World Glacier Inventory — Inventaire mondial des Glaciers
(Proceedings of the Riederalp Workshop, September 1978; Actes de l'Atelier de Riederalp,
septembre 1978): IAHS-AISH Publ. no. 126,1980.
Glacier balances in the Dry Valleys area, Victoria Land, Antarctica
T. J. Chirm
Abstract. The glaciers of this cold desert occur in topographically favoured positions in coastal
and elevated areas where snow accumulation exceeds sublimation and other losses. Mass balance
measurements have been made since 1969-1970 on three glaciers whilst ablation and other
measurements have been made on a further eight. Measured mass changes are extremely small a n d
indicate that all the glaciers are close to equilibrium although studies of marginal morphology
and movement do suggest that the glaciers are slowly expanding.
Bilans glaciaires dans la région des Dry Valleys, Victoria Land, Antarctique
Résumé. Les glaciers de ce froid désert se forment en des lieux favorisés par la topographie des
zones côtières et élevées où l'accumulation de neige est supérieure à la sublimation et aux autres
pertes. Depuis 1969-1970 on a étudié le bilan de masse de trois glaciers alors que des mesures de
l'ablation ainsi que de certaines autres grandeurs ont été effectuées sur huit autres glaciers. Les
variations de masse mesurées sont extrêmement faibles et indiquent que tous les glaciers sont dans
un état proche de l'équilibre, bien que des études de la morphologie marginale et des mouvements
semblent indiquer une lente croissance des glaciers.
INTRODUCTION
The 'Dry Valleys' region of Southern Victoria Land, Antarctica, is a cold desert of
over 2500 km2 where the ground surface is practically free of snow and ice throughout
the year. The area comprises three major valleys — the Taylor, Victoria and Wright
Valleys separated by east-west trending mountain ranges up to 2400 m in elevation
(Fig. 1). These ranges support alpine-type glaciers, while large outlet glaciers flowing
from the Antarctic ice sheet enter the valley heads. Broad low piedmont glaciers,
nourished by offshore winds, occupy the eastern coastal regions.
CLIMATE
Bare, snow free ground is characteristic of the area as sublimation and evaporation
losses exceed precipitation except in some higher altitude valleys where conditions
favourable to accumulation of snowdrift have formed glaciers. Estimates of annual
precipitation are difficult to make because it is so very low. Meteorological data from
the New Zealand station at Lake Vanda indicate a mean annual precipitation of
between 7 and 82 mm of snow (Thompson, 1973), which could be equivalent to
about 0.7-8.0 mm of water. Strong, persistent easterly and westerly winds are
characteristic of the valleys, with an increase of westerly winds during the winter
months. Mean annual temperature at valley floor level is about —20°C, with a greater
range than that experienced in other Antarctic stations. Summers are of up to 8°C
warmer and winters up to 10°C cooler than other areas of equivalent elevation.
Relative humidities are consistently low with summer averages of 30-40 per cent and
winter values somewhat higher. Values lower than 10 per cent have been recorded in
periods of westerly winds.
237
238
T. J. Chinn
cirque,scarpC—
10
FIGURE 1.
lake
0
«^
valley side
10
20
30
u>
SI km
Location map.
GLACIERS OF THE DRY VALLEYS
The glaciers of the Dry Valleys area are strikingly clean of surface moraine and have
characteristic margins of vertical, actively calving ice cliffs up to 20 m in height. Alpine
glaciers occur intermittently along the higher ranges between the western polar outlet
glaciers and the lower eastern piedmont glaciers. Glacier mean elevations increase
inland towards the west along with a decrease in glacier size and frequency. Consequently western cirques are empty of ice and there are relatively few alpine glaciers
in the Victoria Valley area. The Asgaard Range, on the southern side of Wright Valley,
supports in transverse cirques and hanging valleys most of the glaciers covered in this
study.
The present glaciers are discordant with their valleys as evidenced by numerous
cases of only partially ice filled valleys, overflowing cirques and by transverse and even
reversed flow directions. All the alpine glaciers are cold and dry based, consequently
producing negligible basal erosion. No ice movement occurs at the bed contact, and
basal velocity gradients are largely accommodated in a shear zone of salt-rich amber ice
approximately 1 m in thickness (Holdsworth and Bull, 1970). The trunks of the larger
alpine glaciers are not incised, but stand above the wind deflated valley sides. This low
erosion activity suggests that such glaciers can flow over a surface for a long period
yet leave the surface essentially unchanged from that before the advance took place.
