Glaciological Research Project in Patagonia : Studies at Glaciar

Home , Patagonian Ice Sheet, Perito Moreno Glacier

Bulletin of Glaciological Research,3 ( ,*++ ) ++1ῌ 1 ῌJapanese Society of Snow and Ice

Glaciological Research Project in Patagonia,**0ῌ ,**3 : Studies at Glaciar Perito Moreno, Hielo Patagónico Sur, in area of Hielo Patagónico Norte, and along the Paciﬁc Coast

Masamu ANIYA+,-. , Pedro SKVARCA , Shin SUGIYAMA , Tatsuto AOKI , Takane MATSUMOTO/0 , Ryo ANMA , Nozomu NAITO 1 , Hiroyuki ENOMOTO 2 , Kazuaki HORI3 , Sebastián MARINSEK , , Keiko KONYA +* , Takayuki NUIMURA ++ , Shun TSUTAKI+, , Kenta TONE +, and Gonzalo BARCAZA +- +Professor Emeritus, University of Tsukuba, Ibaraki -*/ῌ 2/1, , Japan ,Instituto Antártico Argentino, Cerrito +,.2 , C +*+* AAZ, Buenos Aires, Argentina - Institute of Low Temperature Science, Hokkaido University, Sapporo*0*ῌ *2+3 , Japan .College of Natural Sciences, Kanazawa University, Kanazawa 3,*ῌ ++3, , Japan / Centro de Investigación en Ecosistemas de la Patagonia, Coyhaique, Chile 0 Graduate School of Life and Environmental Sciences, University of Tsukuba, Ibaraki-*/ῌ 2/1, , Japan 1 Department of Global Environment Studies, Hiroshima Institute of Technology, Hiroshima1-+ῌ /+3- , Japan 2 Department of Civil Engineering, Kitami Institute of Technology, Kitami*3*ῌ 2/*1 , Japan 3 Department of Environmental Science and Technology, Meijo University, Nagoya.02ῌ 2/*, , Japan +* Research Institute for Global Change, Japan Agency for Marine-Earth Science and Technology, Yokosuka,-1ῌ **0+ , Japan ++ Graduate Student, Graduate School of Environmental Studies, Nagoya University, Nagoya.0.ῌ 20*+ , Japan +, Graduate Student, Graduate School of Earth Environmental Sciences, Hokkaido University, Sapporo*0*ῌ *2+* , Japan +- Dirección de Aguas, Ministerio de Obras Públicas, Santiago, Chile

(Received November+2 , ,*+* ; Revised manuscript accepted February . , ,*++ )

Abstract

The Glaciological Research Project in Patagonia (GRPP),**0ῌ ,**3 was carried out with several objectives at Glaciar Perito Moreno of the Hielo Patagónico Sur (HPS), in the area of the Hielo Patagónico Norte (HPN) and along the Pacific coast. At Glaciar Perito Moreno, hot water drilling was carried out at about/ km upstream from the terminus, reaching the glacier bottom at ca./+/ m, in order to monitor subglacial water pressure. Good positive correlations among air temperature, subglacial water pressure and glacier flow speed were found. Based on+. C dating of tree and organic samples, it is proposed that Glaciar Perito Moreno made two Little Ice Age (LIA) advances at AD+0**ῌ +1**and ca. +-*ῌῌ +** y BP (AD +2,* /* ). Fan deltas located at the mouth of big rivers around Lago General Carrera (Buenos Aires) and Lago Cochrane (Pueyrredon), in the area east of the HPN, were investigated to elucidate their development. The variations of,+ outlet glaciers of the HPN elucidated from aerial surveys for ,**. / */ῌ ,**2/ *3 revealed an areal loss of 2 . 01 km, in four years. A general slowing down of retreats was observed with a few exceptions. Meteorological measurements at Glaciar Exploradores of the HPN from,**/ to ,**3 indicate that air temperature ranged from +1 . .῍ῌ῍ to +* . / . The total annual precipitation was about-*** mm. Glacier surface melt was observed at two spots. Sediment and water discharges from the glacier showed that while water discharge fluctuated a lot, suspended sediment concentration was rather stable in summer. A single channel seismic profiling during the JAMSTEC MR*2ῌ *0 cruise identified a probable submerged moraine formed before the last glacial maximum (LGM) in the Golfo de Penas, south of Taitao Peninsula. Piston coring along the Chilean coast further indicates that ice-rafted debris recorded the LGM and earlier Late Pleistocene events of the glacial advance.

Key words: Patagonia Iceﬁeld, Glaciar Perito Moreno, glacier variation, Glaciar Exploradores, Mirai*2ῌ *0 cruise 2 Bulletin of Glaciological Research

countries, Chile and Argentina (Fig.+ ). It stretches +.Introduction over ca./.* km with the width ranging from ca. 2 km to0* km. At present it comprises two separate ice This is a general, summary report of ‘The Glaci- bodies, Hielo Patagónico Norte (Fig., ) with an area of ological Research Project in Patagonia’ (GRPP),**0ῌ ca. -3/* km, (Riveraet al. , ,**1 ) and Hielo Patagónico ,**3(Project No. +2,/+**, ), which was the continuation Sur (Fig. - ) with an area of ca. +,//* km, in ,**3 (P. of the project that started in+32- and has been Skvarca, pers. comm.). Together it is the largest tem- making great contributions to the better understand- perate ice body in the Southern Hemisphere. The ing of the Hielo Patagónico (Patagonia Icefield,i.e. , HPN has,2 outlet glaciers, while the HPS has .2 outlet Nakajima,+32/ , +321 ; Naruse and Aniya, +33, , +33/ ; glaciers. The HPS has the largest glacier in the Ameri- Aniya and Naruse,,**+ a, ,**+ b; Aniyaet al. , ,**/ ; cas, Glaciar Pío XI with an area of ca. +,/* km, . Two Aniyaet al. ,,**1 b). other glaciers, Viedma and Upsala exceed2** km, in In the course of fieldwork, the initial objectives of area. The outlet glaciers have been in general re- the project had to be slightly modified and the final treating since+3./ , with two exceptions in the HPS. objectives became as follows: Glaciar Pío XI has been more or less advancing, and (+ ) Mechanism of short-term flow speed variation of Glaciar Perito Moreno has been stable (Aniyaet al. , Glaciar Perito Moreno, Hielo Patagónico Sur (HPS,+331 ). Southern Patagonia Icefield), The variation of,+ major outlet glaciers of the (, ) Little Ice Age (LIA) advance of Glaciar Perito HPN has been closely monitored since+3./ (i.e. , Aniya Moreno,+33, , ,**+ , ,**1 ; Aniya and Wakao, +331 ) and varia- (- ) Lake-level changes and fan delta evolution of tions were updated to,**2 / *3 from aerial surveys in glacial lakes in the area of the Hielo Patagónico Norte this project. The variations of.2 outlet glaciers of (HPN, Northern Patagonia Icefield), the HPS were elucidated using a Landsat mosaic and (. ) Continued monitoring of glacier variations of the aerial photographs for+3./ῌ +320 by Aniyaet al. ( +331 ), HPN, and and some of them have been updated using satellite (/ ) Late Pleistocene glacial advances in Patagonia images such as Radarsat (Aniyaet al. ,,*** ), Landsat recorded in the ice-rafted debris from o# shore piston (Skvarca and De Angelis, ,**, ), and ALOS (Aniya coring along the Chilean coast.et al. ,,**2 , ,**3 ). In the original proposal, we listed another objective: ‘A mass balance study at Glaciar Ste# en of the ,,. Glaciar Perito Moreno, HPS HPN’, through ice coring, flow velocity and ice thick- Glaciar Perito Moreno is located at/*ῌ -*ῌ S and ness measurements and meteorological observations.1-ῌ W on the east side of the HPS (see Fig. - ), with an A mass balance study at an outlet glacier of the area of,/2 km, and an AAR (Accumulation Area Ra- Patagonia Icefield is one of the major topics that still remain to be challenged, because due to the harsh environment and di$ cult access, the continuous field measurements of snowfall/ablation in the accumulation area have not been carried out yet. The source area of Glaciar Ste# en, the third largest in the HPN, lies to the west of Cerro Colonia (--0/ m), the second highest mountain in the HPN. However, due to many unforeseen di$ culties, we had to regrettably give up this objective. On the other hand, a project of o# shore piston coring, SeaBeam and single-channel seismic profilings along the Chilean Patagonia coast was added because this project, which one of the CIs, Anma, proposed to the JAMSTEC (Japan Agency of Marine-Earth Sci- ence and Technology) using Research Vessel ‘Mirai’ , was approved for,**2ῌ ,**3 .

