BulletinofGlaciologicalResearch22（2005）1−8◎JapaneseSocietyofSnowandIce

ArticleAlargeamountofbiogenic＄urfacedust（cryoconite）onaglacierinthe
Qilian Mountains，China

NozomuTAKEUCHll．YoshihiroMATSUDA2．AkikoSAKAl2andKojiFUJITA2

1ResearchlnstituteforHumanityandNature，335TakashimachoKamigyo−kuKyoto−CityKyoto6020878Japan

2Graduate SchoolofEnvironmentalStudies，Nagoya University，Nagoya4648601，Japan（ReceivedJuly2，2004；RevisedmanuscriptreceivedOctober18，2004）

Abstract
Surfacedustonglacierscansignificantlyaffectsurfacealbedoandsubsequentlythemassbalance

Oftheglaciers．Thecharacteristicsofsurfacedust（cryoconite）wereinvestigatedinSeptember20020n
theJulylstGlacier（QiyiGlacier）intheQilianMountains，China．Thebareicesurfaceoftheglacierwasmostlycoveredbyfinebrowndust．Theamountofthesurfacedust（dryweight）rangedfrom30．4
to873gm2（mean：292gm2，Standard deviation：196），Whichis significantly higher than that on

glaciersinotherpartsoftheworld，andisequivalenttothatonHimalayanglaciersonwhichthelarge
amountsofdusthavebeenreported．Ananalysisoforganicmatterandmicroscopyofthesurfacedust

revealedthatthedustcontained highlevelsoforganicmatter，includinglivingcyanobacteria．This
suggeststhatthedustconsistsnotonlyofdepositofwind−blowndesertsand，butisalsoaproductof

microbialactivity on the glacier．Measurements of surface albedo showed that the mean surface
albedointheiceareawassmallerthanthatoftheclean bareicesurface，SuggeStingthatthealbedo
wassignificantlyreducedbythesurfacedust．Largeamountsofsurfacedustmaybeduetoabundant
windblowndepositsofdesertsandandhighbiologicalproductivityontheglacialsurface，PrObablya
COmmOnCharacteristicofAsianglaciers．

1．lntroduction
SurfacedustisoneofthemaJOrfactorsaffecting

the surface albedo of glaciers（e．g Brock etal．，2000；
Cutler and Munro，1996）．The reduction of albedo by

Surfacedustresultsin moremeltingofsnow andice．
Thus，thequantityandcharacteristicsofsurfacedust
are important parameters for the mass balance ofglaciers．Recentinvestigations have revealed a sub−Stantialthinning and terminus retreat of glaciersin

many parts of the world（IPCC，2001）．Although cliTmate change such as globalwarming usually ac−
COuntSfortherecentglacialshrinkage，thevariations
insurfacedustarealsoapossiblecauseofshrinkage．
Surfacedustusuallyconsistsofmineralparticles

and bacteria．They are specialized species that haveadapted to extremely cold environments and spend

their wholelives on glaciers（e．g．Hoham and Duval，2001；Kohshima，1987）．Surfacedustcontainsproducts

SuChastheorganismsthemselves，theirdeadremains

and decomposed organic matter（humic substances）．

Since these organicparticlesin dustareusuallydar−
kly colored andlargein volume，Organic matterin
dustisoptica11yeffectiveonthesurfacealbedo（Takeuchi，2002b；Takeuchietal．，2001b）．

Both the quantity and characteristicsofduston
the glacialsurface vary from glacier to glacier．On
glaciersinPatagoniaandtheArctic，effectofduston
Surface albedoisinsignificant due to the smallamoT

untsaccumulatingthere（Takeuchietal．，2001a；2001c）．

Incontrast，1argeramountsofsurfacedusthavebeen

and organic matter（e．g．Takeuchietal．，2001a）．The reportedonsomeAsianglaciers．Thewind−blownde−

mineralparticlesin the dust usually orlglnate from

SertSanddepositedonaTibetanglacier（theTanggula

portion of dust orlglnateS from wind−blown organic

bedo，thus affecting the mass balance of the glacierbasaltilland／orwind−blownsands，Whiletheorganic Mountains）has substantially reduced the surface aト

matter（e．g．pollen，plantfragmentsandsoilparticles） （Fujita，2002）．On some Himalayan glaciers，a darkbiogenicdust（cryoconite）thatcoverstheglacialsurTand from biologicalactivity on the glacialsurface．
facesignificantly reduced thesurfacealbedo（Takeu−
TherearediverseorganismslivingontheglacialsurT
face，SuChassnowalgae，insects，iceworms，prOtOZOaChietal．，2001a；Kohshimaetal．，1993）．This biogenic

