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Abstract

. Introduction

Shin SUGIYAMA , Pedro SKVARCA , Nozomu NAITO , Kenta TONE , Hiroyuki ENOMOTO ,

Kunio SHINBORI , Sebastian MARINSEK and Masamu ANIYA

Hot-water drilling at Glaciar Perito Moreno, Southern Patagonia Icefield

27Bulletin of Glaciological Research ( )

Japanese Society of Snow and Ice

Institute of Low Temperature Science, Hokkaido University, Nishi- Kita Sapporo, Japan

Dirección Nacional del Antártico-Instituto Antártico Argentino, Cerrito , Buenos Aires, Argentina

Department of Global Environment Studies, Hiroshima Institute of Technology, , Miyake, Saeki-ku, Hiroshima,

Japan

Department of Civil Engineering, Kitami Institute of Technology, , Koen-cho, Kitami, Japan

Professor Emeritus, University of Tsukuba, Tsukuba, Japan

(Received November , ; Revised manuscript accepted December , )

(Aniya ; Aniya, ; Rignot ; Rivera

Glaciar Perito Moreno is one of the major freshwater calving glaciers in the Southern Patagonia

Icefield. Its fast-flowing characteristic is probably due to high water pressure at the glacier bed,

however, subglacial conditions have never been observed in Patagonia until our recent undertaking.

To investigate the role of subglacial water pressure in the calving glacier dynamics, we performed

hot-water drilling at Glaciar Perito Moreno from February to March . This study represents the

first attempt ever at hot-water glacier drilling in Patagonia. Two boreholes were drilled to the bed at

. km upglacier from the terminus, where the ice was revealed to be m thick and the bed

located at about m below the proglacial lake level. The water levels in the boreholes were m

above the lake level, which indicates that more than of the ice overburden pressure was balanced

out by the subglacial water pressure. Water in the boreholes had drained away before the drilling

reached the bed, suggesting the existence of an englacial drainage system. These results provide

crucial information for understanding the hydraulic and hydrological conditions of calving glaciers.

In order to drill a m deep glacier, an existing hot-water drilling system was adapted by increasing

the number of high-pressure hot-water machines. The drilling operation at Glaciar Perito Moreno

confirmed the system’s capacity to drill a -m-deep borehole at a rate of m h with fuel

consumption rates of . l h for diesel and . l h for petrol.

Key words: calving glacier, hot water drilling, subglacial water pressure, borehole, Patagonia

proglacial water body. Since a large amount of ice is

discharged from the fast-flowing calving glaciers in

Patagonia (Naruse ; Skvarca ;

The close examination of physical conditions be- Warren a; Warren b; Rott

neath a glacier ( , water pressure, drainage system, ), the dynamics of these glaciers plays a key role

unconsolidated sediment layer, bedrock roughness) is in the recent ice mass loss of the Patagonia Icefields

important for understanding the role of basal pro-

cesses in glacier motion. Subglacial conditions deter- ). Nevertheless, detailed studies on glacier

mine the speed of ice sliding over a bedrock as well as dynamics are very scarce and subglacial measure-

the deformation of a subglacial sediment layer, caus- ments have never been carried out in Patagonia.

ing substantial changes in glacier flow speed. These Glaciar Perito Moreno is a fast-flowing freshwater

basal ice flow processes are particularly important in calving glacier in Patagonia. The glacier extends over

outlet glaciers in Patagonia Icefields since most of km to the northeast from the Southern Patagonia

them terminate in lakes or the ocean (Warren and Icefield and covers an area of km (Aniya

Aniya, ; Rignot ; Rivera ). ). The glacier front currently terminates in Brazo

Calving glaciers flow faster than land terminating Rico and Canal de los Témpanos ( m a.s.l.) (Stuefer

glaciers, particularly because the basal flow processes ), forming a narrow water channel between

are enhanced by high water pressure generated by the the glacier snout and Península Magallanes. (Fig. a).

et al., et al.,

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. Hot-water Drilling System

28 Bulletin of Glaciological Research

Figure . (a) Satellite image of Glaciar Perito Moreno

with the drilling site indicated by ( ). Drilling

equipment was transported by a helicopter from

the site indicated by ( ). The image was taken

on March (image courtesy of the Image

Science & Analysis Laboratory, NASA Johnson

Space Center). (b) Longitudinal cross section of

Glaciar Perito Moreno along the central flowline.

The bed profile is drawn by interpolation of

observational data points ( ) (Stuefer ).

The lake water level and ice flotation level are

indicated by the dot-dashed and dotted lines.

margins.