,. Study Area

,+. Hielo Patagónico The Hielo Patagónico is located at the southwest- ern end of South America, between latitudes .0ῌ -*ῌ and/+ῌῌ -*ῌῌ S along longitude 1- -* W, straddling two Fig.+ . Location of Hielos Patagónicos, South America. ANIYA et al. 3

Fig., . Satellite image of the Hielo Patagónico Norte, with glacier names (Landsat TM mosaic, March+, , ,**+). A rectangle indicates the area of Glaciar Exploradores where meteorological and hydrological measurements were carried out. Fig.- . Hielo Patagónico Sur (Landsat TM mosaic, March+, , ,**+ ), with the study area, Glaciar Perito Moreno indicated. tio) of* . 1- (Aniyaet al. , +330 ). It terminates in Lago Argentino with two calving fronts, one in Brazo Rico to the south and the other in Canal de los Témpanos to tion, extensive glaciological and geophysical studies the north. The glacier is known for repeated ad- were carried out on glacier dynamics and mass bal- vances and subsequent snout collapses that started ance (e.g. , Rott et al. ,+332 ; Stuefer, +333 ; Stuefer et al. , around the turn of the,*th century (e.g. , Mercer, +30, ; ,**1 ), as well as glacier flow by radar interferometry Aniya and Skvarca,+33, ). Since a neighboring gla- (Michel and Rignot, +333 ). The contrasting behavior cier to the north, Glaciar Ameghino, whose accumula- of Glaciar Perito Moreno and Glaciar Ameghino was tion area is situated in the same topographic setting discussed (e.g. , Nichols and Miller,+3/, ; Warren, +33. ). as Glaciar Perito Moreno, has been retreating, we do not know thoroughly yet the causes and mechanisms ,-. Glaciar Exploradores, HPN of rapid, repeating advances and retreats (i.e. , Nichols Glaciar Exploradores is located at.0ῌ -*ῌ S and and Miller,+3/, ; Aniyaet al. , +331 ) 1-ῌ +*ῌ W on the north edge of the HPN (see Fig. , ). Since the access to Glaciar Perito Moreno is rela- The accumulation area lies on the north wall of Monte tively easy, many studies were carried out at this San Valentin, the highest mountain in Patagonia with glacier, and the GRPP has been carrying out research-3+* m, and hence it is not directly connected to the here since+33* , in order to understand the mechanism icefield. The area is ca.+,+ km, with an AAR of * . 00 of the repeated advances and retreats (e.g. , Aniya and (Aniya,+322 ). The snout is heavily covered with debris Skvarca,+33, ; Naruseet al. , +33, ; Naruse et al. , +33/ a; and the snout position has not substantially changed +33/b; del Valleet al. , +33/ ; Takeuchi et al. , +330 ; Skv- since +3./ . However, ice thinning has been consider- arca and Naruse,+331 ; Naruseet al. , ,**+ ; Iizuka, et al. , able since the +33* s and it is a matter of time before it ,**.; Skvarcaet al. , ,**. ; Aniya et al. , ,**1 b). In addi- will commence a rapid recession. A GRPP carried 4 Bulletin of Glaciological Research out extensive research at this glacier between,**- every hour with a sensor (Vaisala, HMP -/ AC) in- and,**/ (Aniyaet al. , ,**1 a, ,**1 b), in which we initi- stalled at , m above a rock surface at the shore of ated meteorological and hydrological measurements Brazo Rico approximately/** m from the glacier front that have been continued to today. (Fig.. ). The flow speed at GPS+, and GPS varied in a clear -. Research at Glaciar Perito Moreno diurnal manner during the study period (Fig./ a). The speed variations at GPS- were smaller than the -+. Short-term flow speed measurements and hot water others, but diurnal signals are recognizable. The drilling at Glaciar Perito Moreno daily maximum and minimum speeds were observed -++. . Introduction in the afternoon and in the early morning, respec- Glaciar Perito Moreno is a fast flowing calving tively. The diurnal flow speed variations have been glacier in the HPS. The glacier flows at a rate῎.** m aῌ+ observed before at several hundred meters from the in the region extending+* km from the terminus, margin of Glaciar Perito Moreno (Naruseet al. ,+33/ a); dissipating approximately.**῍ +*0+ t aῌ of ice by calv- but this study provides the first detailed data set of ing into proglacial lakes, Brazo Rico and Canal de los short-term glacier flow changes in Patagonia. The Témpanos (Fig.. ) (Rottet al. , +332 ). The glacier bed mean flow speeds over the measurement period are is several hundred meters below the lake level in the+-1 . m dῌῌ++ (GPS + ), *2. . m d (GPS , ) and *+/ . m d ῌ + (GPS - ), terminus region (Stueferet al. ,,**1 ), which implies the which agree with the previous studies in this region subglacial water pressure is consistently high. Thus, (Rottet al. ,+332 ; Michel and Rignot, +333 ; Stuefer, it is expected that a large portion of the glacier motion+333 ; Stueferet al. , ,**1 ; Floricioiu et al. , ,**2 ; Ciappa is due to sliding or sediment deformation occurring atet al. ,,*+* ). The diurnal flow speed variations were the glacier bed. Dynamics of such a glacier terminat- correlated with air temperature (Fig./ b). This obser- ing in water is of great importance in the field of vation suggests that surface melt water elevated sub- glacier research as many calving glaciers are rapidly glacial water pressure during the day, resulting in retreating and thinning in Patagonia (e.g. , Aniya et al. , acceleration in the basal ice flow. The close correla- +331; Aniya, +333 ; Rignotet al. , ,**- ) as well as in Alas- tion between the flow speed and temperature is proba- ka (e.g. , Boyce et al. ,,**1 ), Greenland ( e.g. , Thomas bly due to the water pressure variations above a et al.,,**3 ) and Antarctica ( e.g. , Wingham et al. , ,**3 ). certain level, which is maintained by hydraulic con- Despite the importance of the subject, detailed study nections to the lake. Observations in other glaciers on the glacier dynamics is lacking in Patagonia. To have shown that pressure dependence of basal flow better understand the calving glacier dynamics, par- speed increases as water pressure approaches ice over ticularly the role of subglacial hydraulic conditions on burden pressure (Iken and Bindschadler,+320 ; Jansson, short-term flow variations, we carried out high fre-+33/ , Sugiyama and Gudmundsson, ,**. ). quency GPS ice-flow measurements on Glaciar Perito Moreno in,**2 / ,**3 and ,*+* (Feb.-Mar.) austral sum- -+-. . Hot water drilling mer seasons. The GPS measurements in,*+* were To test the hypothesis described above, hot water accompanied by subglacial water pressure measure- drilling was carried out in the next season from Feb- ments in two boreholes drilled to the glacier bed. ruary to March,*+* . A hot water drilling system This was the first subglacial observation in Patagonia. developed in the Institute of Low Temperature Sci- ence, Hokkaido University was exported to Argentina -+,. . Short-term flow speed measurements and approximately+*** kg of materials were trans- From December,2 , ,**2 to January 2 , ,**3 , we ported to the glacier by a helicopter. Two boreholes installed three GPS receivers (Leica System+,** ) on were drilled to the glacier bed through/+/ -m-thick ice the glacier surface at about/ km upglacier from the in the vicinity of GPS+ . Measurements in the bore- terminus (GPS+-ῌ in Fig. . ). We mounted GPS an- holes showed that the subglacial water pressure was tennae on the top of the poles to record the L+, and L more than3*ῌ of the ice overburden pressure and GPS signals every hour for-* minutes. The collected very small pressure fluctuation was driving the diur- data were processed in a static mode with those from nal flow speed variations. These results confirm the a GPS fix station established on a stable boulder on a hypothesized mechanism of the diurnal flow speed lateral moraine (see Fig.. ). The positioning accu- variations. Details of the hot water drilling on Gla- racy was several millimeters according to control ex- ciar Perito Moreno were described in Sugiyama et al. periments under similar conditions (Sugiyama and (,*+* b) and borehole measurements will be presented Gudmundsson,,**. ; Sugiyamaet al. , ,*+* a). Three- elsewhere. dimensional positions of the poles were filtered in (carried out by Sugiyama, Skvarca, Naito, Enomoto, time with a Gaussian smoothing routine and ice flow Tsutaki, Tone and others) speed was computed from the horizontal components of the displacements. Air temperature was measured ANIYA et al. 5

(Mercer,+30, ). The glacier is regarded to be more or less stable since the+3.* s (Aniya and Skvarca, +33, ; Stueferet al. ,,**1 ). Although there is a very distinctive vegetation trimline on both sides of the glacier, and on the shore of Brazo Rico in which the glacier front calves, there has been no study that has tried to address the age of these vegetation trimlines. It seems that the age of the vegetation trimline above the glacier has been casually assumed to be of the Little Ice Age: however, the actual age of the LIA is not known. The LIA advances in the Patagonia have been Fig.. . Satellite image of Glaciar Perito Moreno studied at only several outlet glaciers, from which showing the locations of the GPS stations (῎ ), the advances at AD+0**ῌ +1** and the late +3th century temperature sensor (῏ ) and the hot water drilling have been in general recognized (e.g. , Nichols and site (ῌ ) (Image courtesy of the Image Science & Miller,+3/+ ; Aniya, +33/ , +330 ; Aniya and Naruse, +333 ; Analysis Laboratory, NASA Johnson Space Harrison and Winchester,,*** ; Aniya and Shibata, Center). The arrows are the mean ﬂow velocity ,**+; Aniyaet al. , ,**1 a). Masiokas et al. ( ,**3 ) pro- for the period from December-+ , ,**2 to January 1, ,**3 (scale indicated by /** m a῍+ ). vided a thorough review of this subject. From these LIA studies, it appears that during the LIA some glaciers made two advances; however, we still need more studies at individual glaciers before the LIA ages in Patagonia can be ﬁrmly established.