BulletinofGlaciologlCalResearch

2

dustisderivedfromsnowalgaeandbacterialivingon

ationsinthisreglOnisimportantforresearchintothe

theglaciers．Thus，SurfacedusthasamaJOrinfluence long human history as well as the future water re‑

On the glacialmass balance，particularly on Asian

SOurCeSaVailabletothepresenthumanpopulationin
glaciers．However，Ourinformationaboutsurfacedust this basin．The glacierflows south to north from aremainslimited．Inordertounderstand the variationsin the recent changein glacialmass balance，itis
importanttostudythecharacteristicsofsurfacedust
Onglaciers．
This paper aims to describe the quantity andCharacteristicsofsurfaceduston theJulylstGlacier（QiyiGlacier）in the Qilian Mountains，China．After

Surface dust was collected from various parts of theglacierin September2002，it was quantified and ana−

1yzed biologlCa11yln alaboratory．Its characteristics
WereCOmparedwiththoseonotherglaciersacrossthe
WOrld．The spatialvariationsin surface albedo werealso measured on theJulylstglacier，and theeffects

Of surface dust on the surface albedo are discussed．

2．Studysiteand methods
OurinvestigationwascarriedoutontheJulylst

Glacier（orQiyiGlacier，39015′N，97045′E）intheQilian
MountainsofChinafromlOJuneto7September，2002．

The Qilian Mountains，located along the northeast
margin of the Tibetan Plateau，eXtend from east to
WeStforadistanceofapproximately500kmalongthe

border between Gansu and Qinhaiprovinces（Fig．1）．

Glaciersin theQilian Mountainssupply waterto the
Heife River Basin，Whichis one of the majOr OaSis

regionsin western China．The study of glacialvari−

mountain peak（5159ma．s．1．）down toits terminus atanelevationof4305ma．s．1．（Fig．1）．Thisglacierisone

Of the most easily accessiblein China，and has beenStudiedintermittentlysince1958bytheColdandArid
Regions Environmental and Engineering ResearchInstituteoftheChineseAcademyofScience．Theglacierhasreportedlyretreatedlr2metersperyearonaver−ageinthe1970sand80s（Xieetal．，1985；Liuetal．1992）．

Remote−SenSingstudiesalsoshowedthattheareaand
VOlumeofglaciersin theQilian Mountains havegen−erallydecreased（Liuetal．2003）．Mostofthesurfaceof

theglacierisbareiceorsnowdevoidofrockorstonedebris．Thelengthandareaoftheglacierareapproxi−
mately3kmand3．04km2，reSPeCtively．Thesnowline
in our study period（early September）was approxi−
mately4900ma．s．1．，andwaslocatedbetweensitesSlO
and Sll．Meteorologicaland glaciologicaldata col−lected in the study period have been published by
Matsudaetal．（2004）．

In order to quantify the amount of dust on theglacialsurface andits organic−matter COntent，ice／

SnOW On thesurfacelayerwascollected withastain−
less−Steelscoop（approximately15×15cminareaand

卜3cmindepth）at5sitesinthebareicearea（S2，S4，S
6，S8，and SlO）andlsitein thesnow area（Sll）．Five

Samples were collected from randomly selected sur−faces at each study site．The co11ection area on the
Surfacewasmeasured tocalculatethe amountofdust

per unit area．To arrest the biologlCalactivity，theCOllectedsamplesweremeltedandpreservedasa3％
formalinsolutionincleanlOOmlpolyethylenebottles．
All samples were transported for analysis to the Re‑
SearChInstitute for Humanity and Naturelocatedin

Kyoto，Japan．In thelaboratory，the samples weredried（600c，24hours）in pre−Weighed crucibles．The

amount of dust per unit area of the glacier was ob−
tainedfrom measurementsofthedryweightandthe

Sampling area．The dried samples were then com−bustedforlhouratlOOOOcinanelectricfurnace，and
Weighed again．The amount of organic matter was
Calculated from thedifferenceinweightbetweenthe

driedandcombustedsamples．Aftercombustion，Only

mineralparticlesremained．Inordertoinvestigatethe

COmpOSitionofthesurfacedust，Othersamplesofsur−
faceice／snowwerecollectedandexaminedin alabo−

ratorywithopticalmicroscopes（NikonSMZ800andE

600）．

Fig．1．Locationand mapoftheJulylstGlacierin the
Qilian Mountains，China．Study sites areshown onthemap．

