ON THE RELATIONSHIP OF SNOW ACCUMULATION TO
SURFACE TOPOGRAPHY AT "BYRD STATION",
ANTARCTICA
By ANTHONY J . Gow and ROBERT R OWLAND
(U .S. A rmy Cold Regions Research and Engineering Laboratory, H a nover , New Hampshire,
U. S.A. )
ABSTRACT. R ecent measurements of snow acc umulation on undulat ing surfaces around " Byrd station " ,
Antarctica indicate that the undulations a re tending to be filled in. These resu lts are discussed in the lig ht
of c urrent knowledge of the or igin and migration of such features.
RESU ME. Relalion mire I' accwnulalion de la "eige el la lopographie sllperjicielle cl la statioll " By rd" , Anlarctique. D e
recentes m esures d' accumu lation de la neige sur la surface ondu lee a utour de la station " Byrd", indiquent
que les ondulati ons ont une tendan ce it etre comblees. Ces resu lta ts sont discutes it la lumi ere de la con naissance courante de l'origin e et de la m igration d e re li es formes.
ZUSAMMEN FASSU NG. D er Zllsammenhang ;:.wischm Schneeauftrag lI"d Oberjldchenrelief an der " Byrd-Station",
Antarktika. Neue Messungen des Schneeauftrages li ber gewell ten Flachen urn d ie "Byrd-Station" zeigen an,
dass eine Tendenz zur Auffli llung der Welle ntaler bes teht. Diese Erge bnisse werden im Lichte der bishe rige n
K enntnis liber di e Entstehung und W a nde rung solch er Erscheinungen diskutiert.
STEPPED surfaces and undulations of wavelengths of 5- 30 km . are now know n to characterize
much of the surface of the Greenland a nd Antarctic I ce Sheets, particularl y the latter, and
there has been som e speculation as to how these features might form. Nye ( 1959) for example
would attribute surface waves of these dimensions (mea n am plitudes of about 20 m. ) to
irregularities in the underlying bedrock, but Bader ( 196 1) believes that drifting snow is
responsible for the formation of wavy surfaces in the high interior of Greenland.
A fairly considerable surface relief is to be observed in the general area of new " Byrd
station" , Antarctica. New " Byrd station " was constructed under the snow near the bottom
of a broad depression and between it and the old " Byrd sta tion" located 10 km . to the west
there are two smaller valleys. An examination of the surface in February 1 962 indicated that
the valleys were accumulating much m ore snow than the crests of these undulations. In order
to obtain some quantitative data on this r elationship between accumul ation a nd surface
topography, two stake lines were set up, one oriented pa ra llel to the prevailing wind direction
and the other normal to it . The " east- west" line, (Fig. I) comprising 21 stakes emplaced at
intervals of 0·5 km. extended from the south-east corner o f the stake farm at o ld " Byrd" to a
point about a kilometer north of the radio noise tower at new " Byrd station". The second line
of 22 stakes was begun just to the east of the V .L.F. antenna and extended d own-wind in a
southerly direction for a distance of 10·5 km . The elevati on at each stake was measured
barometrically. In Figures 1 and 2 these elevations have been conve rted to absolute values
based on the elevation at the gravity pier at new "Byrd station".
As indicated in Figure I , the "east- west" line traversed two small valleys superimposed on
a surface that sloped upward to the east. The relief along the " north- south " line of stakes
(Fig. 2) differed somewhat in that it took the form of a fa irly steeply sloping surface intersected
by two small steps. The impression gained in the field was that the " north- south" stakes
traversed a major structural feature of the surface a nd that the undulations a long the "eastwest" line were superimposed upon this structure. However , it is difficult to say from observations over such a limited area of the surface whether or not the undulations are oriented in
any particular direction. Nevertheless, a fter just three years o f observations the stake measurements have yielded some interesting data.
First, the pattern and magnitude of accumulation for the three years ending 30 January
1963, 30 January 1964 and 9 January 1965 are remarkably similar. Along the "east- west"
843
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Fig.
m.