-,,. . Vegetation trimline around Brazo Rico Along the shoreline of Brazo Rico, there is a pro- minent vegetation trimline at ca.,- . / m (Stuefer, +333 ) above the present lake surface, below which completely bare bedrock is exposed. Because the trimline is completely level, it is apparent that it was formed during the prolonged stage of high water level of Brazo Rico, which was undoubtedly caused by damming due to glacier advance. In order to wash away soils developed on the bedrock completely, water must have stayed for a long time at this level. A comparison of+3.1 and +302 aerial photographs taken by the Instituto Geográﬁco Militar of Argentina and the damming record of+3/.ῌ /0 (Mercer, +30, ) indicate that the present vegetation trimline was formed during the+3/.ῌ /0 damming when the lake level was the highest after+3.1 , because the vegetation trimline on Fig./+- . (a) Ice ﬂow speed at GPSῌ and (b) air the+3.1 photograph was lower than that on the +302 temperature from December,2 , ,**2 to January 2 , photograph. ,**3. On the west shore of Brazo Rico, near the glacier, there is a fan delta below the trimline, on which litters -,. Little Ice Age advance of Glaciar Perito Moreno of large dead trees (Diameter at Breast Height: /*ῌ 1* -,+. . Introduction cm) are scattered, with some still standing. These Glaciar Perito Moreno is very easy to reach and is trees indicate that there was once a warm period that probably the most-studied glacier among more than lasted long enough to develop such a forest on the fan seventy outlet glaciers in Patagonia (see Sec.,, . ). delta, and they were subsequently killed by submer- Most of these studies focused on the variation of sion in water. terminus in the,*th century, with some focusing on So if we know when these trees were killed by glacier dynamics. Glaciar Perito Moreno started ad- high water that was caused by glacier advance, we vancing around the turn of the,*th century and since may be able to infer the age of glacier advance. On then, it has repeatedly made advances and retreats, this premise, four wood samples were taken for+. C thereby reaching the opposite bank, Peninsula Magal- dating in,**1 (Fig. 0 ). Three samples out of the four lanes, and damming up the southern lake, Brazo Rico yielded the identical calibrated ages of AD+0/* . 6 Bulletin of Glaciological Research

and a conventional radiocarbon age of+*, y BP; ( , ) water-submerged and killed tree in a pond that was formed by damming of a stream from hillslope by newly-formed lateral moraine, yielding a calibrated age of AD+02* ; and ( - ) organic matter deposited or wood piece embedded in water pond that was formed by a lateral moraine, with conventional radiocarbon ages of+*3 y BP and ++* y BP. In,*+* , beside the aforementioned samples, four additional samples were taken. Two wood samples taken at the trimline yielded a calibrated age of AD +02*, and a conventional radiocarbon age of +,1 y BP. The latter is located very close to a,**2 sample that yielded a conventional radiocarbon age of+*, y BP. Fig.0 . Location of+. C sampling at Glaciar Perito Another two wood pieces were collected from scat- Moreno, with ages (conventional radiocarbon age tered tree litters on a lateral moraine by the glacier indicated with y BP). Dots indicate samples taken surface, which were brought to the surface and depos- in Dec.,**1 , triangles indicate those in Dec. ,**2 , ited by thrusting from the glacier bed. Because tree and white dots are those in Feb.,*+* (Satellite image, ALOS PRISM, March,2 , ,**2 , courtesy of litters here are very extensive, they were probably JAXA). killed en masse by advancing glacier and subsequently incorporated into the glacier and transported Since one sample showed anomalous age (modern), sub/en-glacially to the present site before emerging another sample was taken from the same tree in,*+* , onto the surface by thrusting. Their calibrated ages which yielded a calibrated age of AD+00* . At the are AD +00* and AD +./* . same time in order to reinforce the data, another tree in the same area was sampled in,*+* ; one from the -,.. . Conclusion center (core) and another from the surface of the tree, From these ages, it appears probable that Glaciar yielding the identical calibrated ages of AD+0/* . A Perito Moreno made two LIA advances at AD +0**ῌ sample taken in,**2 from a dead but still standing +1** and +-*ῌῌ +** y BP (probably equivalent to AD +2,* tree almost next to the glacier yielded a calibrated age/* ). While the first LIA advance is similar to the of AD+02* . These ages indicate that the trees were neighboring Glaciar Ameghino, the second advance is killed by the same event, that is, water submersion o#-*/* by aboutῌ years. This is not significant, how- due to damming by advancing glacier. ever, if we consider that variations of both glaciers at Aniya (+330 ) recognized two rows of terminal mo- present are independent. raines at Glaciar Ameghino that is located several (carried out by Aniya and others) kilometers north of Glaciar Perito Moreno and obtained an age of the outer moraine to be around AD .. Research at Hielo Patagónico Norte Area +0**ῌ +1**. The inner moraine is probably correlated to an advance around AD+21*ῌ 2* of Nichols and Miller .+. Lake-level change and fan delta evolution of glacial (+3/+ ), indicating that there were two LIA advances at lakes in the area east of the HPN Glaciar Ameghino. Because the accumulation areas .++. . Introduction of Glaciar Perito Moreno and Ameghino are located in During the retreat of the Patagonia Ice Sheets the same topographic situation next to each other, it since the Last Glacial Maximum (LGM), large mo- could have been possible that both glaciers advanced raine-dammed lakes developed along their eastern at a similar time, that is, around AD+0**ῌ +1** . The margins such as Lago General Carrera/Lago Buenos ages AD+0/* , +00* and +02* perfectly fit into this age Aires (hereafter LGC/LBA) and Lago Cochrane/Lago bracket of the LIA. Pueyrredon (hereafter LC/LP). Many rivers empty into these lakes and form lacustrine fan deltas at their -,-. . Vegetation trimlines at Glaciar Perito Morenomouths (Glasser et al. ,,**/ ). Raised or stepped fan There are two trimlines on the bank slope of deltas are also found at the mouth of these rivers. Glaciar Perito Moreno, one very distinctive and the Turneret al. (,**/ ) and Bell ( ,**2 ) reported the lake- other less distinctive below it. In order to check level fluctuation and evolution of these deltas. How- those ages obtained for the lake trimline, we collected ever, there are still many questions,e.g. , the timing, in,**2 seven samples for+. C dating from those associ- frequency and magnitude of lake-level falling and the ated directly with the glacier advance: (+ ) trees up- resultant landform evolution around the lakes. Aoki rooted by lateral moraines formed by advancing gla- and Hori have investigated the characteristics of the cier, yielding calibrated ages of AD+0/* and AD +1+* , fan deltas around both lakes by field survey, aerial ANIYA et al. 7 photograph interpretation, and terrain analysis (Fig. The eastern margin of LGC/LBA is dammed up 1). We also discussed the relationship between the by the Fenix moraine system formed by an ice lobe evolution of the fan deltas and lake-level change by from the Patagonia Ice Sheet during the LGM (Kaplan taking into account the age and the height of relatedet al. ,,**. ). The height of this moraine system is landforms such as terminal moraines located by and approximately./* m a.s.l. There is a wind gap on the around the lakes. Field surveys were conducted Fenix moraine system toward the Atlantic Ocean. from,**0 to ,**2 to investigate morphology and de- The altitude of the gap bottom is around.** m a.s.l., posits of fan deltas, fluvial terraces and related land- suggesting that the water of the LGC/LBA had an forms around both lakes.

.+,. . Lago General Carrera/Lago Buenos Aires The classification of the fan deltas was mainly based on aerial photograph interpretation. Aerial photographs were taken by Servicio Aerofoto- gramétrico (SAF), Chile in+31* . A map with / -m contour interval was produced from the Shuttle Ra- dar Topography Mission-Digital Elevation Model (SRTM-DEM). The present and emergent fan deltas are classified generally into three levels including the present one (Fig.2+,- ), which we call fan delta , , and in descending order. Notably, fluvial terraces cutting into the surfaces of the fan deltas+, and are not observed clearly along the rivers. The altitude of the terminal edge of the fan-delta+ lies between -2* and ..* # m a.s.l. The elevation di erence between the Fig.1 . Study area around Lago General Carrera edge and the surface of the fan delta,1* is about to (Buenos Aires) and Lago Cochrane (Pueyrredon) +** m. and the location of Fig.23 and Fig. .

