Abstract. In order to evaluate the effect of cryoconite on surface albedo on glaciersï¼Surface albedoï¼. Characteristics of cryoconiteï¼and snow algalcommunities ...
2J
BulletinofGlaciologicalResearch20（2003）21−27
⑥JapaneseSocietyofSnowandIce
Effect of cryoconite and snow a［gaJcommunities on surface albedo on marjtime glaciersin SOuth Alaska Nozomu TAKEUCHll，Shiro KOHSHIMA2and TakahiroSEGAWA2
In order to evaluate the effect of cryoconite on surface albedo on glaciers，Surface albedo，
Characteristics of cryoconite，and snow algalcommunities wereinvestigated on two maritime
glaciers；WorthingtonandMatanuskaGlaciersinsouthAlaska，U．S．A．Thesurfacealbedointheice arearangedfromO．37toO．74andthemeanwasO．53．Theamountofcryoconiteontheglaciersurface rangedfromO．2to14gm2andthemeanwas3．8gm．2．Organicmattercontentinthecryoconite ranged froml．O to9．8％and the mean was4．7％．Snow algalcommunities on the glaciers were dominatedbythreegreenalgae，WhichwereMesoiaenium br喝gYmii，Anqlonemanordenskioldiiand Chhl〝叩domonasnivalis．ThecellvolumebiomassofthesnowalgaerangedfromO．015toO．056mLm▲2 andthemeanwasO．039m￣2．Ascomparedwithaninlandglacier ofAlaska，Gulkana Glacier，the
（Takeuchi，2002b；Takeuchiet al．，2001b）．Thereduc− tion of surface albedo increases the solar radiation
absorbed by the glacier surface and result in more meltingoftheglacier．Sincetheorganicmatterinthe （e．g．Gajda，1958；Wharton et al．，1985）．Cryoconite CryOCOniteis produced by the organismsliving on usually consists of mineral particles and organic glaciers，thebiologicalactivity ontheglacierwould matter．Theorganicpartofcryoconiteisderivedfrom affect thesurface albedo and ablation oftheglacier biologicalactivityontheglacier andconsists ofthe and then may affect shrinkage of glaciers．Recent Organisms themselves，their dead bodies，and investigationsrevealedsubstantialthinningandtermi− decomposed organic matter（humic substances）．The nusretreatofglaciersinmanypartsoftheworld（e． Organismsinclude snow algae，insects，ice worms， g．Arendt et alリ2002）．Thecryoconitemaytakepart protozoa，andbacteria（e．g．HohamandDuval，2001）． Oftheshrinkage ofglaciers．Thus，itisimportantto They are special species adapted to the extremely Study the formation processes of cryoconite on the cold environment and spend their whole lives on glacier．
glaciers．Cryoconiteis formed as a result of their biologicalactivityontheglaciers． Surfacealbedoofsnowandicecanbereducedby
impuritiessuch as cryoconite（e．g．Warren and Wis− COmbe，1980）．Cryoconite can thereby contribute to acceleration of melting of the glacier surface．Espe− Cially，Organicmatterincryoconiteisopticallyeffec−
tiveonthealbedoreduction，Sincetheorganicmatter is usually dark−COlored andlarge volume particles
glaciersurfaceisratherclean（Takeuchietal．，2001a； ateglacier andflowswest to east from a mountain 2001c）．Theeffectofcryoconite onsurface albedois peak（2550ma．s．1．）towardeastdowntotheterminus
tralalbedoandamountofcryoconiteweremeasured Ontheicesurfaceoftheglaciers．Thecharacteristics of the cryoconite and snow algal community on the glacier surface were analyzedin alaboratory．The resultsarecomparedwiththoseofaninlandglacierof Alaska，Whichisindifferentgeographicalandclimate COndition．
Fig．2 View of Worthington（a，September，2000）and Matanuska Glaciers（b，August2001）．The picture of Matanuskawastakenayearafterthisfieldwork．The Samplingsitesareshownineachpicture．
Takeuchiet al．
2ヲ
Wide．Thesnowlineatthestudiedtimewasapproxi− SekkeiCo．Japan）within3hoursoflocalsolarnoon． The weather condition was cloudy on Worthington matelyl150m a．s．1．Matanuska Glacieris along
valley glacier and flows from some mountain peaks
Glacier and clear on Matanuska Glacier．The mea・
The size of the glacieris approximately130kmin lengthwith3kmwide．Thesnowlineatthistimewas