In the / austral summer season, we car-

ried out high-frequency ice flow measurements on

Glaciar Perito Moreno and found clear diurnal flow

speed variations in the central region of the glacier at

about km from the terminus (Sugiyama ).

The flow speed was closely correlated to air tempera-

ture, suggesting that meltwater production is control-

ling the basal ice flow by swiftly changing subglacial

water pressure. The flow speed was very sensitive to

the meltwater input, probably because the relation-

ship between the water pressure and flow speed is

highly nonlinear when the pressure rises close to the

overburden pressure (Bindschadler, ; Tru er and

Iken, ; Sugiyama and Gudmundsson, ). To

test this hypothesis, we drilled Glaciar Perito Moreno

using a hot-water drilling technique to measure sub-

glacial water pressure. This was the first attempt in

Patagonia to drill through a glacier for the purpose of

conducting subglacial observations. The aim of this

paper is to describe the hot-water drilling system used

for this project and report the drilling field campaign

carried out in early .

The hot-water drilling system was prepared by

adapting an existing system developed at the Insti-

tute of Low Temperature Science, Hokkaido Univer-

sity (Sugiyama ; Tsutaki and Sugiyama,

). The original system was designed for drilling

as deep as m, thus it was necessary to increase the

drilling capacity to drill through Glaciar Perito Moreno

Unlike the other glaciers in Patagonia, no significant with expected thickness of m at our study site.

retreat is being observed in Glaciar Perito Moreno We installed an additional high-pressure hot-water

(Aniya and Skvarca, ; Skvarca and Naruse, ; machine (Kärcher HDS BE) and constructed pip-

Stuefer, ; Stuefer ). Its front position ing to bring together hot water from two machines

has oscillated within several hundred meters since the (Fig. a). The length of the drilling hose was ex-

early th century (Skvarca and Naruse, ). The tended to m. An electrically powered winch sys-

glacier flows at a rate of m a in the region tem (Fig. b) was developed to lower down and lift up

extending several kilometers from the calving front the hose in a borehole, as the hose is too heavy to

(Rott ; Michel and Rignot, ; Floricioiu handle by man power alone during deep drilling.

; Ciappa ). According to seismic The winch was controlled by hand using a handle

soundings performed by Stuefer ( ), the glac- connected to a gear system as observed in Figure b.

ier bed elevation is m below the lake level Electric power from a generator was used only to

within the reach of km from the terminus (Fig. b). wind up the hose after the completion of drilling.

The glacier bed is thus expected to be at high water The winch was equipped with a brake system (lower

pressure under the influence of the proglacial lakes. right in Fig. b) designed and constructed at the wor-

A substantial part of ice overburden pressure is bal- kshop of the Institute of Low Temperature Science.

anced out by the subglacial water pressure, which is a This brake keeps the hose tightly wound around the

preferable condition for the basal ice flow processes winch drum, so that the necessary friction was gener-

( Bindschadler, ). Annual flow speed varia- ated at the interface between hose and drum.

tions are relatively small (Stuefer ), whereas The hot water machines draw water with petrol-

a clear seasonal flow speed change has been observed driven pumps from a water basin or supraglacial wa-

by a recent study using satellite data (Ciappa ter source. The water is warmed up with a heater

). Naruse . ( ) reported diurnal flow speed which uses diesel as fuel. Hot water flowed through

variations at a few hundred meters from the side . mm inner diameter high pressure hoses (Bridges-

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. Overview of Field Campaign

29SUGIYAMA

Figure . Flow rate ( ) and water jet temperature ( )

of the hot-water drilling system obtained using

water jet nozzles with di erent diameters. The

closed circles and squares ( , ) are flow rate and

temperature reported for the old system, which

uses one hot-water machine (Tsutaki and Sugiyama,

).

Figure . Photographs showing hot-water drilling on

Glaciar Perito Moreno. (a) High-pressure hot-water

machines. The machines discharge hot water

through the black hoses, which are combined into

one by means of the piping. (b) Winch system

with a brake in the lower right. (c) The hot-water

drilling system set up on the glacier. The bore-

hole is at the middle left.

hose length. After a reconnaissance visit on February,

l hr and a pressure of MPa (Fig. ). The water

temperature and the flow rate show that the new

system generates approximately more power

(heat in a unit time) than the original system (Fig. )

(Tsutaki and Sugiyama, ).

The field campaign began on February .

