BulletinofGlaciologicalResearch22（2005）8997．†リ◎JapaneseSocietyofSnowandIce

Snowpitstudiesandradio−eChosounding＄On Mt．McKinley2004

SyosakuKANAMORll．YoshitomiOKURA2，TakayukiSHIRAIWAlandKenjiYOSHIKAWA3
1InstituteofLowTemperatureScience，HokkaidoUniversity，Kita19Nishi8，Kita−ku，SapporoO60−0819Japan
202Co．，LTDリ45−4−3FIidabashi，Chiyoda−ku，TokyolO20072Japan

3WaterandEnvironmentalResearchCenter，UniversityofAlaskaFairbanks，P．0．Box755860Fairbanks，Alaska997755860
U，S．A．
（ReceivedOctober5，2004；RevisedmanuscriptreceivedNovember24，2004）

Abstract

InJune2004，Wemadesnowpitstudiesandradio−eChosoundingstoseekicecoredrillingsiteson
Mt．McKinley（630N，15lOw，6194ma．s．1．），Alaska．PitstudiesatDenaliPass（5560ma．s．1．）andMe
Camp（4350ma．s．1．）showhigh−densitylayersnearsurface．Theselayersseemtorelatewithstrong

Wind．From thecomparisonoftheobservedtemperaturesatthepitsand temperaturesatotherice

COring sitesin Alaska and Yukon，We SuppOSe thatnoslgniBcant meltingoccursatobserved sites．
Radio−eChosoundingsshowthattheicethicknessesatHighCamp（5220ma．s．1．）andDenaliPassare
46−48m and60¶67m，reSPeCtively．Although we havealittleinformation aboutaccumulation rates，

thethicknessesaretoothintodrilltheicecoreswhichcanprovidetheclimaterecordformorethan
hundreds years．WesuggestthattheeastwardofDenaliPassand the SummitPlateauofthe North

Peak（5690ma．s．1．）may havethickerice．

l．lntroduction
For reconstructing past climate history，SeVeral
ice coresare obtained from glaciersin the Wrangell−
St．Elias Mountainsin southern Alaska and south

drilling sites which provide the climate record formore than hundreds years on Mt．McKinley．InJune

2004，We made reconnaissance and carried out snow

pitstudiesandradio−eChosoundings．Thispaperpre−

SentSthepreliminaryresults．

WeStern Yukon Territory（e．BI Benson，1984；
2．Observation sites
Holdsworthetal．，1992；Yalcin and Wake，2001；Goto−
Azumaetal．，2003，InteragencyArcticResearchPolicy
Figure2shows the vicinity of Mt．McKinley．In
Committee，2004；Shiraiwaetal．，2004）（Fig．1）．Remark− general，therearecliffsonthesouthandwestfacesof
ablemeltingthatdisturbspastclimatesigna11argely
the South Peak（6194m a．s．l．）．The east face of thedoes not occur at the ice coring sites and various
Slgnalsarepreservedintheicecores．Theseicecores
arethoughttoreflectclimateandenvironmentalcha−
ngein NorthPacificregiononinterannualtomillen−

SouthPeakisalsosteepandcoveredbyglacier．North
Side ofthe SouthPeakislesssteep．ThereisSummit

ingsitesareclosefromtheNorthPaciRcOcean．How−of Mt McKinley is the South Peak and few people

Wrangell−St．Elias Mountains．To develop ourunder−

Saddle between North and South Peaks．Eastern side
OfDenaliPassisagentleslopeanditisbeginningof
the Harper Glacier．Western side of DenaliPassis a
SteepSlopeandWestButtressroute，Whichisthemost
popularclimbingroutetraversestheslope．Thereisa

nialtime scale becauselocations of theice−COre drill−

ever，the previousice coring siteslocate onlyinStanding climate or environmentalchangein North

Pacific reglOn，ice−COre reCOrds from other area areneeded．Tocompareanddevelopthestudyonvarious
time scales，the newicecoresthatcan provide morethanafewhundredyearshistoryofclimatearedesir−able．

Plateau（5690ma．s．1．）onthewesternsouthsideoftheNorthPeak（5934ma．s．1．）．TheareaofSummitPlateau
OftheNorthPeakisabout800×500m．Themainpeak