Glacier tongues standing proud of the valley sides imply that this protection of
surfaces by ice cover leads to wind deflation exceeding glacial erosion in exposed sites.
Glacier balances in the Dry Valleys area, Antarctica
239
Debris
The glaciers carry very small loads of debris, largely as wind blown dust and sand
carried in with drifting snow, consequently recently constructed moraines are very
limited in volume. The majority of these moraines are found as a thin line of debris
located between active glacier ice and the ubiquitous snow wedge infilling against t h e
glacier margin. The Taylor Glacier is one exception, as this glacier carries large
quantities of basal till. This phenomenon is related to the high salt content of the ice
and the till which has apparently depressed the pressure melting point to the present
basal ice temperature at some position under the glacier (Black and Bowser, 1968).
Surface moraines consist mainly of boulders and debris derived from rockfalls off
the headwalls, and of sand of aeolian origin. Wind blown sand constitutes a major
fraction of surface moraines, particularly on the lower level glaciers. Beside these
glaciers, interbedded sand and snow layers are not uncommon, to the extent where the
Sandy Glacier, above Bull Pass, comprises up to 50 per cent by volume of sand of
aeolian origin (Dort, 1967).
Wind blown sand carried by the prevailing westerly winds accumulates at the eastern
ends of the Victoria and Wright Valleys where deposits on and against ice influence
the regimes of the glaciers. Accumulations of sand on Lower Wright, Lower Victoria
and on Packard Glaciers significantly increase their summer ablation rates, while this
sand is eventually deposited as a moraine at the glacier margins. Barchan sand dunes
occur at the snouts of the Packard and Lower Glaciers, while immature dunes have
formed against the margin of the Lower Wright Glacier. In this location, complex
deposits of dune sand, stream alluvium and glacial till occur together. The sand
deposits are normally ice cemented by moisture accumulated from interbedded snow
layers.
Snow accumulation
Extremely light snowfall occurring throughout the Dry Valleys allows wind to play
the dominant role in governing the location of accumulation areas. Without wind t o
redeposit snow into drifts it is unlikely that any glaciers would exist, as ablation
exceeds precipitation at all altitudes.
Because of the influence of strong winds and low temperatures on accumulation
patterns, accumulation areas may occur on a glacier at different locations and elevations
separated by ablation zones. These alternating accumulation and ablation areas are a
common occurrence and prevent these glaciers from having a definable equilibrium
line altitude. Redeposited snow accumulating in valley heads and against steep slopes
becomes the source of the majority of the alpine glaciers. In many instances this snow
is transported through low saddles from external snowfields. The upper Jeremy Sykes
Glacier névé is connected to the snowfields of the south side of the Asgaard Range b y
a low saddle with wind ridge and scoop features in snow indicating a prevailing southwest wind direction at this altitude. This glacier owes much of its size to accumulation
derived from these snowfields of the Taylor Valley, as the adjacent Odin Valley,
which is separated from the southern névés by a high saddle, is almost completely free
of snow.
The valleys of the Heimdall Glacier have high valley head ridges to the south and
these valley heads also are essentially 'dry' of ice. The glacier itself is developed on
Mt Wotan, immediately above the Wright Valley and close to Lake Vanda. During calm
summer weather, thermal convection currents originating from the warmer valley floor
generate persistent cumulus clouds in the Mt Wotan area. These clouds deposit light
dustings of snow, suggesting that moisture evaporated from Lake Vanda may be
important to the survival of the Heimdall Glacier in this location.