Fig.2 . Aerial photographs showing fan deltas at the mouth of major rivers emptying into LGC/LBA: (a) Río Los Maitenes; (b) Río Avilés; (c) Río Ibáñez; and (d) Río Avellano. Emergent and modern fan deltas named as fan deltas+, , , and - are labeled. The photographs were taken in+31* . 8 Bulletin of Glaciological Research outlet to the Atlantic Ocean when the lake level stayed above.** m a.s.l. We obtained two radiocarbon ages related to the evolution of the fan delta+ . One age, +1-1* cal y BP obtained from the soil block taken from gravel layer of the fan delta+ , indicates the maximum age of the end of gravel layer deposition and the emergence of the fan delta+ . The other age, 2.** cal y BP obtained from aeolian deposits overlying the fan delta+ indicates the minimum age of the fan delta+ . The development of the fan delta, can be inferred based on the moraines found on the fan delta, of the Río Aviles. Douglasset al. (,**/ ) suggested the formation ages of these moraines at ca.2/ . and 0, . ka with the cosmogenic surface-exposure ages (+* Be and -0 Cl). These ages indicate the minimum age of the emergence of the fan delta, .

.+-. . Lago Cochrane/Lago Pueyrredon Several emergent fan deltas as well as the present fan deltas are distributed along LC/LP. Topographic continuity of the emergent fan deltas, however, is poor and the altitude of the emergent fan-delta terminal edge shows no systematic trend. For example, in Figure3 a, three to four emergent fan-delta terraces are identiﬁed, with their edge altitudes approximately 0*/, ./* , -./ , and +0/ m a.s.l. On the other hand, only Fig.3 . Aerial photographs showing fan deltas at the one emergent terrace can be recognized clearly in mouth of rivers (no names) emptying into LC/LP. 3 -,/ Figure b, with terminal edge at ca. m a.s.l. The photographs were taken in+31* .

.+.. . Reconstruction of lake-level changes The distribution of the raised and present fan del- that rapid, large drawdowns had also occurred repeat- tas by the LGC/LBA indicates that a large drop of the edly. Unfortunately, however, we cannot discuss the lake level had occurred at least twice. The edge of the timings due to the lack of absolute ages about the emergent fan deltas registered roughly the paleolake landforms and their deposits. level. Therefore, it is considered that two past lake Some previous studies (e.g. , Turner et al. ,,**/ ) levels stayed at around.** m a.s.l. and -** m a.s.l. As discussed the LGC/LBA and LC/LP had united after the present lake level is located at about,** m a.s.l., the the LGM. The altitudes of the fan deltas by these magnitude of each lake-level falling reached ca.+** m. lakes, however, do not show the matching similarity The rate of lake-level falling was probably very rapid, to each other. Thus, it is unlikely that the two lakes because the emergent fan deltas have steep escarp- had coalesced. The outlet glaciers on the east side of ments at the front and fluvial terraces cutting into the the HPN separated these lakes. Moreover, the ad- fan deltas+, and are unclear along the rivers. vance and retreat of these glaciers would have infl- The timings of the lake-level fallings are estimated uenced the drainage of lake waters. The shape of the based on the radiocarbon ages and cosmogenic surface- edge of the fan deltas and terraces along the rivers exposure dating as follows. The older lake level drop that incised the fan deltas indicate that the lake level occurred between+1 and 2 . . ka. In addition, a model- changed very quickly as if outburst flood(s) had oc- ing of the ice sheet extent during the LGM and the curred. So, further information on the changes in the subsequent deglaciation of the HPN showed that a HPN glaciers and an evidence for an outburst flood rapid collapse occurred ca.+. ka (Hubbardet al. , ,**/ ). such as deposits need to be collected for the discussion These existing dates are concordant with our estimate of behaviors of these lakes. of the age of the fan delta+ . Moreover, they may (carried out by Aoki and Hori) restrict the beginning of the fan delta+ formation after +.ka. On the other hand, the younger dropping is .,. Glacier variations of the HPN, with an emphasis on probably soon after0, . ka, which is inferred from gla- between,**. / / and ,**2 / *3 cial advances at the Río Aviles (Douglasset al. ,,**/ ). .,+ . . Introduction Several raised fan deltas around LC/LP suggest During this project, three aerial surveys of the ANIYA et al. 9 snouts of,+ outlet glaciers were carried out over the HPN; March/ , ,**1 (representing austral summer season,**0 / *1 ), March +1 , ,**2 (likewise ,**1 / *2 ) and January++ , ,**3 (likewise ,**2 / *3 ). An aerial survey for the austral summer season,**3 / +* could not be carried out due to unforeseen circumstances. Using these oblique aerial photographs, the position of the snout was mapped onto the+ : /**** topographic maps with a/* -m contour interval published by the Chilean IGM (Instituto Geográfico Militar) as with before (i.e. , Aniya,,**1 ) Next, the snout-position map of,**0 / *1 (hereafter referred to as,**1 ) was overlaid onto the map of ,**/ that was produced in the previous GRPP project (Aniya,,**1 ), in order to elucidate the variation in two years between,**/ and ,**1 . Likewise, the maps of ,**1, ,**2 and ,**3 were overlaid onto each other in order to elucidate the yearly change of,**1ῌ ,**2 and ,**2ῌ ,**3. Because the yearly changes were rather small, the four-year variation of,**/ῌ ,**3 was also elucidated for discussion. In the course of locating snout positions in,**1 by comparing with those in Fig.+* . The HPN glacier variations for +3.. / ./ῌ ,**2 / *3 . ,**/, the snout positions in ,**/ of some glaciers (Gros- One tick on the right ordinate indicates an area - , se, Benito, HPN , Colonia, Cachet N, Soler, León and change of+ km (downward, decrease: upward, Fiero) were slightly modified, and the statistics for increase). Dot line indicates data missing between ,**-/ *.ῌ ,**. / */ changes were accordingly measured two dates. Broken lines are used to avoid con- again. These modifications, however, do not a# ect fusion of glaciers when lines are crossing at the any previous discussion in Aniya (,**1 ). As with same point. before, an area lost due to retreat and a distance glacier front retreated were measured. The follow- Rafael changed a little year to year; however, its posi- ing discussion is mostly based on the area loss rather tion was stable at where the width of the fjord widens. than the distance, because the glacier front normally It appears that the supply and waste of ice were retreats very irregularly and hence it is often very balanced at this position after,**. . Glaciar San Quin- di$ cult to use distance as a variation criterion for tin, the southern neighbor of Glaciar San Rafael, on discussion. the other hand continued a rapid retreat due to peri- Figure+* shows variations of the ,+ outlet gla- odic snout collapsing that started around +320 . It lost ciers of the HPN since+3.. / ./ , in which the new data a total area of . . +. km, in four years, which is by far obtained in this project were added to the previous the largest in the HPN. The snout in the proglacial data (Aniya,,**1 ). lake is heavily broken up now with splaying and crisscrossing crevasses and many patches of open .,,. . General trend water in the snout area, making the definition of the In general, the variation between,**/ and ,**3 snout outline very di $ cult. Since it has been produc- was rather small, compared with the previous varia- ing large, flat icebergs, the snout area is probably tions, except for a few glaciers such as Glaciar San floating or at least at near floating point. Quintin, Ste# en and Colonia. The total area lost in Another heavily calving glacier, Glaciar Ste# en, four years is2 . 01 km,,+ , or + . 01 km aῌ . This is consid- lost + . // km , in four years, with a yearly average of * . -ῌ erably smaller than the previous years after,*** (i.e. , * . . km, . These rates are more or less similar to the Aniya,,**1 ). For example, an area loss for ,**.ῌ ,**/ previous years, indicating that heavy calving and was/0* . km, . There are five glaciers whose variation rapid recession continued, which started around,*** . was nil or substantially nil: Glaciar Reicher, San Ra- Glaciar Colonia has lost a large area of*13 . km, in four fael, Arco, Cachet and León. years, the third largest among the HPN outlet glaciers. A large retreat started in,**.ῌ ,**/ when it lost * . 2+ .,-. . Discussion of variation characteristics of some km, in one year (Aniya,,**1 ). This is probably due to glaciers prolonged thinning that resulted in snout floating (or Again the behaviors of the two largest glaciers of near floating). This thinning probably induced unex- the HPN, Glaciar San Rafael and San Quintin were pected sudden drainages of Lago Cachet Dos, which is very contrasting. The frontal shape of Glaciar San dammed by Glaciar Colonia at the left side. Lago 10 Bulletin of Glaciological Research