Climb the NorthPeak．DenaliPass（5560m a．s．1．）isa

place called High Camp（5220m a．s．1．）at the baseof

this slope．West Buttress hit the body of the South

Mt．McKinley（630N，15lOw，6194m a．s．l．）inthe
Peak near High Camp．MedicalCamp（4350m a．s．1．）

Alaska Rangeis oneofthecandidatesforicecoring．
The purpose of this studyis to seekidealiceTCOre

locates bottom of the cliff at east face of the South

Peak．Rangersofthe DenaliNationalPark and medi−

タβBulletin ofGlaciologlCalResearch

Fig．1．LocationsofMt．McKinley（6194m a．s．1．）．Ice coreslongerthan40m wereobtained from6sites close
to Mt．McKinley：Mt．Logan（Northwest Col：5340m a s．1．；Holdsworth etal．，1992，Prospect−RussellCol：
5340m a．s．1．and King Col：4135m a．s，1．；Goto．Azumaetal．，2003），EclipseIce Field（3071m a．s，1；Yalcin
and Wake，2001），Bona−Charchill（4420m a，S．1．；Interagency Arctic Research Policy Committee，2004）and
Mt．Wrangell（SummitPlateau：4100ma．s．1．；Benson，1984；Shiraiwaetal．，2004）．

丁ご．Ⅳ。IIL「丑≡ミ∵ニーニ＝ニ

芸琶≡

＋

：二

二こ．

Fig．2．Topographicalmap of Mt．McKinley．A brokenline shows the most popular climbing route，West
Buttress Route．Double squares show candidate sites forice core drilling and gray squares show
observation sites．Thin solidlines showlOO−mintervalcontours of the surface elevation，Origlnaldigital
elevation data was Globa130Arc Second Elevation Data（GTOPO30）by U．S．GeologicalSurvey，http：／／
edcdaac．usgs．gov／main．asp

caldoctorsstayhereeverysummerforclimbers．Mostof climbers camp at High Camp and Medical Campbecause they arelogistically the bestplaces tocamp

forclimbingtheSouthPeak．

Oneoftheauthors（Y．0．）builtandmaintainedthe
weather station at5715m a．s．1．for15years．This

Kanamorietal．

タJ

WeatherstationisonaridgenearDenaliPass（Fig．2）．

Prevailing wind on Mt．McKinleyis from south or
SOuthwestin winter and no prevailing directionin

Summer．We think wind speed on Mt．McKinleyis

extremely high because the wind gauges were de−
StrOyed ordeformed every year．We assume wind at
DenaliPassisstrongbecausethesaddleshapeseems
to concentrate wind．

Ice−COredrillingsitesrequireflatsnowfieldandno

COntamination by climbers．More thanl，000climbers
COme tO Mt．McKinley every year，SOthecontamina−tion by themis not negligible．In the vicinity of Mt．
McKinley，Summit Plateau ofthe North Peak，Denali

PassandHighCampanswertotherequirements．We
thought thesesitesthecandidatesofice−COredrilling
Sites．Remarkable melting that can disturb climate
Signalslargelyis also aproblem forice cores．These
Sitesseemtobefreefromconcernformeltingbecause
the elevation of these sites are higher than most ofpreviousice coring sitesin the North Pacific reglOn

Fig．3．A view of the summit plateau of the North
Peak from the SouthPeak．（June27，2004）．

Which are shownin Fig．1．As afirst step，We maderadio−eCho soundings at DenaliPass and HighCamp
andsnow−PitstudiesatDenaliPassandMedicalCamp
due tologisticlimitation．We could not make any
measurement at Summit Plateau of the North Peakand we havelittleinformation about this site．How−

ever，WeSupPOSethatthesitehaspossibilitytobean
idealsiteforice−COredrillingbecausewecouldrecog

nizethatwidebasinwascoveredbysnowthere（Fig．3）．
At High Camp，radio−eCho soundings were con−ducted．HighCampis340mlowerthanDenaliPassin

elevation and the horizontal distance from Denali

Passisl．2km．Most of climbers camp at the same

pointneartheedgeofWestButtress．Thetargetoftheradio−eChosoundingsisaflatsnowfieldwhichlocatesFig．4．High Camp（June 26，2004），a：A view of the
Observation site．b：An enlarged picture of Fig．4a．
Theobjectatroughsurfaceisaniceax．

