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Annals of Glaciology 40 2005

Surface strain anomaly induced by the storage and drainage ofenglacial water in Koryto glacier, Kamchatka, Russia
Shin SUGIYAMA,1 Renji NARUSE,2 Yaroslav D. MURAV’YEV3
1

Laboratory of Hydraulics, Hydrology and Glaciology, ETH-Zentrum, CH-8092 Zürich, Switzerland
E-mail: sugiyama@vaw.baug.ethz.ch2Institute of Low Temperature Science, Hokkaido University, Sapporo 060-0819, Japan
3
Institute of Volcanology, Russian Academy of Sciences, 9 Piip Boulevard, 683006 Petropavlovsk-Kamchatsky, Russia
ABSTRACT. To investigate short-term flow-pattern variations of a temperate glacier, longitudinalsurface strain was measured with a wire strainmeter in the ablation area of Koryto glacier, Kamchatka,
Russia. Strain-rate anomalies were observed in late summer 2000 that were triggered by a water
overflow from a moulin near the measurement site followed by the drainage of accumulated water. The
strain event started with (compressive) strain rates of >–10–3 d–1 lasting for 6 hours, which then became
tensile. Similar strain-rate variations were observed again on the next day. During the event, basal
sliding speed measured at the margin in the lower reach of the glacier fluctuated by about 50% of thedaily mean. Smaller and larger sliding speeds corresponded to the compressive and tensile surface
strains, respectively. These measurements suggest that the storage and sudden drainage of water caused
spatially non-uniform water-pressure fluctuations along the glacier, changing the sliding regime overshort time periods.

INTRODUCTION
The flow speed of a temperate glacier fluctuates under the
influence of basal conditions. Because subglacial water
plays an important role in basal flow processes, short-termflow variations are often induced by changes in water input
caused by an intensive melt event (e.g. Iken and others,
1983; Naruse and others, 1992; Mair and others, 2001),
diurnal meltwater production (e.g. Iken and Bindschadler,
1986; Sugiyama and Gudmundsson, 2003), heavy rainfall(e.g. Jansson and Hooke, 1989; Gudmundsson and others,
2000) and drainage of a glacial lake (e.g. Nolan and Echelmeyer, 1999).
To study the response of a glacier to short-term variations
in water input, high-frequency ice-flow measurements are
required. Automatic operation of a distance meter (Hansonand others, 1998), theodolite (Gudmundsson and others,
2000) and global positioning system (Gudmundsson, 2002)
have been used for surface flow speed measurements with

Fig. 1. (a, b) Schematic diagrams showing the installation of thewire strainmeter for (a) surface strain and (b) marginal sliding
measurements. (c) The key component of the strainmeter whichmeasures the tilt of the metal block with the displacementtransducer.

intervals of hours or less. Alternatively, surface strain has
been measured on several glaciers with specially preparedstrainmeters (Raymond and Malone, 1986; Jansson andHooke, 1989). Raymond and Malone (1986) installed
several strainmeters on Variegated Glacier, Alaska, USA,and observed propagation of strain anomalies during fastflow events.
We operated a wire strainmeter on a temperate valley
glacier in Kamchatka, Russia, and used the same apparatus
to measure marginal sliding speed. This paper reports theobservations of surface strain anomalies and sliding-speed
variations induced by water stored in the glacier. Results
reveal the influence of non-uniformly distributed subglacial
water pressures on the flow regime of the glacier.

MEASUREMENT APPARATUS
The wire strainmeter constructed for this study was similar tothat used on Variegated Glacier (Raymond and Malone,1986). Changes in the distance between two metal poles(36 mm diameter, 1 m long) installed on the glacier were
measured using a Super Invar wire (0.25 mm diameter). One
end of the wire was fixed to one of the poles, while the otherend was connected to a metal block balanced with a pivot on
the second pole (Fig. 1a). The metal block tilts when theglacier surface strains, and the tilt was sensed by a displacement transducer (Keyence AT3-001) placed in contact withthe block. Direct-current output from the transducer wasrecorded every minute with a datalogger (Hioki 3635-05)
with a resolution of 10–3 mm, corresponding to a strain of
10–6 when the poles were installed 1 m apart.
The apparatus was tested in a cold room by measuring thethermal strain of an ice block (1000  500 250 mm)
between two poles installed 600 mm apart. Because thethermal expansion coefficient of Super Invar (10 6 K 1 ) is
about 2% of that for ice, the influence of thermal stretchingof the wire was neglected. To evaluate the measurement
result, the thermal strain caused by temperature changes inSugiyama and others: Surface strain anomaly in Koryto glacier