Cachet Dos has an outlet stream that ﬂows in a rocky to disintegrate at any moment. The previous snout valley located on the east side of Glaciar Colonia and collapse was observed during,*** / *, (Aniya, ,**1 ). drains into Lago Colonia. Due to excessive thinning of Glaciar Colonia, the glacier was uplifted by the .,.. . Future trend hydrostatic pressure of Lago Cachet Dos and water During the+31* s and +32* s, many glaciers became was suddenly drained subglacially under Glaciar Co- calving glaciers due to recession: however, due to lonia. It occurred ﬁrst time in April,**2 and since rapid recession during the late +33* s and ,*** s, some then water outburst occurred a few times; in October glaciers have become or are becoming land-terminat- and December,**2 , and March and September ,**3 , ing glaciers. Examples are Glaciar Reicher, Gualas, each time draining about,** million m- (Dussaillant HPN + , HPN , , Piscis, and Cachet N and S. On the et al.,,*+* ). other hand, Ste # en, Colonia, Nef, Soler and Fiero will Glaciar Grosse is one of the four heavily debris- continue to calve for a while. Slowing-down or vir- covered glaciers in the HPN and has been slowly tual stop of the retreat observed at a few glaciers may wasting in the proglacial lake that started to form suggest that the glacier terminus has reached the during the early+33* s. It does not calve at all: in- equilibrium with the diminishing supply of ice from stead it melts away in the lake in the following man- the accumulation area after the rapid recession ob- ner. Because of heavy debris-cover, surface melting served at many glaciers during the+33* s and early is very irregular and the glacier surface becomes pit-,*** s. ted or hummocky due to uneven surface lowering, (carried out by Aniya) thereby producing many supraglacial lakes/ponds. As these lakes/ponds enlarge due to continued melt- .-. Meteorological and hydrological characteristics of ing, they coalesce into each other to become larger Glaciar Exploradores, HPN and eventually breach the wall separating from the .-+. . Seasonal variations in air temperature and pre- proglacial lake, which as a result enlarges. Conse- cipitation quently, at times, there are many ice-mound islands in In order to clarify the characteristics of climate the proglacial lake. So it has retreated a sort of inter- conditions around Glaciar Exploradores of the HPN, mittently with a period of no change succeeding a an automatic weather station (AWS) was installed at period of retreat. It retreated ca.+** m between ,**/ the base camp (BC) site near the terminus at +2, m a.s.l. and,**1 , and ,/* m between ,**1 and ,**2 , but there (Fig. ++ ) in December ,**. (Aniyaet al. , ,**1 b). It has was no substantial change between,**2 and ,**3 . been monitoring air temperature and precipitation This is quite a contrast to another heavily debris- since then. Variations in the daily mean air tempera- covered, neighboring glacier, Glaciar Exploradores, ture and the daily sum of precipitation at BC from whose snout outline has remained the same although with considerable thinning. Probably when the thinning reaches at a critical stage (whatever), it will commence a rapid frontal retreat, by enlarging proglacial lake and coalescing supraglacial ponds. Glaciar Reicher and Gualas, which are located side by side on the northwest side of the HPN, made no change and a little change, respectively. The front of Glaciar Reicher is hanging, suggesting that it has reached the upper end of the proglacial lake, although the bedrock beneath cannot yet be seen. On the other hand, at the front of Glaciar Gualas, the bedrock becomes visible under the ice at either edge, and soon it will become a land-terminating glacier. The very irregular shape of the snout of HPN+ suggests that the proglacial lake is shallow with irregular bedrock protruding above water and the ice is thin. It will soon become a land-terminating glacier. HPN, did not change after ,**1 with the smooth front where the slope of glacier surface changed, suggesting that it has reached the upper end of the proglacial lake and become stable for the moment. Contrasting to HPN+, and HPN with which sharing the accumulation area, HPN- continued to retreat in the proglacial Fig.++ . Locations of meteorological and hydrological lake and as of,**2 / *3 the snout appeared to be ready stations on and around Glaciar Exploradores, HPN. ANIYA et al. 11

layer along the left side margin. At these two stations, the following were measured and recorded: global and atmospheric (incoming longwave) radiation, air temperature, relative humidity, and wind speed and direction. The surface melt at these sites was obtained by measuring the changes in stake heights, assuming that the density of the ice was3** kg mῌ- . In addition, the reflected shortwave radiation and out- going longwave radiation were measured and recorded at VE. . Fig.+, . Variations in the daily mean air temperature The meteorological conditions during the cloudy/ and the daily sum of precipitation at BC from ,**/ rainy days (Dec.,1 -Jan. - ) were a # ected by strong up- to,**3 . Arrows in the precipitation data indicate slope winds blowing from the Río Exploradores valley periods of data missing. into the glacier basin, and partially by weak glacier winds. As a result, the turbulent heat fluxes and the ,**/to ,**3 are shown in Figure +, . The annual net radiation at VE . were 0 . 0 and ++ . * MJ mῌῌ,+ d , mean air temperature in these years varied between respectively, on average, and the total heat source for 0. 2 and 1 . -῎ . Aniyaet al. ( ,**1 b) reported that the melting was +2 . 2 MJ mῌῌ,+ d on average. On clear monthly mean air temperature was the highest in days (Jan..1ῌ ), the strong stability due to weak gla- February and the lowest in August in,**/ . During cier winds resulted in a small contribution from the five years from,**/ to ,**3 , air temperature tended to turbulent heat fluxes ( , . - MJ mῌῌ,+ d ). The dominant be the highest in January or February and the lowest source for melting during this period was the net in July or August. The highest and the lowest values radiation (+. . 0 MJ mῌῌ,+ d ), and the total heat source of the daily mean air temperature during this period for melting was+0 . 3 MJ mῌῌ,+ d on average. Konya were+1 . .῎ῌ῎ (January ,/ , ,**2 ) and +* . / (July 2 , and Matsumoto ( ,*+* ) pointed out that a decrease in ,**1), respectively. There were only few days with a air temperature at the ablation area due to the devel- negative value of the daily mean air temperature at opment of the glacier boundary layer on clear days, BC (Aniyaet al. ,,**1 b). Even in the coldest winter of when air temperature on the outside of the glacier ,**1, the number of such days was only +- . There- tends to increase, will limit the application of the fore, melting can occur almost all through the year in glacier melt estimation method that uses the air tem- the ablation area of this glacier. perature at a nearest weather station for a large mari- The annual sum of measured precipitation at BC time glacier. was,13. mm in ,**/ (with ,3 missing days), ,221 mm in,**1 (no missing day), and ,3-1 mm in ,**2 ( ,2 .--. . Sediment and water discharges from the glacier missing days). The actual annual precipitation for A hydrological gauging station was installed to ,**/and ,**2 may have been nearly or over -*** mm. measure and record the water level of Río Deshielo, an Precipitation intensity was generally low (usually outlet stream from Glaciar Exploradores at a site quite lower than/ mm hῌ+ ) in this area; however, in con- close to the terminus (see Fig.++ ) in December ,**. . trast, the number of days with precipitation was quite Hourly stream discharge was calculated from the re- large. Konya and Matsumoto (,*+* ) reported that corded water level and the stage-discharge curve that daily precipitation larger than*/ . mm was observed in was obtained from nine discharge measurements more than one half of each month in,**/ and ,**0 at (Aniyaet al. , ,**1 b). In order to monitor the seasonal BC, except for February. variations in suspended sediment concentration (SSC) of the stream water, a turbidity sensor of back- .-,. . Glacier surface melt scattering type using an infrared ray was also in- The meteorological observations were carried out stalled at around-** m downstream from the gauging at two sites on the ablation area of Glaciar Explora- station during the following two observation periods: dores from December,1 , ,**0 to January 1 , ,**1 , in December +3 , ,**/ - April + , ,**0 and August +, , ,**0 - order to clarify how the di# erences in weather condi- December ,, , ,**0 . Eleven samples of stream water tions a# ect the surface heat balance of a large mari- were taken at the time of turbidity measurements time glacier (Konya and Matsumoto,,*+* ). Two me- during these two observation periods and filtered teorological stations were established on a flat surface with glass fiber filters (pore size῍*0 .m m) to obtain of the clean ice approximately, km upglacier from SSC. Then the measured turbidity was converted the terminus at a height of around,** m a.s.l. (see Fig. into SSC using a linear relationship between turbidity ++). One station, VE . , was located along the central and SSC. flow line, and the other station, VE+0 , was -* m from a Figure +- shows the variations in the daily and longitudinal ridge of ice covered with a thick debris hourly stream discharges and SSC of Río Deshielo and 12 Bulletin of Glaciological Research

ture of SSC variations implies the development of a shallow reservoir beneath the glacier in summertime where suspended sediment is once mixed completely and then transported out from the glacier with the stable concentration regardless of variations in discharge. Currently, however, we have absolutely no information on the subglacial environment of this glacier, with which to verify this hypothesis. (carried out by Matsumoto and Konya)