Ontheeastsideofthecampsite（Fig．4a）．Areaofthis
SnOWfieldisabout150×150m．Thesurfacewasrough．

HeightandlengthofeachreliefwereaboutO．5mand

SeVeralmeters，reSpeCtively（Fig．4b）．Bedrocks were

exposed to thesurface atsouth and westedgeofthe

SnOWfield（not shownin thefigure）．Theobservation

point was about150m southeast from the campsite
andit was close to the center of the snowfield．

At DenaliPass，radio−eCho soundings and a pit

Study weredone．Theobservation site wasabout300
mfarfromtheclimbingroute．Bedrockswereexposed
tothesurfaceatthewestedge．Gentleslopelessthan

50continueseastwardfor700mfromtheedge（Fig．5）．

The observation site was about 150m east from theedge（Fig．6）．The surface shape was partly rough．

Heightandlengthofeachreliefwereseveralcentime−ters and severaltens centimeters，reSpeCtively．The

SnOWpitwasdugatapointwithsmoothsurface．
Snow pit studies were carried out at Medical
Camp．Thisplaceis1200mlower than DenaliPassin
elevation．Thereisinformation about accumulation
rateatthissite．RangersofDenaliNationalParklefta

Fig、5、A view ofDenaliPassfrom the weatherstation（June27，2004）．

metalpole，Which wasapartof antennas atMedical
Campin summer2003．The pole had been buriedin
SnOW．Wemettherangersdiggingthepoleforusingit

Bu11etinofGlaciologicalResearch

タ2again．Thepolestillstoodinsnowanditsbottomwas

about4m below thesurface．Itimplies that theaccu−

mulation from summer 2003 to summer 2004 wasabout 4min snow thickness．This valueis not soaccuratebecauseitisunclearthathowdeepthepole
was stuckinto snowin2003and exactly date when

usefulasanapproximation．
The high accumulation rate at Medical Camp
SeemS tO be caused by concentration of snowdrift．
Becausetherearewallsofmorethanseveralhundred
meters high at the north and the east of Medical

Camp．Atthecandidatesites，HighCamp，DenaliPassthe rangers stood the pole．However，this valueis and the Summit Plateau on the North Peak have nohuge walls that may catch snowdrift like Medical
Camp．Therefore we assume thataccumulation rates
at the candidate sites are smaller than in Medical
Camp．

3．Snowpitstudies
Densitiesandsnowtemperaturesaswellasstra−
tigraphic features were examined at the snow pits．
Density measurementswerecarriedoutevery30mm

bytheconventionalweighingmethod．Snowtempera−

tures were measured by using a thermistor digital
thermometer．

、■J．ノ．／）りM〃Jk∬

Fig．6．The observation site at DenaliPass（June28，2004）．Allphotosin Figs．36 are taken by S．
Kanamori．

Figure7showsvisiblesnowstratigraphy，density
and temperature at DenaliPass．Depth and width ofthepitwerel．15mandlm，reSpeCtively．Topl．15mof（a）Stratigraphy（b）Density［kgm−3］（c）Temperature【OC］
200 300 400

︻
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工
五
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凸

−30 −25 −20 −15 −10

0．6●：Compactedsnow

h：HardS二SoftFig．7，Results of pit studies at DenaliPass．a：Visible stratigraphy；b：density pronle．A brokenlineis
estimated valuebystratigraphy；C：temperatureprOnles．

Kanamorietal．

†t■J（a）Stratigraphy（b）Density［kgm−3］（C）Temperature【OC］
200 300 400−25 −20 −15 −10 −5

●●

0、4

＝＝＝■＝●＝亭＝＝●●＝＝＝●＝●＝h＝

0、8

●●

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上
巳
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凸

●：Compactedsnow
h二Ha「ds：SoftFig・8・ResultsofpitstudiesatMedicalCamp・a：visiblestratigraphy；b：densityprofi1e；C：temperatureprOfi1es．

the snow consisted of compacted snow and no ice
layers were found．Hardlayers and softlayers werealternatedandeachsnowlayershadnoinclination．It
impliesthatroughsurfacestructurelikesastrugidid

layers werefound．Thesurfacewassmoothand each
SnOWlayer had noinclination．There were a softer

layeratO．400．41mandaharderlayeratO．56−0．57m．It

heavily snowed for thelastfive days following to

notdeveloplargelyhere．Variationsofthesnowhard− SeVeralsunny days so thatitislikely that the har〔1ness are coincident with visible stratigrapy．Soin
densitymeasurement，densitywasassumedtobethe