made at30cm abovethesurface．Themeasuredarea
easilyaccessiblefromhighway．Mostofthesurfaceof
from the totalof reflectedirradiance of the surface
（around3200−3700ma．s．1．）towardsnorth．Thetermi− Suredwavelengthswere12pointsinvisibleandnear nusis at an elevation of approximately500m a．s．1． inferred region（400，450，500，550，550，600，650，700， 750，850，950，andlO50nm）．Themeasurementswere
approximately1650m a．s．1．Both the glaciers are WaSapprOXimately80cm2．Thealbedowascalculated
and that of a standard white reference plate．The mean albedo was obtained from values of5different Surfaces，Which were randomly selectedin an area surement and ice sampling were carried out at two SitesonWorthingtonGlacier（WOlandWO2）andone approximatelylOOxlOOm2ateachsite． Inordertomeasuretheamountofcryoconiteon Site on Matanuska Glacier（MAl），locating between the glacier surface and organic matter content of 550mandlllOma．s．1．（Fig．1）．Thesurfacecondition Of the sampling sites was bareice onboth glaciers． CryOCOnite，iceinsurfacelayerwascollectedwitha
both glaciersis bareice or snow（Fig．3）without debris cover（rock and stone）．Surface albedo mea・
andl−3cmindepth）at the area wherethe spectral
albedo was measured．The five samples were coIT lected at each studied site．The collected area onthe surface was measured to calculate the amount of
Sured with a portable photometer（mode12703，Abe CryOCOnite per unit area．Cryoconite also existed at
thebottomofcryoconiteholes，Whicharewater−fi11ed
Cylindricaldepressionsontheglaciersurfaceofboth
glaciers．Thesizerangedfrom7to13indepth，from
3to8indiameter．Thecryoconiteincryoconiteholes also was collectedwith a pipetin five holes at each Studiedsite．The collected samples weremelted and preservedasa3％formalinsolutionin125mLclean polyethylene bottles to fix biologicalactivity．All SamplesweretransportedbycartotheInternational
Arctic Research Center，University of Alaska Fair− banks，for analysis．In thelaboratory，the samples Weredried（650C，24hours）inpre−Weighedcrucibles．
Theamountofcryoconiteperunitareaoftheglacier WaS Obtainedfrom the dryweight and the sampling
area．Then，the driedsampleswere combustedforl
hour atlOOO OCin an electric furnace，and weighed again．The amount of organic matter was obtained from the difference the weight ofbetweenthe dried
andcombustedsamples．Aftercombustion，Onlymin，
eralparticles remained．The composition of the CryOCOnitewasexaminedwithanopticalmicroscope （NikonSMZ800andE600）．
astainless−Steelscoop（ト2cmindepth）．Thecollected area on the surface was measured to calculate the
Fig．3 Thebareicesurfaceofeachglacier（a，SiteWO20n Worthington Glacier；b，Site MAlon Matanuska Gla− Cier）．Cryoconite（dark−COlored dust）can be seen to COVerthesurfacepartly．
amount of the algalvolume biomass per unit area． Thefivesampleswerecollectedatrandomlyselected Surface at each studied site．The collected samples Weremeltedandpreservedasa3％formalinsolution inclean125mLpolyethylenebottles．Theseformalin Samples were used for cellconcentration counting． Foridentificationofalgalspecies，Othersampleswere COllected and kept frozenin a cooler．Allsamples were transported by car to the International Arctic
Thealgalbiomassofeachsitewasrepresentedby the cell number per unit water volume and algal VOlumeperunitarea．Cellcountsandestimations of Cellvolume were conducted with an opticalmicro−
asthewavelengthincreased．Especially，atthesiteof
Matanuska Glacier in which the highest albedo was Observed，thealbedowasparticularlyhighinshorter
SCOpe（Nikon E600）．The samples were stained with O．5％erythrosine（0．1mL was addedto3mL ofthe
algal biomass was estimated by summing values obtained by multiplying algal concentrations by the
0 0
meancellvolume．Thiscalculationwasdoneforeach
