord ill era Canta brica, north west Spa in" by Go nd tl ez S u,irez and Al onso.]. Glaciol .. 4l ( 138 ), +30-432. Go nz;tl ez Smirez, J .J . a nd V . Al on50. 1994. Co rres pond ence. G lac iers in Pi cos de Euro p a, Co rdill era Ca nt ilb ri ca, north west S pa in . J. Glaciol., 40 ( 134 ), 198- 199 . \Iartin ez de Piso n , E. and r-!. Arc nill as Pan·a. 1988. Los g laciares act ua les d el Pirin eo es panol. III La lIin'e ell el Pirilleo espm/ol. ilI ad rid . :--li nisteri o d e Ob ras Pllblicas y U rba nismo, 29- 98. i\1 inisleri o de O b ras Pub li cas, Tra nspo rtes y t-I edi o Alllbi ente . 1992. La lIift'e en las cordilleras eS/HlIiolas. Programa ERI-ll. \', . l lio 1990/9 1. l\l adrid , ~I in i s t cr i o de O b ras Publicas, Tra nspon es \" i\lccl io Alll bicnt e. Direccion Ge nera l de Obras Hidra uli cas. Sen'at, D. a nd J . Vc n tura. 1993. G lac iers of Europe g lac iers of the Pyrenees, S pa in a nd France. U.S. Geol. 111"1' . ProJ. Pap. 1386-E , E+9E6 1.

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1933 1943 1953 1963 1973 1983 0 ....... -500 ...... ....... -1000 ....... ....... -1500 ....... ....... Swiss Alps (L>lO km) -2000 ....... -2500 (c) -3000 Hailuogou Glacier (L=13 .1 km)

---- --

Fig. 5. ComjJal'ison between average change in length of Swiss glaciers and changes in length of individual Chinese glaciers.

over vari a bl e tim e intervals a nd hence may b e compared with deta il ed Swiss record s. A general trend towards retrea t has obviously predomina ted during th e past 30 yea rs for th e in vestigated glacier sizes in China as well as in Switze rl a nd. It is also notewo rth y that th e contin ental Qi yi Glacier reac ts less and the m a ritime Hailuogou Gl acier more sensitively th an Alpin e g laciers with th eir tra nsitiona l clim a te. Th e similarity of long -te rm g lacier-length ch a nges in C hin a a nd Switzerl a nd a lso a ppears in the sta tistics [or different classes of glacier len g th (T a ble 2) . In cr eases and d ec reases in th e percentage of retreating glacier snouts during different time inter vals roughl y follow th e same pa ttern in both countri es, es pecially with respect to glaciers shorter than 10 km. Glacier retreat clea rl y predomin a tes, with the exce ption of th e intermi tten t advan ce of long Chinese glaciers a fte r th e middle of th e present century and during the period a round 1980 when 2- 5 km long glaciers ad vanced in b o th countri es . In ge nera l, percentages and rates of re trea t for glaciers shorter th a n 10 km wer e high er during th e 1950s but d ecelera ted sin ce th e 1960s, leading to a te nd en cy towards intermittent advance in the 1970s with a p eak from the middle of th e 1970s to the b eginning of th e 1980s. The re treat of th e Chin ese glaciers longer than 10 km during va rious time peri od s a ppears to be less stead y a nd less homoge nou s than in Switze rla nd. In fac t, th ere see ms to be a dis tin c t difference b e tween the two countries with respec t to the a ve rage ra tes o f g lacier-leng th changes and to perce ntages of adva nce/ re trea t [or large glaciers. On e