1ayerisasun−CruStlayerandthetopO．56−mSnOWhad

hard todigthepitdeeperwithshovels．Density was

depths deeper thanl．02m，meaSurement WaS done

layer andits density was450kgm3．Density of thehardlayeratthebottomalsoseemedtobehigh．We
SpeCulate thatsuch high−densitylayers relatestrong

dailyfluctuationatthesurface．TemperatureatMediq
CalCamp was70c higherthan atDenaliPassin the

been deposited for thelast five days．Density was

SameValueinasimilarlayer．Snowatl．15m wastoo measuredcontinuouslyfrom thesurfacetol．02m．At

everyO・1m・Densitywas350kgm3ato．75mdeepand
deep．AtdepthsdeeperthanO．42m，densitywasmeas− 430kgm3ato・90mdeep・Atl・5mdeep，densitywas
uredateachlayer．AtO．6mdeep，therewasveryhard
relativelylow．In the temperature profi1e，thereis ameasured continuously from the surface to O．42m

Samedepth．

wind．Snow temperature wasloweratdeeperdepth．
Atl．1mdeep，thetemperaturewas−24．80c．

ヱ3．βよsc〟Sぶわ乃0ナ7Jゐβざれ0仙♪才JsねJdgβS

3．2．肋dgcαJCα椚♪

files．Althoughthelow−densitysnowatthesurfaceof

Figure8showsvisiblesnowstratigraphy，density

Densityatthepitsshowsfluctuationsinthepro，MedicalCamp may blow off，Other relativelow−

andtemperatureatMedicalCamp．Thepitwas2．50m densitylayers seem to be preserved．Kanamorietal．
deep．Snowinthepitseemedtobeaccumulatedwith− （unpublished）obtained detaileddensity profi1esfrom
in one year because the accumulation from previous
icecoresatMt．WrangellandKingCol，Mt．Loganthat
yearwasapproximately4minsnowhere．Top2．5mof locateinWrangellTSt．EliasMountains（Fig．1）．Thesethe snow consisted of compacted snow and noicesites are cold mountain ISlacier like the observation

BulletinofGlaciologicalResearch

94

Tablel．SnowtemperaturesonMt．McKinleyandattwodrillingsites，DenaliPass，

MedicalCamp，

Mt．Wrangell
Temperature at

1．1rmdepth（℃）

14．6

−24．8

Date

June28，2004

Latitude

63004′57

Longitude

15lOol′43′′w

Elevation（ma．s．1．）

KingCol，

Mt．McKinley Mt．McKinley Mt．LoganN−17．8＊

June22，2004
63004′11N

15lOo4′25

5560

w

4350

−16．5＊＊

May26，2002

June25，2003

60035′20 N

6lO59′54 N

140036′15w

4135

144002′30w

4100＊Goto−Azumaefal．（2003）；＝Shiraiwaetal．（2004）

SitesinMt．McKinley．Theyfoundthatdensityfluctu− Withaportableoscilloscope．
At each site，antennaS Were Set On the surface．
ationexistoverdepthsof50m thereand discuss themeaningaspastclimatesignals．Wespeculatethatthe

densltyfluctuations on Mt．McKinley are also pre−servedinfirnlayers and thefluctuations have somemeaning as past climate signals which relate withwind and otherfactors．

There were noicelayers at the snow pits．How−

ever，it does not mean no melting occur through ayear．Because we may notdig thelayers ofprevious

summer at the pits．Therefore，tO eXamine whether

Distancebetween the antennas wassetat30m and50

m．Thelong axis of the dipole antenna was set to
Orientbarewallsandridgestodecreasecluttersfrom

them・Inaddition，Wemadeanothermeasl！rementfor

theorthogonalantennaorientationatDenaliPass．
The thicknessoficediscalculated usingd二（笠）2−エ2，（1）

meltingoccuratthecandidatesitesonMt．McKinley
OrnOt，WeCOmParedsnowtemperatureatpreviousice