SpeCiesateachsite．Toobtainspatialbiomassateach Site，the totalbiomasswas represent as cellvolume
perunitareaofglaciersurface（JLLm￣2）．Community
StruCtureWaSrepreSentedbythemeanproportionof each species to the totalalgalvolume at each sam− plingpoint．
5
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Ⅵ由v8length（nm）
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0 0 の
読 の
︻ 古 O ﹁
白 の O L
Fig．4 Spectralalbedo of theice surface of the three Sampling sites on Worthington and Matanuska Gla． ciers．The curves are the mean surface albedo of 5 surfaces at each site． エフ（Ⅵ〟…（、／りブゞ／ん、∫（l／（、Jγ）（てけ血一口〃仙、gん7（、∫tりS
Thedryweightamountofcryoconiteonthebare
icesurfacerangedfromO．2to9．5gmL2（mean：4．Og m￣2）forWorthingtonGlacier andfrom O．2to13．9g 3．JA／∂g（わ〆娩ggんzcわγ5〝，カce m￣2（mean：3．3gm￣2）for MatanuskaGlacier（Table l）．There was statistically no significant difference The surface albedo measured on both glaciers WaSShowninTablel．ThealbedorangedfromO．37to between the studied sites（t−teSt：WOIvs．WO2，t＝ O．58andthemeanwasO．46forWorthingtonGlacier， 1．96，P＝0．085＞0．05；WOIvs．MAl，t＝0．429，P＝ and from O．55 to O．74 and the mean was O．66 for 0．679＞0．05；WO2vs．MAl，t＝0．809，P＝0．442＞0．05）． Matanuska Glacier．Thereis statistically no signifi− The mineralparticles containedin the cryoconite Cant difference between two sites on Worthington ranged from O．16to9．1g m￣2（mean：3．7gmL2）for Glacier（t−teSt：Statistic tvalue（t）＝0．719，prObability Worthington Glacier and from O．15to13．2g m￣2 （P）＝0．49＞0．05）．However，aStatisticalanalysisshows （mean：3．2gm￣2）forMatanuskaGlacier（Tablel）． 3．Res山ts
that albedos for two sites on Worthington Glacier Were Significantly smaller than that of the site on
Organicmattercontentofthecryoconite onthe
bareicesurfacerangedfrom4Ato9．8％（mean：6，2％）
Tablel．Surface albedo and characteristics of cryoconite on Worthington and Matanuska Glaciers．SD＝Standard deviation．
glaciers（1ess than2％）．The most dominant species WaSdifferentbetweenthetwoglaciers．M．
from3．3to5．9（mean：4．4％）onWorthingtonGlacier， from2．8to5．2％（mean：4．1％）onMatanuskaGlacier WaS dominant at both two sites on Worthington （Tablel）．The organic matter contentin the Glacier，While A．no7denskioldiiwas dominant on CryOCOniteholeswasslightlysmallerthanthatofthe Matanuska Glacier．Percentage of M．b昭greniiin
bareice surface on Worthington Glacier，While the Organicmattercontentincryoconiteholeswaslarger than on the bareice surface on Matanuska Glacier．
However，the differences of organic matter content betweenthecryoconiteholeandbareicesurfacewere notstatisticallysignificantatanystudiedsite．
Oscillatoriaceae cyanobacteria．The three species of greenalgaehavebeenreportedascommonalgaeon glaciersinNorthernHemisphereaswellasinAlaska （e．g．Yoshimura et alリ1997；Kol，1942）．
Thetotalcellvolumebiomassofthesnowalgae
WaSgenerallysmallonbothglaciers（Fig．5）．Itranged fromO．0004toO．24mLmL2（mean：0．051mLm¶2）for WorthingtonGlacier，fromO．OtoO．048mLm￣2（mean： 0．015mL m．2）for Matanuska Glacier．There was
Statistically no significant difference between the
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Fig．6 Communitystructureofsnowalgaeofeachstudied SiteonWorthington and Matanuska Glaciers（propor− 0
tion ofcellvolumebiomass），Showingwiththat ofan inlandglacier（Gulkana Glacier）in Alaska（Takeuchi， 2002a）．
assuggestedbypreviousstudies（e．g．Takeuchietal、， 2001b），the relation of albedo，CryOCOnite，and algal
一 ∴︸ ＼ ．、 い．
biomassin Fig．7seems toindicate that the smaller algal production causes the smaller amount of CryOCOnite，andthenthesurfacealbedobecamehigher Onthemaritimeglaciers．Thesnowalgalactivityon theglacialsurfaceusuallydependsonnutrient，SOlar
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data are not availableinthis study．Althoughthe radiation data are also not available，the radiation COnditionofthemaritimeglaciercanbeconsideredto