Ablation
Mass wasting from the glaciers is predominantly by sublimation, and meltwater is
240
T. J. Chinn
rarely seen above 1500 m altitude even on the warmest summer days. Below 1500 m,
meltwater channels run intermmittently beside the tongues of the lower glaciers for
approximately two months per year, but the proportion of the total losses from the
glacier by melt is minimal. On the Meserve Glacier melt amounts to only 2 to 3 per
cent of the loss from the tongue (Bull and Carnein, 1970). The rarity of meltwater
above 1500 m may be seen from the effects of one extreme event. During the first
week of January 1974, the Dry Valleys experienced abnormally high temperatures,
with a maximum temperature of +15°C being recorded at Lake Vanda (Anderton and
Fenwick, 1976). During this week, meltwater from the Jeremy Sykes Glacier formed
a pond at the glacier margin some 20 m in length, where previously no pond had existed.
The surface of this ice-pond at 1250 m is lowering at the mean annual ablation rate of
about 80 mm per year. At present, several years after the event, this pond is little
diminished in size, demonstrating the lasting effects of infrequent extreme events.
Ice and snow ablation rates increase directly with both temperature (altitude and
seasonal changes) and exposure to wind. Measured ablation values show that losses
are highest on convex slopes exposed to the wind where the surfaces are deflated t o
bare ice.
Snow stratigraphy and densities have been studied in a number of snow pits.
Because no melt occurs and wind action makes the surfaces of each layer very irregular,
annual layers cannot be distinguished by stratigraphy. Although variable within each
pit, near the surface snow densities generally have a mean of 0.35 Mg/m3over the
accumulation areas studied. From these studies, a mean water content value of
0.35 Mg/m3 was used to derive the water equivalent of the accumulation areas, while
a density of 0.50 Mg/m3 was used for icy snow near the boundaries of ablation/
accumulation areas.
Estimates of mass balance
Accumulation and/or ablation measurements have been made on a total of eight
glaciers, but only on three of these have serious attempts been made to measure a full
mass balance (Anderton and Fenwick, 1976; Chinn, 1971 and 1976; Fenwick and
Anderton, 1975; Hawes, 1972). These are the Jeremy Sykes, Alberich and Heimdall
Glaciers, where base maps are of sufficient quality to calculate glacier areas with
reasonable accuracy. Averaged ablation and accumulation figures are available for the
Meserve and Packard Glaciers and for the Lower Wright-Wilson Piedmont Glacier b u t it
is considered that neither the stake array coverage nor the base maps are of a sufficient
standard to reliably estimate mass balance values of these glaciers (Table 1 ).
Ablation studies have been undertaken on the tongues of the Clark and Lower
Wright Glaciers to give information on the meltwater source of the Onyx River. To
compare these areas with inland areas, ablation measurements were initiated on the
Upper Wright Glacier towards the end of the period covered (Table 1).
TABLE 1. Comparison of ablation measurements on glacier tongues, winter 1973 and
summer 1973-1974
Glacier
No. of stakes
Approx. mean
altitude [ma.s.l.]
Lower Wright
Meserve
Packard
Heimdall
Jeremy Sykes
Alberich
Upper Wright
9
10
10
8
18
8
16
350
800
850
1300
1300
1500
1100
Ablation
[mm water equivalent]
Winter
Summer A n n u a l
-49
- 149
-90
- 119
- 5
- 110
-47
- 51
-32
- 35
-21
- 25
(1975 only)
-
198
209
115
98
67
46
172
Glacier balances in the Dry Valleys area, Antarctica
241
The individual annual mass balances for the three glaciers studied over 5 and 6
year periods are compared in Table 2 and Fig. 2. All three glaciers studied are approximately in equilibrium. The measured balance changes of approximately ±20 mm water
equivalent per year are very small, and an order of magnitude less than comparable
changes on a temperate glacier. A single snowfall of this amount (20 mm water
equivalent), would significantly alter the mass balance. Consistently small balance
changes each year on these glaciers indicate that most snowfalls are well under 20 m m
water equivalent. Measurement errors at individual points can be of the same order as
the balance changes. However, by using a large number of points over a number of years,
it is unlikely that this error will have any detectable effect on the results.
Jeremy Sykes Glacier
The Jeremy Sykes Glacier occupies a compound cirque basin and is located at 77°
36'S, 160° 33'E. The glacier has a main tongue 7.6 km long which is joined by a 2 k m
GLACIER
SEASONAL
BALANCE
MEANS FOR EACH GLACIE R
Annual
balance
Mean of 3
glaciers
1970
Figures in
1971
1972
1973
mm water equivalent
1974
1975
FIGURE 2. Summer and winter area averaged mass balance variations for Jeremy Sykes,
Alberich and Heimdall Glaciers from 1970 to 1975.