WhereLJ（rrusl）isthepropagationspeedoftheradio

facedatainearlysummerseason，SOWeCOmParedthe
temperature data at depth ofl．1min early summer

two−WaytraVeltimeintoicedepthandthespeedcan

shows that the surface snow temperature at Denali
Passwaslowerthanthetemperaturesattheprevious
icecoringsitesandalittlehigheratMedicalCampin

the firn．It can be calculated by Looyenga s eauation

COringsitesatMt．LoganandMt．Wrangell．Thetem−
Perature data on Mt．McKinleylSlimited to the sur，

WaVe，T山s）isthetwo−WaytraVeltimeand2L（m）isthe distance between the antennas（Matsuoka et1999）．Thepropagationspeedvisrequired toconvert

bewrittenas300／J｛（m〟S1），WhereEispermittivity

withotherice coringsites（Tablel）．Thecomparison Offirn．ThepermittivltyOffirnedependsondensityof

earlysummerseason．Wesupposethatseasonalvaria−

tion of temperatureon Mt．McKinleyis similarwith

that on Mt．Logan and Mt．Wrangellbecause themountains a11locatein North Pacific regionin the
North America andlatitude of them are close．From
thecomparison，WegueSSthatthesnowtemperatureofthecandidatesites，Whichlocateabove5220ma．s．1．

arelowerthansnow temperaturesoficecoringsites（Glen and Paren，1975）：（2）と‡1＝言（ふ1）・

Here，Eiisthepermittivityofpureice，thatiseventu−
a11yindependent offirn temperature（Fujita etal．，
2000），Pis density of the glacier andpiis density of
pureice．Ourdensitymeasurementwasdoneonlyfor
topseveralmeters，SOthatweassumedpfromdensity
profi1es of other glaciers．In mountain glaciers，thethicknessoffirnlayerstakelargepartoftheallthick−atKingCol，Mt．LoganandMt．Wrangell．FromtheicenessanditcontroIsthedensityofa11thickness．Sowe
COreS，meltinglSinslgni百cantat King Col，Mt．Loganassumed that density at any depthon Mt．McKinley（Shiraiwa etal．，2003）and Mt．Wrangell（Shiraiwa et
ranges between the densities of the same depths atal．，2004）．Therefore，We gueSS that melting are also
insignincant at the candidate sitesin Mt．McKinley． twoglaciers that have extremely thin and thick丘rn

Noicelayersatthevisiblestratigraphiessupportthis

idea．

layers．We used the density profiles at King Col，Mt．
Logan（firn thickness：50m；Shiraiwaetal

2003）and

Mt．Wrangell（firn thickness：100m）as the two ex−

4．Radjoqechosoundings

treme values．In this assumption，the density p de−

4．ノ．肋〃10d

Speed v to be169−205mFLSlasfirst estimate from

Theice−penetrating radarsystem was composedof an impulse transmitter and a set of transmission

and receiving antennas．The antennas were half−
wavelengthdipole．Thecentralfrequencywas5MHz．

The time series of received voltage were digitized

Pendsonthethickness，d．Sowegavethepropagation

densityof550−900kgm3andcalculatedtentativethi−
ckness d′from Eq．1．The range of the densityis

enough wide toinclude density of allcold mountainglaciersintheworld．Next，WeeStimateddensityfrom

the tentative thickness，d′and recalcuiated d′using

Kanamorietal．

5彷

0．0 0．2 0．4 0．6 0．81．01．21．41．6

4
2

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謬
l
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一
2
〇
＞
4
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U
＞ 2
4
U
．
6
U ●
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0．0 0．2 0．4 0．6 0．81．01．21．41．6

Two−WaytraVeltime［ps］★：Peakbydirectwave
Fig．9．ThetimeseriesofradioechoatHighCamp．a：Antennaseparation was30m；
b：Antenna separation was 50m．Arrowsindicate clear reflections that weinterpreted theechofrom thenadirbedrockbeneaththeice．

newly estimated density and v．The calculation was
repeateduntilrangeofdensityconverged．Inthecase
OfHighCamp，WeaSSumethepropagationspeedu tobe196−202mps1from theestimatedmeandensityof