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Ding and Haeberli: Correspondence Table 2. ComjJarison oJ length changes Jor comparable length classes (km ) oJ glaciers ill China and Switzerland ( % is percentage oJ retreating glaciers with number o[ glaciers in brackets; rate is average rate oJ length change ill m a / Jor the entire sam/Jle of the size catego?)1and tlte considered time interval ) . The locations of the Chin ese glaciers Jor the individual time intervaLs are as JoLLows : (/) = Qj.Lianslwn ( eight gLaciers); ( 2 ) = Tien Shan ( two gLaciers ) and Qjlianslzan ( one gLacier; (.1) QjLianshan ( nine gLaciers); ( 4 ) Qjlianshan (jour gLaciers) and Tien Shall ( three gLaciers); (5) Qj.Lianslzan ( six gLaciers ) , Tien Slwn ( one gLacier) and Kunlunshan (seven glaciers) ; ( 6) Qj.l£anslzan ( two glaciers ) and NianqingtangguLashan ( one glacier) ; ( 7) Qj.Lianshan (jour gLaciers) and ALtaishan ( one glacier); (8) Qjliallshan ( 11 gLaciers) , Tien Shan ( 11 gLaciers) and KllllLllnshall ( six gLaciers) : ( 9) TielZ Slum ( one gLacier) , Pamir ( one gLacier ) and KllnLllllshalZ (jollr gLaciers); ( / 0 ) T ien Shall ( two gLaciers) and Hengduanshan ( one gLacier ); ( 11 ) Qjliallshan ( one glacier), Karakoram (jollr gLaciers), H imaLaya ( one glacier) and Hendllanshan ( two glaciers ) ; ( / 2 ) Tien Slum ( 11 gLaciers ) ; ( /3) Qj.Lianshan (o ne gLacier), Tien Shan ( 11 gLaciers), KllnLuns/zan ( 17 gLaciers) , K arakoram ( two gLaciers) and H imaLaJa ( one gLacier ); ( / 4) Qjlianshan ( one gLacier ), TanggllLaslzan ( one glacier) , KlInlu1Zslzan ( two gLaciers) and H engduansha/1 (jour gLaciers) .. ( / 5) QjLianshan ( one glacier), Karakoram ( one gLacier), 1-lengdllanshall ( two glaciers ) ; (/ 6 ) Tien Slum (six gLaciers) ; ( /7 ) Qj.Lianslzan ( one gLacier), Tien Shan ( two glaciers) , J.."llnlllnshan ( ten glaciers ) , . H imalay a (o ne gLacier) and Karakoram ( one glacier) ; ( / 8 ) Qjlianshan (o ne gLacier) , Tr/llgglllaslzall (o ne glacier), H engdllallshan ( three glaciers) and Kunlllllshan (o ne gLacier)

% Length

=

%

Rate

%

Rate

Rate

=

100 (8) - 12 .8 84 (32 ) -3.5 1956- 76 I )

67 (2) - 7.2 63 (24) - 1.1 1965- 77 ' 2

100 (9) - 10.4 83 (38 ) - 8.4 1956- 77 3 ,

43 (3) - 6.5 64 (28 ) -4.7 1966- 73 ·1

36 (5) - 4.3 6 1(28 ) 4 .6 1966- 76 :;

33 ( I ) 2.7 39 ( 18) 3.2 1977- 84 6

100 (5) -5 .8 77 (24) - 14.8 1956- 77 7

54 ( 15 ) - 4.5 74 (23) - 8.2 1966- 76 8 1

33 (2) -3.9 58 ( 18) 4 .5 1973- 80 9

33 (1) - 1. 9 55 ( 17) - 2.5 1973- 84 ' 10

63 (5) - 6 1. 8 100 (5) - 18.7 1937- 68 ' 11

55 (6 ) - 11.3 100 (5 ) - 20 .0 1942- 76 12,

6 1(20 ) 19.8 23.4 100 (5) 1963- 76 13

63 (5) - 9.9 80 (4) - 17. 3 1968- 89 (14

100 (4) - 93 .5 100 (4 ) - 17.9 1937- 68 15

83 (5) 4.4 100 (4 ) - 19.2 1942- 76 16

80 ( 12) - 2 1. 8 100 (4 ) - 21.7 1963- 76 17

83 (5) - 13.2 75 (3) - 17.5 1968- 89 (18)

2- 5 km

Chin a Swi tze rl an d Dura ti on

Length

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~2km

China Sw i tzerland Duration

Length

Rate

5- 10 km

C hin a Swi tzerland Duration

Length > 10 km C hin a Swi tzerland Dura ti o n

Length

=

10- 20 km

China Swi tzcrland Duration

reaso n may be that 51 Chinese glaciers with lengths exceeding 10 km , including 18 glaciers longer than 20 km , a re used fo r th e ana lysis, whereas there a re onl y fi\'e Swiss glac iers longer than 10 km and o nl y o ne (Aletschgletsc her ) longer th a n 20 km . Another reason ma y be the la rger errors for glaciers in Ch ina , beca use d ata o n length cha nges of large g laciers in C hin a a re mos tl y estimated from satellite im age ry with resolu tions and accuracies of abo ut 100 m. Comparin g percentages of retreating glaciers therefore may be more rep rese ntati ve in th is special case of la r ge glac iers an d ind eed gives so mewhat simil ar resu lts for both regions. Figure 6 summ arizes percentages of a d va nce/retrea t for a ll glaciers monitored in Ch in a a nd Switzerland over decadal tim e in tervals. Histori call y, thi s ap proach has