The surface albedo was measured manually on

August18witha portable albedo meter（Model：MR−
40，EikoSeiki，Japan）atthirteensitesbetween4200m
and5000ma．s．1．along alongitudinalline（Sl・S14ex−
CePt Sll，Fig．1）．These sites wereselected becauseof
their safe and easy accessibility．Moreover，the sites

Takeuchietal．

．●i

Tablel．Surfaceslopeanglesforsitesinthisstudy，Site SI S2 S3 S4 S5 S6 S7 S8 S9 SlO S12 S13（）1012 514 816141411121410

Were Visibly representative of the surface conditions
around each site in terms of surface roughness andamounts of dust．The measurements were madein ahorizontalplanelmabovethesurfacewithin3hours
oflocalsolar noon and under stable weather condi−

tions，irrespective of cloudiness．The albedo was ob−

tained from the mean of3−8measurements taken ateachsite，Witheachmeasurementrequiring approxi−

mately three minutes．Since surface slopes variedamongthestudysites（Tablel），theobservedhorizon−

talalbedoinvolvedanerrorduetotheslope（Jonselletal．，2003）．Theerroneouslyobservedalbedos werecor−

rectedtomatchalbedospara11eltothesloplngSurface
usingthefollowingequationintroduced byJonsellet

αJ．（200乳

月わ
COSβcosZ＋sinβsinZcos（E2−㊥）
cosZ
（1）

Whereαtisthealbedoparalleltotheslopingsurface，Rhisthereflectedshortwaveradiationonahorizontal

plane，Ghis the globalradiation，dis the diffuse porTtion of Gh，Zis the solar zenith angle，E2is the solar
azimuthangle，andβistheslopeangleofthesurface
with an azimuth angle O．In this study，the diffuse

portionis equated with zero to simplify the calcula−tions．Inaddition，30degrees，Whichisthezenithangle
Oflocalnoononthedayofobservation（August18），is
applied toZ．E？and elare180and Odegrees，reSpeC−

tively．

3． Results
Most of the glacialsurface of theice area wasFig．2．Pictures of the surface ofJulylst Glacier（toward top of the glacier from site S8）．（a）Bare
ice surface covered with fine brown dust（cryo−
COnite）（5September，2002）．（b）Fine brown colored
dust on the bareice surface．Scale barisIcm．

highernumbersofcryoconite holeswereobserved at
SiteS2，WhereasonlyafewwereobservedfromsitesS

4to S6．In thesnowarea，thedustamountwasmuch

Smallerthanthatintheicearea，ranglngfrom21to31

COVeredwithfinebrowndust（Fig．2，3）．Theamounts gm 2（mean：24Agm2，SD＝4，SiteSll）．

Ofdustonthebareicesurfacerangedfrom30．4to873

gm2（mean：292gm2，Standarddeviation（SD）＝196）

Thesurfacedustcontainedlevelsoforganicmat−

terrangingfrom4．1to12．6％（mean：8．6％，SD＝1．9）inindryweight．Thealtitudinalprofileofthoseamounts
dryweight（Fig．5）．Thepercentagewashighestatsiteof dust showed that the amount at thelowest eleva−
S4（11．1±1．8％，mean±SD），and gradually decreased
tionsite（S2）wasrelativelysmallerthan thoseatthe
down to site SlO（7．3±0．37％）as the elevationin−othersites（76．7versus236536gm2，Fig．4）．Thelarg− CreaSed．The organic−matter COntentin dust on theestamountofdustwasatsiteSlO（4827ma．s．1．），Which snow surface wassmallerthan thaton theicesurface
WaS the highest elevationin theice area．At each（site Sllin Fig．1），ranging from4．9to5．3％（mean：
Study site，dust was not uniformly distributed．In
5．0％，SD＝0．14）．
Particular，dust on theice surface tended to concen−
The amount of organic matter per unit area on
trate alonglongitudinallines（Fig．3a）that formed
theglacialsurfacerangedfrom2．1to64．Ogm2（mean：
longitudinalstripes50rlOOcm wide on the bareice
25．4gm2，SD＝16．5）ontheicesurface，andfroml．1to
Surface．In some areas，dust had accumulated up tol．6（mean：1．23gm2，SD＝0．22）on the snow surface
SeVeralcentimetersin thickness．Dust also deposited（Fig．6）．Theamountwasrelativelyloweratthelowest
atthebottomofcryoconiteholes（Fig．3b）．Relatively
site（6．2±3．7gm2，S2）and higheratsitesS4andSlO