233

Fig. 2. Air temperature in the cold room (top line), and measured(middle line) and computed (bottom line) strain of the ice block.
The computational results are indicated by the asterisks, and thedashed line is drawn arbitrarily.

the cold room was computed with finite-element commercial software ANSYS. The model solves a transient thermomechanical problem in a vertical cross-section along themeasurement axis. Figure 2 shows air temperature and themeasured and computed strain, taking tensile strain as
positive. Although the magnitude of the measured strain issmaller than the model result, the timing of the compression
due to the drop in temperature and the subsequent transition
from compressive to tensile strain rate were consistent
between measured and modelled results. Considering thesimplification introduced in the finite-element modelling,arising for example from the model’s two-dimensional
nature and simplified boundary conditions, the accuracy ofthe strainmeter was difficult to assess. It is possible that the
instrument did not fully respond to the strain because of its
mechanical play. Nevertheless, the test result confirmed thepotential of the apparatus to measure changes in strain witha magnitude of 10 5 , and we focus more on the timing andthe sign of the strain measured in the field rather than its
magnitude.

FIELD MEASUREMENTS
Study site
Koryto glacier is a temperate valley glacier located on theeast coast of Kamchatka peninsula, ranging in altitude
between 320 and 1200 m (Fig. 3). It is a maritime glaciercharacterized by large winter accumulation (>7 m w.e. near
the top) and summer ablation (>7 m w.e. near the terminus)(Shiraiwa and others, 1997). During the ablation season, thesurface flow speed varies under the influence of meltwaterand precipitation, suggesting that basal motion plays animportant role in the dynamics of this glacier (Yamaguchi
and others, 2003).

Surface strain measurement
From early August to mid-September 2000, surface strain
was measured with wire strainmeters at several locations in
the ablation area. For most of the measurement period, it
was necessary to reinstall the strainmeters every 2–3 days
due to large melting rates reaching 100 mm w.e. d 1 . The
data presented here were obtained at site KK4 (Fig. 3)

Fig. 3. Map of Koryto glacier showing the locations of the surface
strain (KK4) and marginal sliding (BS1) measurements. Contour
lines indicate the surface elevation in m a.s.l.

from 27 to 30 August with poles installed 1.5 m apart along
the flowline. During this period, the measurement wascontinuous without reinstallation owing to a relatively low
melt rate of 33 mm w.e. d 1 , and a lack of precipitation.

Basal sliding measurement
The wire strainmeter was also utilized for the measurementof basal sliding at the glacier margin. Instead of using twopoles, one end of the wire was anchored on the side of theglacier in basal ice with an ice screw, and the metal block
was balanced with a pivot which was fixed on bedrock(Fig. 1b).
Sliding was measured from late August to mid-September
at site BS1 (Fig. 3). We were able to reach a point along theglacier margin where 10–20 m thick ice was sliding overbedrock with no underlying sediment. Data from the wire
meter were obtained intermittently, as they were interrupted
by both melting out of the ice screw and failures of thebattery. Although the exact direction of the glacier sliding
was not known, the wire was likely not parallel to the ice
motion. Displacement measured by the apparatus therefore
represents an unknown but likely steady fraction of thethree-dimensional movement of the basal ice. However,here we call the rate of the measured displacement simply‘sliding speed’.