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Fig. 6. Variation ill t/ze position of ji-onts Jor about 200 glaciers in China and 160 glaciers ill Switzerland.

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synchron o us with ba la nce \'a riations a nd the cun'e of (cum ul a ti ve ) glacier-l ength c hanges is not much smooth er than the o n e of (cumul a ti ve ) mass balance. Almost synchro n o us ch anges in le ngth a nd mass b a la nce can also be found m'e r \'arious time inten'als at Uriimqi Glacier No. 1, th o ug h its length c ha nges ha ve no t be e n continuou sly meas ured. vVith increasing glacier lengt h, tongue r eac tions seem to be slower and th e smoothing of curves from cumul ative length cha nge with respect to mass-ba la n ce reco rds a re more pronounced. F o r Silvrettagletsch er, synchrono us variations still exist but a re less obvious. No short-term (yea rl y to multi-annua l) relation between le ng th change a nd m ass balance exists for Aletsch gletsc her, a glac ier more th a n 20 km long. I ts reaction tim e, i. e. th e tim e lag b e tween a ma rked cha nge in cumul ative mass balance and the onse t of the corresponding advan ce /retrea t of the g lacier snou t, may be 30 yea rs or more; tim e for full dynamic response and adju stment to a new equilibrium length is es tim a ted a t a bout 70- 80 yea rs (H aebe rli , 1994; H aebe rli and Hoelzle, 1995 ) . Such long delays will essenti ally smoo th out short-term effects of climate a nd mass-ba lance forcing on g lacier-length changes, so th a t year ly to decada l g lacier-terminu s reactio ns to cl im a ti c cha nge will be uncl ear. F ig ure 8 summarizes the relation between mean mass ba la nce a nd mean a nnu a l length change for four length classes of Swiss glaciers. Th e length changes for th e shortes t g laciers ( ~2 km ) a re indeed a lmost perfec tl y sy nchronou s with va ria tions in mass ba lance. L engt h changes for la rger glaciers ( total leng th = 2- 5 km a nd 510 km ) a ppear to follow afte r a time lag of a few years. The le ng th changes for 5- 10 km lo ng g lac iers ha\"C a sli ghtl y longer time lag co mbin ed with more pro nounced smoothing but the diffe rences with respect to the 2- 5 km lo ng glaciers are too sm a ll to make sharp distinctions . Interp reta tion of the leng th-change sig n a l of glaciers longe r than 10 km a nd for the time in terval cove red by

Fig. 7. Relationship between cumuLative mass baLance (CN1 B ) and cumuLative Length change (CLC) Jor glaciers of dijJerent Lengths.

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been popular. It is, however, hi g hl y problem a tic, beca use o f th e different response types il1\'olved and can , a t best, gi\'e on ly a \'ery gen eral o utlin e. Beca use of th e som ew h at stead y retrea t for large glaciers, Figure 6 shows princi p a ll y decadal reactions of sm a ll e r g laciers and , as su c h , te nd s to co nfirm th e similarity of g lacie r changes in both co untri es beyond the tim e-sca le of o ne or a few yea rs.

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RELA TION BETWEEN MASS BALANCE AND GLACIER-LENGTH CHANGES The reactions of g laciers to climatic cha nge il1\'olve a compl ex chain of processes. M ass balance is the direct, und elayed consequ ence of clim atic fo rcing, while th e le ngt h cha nge is a n indirec t, del ayed reaction. Th e Ou c tu a ti ons described a bove for sm a ll er glaciers in bot h co u n tri es demonstra te th eir sensi tive reactions to c1ima tic c ha nge. Actuall y, length reactions to m ass-bala nce forcing for sm a ll glaciers a re very quick (Fig. 7) . Length changes for th e small Pl attalvagletsc her, for instance, a re a lmost

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