BulletinofGlaciologicalResearch

︵
り
∈
学
習
P
ひ
じ
e
t
⊃
の
ー
O
I
U
⊃
○
∈
＜

50 0
4
3
2
0 0

0

0

0

0

4200

4400

4600

4800

5000

5200

Altitude（ma．s．F．）
Fig．4．Altitudinaldistribution of amounts of surface
dust onJulylst Glacier．Error barsindicate stand−ard deviation．

1

6
4

1

1

︵
辞
︶
乱
雲
∪
￠
0
﹂
O
d

2
0

1

8
6
4
2
0

Fig．3．SpecificfeaturesofthebareicesurfaceonJuly
lst Glacier．（a）Dust was concentrated along a
longitudinalline．（toward upper stream at site S6
0n4September，2002）．（b）Cryoconite holes．Surface
Out Of the holesis white weatheredice，（site S20n
4September，2002）．

（37．9±18．5and38．5±12．4gm2，reSPeCtively）．

The surface dust microscoplCally revealed min−

4200

4400

4600

4800

5000

5200

Altitude（ma．s．l．）

Fig．5．Altitudinaldistribution of organic matter con−tentsin surfacedustonJulylstGlacier．Errorbars
indicate standard deviation．

ranged from O．13to2．7mm（mean：0．55mm，SD＝0．27）．

eralparticles，amOrphous organic matter，andliving
CyanObacteria（Fig．7）．Althoughthepercentageofor−

Observation with afluorescence microscoperevealed
atleasttwospeciesoffilamentouscyanobacteriawith
autofluorescence densely covering the surface of theulesindustfrom theiceareaweresphericalinshapeand contained abundant filamentous cyanobacteria
andmineralparticles．Thesizeoftheorganicgranules

ranged from O．10to O．41（mean：0．21）in theice area
（Fig．8）．The albedos corrected for a sloping surface

ganic matter was not largely different between the

granules．One was3．9±1．0〃m（mean±SD）in celldi−
dustin snow andice areas（8．6％versus5．0％），their ameterwithasheath（Fig．7c），andtheotherwas2．3±
COmpOnentS aS Observed by microscopy clearly diff−
0．37pmincelldiameterwithoutasheath（Fig．7d）．Theered（Fig．7）．Brown organic granules were the main mineralparticlesin the dust were brown，White，Or
COmPOnentindustfromtheicearea（S2−SlO），Whereas，transparent．Thesizeoftheparticlesobservedwitha
mineralparticles were the main componentin the
microscoperangedfrom25to165FLm（mean：69FLm，SD
SnOWareadust（Sll，Fig．7）．Thebrown organicgran−＝25）in diameter．

The observed horizontal albedos on the glacierTakeuchietal．

︵
N
．
∈
空
﹂
小
宅
∈
0
モ
亀
﹂
○

4
3
つ
﹂
1

0

0

︵
U
O

4200

4400

4600

4800

5000

5200

AItitude（ma．s．I．）

Fig．6．Altitudinaldistribution of amounts of organic
matter on the surface ofJulylst Glacier．Error
barsindicate standard deviation．

4200

4400

4600

4800

5000

AItitude（ma．s．l．）

Fig，8．Altitudinalprofi1e of horizontalalbedo obserL
Ved on18August，2002and the corrected albedos
for the sloplng Surface．The corrected albedo still
has errors of diffusion，SOlar zenith and azimuth
angle at observed time．True albedo should be
SOmeWhat between the two values．Allstudied
sites were bare ice surface without snow on the
day ofmeasurement．

Fig．7．Microscopicview ofsurfacedustontheJulylstGlacier．（a）Dust（cryoconite）ontheicesurfacecollectedfromsite
S20n4September，2002．DustCOnSisted mainlyofsmallbrowngranulescontainingcyanobacteriaandorganicmatter．
（b）Thedustcollected on thesnowsurfacefrom Sllon5September，2002consisted mainlyofmineralparticles．（C）（d）
Twodifferentspeciesofcyanobacteriacontainedin thedust．Scalebarsarelmm for（a）and（b），10pm for（c）and（d）．