It was ascertained that the location of the drilling site

fulfilled the requisite conditions such as: availability

of water, relatively flat surface for drilling and heli-

copter operations, proximity to the / GPS meas-

urement sites, and ice thickness not greater than the

the drilling site was chosen at S . , W

. (Fig. a). The site was . km from the terminus

and several hundred meters o the central flowline.

The ice thickness was estimated as m, based

on the seismic data (Stuefer ). Water was

tone WAR , outer diameter is . mm) before it emit- available in a nearby supraglacial pond. The drilling

ted a narrow water jet from a . mm diameter nozzle equipment and fuel ( l of diesel for the heaters and

(Katorigumi Inc. K- ). The nozzle was mounted on l of petrol for the pumps and generator) were

a -m-long metal pipe, which provided a load to transported on February by a helicopter of the

straighten the hanging hoses for drilling a vertical Gendarmería Nacional from Puerto Bajo de las Som-

borehole. For drilling of shallow boreholes, a tripod bras located at . km east of the drilling site (Fig. a).

and pulley system was used instead of the winch. The system was set up immediately upon arrival at

The weight of all the drilling equipment was approxi- the site, and drilling began on February. As the

mately kg, excluding fuel. drilling site was a two-hour walk from our camp, the

The drilling system was tested before the cam- daily activity on the glacier was limited to h.

paign at the Institute of Low Temperature Science Drilling operations continued until March and the

using a water basin filled with water from a tap. The equipment was evacuated by helicopter from the glac-

temperature of the water jet was measured with a ier on the following day.

temperature logger (HIOKI ) following a method

described in Tsutaki and Sugiyama ( ). The sys-

tem generated hot water at about at a rate of

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. Drilling

30 Bulletin of Glaciological Research

Figure . Drilling depth v.s. duration for the drilling

of BH (black) and BH (bold gray).

Table . Depth of the boreholes, drilling speed and

fuel consumption rates of the hot water system.

Figure . Weight of the drilling hose measured during

the drilling of BH ( ) and BH ( ). The dashed

lines are weight of the hose estimated for the

indicated water levels (relative to the surface).

The inset shows details near the bed in BH .

thickness at the drilling site was m plus stretch-

Drilling did not progress e ciently until Feb-

ruary because one of the pumps needed to be repaired

and the winch system had to be tested. The first

borehole (BH ) reached the glacier bed on March

after the consumption of l of diesel and l of

petrol. The total duration of the hot-water system

operation was hours, including time spent for test-

ing the devices. The total fuel consumption rates

were . l h for diesel and . l h for petrol. The

diesel consumption rate was lower than the normal

value of the system because one of the two hot water

machines was out of order during the first half of the

drilling. The second borehole (BH ) was drilled ap-

proximately m downglacier from BH . Drilling be-

gan on March and completed the next day after .

hours of operation. The diesel and petrol consump-

tion rates were . and . l h , respectively.

Figure shows drilling depth as a function of

drilling duration. The depth was known from the

hose length plus its extension due to the own weight.

The extension was calculated from the extension rate

( . N ) and hose weight ( . kg m ) reported

by the manufacturer (Bridgestone Co.). The drilling

rate for BH was not uniform because we began drill-

ing by hand with the tripod and pulley system and

then the system was replaced by the winch at the

depth of m. Hand drilling is generally more e -

cient unless the hose in a borehole is too heavy to

handle. The winch system was used for the entire

part of BH to avoid an interruption due to the ex-

change of the systems. Drilling rates from the sur-

face to the bed were and m h for BH and BH ,

respectively. The drilling speed and fuel consump-

tion rates are summarized in Table .

In order to detect the glacier bed during drilling,

the weight of the drilling hose hanging in the bore-

hole was measured every to m (Fig. ). A rope

was twisted around the hose to hang it under a hook

of a spring scale. Sudden increases in the load were

observed at hose lengths of m in BH and m in

BH . These clear changes occurred because of water

drainage from the borehole as described later in this

section. At hose lengths between m (BH ) length ( . ), which equals to m. This result

and m (BH ), the load suddenly dropped and is consistent with the seismic data (Stuefer ),

decreased progressively as we continued the drilling. although detailed comparison is not possible as the

Detailed measurements in BH showed that the seismic measurements were performed several hun-

change could be reproduced by lowering and lifting dred meters upglacier from our drilling site.

the hose at this depth (Fig. inset). These were clear Boreholes are usually filled with water during

indications that the drilling nozzle hit the bed. The hot-water drilling. The water often drains away

load decreased because the nozzle came into contact when a borehole reaches the bed, but drainage can

with the bed and the hose leaned on the borehole wall. also occur beforehand, within the glacier. These drain-

Based on these observations, we conclude that the ice age events provide important information on sub-

glacial and englacial hydrological connections. Wa-

ing of the hose ( . m) and ambiguities in the hose ter in BH first drained at m from the surface.