580−630kgm3andin the case of DenaliPass，Weassumevtobe190−198mpslfromtheestimatedmean
densityof610680kgm3．
OriglnOftwoTWaytraVeltimeisuncertaininthis

radar−SyStem．So we consideredfirst highest peak at

the time series of radio echo as a standard point of

direct wave．The zero point of two−Way traVeltime
WaS COnSidered to be2L／300山s）before the standard

point．

4．Z 斤es〟J〜s
4．2J．〟由んCα∽♪

Figure9shows time series of the radio echo at

the measurement site，Or Off nadir reflection frombeneath theice．

ThemeasurementsiteiscIosetothecenterofthe
150m by150m area thatis covered by snow．Sincebare bedrock was found at the edge of this area，thethicknessofthesnowandiceincreasesfrom Om to46
−48m within thelateraldistance of75m．

Targetoftheicecoreisatleastmorethanafew
hundredyears．Thethicknessseemstoothintoobtain
SuChagedicecores．
4．2ま βgれαJgfわss

FigurelOshowsthetimeseriesoftheradiowaves
at DenaliPass．FigureslOa andlOc are the case thatthe long axis of the dipole antenna was set to orientbare wallsand ridgestodecreasecluttersfrom them．
FigurelOb andlOd are the case of the orthogonalHigh Camp．Clear echoes are shown at O．5andl．1FLS． antennaorientation．Clearechoesareshown atO．7ps．
The measurementsiteis150−200m far from the walls

The two−Way traVeltime of the clear echoes were alittleshorteratshorterantennaseparations．Thismay
befromuncertainofthezeropointoftwo−WaytraVeltime of the echoesl．01．3ps．Therefore，Weinterpretthat the echoes at the two−Way traVeltime of O．5ps

thewallsthatislikelytoreflecttheradiowave．Iftheradio waveis reflected offthe wall，the propagation
speed through the air of300mpslglVeS tWO−Way

thatislikely to reflect the radio wave．If the radio
WaVeis reflected offthe wall，the propagation speed
through the air of300mpslglVeS tWO−Way traVel

was reflected off the bedrock beneath theice．Thick−ness ofice was calculated as46−48m with T and2L

Shownin Fig．9．The echoes atl．1〟S Seem tO be re−flectedoffthebaredbedrockorsurroundingridgesof

time．The measurement siteis about150m far fromtraveltimeoftheechoesl．3／JS．Therefore，Weinterpretthat the echoes at the twoTWay traVeltime of O．7FLS
WaS reflected offthe bedrock beneath theice，nOt theBulletinofGlaciologlCalResearch

9∂60．0 0．2 0．4 0．6 0．81．01．21．41．6

4
2
0
2

4
2
n
V

︻ 4
＞
﹈●
温
室●
○
＞ 丘
U
P
U 6
＞
U
4
． 2
召 0
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4

■

丘
U

■

6
4
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U

0．0 0．2 0．4 0．6 0．81．01．21．41．6

Two−WaytraVeltime［ps］★：Peakbydirectwave

Fig．10．The time series of radio echo at DenaliPass．Arrowsindicate clear ref−1ections．aand b：Antennaseparation was30m；C and d：Antennaseparation was

50m．a and c，b and d were obtained with the orthogonalant冒nna Orientations
each other．See text for detail．

bare bedrock or surrounding ridges of the measure−mentsite．Thethicknessoficewascalculatedas6067m

Ward．Thuswecanexpectmuchthickericeattheeastof the observation site．

thicknessdoesnotseemtobeenoughtoobtainaged

5．Concluding remarks

Cierincreaseseastward．Atthewestedgeofthissnow
field，bedrock was exposed to the surface and at themeasurementsite，bedrock wasabout60m below the

SOundings on Mt．McKinley toseek theidealice−COreWith the T and2L，Showninfig．10．The measured
ice cores．However，WeSuppOSethatthicknessofgla−surface．Gentle slope ofless than50continues east−

We carried out snow pit studies and radio−eChodrillingsitewhichcanprovideicecorewithatleasta

fewhundredyearsofclimaterecord．Annualaccumu−

Kanamorietal．

タ7

1ation at MedicalCamp was about4min snow．We

consider that drift snow was concentrated at Medical

References

nual accumulation rates at the candidate sites are

Benson，C．S．（1984）：IcecoredrillingonMt．Wrangell，Alaska，
1982．2ndInternationalWorkshop／SymposiumonIceDri−
11ingTechnology．CRREL SpecialReport，84r34，6ト68．
Fujita，S．，Matsuoka，T．，Ishida，T．，Matsuoka，K．andMae（2000）：Asummaryofthecomplexdielectricpermittivity
O魚cein the megahertz range andits applications forradarsoundings of polarice sheets．Physics ofIce Core
Records，Hondoh，T．（ed），HokkaidoUniversityPress，185