Observation of a moulin at KK4
About 30 m up-glacier from the surface strain measurement
site, one of the largest moulins of the glacier collected
meltwater produced in the region. Several shafts in a healed
crevasse were enlarged by water flow and had developed toa 1–2 m wide, 20 m long water inlet in summer 2000. A
series of inactive moulins were found down-glacier along
the flowline with intervals of about 50 m, suggesting that themoulins were formed annually at the same location.
On 28 August at 1930 h, we observed the moulin
completely filled with water and overflowing onto theglacier surface for the first time (Fig. 4a). By the next day at
1400 h, water stored in the moulin had already drained

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Sugiyama and others: Surface strain anomaly in Koryto glacierFig. 5. Surface strain at KK4 obtained with a wire strainmeter. Timesof drastic changes in the strain are indicated, and observed
conditions of the moulin are described at the top.

strain rate at KK4 are well correlated: lower and higher
sliding speeds correspond to compressive and tensile strain
rate, respectively. The amplitude of the sliding-speed variations is about 50% of the mean value.

DISCUSSION
Fig. 4. The moulin at KK4 filled with water at 1930 h on 28 August(a), and under normal conditions at 1400 h on 29 August (b).
Photographs are taken looking south.

(Fig. 4b), but similar events, called ‘overflow’ hereafter, wereobserved several times in September.

RESULTSLongitudinal surface strain measured at KK4 is shown in
Figure 5. From 27 to 28 August, before the first observationof moulin overflow, the mean tensile strain rate was
1:4  10 5 d–1 which is in good agreement with the valueof 2:1  10 5 d–1 determined by repeated theodolite surveys
of stakes installed 100 m apart from each other for the period
26 August–10 September. On the afternoon of 28 August, asudden (compressive) strain reaching –5  10–4 followed bya similar amount of extension was recorded. This incident
coincided with the overflow of the moulin. Another strain
event took place at noon on 29 August. Although we did notobserve that the moulin was filled with water on 29 August,this does not mean an overflow did not occur. Inspections
were only made once or twice a day, as we passed by thelocation.
On 29 August when the large strain was observed, downglacier basal sliding showed fluctuations (Fig. 6). Displacement of the basal ice relative to the bedrock at BS1 and its
rate (sliding speed) are shown in Figure 6 together with thesurface strain and strain rate at KK4. Sliding speed and strain
rate were calculated after smoothing the raw displacement
and strain data with the kernel regression method (Brockmann and others, 1993). The sliding speed at BS1 and the

The coincidence of the strain event with the overflow of themoulin on 28 August suggests that extraordinary subglacial
hydraulic conditions caused the changes in the ice-flow
regime. We propose the following interpretation of theanomalous longitudinal strain variations. When a subglacialconduit constricted, meltwater started to fill the moulin,
resulting in a reduction in basal water transport to the lower
reaches of the glacier. Due to the changes in water pressure,
ice-flow speed increased up-glacier and decreased in thelower glacier, inducing a compressive longitudinal strain
rate at KK4 (Fig. 7b). When the conduit regrew, the large
amount of water that was stored in the moulin and nearby
subglacial drainage system drained down-glacier. Flow
speed then increased in the lower reaches and the strain
became tensile (Fig. 7c). The above interpretation explains
why the strain events started with longitudinal compression
and then turned to extension. It also agrees with theobservation that lower and higher sliding speeds at BS1
corresponded to compressive and tensile surface strain rates
at KK4. For the event on 29 August, it is plausible that the
conduit constricted again at 1640 h, and then opened at2130 h (Fig. 5).
It is likely that some of the subglacial drainage conduits
closed because of insufficient conduit water pressure in thelate ablation season. The timing of the events, which started
around noon and ended in the evening, implies that theconstriction and regrowth of the conduits were controlled by
meltwater supply to the bed. Subglacial conduits became
narrower during the night, when water pressure was low.
Then the strain events occurred as meltwater supply
increased and exceeded the subglacial drainage capacity.
The conduits were enlarged toward the evening due to highwater flow and subglacial water pressure until the stored
water was drained. Hourly discharge measured at the outlet

Sugiyama and others: Surface strain anomaly in Koryto glacierFig. 6. Comparison of sliding at BS1 and strain at KK4 from 1100 to1800 h on 29 August. (a) Displacement of the basal ice relative to
bedrock (dashed line) and sliding speed (solid line). (b) Surface
strain (dashed line) and strain rate (solid line).