BulletinofGlaciologicalResearch

Were higher than the measured horizontalalbedos．
The difference between before and after the correc−

tion ofthealbedosranged from O．01toO．06．Thecor−

rectedalbedosstillcontainederrorsduetotheeffects
Ofdiffuseradiationandtheactualsolarangleateachmeasurement．Accordingtoequation（1），thetruealbeT

dos without these errors should be somewhere be−

tween the observed and corrected values．The cor−rected albedos without the slope effect varied from

O．11toO．46（mean：0．23，SD：0．10）．Thelongitudinalpro−
fi1eshowsthatthealbedoswererelativelyhigher（0．27−0．46）atthelowersites（sitesSl−S3），atOnemiddlesite（S7）andatthehighestsite（S14）．Albedosattheother
Siteswassma11erthanO．25．ThelowestalbedowasO．14
at site9．

0

200

400

600

800

Amountofdust（gm−2）

4．Discussion
ThebareicesurfaceontheJulylstGlaciercanbe
Characterizedaslowalbedoduetothelargeamounts
Of surface dust．Surface albedos of snow andice arenegatively correlated with amounts ofimpuritiesin

the snow andice（e．BIAokietalり2003）．There was a

COnSistentlyweakcorrelationbetweentheamountof
dustandsurfacealbedointheiceareaofthisglacier（Fig．9）．Asurfacewithasmalleramountofdust（e．g．
Site Sl）was higher albedo（0．30），Whereasone witha
larger amount（e．g．site S5）waslower albedo（0．17）．

This correlation suggests that variationsin the sur−face albedoin theice area were mainly due to theamountof the duston the surface，indicating，there−

fore，thatdustsubstantiallyaffectsthesurfacealbedo
in theice area．The mean albedoin theice area was

Fig．9．Relationship between dust amounts and sur−face albedosin theice area．Error barsindicate
standard deviation．

ment of weatheredice and cryoconite holes．White

Weatheredice（or weathering crust）is a porousice

Withlooselyinterlockingcrystalsonthesurfacelayer

Ofaglacier（e．g．MtillerandKeeler，1969）．Basedonfield
Observations，Weatheredice was particularly abun−dant in the tongue of a glacier compared with the
middle or upper part．The sma11er dust amounts on
Weatheredicemayresultfromdustsinkingbelowthe
Surface．Thesurfacedustcouldsinkthroughgapsin
the porousice，thus reducing the amountofduston
thesurfacelayer（1r3cmindepthasobservedbythe

Samplingprocedureinthisstudy）．Inaddition，CryOCOnite
O．23，Whichislower than that of a clean bareice holes，Which were ubiquitousin this area（Fig．3），
Surface．Forexample，the mean bareicealbedofora maylowerthedustconcentrationontheicesurface．

Cleansurface hasbeenreportedtobeO．380nglaciersin western China（Baiand Yu，1985）．The difference

between the bareice albedo on theJulylst Glacierand the albedo on a clean surfaceis O．15，Whichis

likelydue totheeffectofsurfaceduston thesurface

albedo．

Thehigheralbedoandsmalleramountsofsurface
dustneartheterminusoftheglacieraretheopposite
Ofthoseon othermountainglaciers．Dustanddebris
usually accumulate in the tongue of a glacier sincetheyaresuppliedfromabovebyglacialfloworfrom

Since thecryoconite holestrap thedustattheirbot−
tom，theice surface around the holes wasless dust
COnCentration．

The mechanism underlying the development ofweathered ice and cryoconite holes at the area neartheterminusisunclear．Apossibleexplanationforthe
formationofthesestructureisthatdryer，1esshumid
airisblownfromthedesertextendingdownstreamof
theglacier．Suchdryaircouldcauseasublimationof
theglacialsurface，particularlyattheterminusareaof

the glacier，and could then cooltheicesurface．That

thebasalbedbymarglnalshearing．Forexample，themay preventthedisappearanceofweatherediceand

belower at the terminus（0．10−0．16）compared withmiddle region（0．2rO．4）due to the accumulated dust

allydecayunderconditionsofpositivelatentorsensi−

albedoonaglacierintheAustrianAlpswasfoundto

CryOCOniteholestructures，Sincethesestructuresusu−

bleheatdominance（e．g．Takeuchietal．，2000）．Further

andthepresenceofabundantmeltwater（VandeWal

Studyoftheformationprocessofthesesurfacestruc−turesisnecessaryforenhancingourunderstandingof
thespatialvariationsofsurfacealbedoontheglacier．