242
T. J. Chînn
TABLE 2.
Mass balance from three glaciers (area averaged values in mm water equivalent)
Glacier
bw
bs
bn
1971 bw
bs
bn
1972 bw
bs
bn
1973 è w
Jeremy Sykes
Alberich
-13
+ 10
Heimdall
1970
b
n
197'4 ô w
*s
bn
1975 bn
Sum bn
Mean & w
Mean bs
-14*
+ 1
+ 19
+ If
-12f
- 5
+ 20
+ 20
-22
+ 18
4
5
1
-24
+ 6
+ 27
-
6
-22
-16
+ 24
-33
+ 9
0
+ 16
- 17
-18
- 6.6
+ 4.4
- 18
- 4
-18
- 17
+ 1
+ 17
- 1
-6Î
+ 16
+ 11
+ 38
-
-14
-44*
+ 9
-18
- 7
-12.3
+ 13.4
9
1
-61
- 0.8
- 14.2
w> bs, bn = winter, summer and net balances respectively.
* Includes bs 1969-1970
f bs, 6 W , bn calculated separately
tributary about 1 km from the terminus. The total area of the glacier is 9.92 km 2 and
the altitude range of the main tongue is from 1200 to 1900 m.
The accumulation and ablation patterns on the 6-year balance map (Fig. 3), are
the sum of measurements made each year at each of about 50 stakes. The balance
calculated in this manner differs slightly by 24 mm water equivalent from the individual
annual balances summed for the 6-year period. Mean annual values for this period
are given in Table 3.
TABLE 3.
Mean annual mass balance for 5 and 6 year periods
6 year area averaged
[mm]
Annual
[mm]
1975)
+ 689
-1108
-418
+ 70
- 112
- 42
+ 11.6
-18.6
- 7.0
Alberich Glacier
(December 1969 to December 1975)
Accumulation
+ 106
Ablation
-136
Balance
- 30
+ 78
-100
- 22
+ 13
-17
-4
Heimdall Glacier
(November 1970 to December 1975)
Accumulation
+ 915
-1809
Ablation
Balance
- 894
+ 115
-227
- 112
+ 23
-45
-22
6 year total
[m 3 x 10 3 ]
Jeremy Sykes Glacier
(December 1969 to December
Accumulation
Ablation
Balance
Glacier balances in the Dry Valleys area, Antarctica
243
FIGURE 3. Cumulative mass balance for Jeremy Sykes and Alberich Glaciers measured
over 6 years, December 1969 - December 1975.
A plot of seasonal mass balance variations (Fig. 2), shows gains to the glacier mass
may occur either over the winter or summer seasons. When averaged over the period
studied, summer and winter gains are approximately equal. Because of the short
'summer' season of two months, this result indicates that the glacier gains mass over the
summer and loses mass over the winter. As summer ablation losses greatly exceed
those of the winter period, then it follows that summer snowfalls are well in excess
of winter snowfalls.
Alberich Glacier
The Alberich Glacier (Fig. 3), occupies a small cirque adjacent to the Jeremy Sykes
Glacier and is located at 77° 35'S, 161° 37'E. The total area is 1.36 km 2 and the
altitude range is from 1400 to 1800m. The glacier terminates in a stable ice cliff w h i c h
244
T. J. Chinn
merges with a snow apron towards the southwest. Mass balance measurements have
been made on a network of 14 stakes plus two lines of margin stakes.
Figure 2 shows that the pattern of balance variations closely follows those of the
Jeremy Sykes Glacier but tend to be slightly greater in magnitude. The results
averaged for the 6-year period are very similar to those of the Jeremy Sykes Glacier,
leading again to the conclusion that summer snowfalls tend to exceed winter
snowfalls.
Heimdall Glacier
The Heimdall Glacier (Fig. 4), lies towards the lower end of a compound cirque basin
located at 77° 35'S, 162° 52'E, and has an area of 7.96 km 2 . The overall length of
the glacier is about 6.0 km and it terminates in a broad lobe bounded by a stable ice
cliff to the west and a convex ramp margin to the north and south. Mass balance
LEGEND
Catchment Boundary
Glacier Boundary
Marker Pole
Area of Positive Balance.