stream (Matsumoto and others, 2004) was examined to finda trace of the drainage events, but significant peaks were notobserved. Because the drainage of the moulin occurred in
the late afternoon, it was presumably obscured by the daily
discharge maximum.
The significant response of surface strain suggested thatwater was stored over an area broad enough to set up a
gradient in the sliding field. The length scale over whichwater is expected to be stored is more than a few times theice thickness (Kamb and Echelmeyer, 1986), which is about
200 m at KK4 (personal communication from Yu. Macheret,2001). If the same quantity of water were stored for longer
periods of time, until the following summer, for example, itwould not only affect seasonal flow-speed variations but also
would impact the water budget of the glacier. That
substantial water was stored within and under Koryto glacierbefore the ablation season is suggested by other studies.
Run-off and ablation measurements in Koryto glacier
showed a 9  106 m3 water deficit from August to September
2000 (Matsumoto and others, 2004). Vertical surface movement during the same period was downward over most of
the glacier, implying that a large amount of water was stored
in basal cavities in the early summer (Yamaguchi and others,2003).
The observed strain events reported here indicated asignificant impact of changing subglacial conditions on
glacier dynamics. Basal water pressure locally exceeded theice overburden pressure when the moulin was filled withwater, so the ice was considered to be decoupled from thebed. Presumably, discharge of the stored water enhanced
basal motion in the lower reach of the glacier by increasingwater pressure there. Such processes can be compared to the235

Fig. 7. Schematic diagrams of a longitudinal cross-section of theglacier showing subglacial water conditions and ice-flow regimes.
(a) Normal conditions. (b) Moulin overflow. (c) Moulin drainage.

formation and rapid drainage of a glacier-dammed lake. On
Black Rapids Glacier, Alaska, USA, drainage of marginaland supraglacial lakes increased the surface flow speed by
up to 400% (Nolan and Echelmeyer, 1999) and also caused
vertical straining in the ice near the surface (Raymond andothers, 1995).
Sliding-speed variations at glacier margins may notdirectly represent the changes in basal motion in the central
area. Nevertheless, the correlation found between the sliding
speed at BS1 and the strain rate at KK4 implies that themarginal sliding was enhanced when the glacier bed waspressurized by the drainage of water stored up-glacier. A
possible effect of such subglacial conditions on sliding at themargin is basal shear stress transfer from the center to themargins. Reduction in the basal traction in the center of theglacier causes increases in the shear stress near the sidewalls, resulting in enhanced sliding at the margins. Glen andLewis (1961) measured the movement of ice at the side ofAusterdalsbreen, Norway, and found greater sliding speeds
during periods of heavy rainfall or high temperature.
Although regional conditions such as bedrock irregularities,boulders in basal ice, or melting at the bed should also be
considered, the increase in marginal sliding can be understood as a consequence of shear stress transfer to the margins.

CONCLUSION
The cold-room test of the wire strainmeter and the operationin the field demonstrated its ability to measure short-termflow variations with a time-scale of <1 hour. It is a uniquetool for investigation of both glacier dynamics and laboratory ice mechanics with a high temporal resolution.

236

The strainmeters were used to measure surface strain andmarginal sliding of a temperate glacier with a temporal
resolution of 1 min. The measurements captured the response of the glacier to the overflow and subsequentdraining of a large moulin during the late ablation season.
We suggest that subglacial water pressure was nonuniformly distributed during the overflow and the subsequent drainage of the stored water. The observation revealed
the influence of short-term local changes in water input on
the glacier flow regime, providing insight into the likely
effects of glacier outburst floods on glacier dynamics.

ACKNOWLEDGEMENTS
The authors wish to thank T. Yamada and T. Aoki for leading
the campaign on Koryto glacier. Thanks also go to
S. Yamaguchi, T. Matsumoto and K. Konya for their help
with the field measurements. The wire strainmeters were
designed and constructed by K. Shinbori at the workshop of
the Institute of Low Temperature Science, Hokkaido
University. C.F. Raymond kindly provided information about
the design and operation of a wire strainmeter. The manuscript was improved by comments from R.S. Anderson,
P. Jansson, G.E. Flowers and U.H. Fischer. This study was
funded by the Ministry of Education, Science, Sports andCulture, Japan (No. 11691166).

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