CauSethesma11eralgalactivity．Generally，theclimate
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radiationintensity，and melt water disturbance（Yo− Shimura et al．，1997，Takeuchi，2001d）．Thenutrients
COnditionofthemaritimemountainregiontendstobe Cloudy as compared to the in1and region because clouds canfrequently formin this reglOn due to a large amount of water vapor came from the ocean
CryOCOnitein theice areais23g mJ20n theinland glacier，Whichis approximately6timeslarger than
reduce the solar radiation on theglacier surface， COnSequently photosynthesis of snow algae would
surface albedo and amount of cryoconite on the ice Surface differed betweenin1and and maritimegla− Ciers．The smaller amount of cryoconiteislikely to CauSehigheralbedoonthemaritimeglaciers． The biologicalactivityis alsolikely to differ between the maritime and in1and glaciers．The Organicmattercontentinthecryoconiteissmallerin themaritimeglaciersthanthatoftheinlandglacier． The organic matter content on theinland glacieris
thesmalleralgalbiomassonthemaritimeglaciers． Thephysicalconditionoftheglaciers，eSpeCia11y ablationoftheglacialsurface，ismorelikelytocause thedifferencesofbiologicalactivityandalsoamount Of cryoconite between the maritime andinland gla− Ciers．Themaritimeglacierischaracterizedbyalarge amount of annual precipitation due to water vapor COmlng from the ocean．Thelarge amount of snow accumulation enables the maritime glaciers to flow
maritime glaciers．The algalcommunities of both maritimeandinlandglaciersweredominatedbysame
lowerelevation，theablationofglaciersurfacewould be greaterin the maritime glaciers．According to
Ciers（Fig．7）thantheinlandglacier．Theamountof On maritime glaciers．The cloudy condition would
that on the maritime glaciers（3．8g mJ2）．Thus，the becomeless active．Thus，the radiation might cause
downlower elevation．For example，terminus eleva・ 7．1％（Takeuchi，2002a），Whichislargerthanthat on thebothofmaritimeglaciers（6．1％forWorthington， tionsofWorthingtonandMatanuskaGlaciers（mari− 2．8％forMatanuskaGlaciers）．Thetotalcellvolume time）are820and500ma．s．1．，reSpeCtively，Whilethat OfGulkanaGlacier（inland）is1220ma．s．1．．Hence，the biomass of thein1and glaciersis also smallerin the maritimeglaciers（Figs．4and6）．Thebiomassonthe altitude of the studied surface differed between the glaciers．The elevation of the studied sites on the inlandglacieris O．52mL m￣2as a mean（Takeuchi， 2001d），Whichis13foldlargerthanthatofthemari− inlandglacieris12701585m a．s．1．，Whichis much higherthanthestudiedsitesonthemaritimeglaciers timeglaciers（0．039mLm￣2）．Onthe otherhand，the （5001110ma．s．1．）．Sinceairtemperatureishigherin COmmunitystructureissimilarbetweentheinlandand
threespeciesofgreenalgae（Fig．6）．Thissuggeststhat
thecommunityconsistingofthethreegreenalgaeis
COmmOn StruCture On both maritime andinland gla・
ciersin Alaska．The smaller algalbiomass on the maritimeglacierssuggeststhatthesnowalgaeonthe glaciersarelessactivecomparedtotheinlandglacier．
Summer ablation measurement on the maritime and
inlandglaciers，theiceablationonWorthingtonGla−
Cier，70mmdayrlistwofoldlargerthan29mmdayql
On Gulkana Glacier（Mayo and Pさw6，1963；Streten andWendler，1968）．Astheresultoflargeablationon
themaritimeglaciers，alargeamountofmeltwateris
27
Takeuchiet al．
1ikelytoflowonthebare−icesurfaceoftheglaciers．