Balance Contour
..
water équivalent)
FIGURE 4. Cumulative mass balance for Heimdall Glacier measured over 5 years,
November 1970 - December 1975.
Glacier balances in the Dry Valleys area, Antarctica
245
measurements have been made on a network of 22 stakes since the summer of
1970-1971. The pattern of mass balance changes (Fig. 2) follows those of the above
two glaciers with only minor differences. Over 5 years, however, the results in Table
2 show that summer balances tend to be negative, while the winter average is close
to zero. This suggests that this glacier either receives less summer snow or undergoes
more wind deflation of the névé than the Jeremy Sykes and Alberich Glaciers.
Ice movement
Flow rates have been measured on a number of the glaciers; the results show typically
low rates of movement. The fastest recorded are those of the steep trunk of the
Meserve Glacier where movement reaches 3 m a -1 (Bull and Carnein, 1970). A number
of stakes surveyed near the lower margin of the Jeremy Sykes Glacier indicate movement rates varying from 0.1 to 0.5 m a - 1 . A cross section of stakes near the centre
of the Heimdall Glacier gave a maximum flow of 1.23 m a""1 and a mean velocity of
1.02 m a - 1 . Ice passing through this cross section travels 5 km from the névé headwall
to the glacier snout. From the mean flow rate, the time taken for ice to travel the full
length of this glacier is a minimum of 5000 years. Thus a kinematic wave response t o
climate change may take nearly one-third of this time to become apparent at the
margin.
The margins of the Dry Valleys glaciers have a variety of transitional forms ranging
from actively calving ice cliffs normally about 20 m in height, to convex ice ramps
through to low angled margins infilled with snow wedges. To investigate the equilibrium
of these features, lines of stakes were installed normal to the glacier margins on the
three different types of these features and have been measured for ablation and
surveyed for movement.
On the Alberich Glacier the vertical cliff and low angled margin types were studied.
The stake lines ran from bare ice across the 'amber ice' band and moraine line marking
the glacier edge, and continued out on to the snow wedge infilling against the glacier
margin. Glacier movement did not cease at the anticipated glacier boundary marked
by the line of moraine: compressive movement continued well out on to the snow
wedge. Similar results were obtained from the Heimdall Glacier where a line of stakes
across a convex ice ramp type of margin was surveyed.
CONCLUSION
The glaciers of the Dry Valleys area, under a very cold and 'arid' climate, show a degree
of activity one to two orders less than for comparable temperate glaciers. Mass balance
changes are very small and are close to the degree of accuracy obtained in their
measurement. The results of 6 years of measurements show that the glaciers of the
Asgaard Range are close to equilibrium, with no suggestion of any trend towards e i t h e r
positive or negative balance. Balance measurements also show that summer precipitation rates are higher than those of the winter. This is to be expected as warmer summer
temperatures and open sea in McMurdo Sound allow the atmosphere to carry greater
quantities of moisture to the area. The very cold climate of the ranges with mean
annual temperatures well below —20° C cause the usual climate-glacier balance
relationship to be reversed, so that a glacier advance would indicate a warming climate
and vice versa. Studies of the movement of the glacier margins show that snowbanks
outside the expected limits of the glaciers are moving under compressive flow. This
phenomenon suggests that the glaciers are undergoing a slow expansion despite the
recession measured on the Meserve Glacier (McSaveney, 1974). This suggestion is
supported by further evidence at the glacier margins. The line of moraine between t h e
glacier ice and the water-ice and snow of the snow edge has no distal counterpart
outside of the present area of glacial movement. Such morainic boulder lines would
246
T. J. Chinn
be expected to be found if the glaciers had undergone recent recession. The closest
moraine sets to these glaciers are positioned similar to those of the late Neoglacial
moraines of temperate alpine glaciers, but a date from a basalt eruption post dating
these moraines puts their age at 3.5 million years (Fleck et al, 1972). Beside a lateral
margin of the Jeremy Sykes Glacier, small meltwater channels have formed which
would take many hundreds of years to be erased by erosion under the present climate.