/.Submerged glacial landforms and Late- Pleistocene glacier advances in Patagonia recorded in ice-rafted debris along the Paciﬁc coast, o# Chile

Fig.+- . Variations in the daily mean and hourly /+. Introduction discharges, suspended sediment concentration of Río Deshielo, and the daily precipitation at BC Patagonian icefields are the only ones that are from July,**/ to December ,**0 . Estimated distributed in the middle latitude of the Southern values of the daily precipitation using data meas- Hemisphere. The Patagonian icefields are sensitive ured at Puerto Aysén, located+-* km north of in climate change, as evidenced by the recent glacier Glaciar Exploradores, are shown with gray bars. recessions (e.g. , Aniya,,**1 ), and provide representa- tive records of the past climate change of the South- the daily precipitation at BC. From December to mid ern Hemisphere. Traces of recessions and advances February in the first observation period, the stream of the Patagonian icefields after the Last Glacial Maxi- discharge varied between,* and 2* m-+ sῌ . It decreased mum (LGM) are recorded in glacial landforms such as to around.* m-+ sῌ in late February and then showed moraines (e.g. , Mercer,+310 ; Aniya, +330 ; Wenzens, some remarkable increases to larger than2* m-+ sῌ due+333 ; Hultonet al. , ,**, ; Heusser, ,**, ; Glasser et al. , to rainfalls in March. In spite of these large varia-,**2 , ,**3 ). However, the pre-LGM records are less tions in stream discharge, SSC was, in general, quite understood. During the LGM, the icefields extended stable during this period. It decreased gradually to the Pacific coast, and covered the coastal area and from around* . +/ g lῌῌ++ to around * . ++ g l showing the continental shelf (Hollin and Schilling, +32+ ; Sug- small sub-daily variations. denet al. ,,**, ; Rabassa and Coronato, ,**3 ). Thus, From austral late winter to spring during the sec- any glacier advance in the past, that is as significant ond observation period, the stream discharge slightly as the LGM event, may be recorded under the sea as varied between,* and -* m-+ sῌ with some increases to submerged glacial landforms or as deposition of ice- .* m-+ sῌ corresponding to rainstorms. It gradually rafted debris (IRD). During the MR*2ῌ *0 cruise of the increased in November and then varied between0* and R/VMirai of the Japan Agency of Marine-Earth Sci- +** m-+ sῌ in December. SSC in August varied be- ence and Technology (JAMSTEC) in March,**3 , we tween*+* . and *+/ . g lῌ+ , and then remarkably in- obtained acoustic data and piston core samples, and creased to*-/ . g lῌ+ corresponding to a small increase in investigated the marine records for the past glacier stream discharge in early September. In early and mid- advances from the Patagonian icefields. October, SSC decreased and remained around*+/ . g lῌ+ , but increased again to*-* . g lῌ+ in late October. Some /,. Acoustic data and submerged moraine in the Golfo other increases in SSC were also found in Río Deshielo de Penas after that; however, the ranges of variations became The study area extends from the sea o# the Tai- gradually smaller, while large variations were found in tao peninsula, the westernmost promontory of the stream discharge. Finally, SSC seems to have been Chilean coast, to the Cape Horn, through fjords devel- nearly stable at around*, . g lῌ+ in late December. oped along the west coast (Fig.+. ). Bathymetrical As a result, the relationship between the stream data were collected using SeaBeam,++, system on the discharge and SSC of Río Deshielo was found to be a R/VMirai. The bathymetry of the Pacific o# Chile is linear regression line with quite a high gradient for characterized by deep trench and narrow continental the period from austral winter to spring, which indi- shelf. Submarine fan deposits related to post-glacial cates high sediment erodibility and/or mobility in the rapid uplift were reported to distribute along the trench stream. Then the gradient becomes lower as the sea- (Bourgoiset al. ,,*** ). The continental shelf (depth to son progresses, and finally it becomes almost flat in ca.,** m) is poorly developed, and corresponds to the midsummer, indicating the stable SSC being inde- extent of the icefield during the LGM (Wenzens,+333 ; pendent of variations in stream discharge. This fea- Hultonet al. ,,**, ; Heusser, ,**, ; Glasser et al. , ,**2 ; ANIYA et al. 13

Sugdenet al. ,,**, ; Rabassa and Coronato, ,**3 ). Rela- careous bioclasts and peloids are also present but less tively large, flat surface was developed only in the Golfo than+/ῌ . Shell fragments were distributed at inter- de Penas (GP in Fig.+. ), which is an embayment near val ,.,ῌ ,1+ cm below seafloor (bsf), and at -2. cm bsf. the HPS. A single-channel seismic (SCS) study was A bivalve from,1+ cm bsf yielded a+. C age of /.,*῍ performed across the continental slope and extended to/* y BP. Thus, the average rate of sedimentation is the shelf during the cruise. The SCS image (Fig.+/ ) estimated at ca. * . / mm aῌ+ and the age of the core obtained from the edge of the continental shelf in the bottom must be as old as+,/** y BP. No IRD was Golfo de Penas indicates the presence of irregular, wavy observed. objects (sediments) thinning seaward to the west (leftPC*0 (Depth,,/3 m: CL, +.++ . * cm): PC *0 was obtained side in Fig.+/ ) underneath rather flat, smooth horizon- from the mouth of Fjord Baker. Sediments consist of tal surface of the seafloor. Assuming the seismic ve- dark greenish gray to dark gray silty clay to clayey silt. locity of the top part of the sediment to be+/ . km sῌ+ , the wavy sediments are approximately,* to /* m high and several hundred meters to ca., km wide. We interpret from their morphology that the wavy sediments represent a submerged terminal moraine field, although we have not obtained any back-up data to verify it. The overlying sediments are also,* to /* m thick. As discussed in the following section, the average rate of sedimentation is ca.*/ . to ca. +/ . mm aῌ+ in the Golfo de Penas. More than--*** years is re- quired to deposit/* m-thick sediments even at the fastest sedimentation rate (+/ . mm aῌ+ ). Thus, the presumed submerged moraine field must have been formed earlier the LGM.

/-. Sediment core samples and distributions of ice- rafted debris (IRD) The sampling sites for the piston coring are indicated in Fig.+. . Observation for visual core description (VCD) of core samples was made on split surface of working half sections (Figs.+0 and +1 ). IRDs were observed only in cores sampled from open sea (PC*1 and PC*3 ). Ages of sediments were estimated using+. C dating on fossils of bivalves and gastropods. Fig.+. . The study area: Hielos Patagónicos and the PC*/ (Depth,+3, m: Core length (CL), 0,. . * cm): PC */ surrounding area. T: Taitao Peninsula. GP: Golfo de Penas. LGM: Extent of the Last Glacial Max- was obtained from the center of the Golfo de Penas. imum (based on Caldenius,+3-, ; Bourgois et al., Sediments consist of silt and clay. Nannofossils, dia- ,***). SCS: Single-channel seismic image in Fig. toms and foraminifers are present (fewῌ ) throughout +/. Numbers starting with PC: Location of the the core. Neritic grains such as coarse-grained cal- piston core samples.

Fig.+/ . Single-channel seismic image of a submerged terminal moraine field with four large, main structures (indicated by arrows) buried by recent sediments beneath the seafloor (flat surface on top). The location of the SCS image is indicated in Fig.+. . The acoustic image is duplicated because of the multiple reflections between seafloor and sea surface. Vertical axis: two-way travel time (TWT in millisecond) of seismic P-wave. Transverse axis: point number used for common depth-point (CDP) gathering (a seismic data processing). One CDP interval is ca.,1 m. 14 Bulletin of Glaciological Research

Fig.+0 . An example of ice-rafted debris (IRD) in the core samples. IRDs are recognized as pebbles or cobbles in otherwise homogeneous ﬁne-grained silty clay in the PC*3 sample. Field of view ca. .* cm.