BE-TWEE N STAKES
stake line. The thin line above the curve of surface
Profiles of slllface reliif and mow accumulation along the "east-wes t"
elevation represents three years accumulation drawn to scale
1.
1
g. cm. - 1 for 1963 and 13' I
line the accumu lation averag ed J 1'0 g. cm. - for 1962, 9 ' 7
of J I . 3 g. cm. - 1 yr. - I. Along
lation
accumu
g. cm. _1 for 1964 which gives a three-y ear mean
1
ted to 10'7 g. cm. - 2 yr. amoun
lation
accumu
mean
the "north- south" line the three-y ear
1
vely.
respecti
1963 and 1964
with annual increme nts of 10' 4, 9' 0 and 12·6 g. cm. - for 1962,
ements at 100 stakes in
measur
years'
Several
d.
expecte
than
smaller
much
were
These values
lation of nearly
accumu
of
rate
average
a J ' 0 km .' grid at old "Byrd" had yielded an
- 2 yr. - I from studies of pits
cm.
.
g
4
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14
of
value
a
d
obtaine
J 8 g. cm. - 1 yr. - I . Gow ( J96 I)
that falls in betwee n those
and cores spannin g 67 yr. of continu ous accumu lation, a figure
the accumu lation for the
gh
obtaine d at the stake farm and along the stake lines. Althou
lts would indicate that
resu
present
the
usual,
period 1962- 64 may have been lower than
2
ntative values of snow
represe
lly
fu
yield
not
may
km.
0
'
I
measur ements in grids as large as
accumu lation in areas of undula ting surface topogra phy.
a strong topogra phic
Second ly, both stake lines, particu larly the "east- west" line, reveal
to accumu late snow
tended
t
gradien
t
constan
of
control on accumu lation rates. While slopes
accomp anied by
bly
invaria
were
slope
surface
in
changes
at fairly uniform rates, abrupt
iably more snow
apprec
lating
pronou nced changes in accum ulation, with the troughs accumu
ly interest ing
special
are
stakes
of
line
than the crests. The results from the " east- west"
storm winds .
the
of
n
directio
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to
angles
right
at
because these stakes cross the undulat ions
R E LATIO NS HIP
OF SNO W
A CCU M U LATI O N T O
SU R F A CE TO P OG RAPH Y
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STAKE NUMBERS
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Fig.
2.
Curves
DJ accumulation
and surface elevation along the " north- sollth" line
DJ stakes
Accordi ng to Nye ( 1959) surface undu lations of w avelengths 3- 40 km. a nd m ea n
amplitude of 20 m. should no t su rvive for mu ch longer tha n a year if they rep rese nt departures
from the equilib rium form of the ice sheet. Sin ce waves of these dimensio ns cannot be bui lt
up by drifting snow in as little as a year, Nye concludes tha t such undulatio ns can best be
interpre ted as sta tionary w aves; related di rec tl y to irregu la rities in the underlying bedrock .
H owever , in the interior of Antarctica where the surface m ovem ent is likel y to be very sm a ll
(of the order of a few m eters per year on ly), a n y relief due to sta tionary waves might tend to
be self-d estructive, simply because of the var ia tions in the su r face acc umula tion such relief
would create; i.e. surface drifting could be ex pected to fill in th e tro ughs. This a ppears to be
the case a t " Byrd sta tion ". Som e simple calculations indicate tha t at the curren t rates of
accumula tion , the surface wrinkles could be substantia ll y sm oo thed ou t in as little as 50 yr .