1985）．

theJulylstGlacierismarkedlygreaterthanongla−

etal．，1992）．Alower albedo at the terminus has beenalsoreportedintheSwitssAlps，Alaska，andwestern
China（Brocketal．，2000；Takeuchi，2002a；BaiandYu，

The smaller amount of dust in the area near theterminus of the glacier may be due to the develop−

The amount ofsurface dust on theicesurfaceof

Ciersin otherpartsoftheworld．Accordingtoprevi−
OuSStudies，theamountsofsurfacedustarelessthanTakeuchietal．

analgalrnatgrowingontheglacialsurface（Takeuchi

ggαg．，2001a），Thus，thesegranulesarelikelytobethe

productsofbiologicalactivity on theglacialsurface．
Themassfractionoforganicmatterinthedustisonly

8．6％indryweigbt，SuggeStingthatmineralparticles
seem to be the main component（more than90％）．

︵
甲 3 0
∈
空
l
毒
筆 2 O〇とq
八U

However，microscopy showed that organic matter
WaSCOmparable to the mineralcomponentsin terms

Of particle volume．The smaller mass fraction of or・

ganic matterislikely due to thelower density ofJulylst Yala TyndaLI Gutkana Devonlce
Glacier Glacier Glacier Glacier cap（QilianMts．＝Himalavasl（Pataqonial（AIaska）（Arctic）

Fig．10．Comparison of amounts of surface dust andtheir components among various glaciers aroundthe world．Error barsindicatestandard deviation．

100gm20nglaciersintheArctic，AlaskaandPatagonia

Organic mattercompared with thatofmineralparti・
Cles．Thus，Organiccomponentsalsoappeartoexerta
majOrirl点uenceon tbesurfacealbedo．Å1thot唱hthe
quantitative contribution of each component to aト
bedo reductionis uncertain，both organic andinor−

ganiccomponentsarelikely to beeffectiveinreduc−ingthesurfacealbedoonthisglacier．

ComparisonsofdlユStCOmpOnentSamOnganum−

ber of glaciers showed that both organic andinor−
ganiccomponentswerehigherontheJulylstglacierCOmpared with those o‡lthe other glaciersくFまg．10）．
Theamountofmineralparticleson theJulylstgla・

Cierwasapproximately13−foldhigherthanthemean

On theother hand，theamo11ntOfdustrecordedonaOf thoseon tbe Patagorlian，Å1askan andÅrcticgla−
ciers（266versus20．3gm¶2），While the amount of or−
ganic matter was approximately38−fold higher（25．4
versus O．67gm山2）．The higher amount ofinorganic

untsofsurfacedustabovelOOgm2wereobservedon
tvootherHirnalayanglaciersinNepaiandoneTibetarl

nentsmaybetheresultofhighbiologicalproductiv−
ityon theglacialsurface．

greater amounts of surface dust may be a common
CharacteristicofAsianglaciers．
The composition of surface dust suggests that
dustin theice area consists not only of deposits of

between a snow surface and a dust coveredice sur−（Takeuchi，2002a；Takeuchi留吉αg．，2001b；Takeuchi
etal．，2001c；Fig．10），WhereastheamountontheJulylstGまacierwasasignはcantlyhigher292gmm2（mean）．

COmpOnentSOntheJulylstglacierisprobablydueto
Himalayanglacierwas225gm▼2（Takeuchietal．，2000
andunpublisheddata〉，Whichisrotlghiyequivalentto itsexposliretOablユndantwind−blowndepositsofde−
thaton theJulylstGlacier（Fig．10）．Moreover，amO− SertSand，Whilethehigheramountoforganiccompo・

glacierin China（Takeuchi，unpublished data）．Thus，

Because of the notable difference in the albedo

face，the frequency ofsnowfaliin summer may sig−

nificantlyaffectthemassbalanceofthisglacier．New

SnOⅥrCOVeredtheentireglacialsurねceseveraltimes
wind・blowndesertsand，butthatitisalsoaproductof duringthesummerofthisstudy（Matsudaetal．．2004）．
AsFujitaandAgeta（2000）havesuggested，SnOWfa11in
microbialactivityontheglacier．Thedesertsurround・i王1gtheglacierisoneofthemajOrSOurCeSOfairborne slユmmerincreasesthesurfacealbedoandreducesheat
incometotheglacialsurface．Duetothisalbedoeffect，desert sand．This kind ofsand has been reported toaccumulateonthesnowandiceofglaciersinwestern