Shell fragments and bioclasts were distributed throughout the core. Bivalves from.12 cm bsf and +++/ cm bsf yielded+. C ages of./0*῍῍ /* y BP and 1/3* /* y BP, respectively. Thus the average sedimentation rate as fast as+/ . mm aῌ+ was calculated, and the age of the core bottom is estimated to be ca.30** y BP. No IRD was observed. PC*1 (Depth,+-22 m: CL, .3/ . 1 cm): PC *1 was collected from open sea o# the Taitao Peninsula. Biotur- bated, dark gray to dark greenish gray silty clay comprises sediments in the uppermost part (*./*ῌ . cm bsf) of the PC*1 . This surface layer is underlain by dark gray silty clay interbedded with very fine sand and silt that continue to the bottom of the PC*1 . This section typically develops few mm to cm thick fine layers of sand and silt throughout the section. IRDs were distributed at intervals+.,ῌῌ +02 cm and ,/* ,1/cm bsf. Below around -0* cm bsf, we did not ob- Fig.+1 . Visual core description for PC *3 . IRDs (marked serve any bioclasts or microfossils. So far, no age by open diamond) are distributed above10* cm data is available from this core. below seafloor.+. C ages of bivalves indicate that the PC*2 (Depth,//2 m: CL, 1.3 . 1 cm): PC *2 was obtained PC*3 contains more than /**** -year records. from the mouth of the Magellan strait. Most sediments consist mainly of siliciclastic grains of clay to core.Puncturella sp. from++. cm bsf yielded a+. C age sand size. Bioclasts are frequently observed and are of+2+-*῍ 3* y BP. Archbenthal bivalves from /,1 cm the predominant component at interval ca.,**ῌ -** cm bsf (Yoldia a # . hyperborea Loven) and 2*+ cm bsf ( En- bsf. Nannofossils and foraminifers were observednucula sp.) were beyond the detection limit of+. C and throughout the PC*2 . No IRD was observed. An older than .-/** y BP. The average rate of sedimen- archbenthal bivalve from1.+ cm bsf yielded a+. C age tation was estimated at * . , mm aῌ+ . The age of the of3/+*῍ 0* y BP. Thus, the average rate of sedimen- core bottom must be at least, as old as/-/** y BP. tation is ca.*2 . mm aῌ+ . IRDs are distributed down to10* . * cm bsf and thus, we PC*3 (Depth,02. m: CL, 331 . , cm): PC *3 was collected detected Late Pleistocene events of glacier advances from the Drake strait, o# the Cape Horn. The surface from the marine sediment cores. layer is++ cm-thick light gray fine to medium fora- minifer sand of the Holocene age (Shiroya, per. /.. Summary Comm.), and is di# erent from underlying thick layer We found a first evidence for probable submerged of dark gray clayey silt with lenses and layers of fine terminal moraines formed before the LGM in the sand (interval++ . *ῌ 10* . * cm bsf) (see Fig. +1 ). This Golfo de Penas. However, there was no IRD in the section is heavily bioturbated and frequently contains cores obtained from the Golfo de Penas (PC*/ and PC IRDs throughout the section. This section is under-*0 ). IRDs were recognized in the o # shore region in lain by very fine sand with parallel lamina, distributed the same latitude (PC*1 ), but ages are unknown. In at interval10* . *ῌ 120 . , cm bsf. Below the sand layer, the southern latitudes, IRDs were more frequently no ice-rafted debris was observed. Interval120 . ,ῌ distributed (PC *3 ), that were deposited during the 331. , cm bsf is composed of dark greenish gray silt and Late Pleistocene. very fine sandy silty clay with bioturbation. Fora- (carried by Anma, Aniya and the JAMSTEC MR*2ῌ *0 minifers, nanno-fossils and sponge spicules were ob- Cruise Shipboard Scientific Party) served throughout the core. Shell fragments were distributed throughout the ANIYA et al. 15

