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An Investigation of the
Hydrological System of a Debris-
Covered Glacier
Catriona Fyffe University of Dundee
Ben Brock, Martin Kirkbride and Doug Mair
Debris-Covered Glaciers
Have a mantle of rock debris across at least part of their ablation area
Usually from rockfall, mixed rock and snow avalanches, and melt out of englacial debris
Where cover thick (on lower parts of the ablation area) ablation reduced due to the insulating nature of the debris
Where cover thinner (on the upper glacier, or on ice cliffs) decreased albedo leads to increased ablation
But how does a debris cover
influence the glacier’s hydrology?
Aims are to….
1. Understand the influence of the
debris on the structure and evolution
of the hydrological drainage network.
2. Understand the influence of the
debris on the water balance of the
glacier.
Methodology
To answer 1:
Glacier velocity measurements using Leica 1200
System differential GPSs
Dye tracing
Analysis of proglacial stream water (for suspended
sediment concentration, pH, conductivity, temperature,
bicarbonate, sulphate and chloride ion concentration)
To answer 2:
Weather data from two automatic weather stations, with
a rain gauge and lysimeter at the lower station
Ablation stake measurements
Pressure transducer on the proglacial stream
The drainage network and glacier velocity
Velocities highest upglacier, around 11 cm d-1, similar on main tongue, and decreasing down glacier to an average of 2.7 cm d-1 on the southern lobe
Velocity variations in June Change from cooler days to more pronounced
diurnal cycle, and an increase in discharge, corresponded with an increase in horizontal velocity (average of 0.71 cm d-1) for several points on Julian day 163
C6 had an increased velocity (to 20.6 cm d-1, compared to a mean of 11.3 cm d-1) during the afternoon of day 162 – relating to an increased daily velocity on day 163 for the other points
Overall increase on most points small, so probably more a variation than an “event” linked to a change in the hydrological regime
Suggests existence of subglacial linked cavity system
Difference from mean velocity and average daily temperature from the
lower weather station
-1
-0.5
0
0.5
1
1.5
2
2.5
158 159 160 161 162 163 164 165 166 167 168 169
Julian Day
Dif
fere
nce f
rom
mean
velo
cit
y (
cm
d-1
)
4
5
6
7
8
9
10
11
12
Tem
pera
ture
(˚C
)
Difference from mean velocity
Temperature
Dye tracing
Most traces gave pronounced peaks with an average minimum velocity of 0.43 ms-1, and traces were detected within 3 hours = channelised flow
One trace from above the snowline into moulin 11 on day 162 had a velocity of 0.69 ms-1
Importantly, the flow was channelized despite it being early in the season, suggesting certain flow paths are never completely closed during the winter
Dye tracing from Moulin 11, 4030 m from
gauging station
-0.5
0.0
0.5
1.0
1.5
2.0
2.5
3.0
13
43
13
48
13
53
13
58
14
03
14
08
14
13
14
18
14
23
14
28
14
33
14
38
14
43
14
48
14
53
14
58
Time
Dy
e c
on
ce
ntr
ati
on
(pp
b)
Dye tracing into englacial conduit, 2650m from gauging station
-0.1
0
0.1
0.2
0.3
0.4
0.5
0.6
0.7
0.8
0.9
13
19
13
29
13
39
13
49
13
59
14
09
14
19
14
29
14
39
14
49
14
59
15
09
15
19
Time
Dye c
on
cen
trati
on
(p
pb
)
Dye injected into an englacial conduit between the eastern and central moraines on the 10th of June – drainage clearly channelised
Minimum velocity = 0.37 ms-1
Influence of debris?
Overall recent thinning of the Miage (Diolaiuti et al., 2009) (debris-covered glaciers tend to thin
rather than retreat) may have increased the
likelihood of the channelised system remaining
over the winter as the preservation of
channelised systems is more likely for thinner
glaciers (Flowers, 2008)
The main supraglacial streams follow the valleys
between the medial, and eastern and western
moraines => drainage is focused, increasing the
inputs into the englacial system
Runoff and Temperature
• Average lag time between peak daily temperature and peak daily
discharge around 7 hours
• The diurnal variation of runoff isn’t as large as on clean glaciers,
possibly due to the debris causing different delays on different parts
of the glacier
Average hourly stage and temperatures
0.370.3750.38
0.3850.39
0.3950.4
0.4050.41
0.4150.42
100
300
500
700
900
1100
1300
1500
1700
1900
2100
2300
Time
Sta
ge (
ma S
D)
0
2
4
6
8
10
12
14
16
Te
mp
era
ture
(˚C)Stage
Air Temperature at lower AWS
• Some lag due to the time taken for temperature cycle peak to reach the ice/debris interface (at an average debris thickness ~ 0.25 m, takes ~ 6 hrs for the rising temperature at the surface to reach the ice/debris interface)
• May also be due to the percolation of water through the debris
Average 10 min temperature through the debris
profile at LOMET during 2005
0
5
10
15
20
25
30
35
10 210
410
610
810
1010
1210
1410
1610
1810
2010
2210
Time
Te
mp
era
ture
(?
C)
0 cm
24 cm
48 cm
72 cm
(°C
)
Conclusions
Majority of dye traces indicated efficient and
channelised drainage, preferential flow paths don’t
close completely over the winter
Suggests combination of cavity system which is only
slightly influenced by changes in input, linked to a
preserved conduit system that transfers the majority of
water
Large lag between temperature and discharge, and
small diurnal amplitude of discharge fluctuations imply
debris increases and varies the time taken for water to
reach the proglacial stream
References
Diolaiuti, G., D’Agata, C., Meazza, A., Zanutta, A. and Smiraglia, C. (2009) Recent (1975-2003) changes in the Miage debris-covered glacier tongue (Mont Blanc, Italy) from analysis of aerial photos and maps, Geografia Fisica e Dinamica Quaternaria (32) 117-127
Flowers, G. E. (2008) Subglacial modulation of the hydrograph from glacierized basins, Hydrological Processes (22) 3903-3918
Acknowledgements
The Geography and Environmental Science department at the University of Dundee for their studentship
Several dissertation students for help in the field
Dr Tim Reid for assistance with fieldwork and equipment
Prof. Joe Holden for the loan of the flourometer
NERC Geohphysical Equipment Facility in Edinburgh for the loan of two dGPS rovers
Milan University for the use of their stake network
Marco Vagliasindi from the Fondazione Montagna Sicura, La Palud, for logistical support
Doug Mair for the loan of a Kovax ice drill
Scottish Crop Research Institute for the loan
of a Campbell logger
My supervisors!