Asian glaciers are more sensitive to climate change

Chinaくe．爵Wake and Mayewski，1994）．Since the mi−
CrOSCOPyOfdustonthesnowsurface（sitell）showed
thatitconsistedmainlyof魚nemineralparticles（Fig．
7），itislikely to be mostlywindTblown desert sand．

COmPared with winter−aCCumulation−type glaciers．

surface was different from that of dust on the snow

faceⅥ7ithoutdust．Thus，thereductioninheatirlCOme

However，the composition of dust on the bareice

Surface．Dustintheice areacontained highlevelsof
organicmatterandcyanobacteria．Themassfraction

Oforganicmatterindustontheicesurねceく8．6％）waslarger than thaton the snow surface（5．0％）．Micros・

COpyShowedthatsuchdustconsistedmainlyofsmall
brown granules，Which were not observed on the

SnOW Surface（Fig．7），Inaddition，theirsize，COmpOSi−tion，and structt汀e agree With those of cryoconite

granules，alreadyreportedonaHimalayanglacieras

SincethealbedoontheJulylstGlacierisparticularly

lowduetosomuchduston theicestlrface，thediffe−
rencein the albedo between new snow and the dust−

COVeredicesurfaceisgreaterthanthatcleanicesur−

totheglacialsurfacebysnowfallislikelytobemore
SlgnificantonthisglaciercomparedtothatonglacierWitbacleanbareicesurface．Thisstudyshowedthat
the factors affecting surface albedo on theJulylst

Glacier are wind・blown deposits，bio10gicalactivity
and the development of weatheredice．Flユrther re−

SearChintoeachoftheseprocessesisimportantfora
moreaccurateassessmentofthemassbalanceofthis
glacier．

βBu11etin ofGlaciologlCalResearchtion and Coadaptationin Biotic Communities，Faculty of
Science，KyotoUniversity，7792．
Acknowledgments
Kohshima，S．，Seko，K．andYoshimura，Y．（1993）：Bioticaccel−
eration of glacier meltingin Yala Glacier，Langtang
We wish thank to Dr．YaoTangdongoftheColdregion，NepalHimalaya．Snow and Glacier Hydrology（Proceedings of the Kathumandu Symposium，Novem−
and Arid Regions Environment and Englneering Re−
ber1992）IAHS Pub．，218，309316．
SearChInstituteoftheChineseAcademyofSciencein
Liu，C．，Song，G．andJin，M．（1992）：Recentchangeandtrend
Lanzhou，Chinaforhislogisticalsupportofthisfield
prediction of glaciersin Qilian Mountains．Memoirs of
WOrk．We are alsoindebted to Dr．Dan Quequin andLanzhouInstitute ofGlaciology and Cryopedology，Chinese AcademyofSciences，（inChinese）7，19．
Other staff members of theinstitute for theirstrong
Liu，S．，Wenxin，A．，Shen，Y，andLi，G．，（2003）：Glacierchanges
SuPpOrtinthefield，aSWellasDr．MasayoshiNakawo
Since the LittleIce Age maximumin the westernand other researchers in the Oasis Project for their
QilianShan，nOrthwestChina，andconsequencesofglacierrun−0ffforwatersupply．J．Glaciol．，49（164），117−124．
Valuablediscussionsonthistopic．Ourpaperhasbeen
Matsuda，Y．，Sakai，A．，Fujita，K．，Nakawo，M．，Du
greatlyimproved by suggestions from Dr．ShiroandYao，T．，（2004）：GlaciologicalobservationsonJulylst
Kohshima and an anonymous reviewer．This study
glacierin Qilian Mountains of west China during sum−
WaSapartOftheOasisProjectfundedbytheResearch
mer2002．Bull，Glaciol．Resリ2l，3136．
Mtiller，F．and Keeler，M．C．（1969）：Errorsin short−term abla−InstituteforHumanityandNature，andwasalsosup−
tion measurementsonmeltingicesurfaces．］．Glaciol，，8portedbytheJapaneseGovernment sSpecialCoordiL
nation Fund for the Promotion of Science and Techr

nology and by Grants−in−Aid for scientinc research（No．1571001軌（52），91−105．

Takeuchi，N．（2002a）：Surface albedo and characteristics of
CryOCOnite（biogenicsurfacedust）onan Alaskaglacier，GulkanaGlacierintheAlaskaRange．Bull，Glaciol．Res．，
19，63−70．