research project in Patagonia in+332 and +333 : Holocene Acknowledgments: glacier variations and their mechanism. Bull. Glacier Res.,+2 ,1+ῌ 12 . Aniya, M. and Naruse, R. (eds.) (,**+ b): Glaciological and This research was funded by the Japanese Minis- Geomorphological Studies in Patagonia,+332 and +333 . try of Education, Science, Sports and Culture, Grant- Rapid Printing Center, Sapporo.,*0 p. ,**+ in-Aid for Scientific Research (A) (Project No. Aniya, M. and Shibata, Y. ( ): The Holocene glacial chronology of Río Soler valley, Hielo Patagónico Norte, Chile. +2,/+**, ,**0ῌ ,**3 ) for . Many individuals and or- In M. Aniya and R. Naruse (eds.), Glaciological and Geo- ganizations provided generous support for fieldwork, morphological Studies in Patagonia,+332 and +333 , 01ῌ 2- . without which we could not have accomplished the Aniya, M. and Skvarca, P. (+33, ): Characteristics and variations of Upsala and Moreno glaciers, southern Patagonia. research. Bull. Glacier Res.,+* ,-3ῌ /- . The drilling equipment was transported to and Aniya, M. and Wakao, Y. (+331 ): Glacier variations of Hielo from the glacier by a helicopter operated by Gen- Patagónico Norte, Chile, between+3.. / ./ and +33/ / 30 . darmería Nacional Argentina. Hielo y Aventura S. A. Bull. Glacier Res.,+/ ,+2ῌ . # Aniya, M., Sato, H., Naruse, R, Skvarca, P. and Casassa, G. o ered logistic support during the field activity at (+330 ): Remote sensing application to inventorying gla- Glaciar Perito Moreno and Toshin S. A. organized the ciers in a large, remote area - Southern Patagonia Ice- transport of materials in Argentina. K. Shinbori of field. Photogramm. Eng. Remote Sensing,0, ,+-0+ῌ +-03 . ILTS, Hokkaido University, constructed mechanical Aniya, M., Sato, H., Naruse, R., Skvarca, P. and Casassa, G. (+331 ): Recent glacier variations in the Southern Pata- parts of the drilling system and the Institute of Low gonia Icefield, South America. Arct. Alp. Res.,,3 ,++,ῌ . Temperature Science, Hokkaido University, provided Aniya, M., Dhakal, A. S., Park, S. and Naruse, R. (,*** ): Varia- a support fund. For the aerial survey of the HPN tions of Patagonian glaciers, South America, using Ra- darsat and Landsat images. Canadian J. Remote Sensing, glaciers, Pilot Roberto León of Transportes Aereos ,0 (),0 /*+ῌ /++ . ‘Don Carlos LTDA’ based in Coyhaique always made Aniya, M., Satow, K., Skvarca, P., Anma, R., Aoki, T., Sawagaki, an excellent flight around and on the treacherous, T., Tanikawa, T., Naruse, R., Glasser, N. and Harrison, S. dangerous icefield. Francisco Croxatto and Tamara (,**/ ): Overview of Glaciological Research Project in Pata- gonia,**- . Bull. Glaciol. Res.,,, , +*3ῌ ++3 . Ullrich are thanked for their support for the meteoro- Aniya, M., Barcaza, G. and Iwasaki, S. (,**1 a): Recent glacier logical and hydrological observations at Glaciar Ex- advances at Glaciar Exploradores, Hielo Patagónico ploradores, HPN. RA’s thanks go, on behalf of the Norte, Chile. Bull. Glaciol. Res.,,. ,.3ῌ /1 . Shipboard Scientific Party lead by Drs. Natsue Abe Aniya, M., Enomoto, H., Aoki, T., Matsumoto, T., Skvarca, P., Barcaza, G., Suzuki, R., Sawagaki, T., Sato, N. Isenko, E., and Naomi Harada, to Captain Akamine of the JAM- Iwasaki, S., Sala, H., Fukuda, A., Satow, K. and Naruse, R. STEC R/V “Mirai” and his crew for their devoted (,**1b): Glaciological and geomorphological studies at e#*2*0 ort that lead the MRῌ expedition fruitful and Glaciar Exploradores, Hielo Patagonico Norte and Gla successful. The ALOS Prism image was provided by ciar Perito Moreno, Hielo Patagonico Sur, South Ameri- ca, during,**-ῌῌ ,**/ (GRPP *- */ ). Bull. Glaciol. Res.,,. , JAXA and RESTEC (Project number P+23***+ , PI 3/ῌ +*1. Aniya). Aniya, M., Barcaza, G. and Kamusoko, C. (,**2 ): Recent variations of some outlet glaciers of the Southern Patagonia Icefield, South America, using ALOS and Landsat data. Proceedings of the First Joint PI Symposium of ALOS References Data Nodes for ALOS Science Program in Kyoto, No- vember+3ῌ ,- , ,**1 , Kyoto, CD-ROM, . p. Aniya, M. (+322 ): Glacier inventory for the Northern Pata- Aniya, M., Barcaza, G., Kamusoko, C. and Iribarren, P.ῌ,**3 ): gonia Icefield, Chile, and variations+3.. / ./ to +32/ / 20 . Detection of glacier surface conditions and recent glacier Arct. Alp. Res.,,* ,+13ῌ +21 . variations in Patagonia using ALOS data. Proceedings of Aniya, M. (+33, ): Glacier variation in the Northern Patagonia ALOS PI,**2 Symposium, Island of Rhodes, Greece, -ῌ 1 Icefield, Chile, between+32/ / 20 and +33* / 3+ . Bull. Glacier November,**2 (ESA SP- 00. , January ,**3 ) CD-ROM. Res.,+* ,2-ῌ 3* . Bell, C.M. (,**2 ): Punctuated drainage of an ice-dammed Qua- Aniya, M. (+33/ ): Holocene glacial chronology in Patagonia: ternary lake in southern South America. Geografiska Tyndall and Upsala Glaciers. Arct. Alp. Res.,,1 ,-++ῌ -,, . Annaler,3*A ,++1ῌ . Aniya, M. (+330 ): Holocene variations of Ameghino Glacier, Bourgois, J., Guivel, C., Lagabrielle, Y., Calmus, T., Boulegue, Southern Patagonia. The Holocene,0 ,,.1ῌ ,/, . J. and Daux, V. (,*** ): Glacial-interglacial trench supply Aniya, M. (+333 ): Recent glacier variations of the Hielos Pata- variation, spreading-ridge subduction, and feedback con- gónicos, South America, and their contribution to sea- trols on the Andean margin development at the Chile level change. Arct. Antarct. Alp. Res.,-+ (, ), +0/ῌ +1- . triple junction area (./ῌῌ .2῍ S). J. Geophys. Res.,+*/ , 2-// Aniya, M. (,**+ ): Glacier variations of Hielo Patagónico 2-20. Norte, Chilean Patagonia, since+3.. / ./ , with special ref- Boyce, E.S., Motyka, R.J. and Tru# er., M. ( ,**1 ): Flotation erence to variations between+33/ / 30 and +333 / ,*** . Bull. and retreat of a lake-calving terminus, Mendenhall Gla- Glacier Res.,+2 ,//ῌ 0- . cier, southeast Alaska, USA. J. Glaciol.,/- (+2+ ), ,++ῌ ,,. . Aniya, M. (,**1 ): Glacier variations of Hielo Patagonico Caldenius, C.C. (+3-, ): Las glaciaciones cuaternarias en la Norte, Chile, for+3.. / ./ῌ ,**. / ,**/ . Bull. Glaciol. Res.,,. , Patagonia y Tierra del Fuego. Geografiska Annaler,+. , + /3ῌ 1*. ῌ+0.. Aniya, M. and Naruse, R. (+333 ): Late-Holocene glacial ad- Ciappa A., Pietranera, L. and Battazza, F. (,*+* ): Perito Mo- vances at Glaciar Soler, Hielo Patagónico Norte, South reno Glacier (Argentina) flow estimation by COSMO America. Trans. Japanese Geomorph. Union,,* ,03ῌ 2- . SkyMed sequence of high-resolution SAR-X imagery. Aniya, M. and Naruse, R. (,**+ a): Overview of glaciological Remote Sensing of Environ.,++. (3 ), ,*22ῌ ,*30 . 16 Bulletin of Glaciological Research del Valle, R., Skvarca, P., Mancini, M. and Lusky, J. (+33/ ): A Mercer, J.H. ( +30, ): Glacier variations in the Andes. Glaciol. preliminary study of sediment cores from Lago Argen- Note,+, ,3-+ῌ . tino and fluctuations of Moreno Glacier, Patagonia. Bull. Mercer, J.H. (+310 ): Glacial history of southernmost South Glacier. Res.,+- ,+,+ῌ +,0 . America. Quat. Res.,0 , +,/ῌ +00 . Douglass,D.C.,Singer, B.S.,Kaplan, M.R., Ackert, R.P.,Mickelson, Michel, R. and Rignot, E. (+333 ): Flow of Glaciar Moreno, D.M. and Ca# ee, M.W. ( ,**/ ): Evidence of early Holocene Argentina, from repeat-pass Shuttle Imaging Radar im- glacial advances in southern South America from cos- ages: comparison of the phase correlation method with mogenic surface-exposure dating. Geology,-- ,,-1ῌῌ ,.* . radar interferometry. J. Glaciol., ./ ( +.3 ), 3- +** . Dussaillant, A., Benito, G, Buytaert, W., Carling, P., Meier, C. Nakajima, C. (ed.) (+32/ ): Glaciological Studies in Patagonia and Espinoza F. (,*+* ): Repeated glacial-lake outburst Northern Icefield, +32-ῌ +32. . Data Center for Glacier Re- floods in Patagonia: an increasing hazard? Nat. Hazards, search, Japanese Society of Snow and Ice,+-- p. /.,.03ῌ .2+ . Nakajima, C. (ed.) (+321 ): Glaciological Studies in Patagonia Floricioiu, D., Eineder, M., Rott, H. and Nagler, T. (,**2 ): +32/ῌ +320 . Data Center for Glacier Research, Japanese Velocities of major outlet glaciers of the Patagonia Ice- Society of Snow and Ice,+1/ p. field observed by TerraSAR-X. Proceedings of IEEE In- Naruse, R. and Aniya, M. (+33, ): Outline of Glacier Research ternational Geoscience and Remote Sensing Symposium Project in Patagonia,+33* , Bull. Glacier Res.,+* , -+ῌ -2 . ,**2in Boston U.S., IV, -.1ῌ -/* . Naruse, R. and Aniya, M. ( +33/ ): Synopsis of glacier re- Glasser, N., Jansson, K.N., Harrison, S. and Rivera, A. (,**/ ): searches in Patagonia, +33- . Bull. Glacier Res.,+- , +ῌ +* . Geomorphological evidence for variations of the North Naruse, R., Skvarca, P., Kadota, T. and Koizumi, K. (+33, ): Patagonian Icefield during the Holocene. Geomorphol- Flow of Upsala and Moreno glaciers, southern Pata- ogy,1+ ,,0-ῌ ,11 . gonia. Bull. Glacier Res.,+* ,//ῌ 0, . Glasser, N.F., Jansson, K.N., Harrison, S. and Kleman, J. (,**2 ): Naruse, R., Skvarca, P., Satow, K., Takeuchi, Y. and Nishida, The glacial geomorphology and Pleistocene history of K. (+33/ a): Thickness change and short-term flow varia- South America between-2῍῍ S and /0 S. Quat Sci. Rev.,,1 , tion of Moreno Glacier, Patagonia. Bull. Glacier Res.,+- , -0/ῌ -3*. ,+ῌ ,2. Glasser, N.F., Harrison, S. and Jansson, K.N. (,**3 ): Topo- Naruse, R., Aniya, M., Skvarca, P. and Casassa, G. (+33/ b): graphic controls on glacier sediment-landform associa- Recent variations of calving glaciers in Patagonia, South tions around the temperate North Patagonian Icefield. America, revealed by ground surveys, satellite-data anal- Quat. Sci. Rev.,,2 ,,2+1ῌ ,2-, . yses and numerical experiments. Ann. Glaciol.,,+ , ,31ῌ Harrison, S. and Winchester, V. (,*** ): Nineteenth- and twen- -*-. tieth-century glacier fluctuation and climatic implica- Naruse, R., Skvarca, P. and Kobayashi, S. (,**+ ): Measure- tions in the Arco and Colonia Valleys, Hielo Patagonico ments of surface height and flow velocity at the calving Norte, Chile. Arct. Antarc. Alp. Res.,-, ,//ῌ 0- . terminus of Perito Moreno Glacier, southern Patagonia, Heusser, C.J. (,**, ): On glaciation of the southern Andes in December+333 .In M. Aniya and R. Naruse (eds.), with special reference to the Peninsula de Taitao and Glaciological and Geomorphological Studies in Pata- adjacent Andean cordillera (ῌ῍.0 -*ῌ S). J. South Amer. gonia+332 and +333 , +.+ῌ +.. . Earth Sciences+/ ,/11ῌ /23 . Nichols R.L. and Miller, M.M. (+3/+ ): Glacial geology of Ame- Hollin,J.T.andSchillingD.H.(+32+ ):LateWisconsin-Weichselian ghino valley, Lago Argentino, Patagonia. Geogr. Rev.,.+ , mountain glaciers and small ice caps. In Denton, G. H. and ,1.ῌ ,3.. Hugh, T. J. (eds.), The Last Great Ice Sheets. New York, Nichols R.L. and Miller, M.M. (+3/, ): The Moreno Glacier, USA, Wiley,+13ῌ ,,* . Lago Argentino, Patagonia: advancing glaciers and nea- Hulton, N.R.J., Purves, R.S., McCulloch, R.D., Sugden, D.E. rby simultaneously retreating glaciers. J. Glaciol.,, , .+ῌ and Bentley, M.J. (,**, ): The Last Glacial Maximum and .0. deglaciation in southern South America. Quat. Sci. Rev., Rabassa, J. and Coronato, A. (,**3 ): Glaciations in Patagonia ,+,.,--ῌ ,.+ and Tierra del Fuego during the Ensenadan Stage/Age Hubbard, A., Hein, A.S., Kaplan, M.R., Hulton, N.R.J. and (Early Pleistocene-earliest Middle Pleistocene). Quat. Int., Glasser, N. (,**/ ): A modeling reconstruction of the last ,+*,.+2ῌ -0 glacial maximum ice sheet and its deglaciation in the Rignot, E.A., Rivera, A. and Casassa, G. (,**- ): Contribution of vicinityof the Northern Patagonian Icefield, South Ameri- the Patagonia Icefields of South America to sea level rise. ca. Geografiska Annaler,21A ,-1/ῌ -3+ . Science,-*, (/0.. ), .-.ῌ .-1 . Iizuka, Y., Kobayashi, S. and Naruse, R. 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