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Acknowledgments

. Conclusion

drill through Glaciar Perito Moreno, a freshwater calv-

ing glacier in the Southern Patagonia Icefield, for

subglacial observations. We drilled two boreholes to

the glacier bed at . km from the terminus. The

drilling revealed the ice thickness at the drilling site

to be m. The completion of the drilling to the

bed was clearly detected by changes in the weight of

the hose hanging in the boreholes. Water in the bore-

holes drained before the drilling reached the bed, indi-

The sudden increase in the hose weight at the depth cating the existence of an englacial drainage system.

m (Fig. ) implies that water drained again and According to inspections of hot water nozzles after

buoyancy force acting on the hose decreased. Judg- the drilling, the glacier is probably underlain by un-

ing from the weight of the hose hanging in the bore- consolidated sediments and gravels. The water level

hole estimated for di erent water levels (dashed lines in boreholes after the drilling was more than of

in Fig. ), the level dropped from to m below the the ice flotation level, which strongly suggests that ice

ice surface at the second drainage. In BH , drainage flow of Glaciar Perito Moreno is influenced by a high

occurred at m depth, as did the increase in weight subglacial water pressure and its variations.

(Fig. ). The change in the weight by . kg implies In order to drill a glacier to a depth of more than

that the water level dropped approximately m. m, two high-pressure hot-water machines were as-

These observations suggest the existence of an engla- sembled together and a winch system was newly con-

cial drainage system in Glaciar Perito Moreno. Ac- structed. The drilling speed from the surface to the

cording to our visual observation of the water level in bed was m h when the system was running prop-

the boreholes, the drainage rate was in the range of erly. The rates of fuel consumption were . l hr

m min . This rate was relatively lower for diesel and . l hr for petrol.

than those of subglacial and englacial drainage that

we encountered in the Alps.

The inspection of the hot-water jet nozzles after

the drilling provided a clue to glacier bed conditions. We thank the members of GRPP (Glaciological

The surface of the brass nozzle often became heavily Research Project in Patagonia) for their help in the

scratched or scraped when it hit bedrock (Sugiyama field and for preparation of the drilling system. T.

). However, the nozzle used for BH had Wyder provided necessary information for the con-

only small scratch marks and the one used in BH struction of the winch and T. Shiraiwa loaned us the

bore no evidence of contact with rocks (Figure ). winch drum. The drilling equipment was trans-

Therefore, it is likely that the glacier is underlain by ported to the glacier by a helicopter operated by

an unconsolidated layer composed of sediment and Gendarmeria Nacional Argentina. Hielo y Aventura

gravels at the drilling site. The di erence in the S. A. o ered logistic support during the field activity

damage to the nozzles used in the two boreholes may and Toshin S. A. organized the transport of materials

be due to the fact that we moved the drill up and in Argentina. Kärcher Inc., Bridgestone Co. and Nak-

down at the bottom of BH , whereas we stopped the amura Service Co. Ltd. assisted in the construction of

drilling in BH as soon as reached the bed. the drilling system. The hose-stretching experiment

After drilling was completed, water-pressure sen- carried out by Bridgestone Co. is greatly appreciated.

sors (Geokon S and HOBO U ) were installed in S. Tsutaki and S. Matoba helped with preparation and

the two boreholes to measure the respective water shipment of the drilling equipment. We thank an

levels. The measurements showed that the water anonymous referee for helpful comments and the sci-

levels in BH and BH correlated with one another. entific editor S. Matoba for handling the paper. The

They fluctuated in a diurnal manner within a level English was corrected by S. Braun-Clarke. This re-

between m from the bed, which corresponded search was funded by the Japanese Ministry of Educa-

to more than of the ice flotation level at the site. tion, Science, Sports and Culture, Grant-in-Aid for

The pressure variations were correlated to surface Scientific Research (A), , - and by a

flow speed and air temperature, implying that our funding program of the Institute of Low Temperature

hypothesis was correct. Detailed analyses of the wa- Science. This support is gratefully ack

ter level variations together with ice flow speed and

air temperature data will be presented elsewhere.

A hot-water drilling technique was employed to

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References

31SUGIYAMA

Figure . Drilling nozzles (a) before the drilling and

(b) after the drilling of BH and (c) BH .

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0

+ ,

+333

, +0/ +1--+

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32 Bulletin of Glaciological Research

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