In Figure 3 the surface p rofiles a fter 20 yr. a nd 50 yr. a r e compa red with the present day
profi le a long the " eas t- west" sta ke line. In calcula ting these profiles corrections were m a d e
for the d ensification of the snow a t the ra tes o bserved by C ow ( 196 r) in pits a nd drill cores
JOURNAL
OF GLACIOLOGY
at " Byrd station". Even after '20 yr. humps would begin to develop in the hollows if the
present rates of accumulation were maintained. Of course any such changes in the surface
relief would tend to be offset by changes in the pattern of accumulation but in a direction
apparently that might eliminate the waves in even less time than 50 yr. During this period
the surface of the ice sheet would probably have moved less than a kilometer. This displacement, of an order of magnitude smaller than the wavelength of surface undulations at " Byrd
station" would have little effect on the overall a ccumula tion . Sin ce an appreciably undulating
surface does exist around " Byrd sta tion" this might suggest then that these undulations are
not directly related to irregula rities in the underlying bedrock. The fact that Bentley ( 1962 )
was not able to find any obvious relationship between the surface relief and the seismi cally
sounded bedrock at "Byrd station" would tend to bear out this conclusion.
1570
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Fig . 3. Surface profiles after 20 y r. and 5 0 y r. rif aCC1llllulation along the " east- west" stake line. The curves were calC1llated on
the basis of present-day rates of snow deposition and have beell corrected also for cOlllpaction
I t now appears however that other factors are involved in the maintenance of undulations
on the surface of the Antarctic Ice Sheet. According to Black and Budd ( 1964) accumulation
of snow on undulating surfaces near Wilkes Station is related more closely to slope than simply
to the existence of humps and hollows on the surface. They found that for undulations of
wavelength of 5- 15 km. the net accumulation maxima occurred slightly down-wind of the
bottoms of the troughs, with minimum deposition occurring down-wind of the tops of the
crests. Rather than filling in the waves this shou ld, according to Black and Budd, perpetuate
them and also move the waves up-slope into the wind at a rate of about 25 m . per year. It
might be possible to explain some undulations by superimposing the effects of surface drift
on standing waves formed on a sloping surface. The formation of stationary waves as postulated
by Nye does furnish a convenient means of creating large-scale fluctuations in surface relief
and if accumulation fails to subdue these waves but creates instead a wave of accumulation
slightly out of phase with the stationary waves then a " migration" of the kind envisaged by
Black and Budd could conceivably occur. In this way an undulation could come to occupy
some new position on the surface of the ice sheet where it no longer bears any relationship to
the underlying topography. This might explain the situation at "Byrd station".
Measurements along both stake lines will be continued for as long as possible. Any changes
in the shapes of undulations in the past could be profitably investigated in cores taken from
RE L A T I ON S H I P
0 F S NO W
Ace U M U L A T I ON
TO SUR F ACE
TOP 0 G RA P H Y
847
d ep th s of 20- 25 m . at in tervals a lon g the surface. I t wo uld be inte resti ng to compare p ast
records of acc umul a tion at say a crest a nd a trough a nd to d etermin e what cha nges if a n y h a d
occurred in th e sh a p e of the in te rve ning surface. M ore di rect m easu reme n ts of this ki n d a re
n eed ed if the q u estio n s of origin a nd m ovement of u nd ul ations in A n tarctica are to be answered
satisfa ctori ly.
111S. received 2 f D ecember f 964 and in revised form 15 i\I1ay 1965
R E F E R ENCES
Bader, H . 1961. T he Green land Ice Sheet. V.S. Cold R egions R esearch and Engineering Laboratory. Cold regions
science and engineering. H a n over, N.H., Pt. I , Sect. B2.
Bentley, C. R . 1962. Su r face slopes and ice th ickness in West A n tarcti ca. Journal of Glaciology, Vo l. 4, No. 33,
P·3 1 5- 1 7·
Black, H . P. , and Budd , W. 1964. Acc u m ulation in th e region of \'Vi lkes, Wi lkes L a nd , Antarctica. Journal of
Glaciolo!{y, Vol. 5, o. 37, p. 3- 15.
Gow, A . .1 . 1961. Dr ill h o le measurements and snow studies at Byrd Stat ion , Antarctica. U.S. Cold R egions R esearch
and Engineering Laboratory. Technical R eport 78.
Nye, .1. F . 1959. Surface topog raphy of t he Anta rctic I ce S hee t. Natllre, Vol. 184, No. 4689 , p. 786- 87.