No further older channels are to be found indicating extended positions of the margin.
The terminal lobes of this glacier also show complex banding, such as would be expected
from folding developed during advancing conditions.
From these studies and the extremely slow activity and response times of these
glaciers (the turnover period for the Heimdall Glacier is some 5000 years), it is
concluded that, although these glaciers are in balance within the limits of measurement,
they are presently slowly expanding in readjustment to the post Pleistocene climatic
amelioration.
Editorial note.
The author's original text was shortened by the editors.
REFERENCES
Anderton, P. W. and Fenwick, J. K. (1976) Dry Valleys, Antarctica 1973-74. Hydrological
Research, annual report no. 37, Ministry of Works and Development, Wellington,
New Zealand.
Black, R. F. and Bowser, C. J. (1968) Salts and associated phenomena of the termini of the
Hobbs and Taylor Glaciers, Victoria Land, Antarctica. In General Assembly of Bern,
25 September-7 October 1967, Commission of Snow and Ice, pp. 226-238: IAHS
Publ. no. 79.
BuU, C. and Carnein, C. R. (1970) The mass balance of a cold glacier: Meserve Glacier, south
Victoria Land, Antarctica. In International Symposium on Antarctic Glaciological
Exploration (Hanover, New Hampshire, USA, 3-7 September 1968), pp. 429-446:
IAHS Publ. no. 86.
Chinn, T. J. (1971) Report on hydrology-glaciology programme, Lake Vanda 1970-71. Report
no. 639, Ross Dependancy Research Committee, Wellington, New Zealand.
Chinn, T. J. (1976) Hydrological research report, Dry Valleys, Antarctica 1974-75. Ministry
of Works and Development, Wellington, New Zealand.
Dort, W. (1967) Internal structure of the Sandy Glacier, southern Victoria Land. / . Glaciol.
6, no. 46, 529-540.
Fenwick, J. K. and Anderton, P. W. (1975) Dry Valleys, Antarctica 1972-73. Hydrological
Research, annual report no. 34, Ministry of Works and Development, Wellington,
New Zealand.
Fleck, R. J., Jones, L. M. and Behling, R. E. (1972) K-Ar dates of the McMurdo Volcanics and
their relation to the glacial history of the Wright Valley. Antarct. J. US 7, no. 6, 245-246.
Hawes, J. (1972) Report on the 1971-1972 hydrological-glaciological programme: southern
Victoria Land, Dry Valleys region. Report of the New Zealand Antarctic Research
Programme, Wellington, New Zealand.
Holdsworth, G. and BuE, C. (1970) The flow law of cold ice: investigations of Meserve Glacier,
Antarctica. In International Symposium on Antarctic Glaciological Exploration
(Hanover, New Hampshire, USA, 3-7 September 1968), pp. 204-216: IAHS Publ. no. 86.
McSaveney, M. J. (1974) A 3.1 meter recession of Meserve Glacier, Wright Valley. Antarct. J.
US 9, no. 4, 166-167.
Thompson, D. C. (1973) Climate of the Dry Valleys area of southern Victoria Land. New Zealand
Geographical Society, Conference Series, no. 7, 259-265.
DISCUSSION
Higuchi:
In your slide, we saw clear circular bands at the surface of one of your glaciers. How
do you explain the formation of such bands?
Glacier balances in the Dry Valleys area, Antarctica
247
Chinn:
This banding at the margin of the Heimdall Glacier is interpreted as the undistorted
stratigraphy of the névé region where dust and sand accumulate between snow falls.
Mùller:
Are the mass balance measurements you described being continued?
Chinn:
Yes, but only on one glacier, the Heimdall However, a number of different glaciers
are being studied for ablation, and 5-year phototheodolite surveys are to be continued
at the margins of 16 glaciers.
Muller:
Do you have suitable maps and air photographs to prepare an inventory of glaciers
in the Dry Valleys?
Chinn:
Yes, aerial photographs are available and the US Geological Survey published a set
of 1:50 000 contour maps of the area this year.
Meier:
Have you checked your mass balance results by measurement of the ice discharge
through a cross section?
Chinn:
No, we have not undertaken the difficult problem of measuring the ice thickness in a
profile on these relatively shallow glaciers.