Camp becauseofits topographicalconditionand an−lower than accumulation rate at MedicalCamp．The
high−densitylayersatthepitsimplythatstrongwind
blowsandrelatestoformingofthelayers．Fromthe
comparison of temperature with previous ice coring
Sites，WeSuppOSethatnoslgnificantmeltingoccurat
the candidate sites．The thicknesses of glaciers are
estimatedtobe4648matHighCampand60−67mat
DenaliPass．ThethicknessofHighCampistoothinto
drillicecoreswhicharesuitableforourpurpose．The−212．

Glen．）．W．andParen，J．G．（1975）：Theelectricalpropertiesof
SnOW andice．］．Glaciol．，15（73），1538．
Goto−Azuma，K．，Shiraiwa，Tり Matoba，S，，Segawa，TKanamori，S．，Fujii，Y．andYamasaki，T，（2003）：Anoverview
thickness at DenaliPass was also thin，however，thi−
Of theJapanese glaciologicalstudies on Mt．Logan，YukonTerritory，Canadain2002．Bull．Glaciol．Res．20，65
Ckericecanbeexpectedtoexistattheeastwardarea

Of the site．In addition，the Summit Plateau of theNorthPeakseemstobeagoodsitein theviewfrom

the vicinity．These two sites，DenaliPass and theSummitPlateauoftheNorthPeakhavepossibility to
beidealsitestodri11icecoreswithhundredsyearsof
Climate history．
Acknowledgments

We thank Roger Robinson and all rangers ofDenaliNationalPark．Theysupportedourclimbingand
transportofequlpment．Wethanka11themembersof

OurClimbingteamandtheteam WindofDenali for
theirhelplnClimbingandscientificoperations．Syun−Ichi−72．

Holdsworth，G．，Krouse，H．R．and Nosal，M．（1992）：Ice core
Climate slgnals from Mount Logan，Yukon，AD1700
1987．In Climate Since A．D．1500，R．S．Bradley and P．D．
Jones（Eds．），Routledge，London，pp．483−504．
InteragencyArcticResearchPolicyCommittee．（2004）：Arctic
research of the United States Vol．18Spring／Summer
2004．，theInteragencyArcticResearchPolicyCommittee，NationalScience Foundation．，pp．5．
Matsuoka，K．，Horikawa，S．，Shiraiwa，TりMuravyev，Y．D．，
Salamatin，A，NリOvsyannikov，A．A．，Maeno，H．andOhi，M．（1999）：RadioLeChosoundingatthesummiticecapof
the Ushkovsky voIcano，Kamchatka．In Naruse，R．（ed）
Cryospheric Studiesin KamchatkaIl，1nstitute of Low
TemperatureScience，HokkaidoUniversity，Sapporo，2O−24．

Shiraiwa，T GotoLAzuma，K．，Matoba，S．，Yamasaki，TSegawa，T．，KanamOri，S．，Matsuoka，K．andFujii，Y．（2003）：
Ice core drilling at King Col，Mount Logan2002．Bull．
AkasofuandItsuroKatosupportedourclimbingteam
Glaciol．Res．20，5763．
in Fairbanks and Anchorage．CarlS．Benson，Kevin
Shiraiwa，T．，Kanamori，S．，Benson，C．S．，Sol
AbnettandGaryNewmansupportedthepreparations
Muravyev，Y．D．（2004）：Shallowice−COredrillingatMount
Wrangell，Alaska．Bull．Glaciol．Res．2l，7177．
forthefieldwork．WealsothankKenichiMatsuokafor
Yalcin，K，and
Wake，C．P．（2001）：Anthropogenic signals re−
the lecture on radar operations and advise on theCOrdedinanicecorefrom EclipseIce頁eld，Yukon Terrトinterpretation of the results．Finauy，We thank the
tory，Canada．Geophys．Res．Lett．，28，44874490．

reviewerfor his／hermanyvariablecomments．