Takeuchi，N．（2002b）：Opticalcharacteristics of cryoconite
References（surfacedust）onglaciers：therelationshipbetweenlightabsorbency and the property of organic matter con−tainedin thecryoconite．Ann．Glaciol．，34，409414．
Aoki，T．，Hachikubo，A．and Hori，M．（2003）：Effect of snow
Takeuchi，N．，Kohshima，S．and Seko，K．（2001a）：Structure，
physicalparameters on broadbandalbedos，J．Geophys，
formation，darkening process of albedo reducing mate−
Resリ108，4616，doi：10．1029／2003JDOO3506．
rial（cryoconite）onaHimalayanglacier：agranularalgal
Bai，Z．and Yu，X．（1985）：Energy exchange anditsinfluence
mat growing on the glacier．Arc．Antarc．Alp．Res．，33，
factors on mountain glaciersin west China．Ann．Gla−
115−122．
Ciolリ6，154157．
Brock，B．W．，Willis，I．C．andSharp，M．］．（2000）：Measurement Takeuchi，N．，Kohshima，S．，Shiraiwa，T．andKubota，K．（2b）：Characteristics of cryoconite（surface dust on gla−
and parameterization of albedo variations at Haut Gla−
Ciers）and surface albedo of a Patagonian glacier，Cierd Arolla，Switzerland．］．Glaciol．，46（155），675688．
TyndallGlacier，Southern PatagoniaIcefield．Bull．
Cutler，P．M．andMunro，D．S．（1996）：Visibleandnear−infrared
Glaciol．Resリ18，65∪69．
re貝ectivity during theablation period on PeytoGlacier，Takeuchi，N．，Kohshima，SりGotoLAzuma，K．andKorner，R．M．
Alberta，Canada．］．Glaciolり42（141），333−340．
（2001c）：Biologicalcharacteristics of dark colored mate．
Fujita，K．（2002）：Impact ofdust on glacier mass balanceof
rial（cryoconite）onCanadianArcticglaciers（DevonandtheTibetanPlateau．JournalofAridLandStudies，11（4），Pennyice cap）．Proceeding of the Memoirs of National355−360．
InstituteofPolarResearch，SpecialIssue，54，495505．
Fujita，K and Ageta，Y．（2000）：Effect ofsummeraccumula−
Takeuchi，N．，Kohshima，S．，Yoshimura，Y．，Seko，K．
tion on glacier mass balance on the Tibetan Plateau
Fujita，K．（2000）：Characteristicsofcryoconiteholesona
revealedbymass−balancemodel．）．Glaciol．，46（153），244r
Himalayanglacier，YalaGlacierCentralNepal．Bull．Gla−
252．
Ciol．Res．，17，51−59．
Hoham，R．W．andDuval，B．（2001）：Microbialecologyofsnow
Van de Wal，R．S．W．，Oerlemans，］．and Van der Hage，J．C．
andfreshwaterice．1nSnowEcology．CambridgeUniversity（1992）：A study of ablation variations on the tongue of
Press，Cambridge，168r228．
Hintereisferner，Austrian Alps．J．Glaciol．，38（130），319
IPCC（2001）：Climate Change2001，Impacts，Adaptation，and
324．
Vulnerability．McCarthy，JJ．，Canziani，0．F．，Leary，N．
Wake，C．P．and Mayewski，P．A．（1994）：Modern eolian dust
A．，Dokken，D．］．and White，K，S．（Eds．），Cambridge
depositioninceltralAsia．Tellus，46b，220233．
University Press，1032pp．
Jonsell，U．，Hock，R．and Holmgren，B，（2003）：Spatialand Xie，Z．，Wu，G．and Wang，L．（1985）：Recent advance andretreat of glaciersin Qilian Mountains．Memoirs of
temporalvariationsinalbedoonStorglaci畠ren，Sweden．
LanzhouInstitute of Glaciology and Cryopedology，
J．Glaciol，，49（164），59−68．
Chinese AcademyofSciences，5，8290（in Chinese）．
Kohshima，S．（1987）：Glacialbiology and bioticcommunities．
In Kawano，S．，Connell，］．H．and Hidaka，T．（eds．），Euolu−