region，NepalHimalaya．Snow and Glacier Hydrology （Proceeding of the Kathumandu Symposium，November 1992）IAHS Publ．218，309−316． Kol，E．（1942）：ThesnowandicealgaeofAlaska．Smithsonian MiscellaneousCollections，101，ト36． On theice surface of the maritime glacier．Thus， Mayo，L．R．，and Pさwe，T．L（1963）：Ablation and net total radiation，Gulkana Glacier，Alaska，Chapter43inIce and 1arger ablation on the maritime glaciers may be SnOWLProperties，prOCeSSeS，and application，Conference， responsible for the smaller amount of algae and MassachusettsInstituteofTechnology，1962，Proceedings： CryOCOnite，COnSequently the surface albedo on the Cambridge，Mass．，M．I．T．Press，633−643． maritimeglacierscanbeashighasthecleanglacial Paterson W．S．B．（1994）：The physics of glaciers3rd ed．， surface． 0Ⅹford，EIsevier，480p． Streten，N．A．and Wendler，G．（1968）：The midsummer heat Sincethedatadiscussedinthispapercoveronly balance of an Alaskan maritime glacier．Journalof threeglaciersinAlaska，thecomparisonbetweenthe Glaciology，7，43ト440． maritimeandinlandglaciersmightbelessconvinced． Takeuchi，N，，Kohshima，S．，Goto．Azuma，K．andKorner，R． Forfurtherdetaileddiscussion，itisnecessarytouse （2001a）：Biologicalcharacteristicsofdarkcoloredmaterial moreextensivedataoftheglaciersinAlaska．Remote （cryoconite）onCanadianArcticglaciers（DevonandPenny icecap），ProceedingoftheMemoirsofNationalInstitute sensing technique would be useful to study surface OfPolarResearch，SpecialIssue，54，495505． albedoandcryoconitecontaminantinextensivearea． Takeuchi，N．，Kohshima，S．and Seko，K．（2001b）：Structure， Thegeographicaldistributionofthecryoconitewould formation，darkeningprocessofalbedoreducingmaterial help to understand formation process of the （cryoconite）onaHimalayanglacier：agranularalgalmat CryOCOniteanditsrelationtobiologicalactivity． growing on the glacier．Arctic，Antarctic，and Alpine Research，33，115−122． Takeuchi，N．，Kohshima，S．，Shiraiwa，T．and Kubota， Acknowledgments （2001c）：Characteristicsofcryoconite（surfacedust ongla− Ciers）andsurfacealbedoofaPatagonianglacier，Tyndall We would thank to M．Ikeda and N．Tanaka Glacier，Southern PatagoniaIcefield，Bulletin of （FrontierObservationalResearchforGlobalChange） GlaciologicalResearch，18，65−69． Takeuchi，N．（2001d）：Thealtitudinaldistributionofsnowalgae for encouragement of this study．We also thank an On anAlaska glacier（Gulkana Glacierin the Alaska anonymous reviewer for helpfulcomments．The Range），HydrologicalProcesses，15，3447−3459． expense of field work and laboratory analyses was Takeuchi，N．（2002a）：Surface albedo and characteristics of SuppOrted by a project of Frontier Observational CryOCOnite（biogenic surface dust）on an Alaska glacier， Research for GlobalChange（funded by theJapan Gulkana Glacierin the Alaska Range，Bulletin of GlaciologicalResearch，19，6370． MarineScienceandTechnologyCenter）．Thelabora− Takeuchi，N．（2002b）：Opticalcharacteristics of cryoconite tory analyses were also supported by Grants−in−Aid （surface dust）on glaciers：the relationship betweenlight forscientificresearch（No．13480154），fromtheMinis− absorbency andthepropertyoforganic matter contained try of Education，Science，Sports and Culture， inthecryoconite，AnnalsofGlaciology，34，409L414． JapaneseGovernment． Warren，S．G．and Wiscombe，W．］．（1980）：A modelfor the SpeCtralalbedo ofsnow．ⅠⅠ．snow containing atmospheric aerosoIs．JournalofAtmosphericScience，37，27342745． References Wharton，R．A．，Jr，McKay，C．P．，Simmons，G．M．and B．C．（1985）：Cryoconiteholesonglaciers，BioScience，35（8）， Arendt，A．AリEchelmeyer，K．AリHarrison，W．I）リLingle，C．S．， 449503． and Valentine，Ⅴ，B．（2002）：Rapid Wastage of Alaska Yoshimura，Y．，Kohshima，S．，andOhtani，S．（1997）：ACommu− Glaciersandtheircontributiontorisingsealevel．Science， nity of Snow Algae on A HimalayanGlacier：Change of 297，382−386． AlgalBiomassand Community Structure with Altitude． Gajda，R．T．（1958）：CryoconitephenomenaontheGreenlandIce Arctic andAlpineResearch，29，126137． CapintheThulearea．Can．Geogrr，No．12，3544、 Zeng，Q．，Cao，M．，Feng，Ⅹ．，Liang，F．，Chen，Ⅹ．，and Hoham，R．W．andDuval，B．（2001）：Microbialecologyofsnow （1984）：Studyonspectralreflectioncharacteristicsofsnow， andfreshwaterice．InSnow＆o10gy．CambridgeUniversity iceandwaterofNorthwestChina，ScientiaSinica（Series Press：Cambridge．168228．
