Glaciological and meteorological studies on the Boas Glacier, Baffin Island, for two contrasting seasons (1969-70 and 1970-7 1)

J.D. Jacobs2, J.T. Andrews', R.G. Barry2, R.S. Bradley2, R. Weaver', and L.D. Williams'

Institute of Arctic and Alpine Research, and Departments of GeoZogicaZ Sciences1 and Geography2, University of Colorado,

Boulder, Colorado, U. S. A.

ABSTRACT: Boas Glacier are presentzd for two contrasting years. the net winter balance (b,) was 0.4m H20 and the net balance for the year (En) was +0.37m H20. were 0.26 m H20 and -0.2 m H20. Meteorological data for summer 1970 show ration apparently made a significant contribution to the heat loss. The contrast between the two ablation seasons is analyzed on the basis of synoptic circulation types and climatological parameters.

The results of mass and energy balance studies on the For 1969-70

For 1970-71 the corresponding figures

that net radiation provides 60% of the energy input. Evapo-

RESUME: de masse et, d'énerpie du glacier Boas au cours de deux années diffé- rentes. En 1969-70, le bilan net d'hiver (bw) a été de 0.4m d'eau et le bilan net annuel (6,) a été de +0.37m d'eau. Les chiffres correspondants de l'année 1970-71 ont été de 0.26m d'eau et de -0.2 m d'eau. Les données météorologiques de l'été 1970 montrent que le rayonnement représente 60% de l'énergie resue. L'évaporation Bvidem- ment a déterminé une perte de chaleur significative. entre les deux saisons d'ablation est analysée en partant de types synoptiques de la circulation et de paramètres climatologiques.

Les auteurs rapportent les résultats des études du bilan

La différence

The Boas Glacier is a small 1.45 km2 glacier located between the heads of Quajon and Narpaing fiords, Baffin Island, 67" 35' N, 65" 16' W (Fig. 1). It extends from 800 m to 1300 m a.s.1. In the upper reaches two accumulation basins appear to exist, but our studies show the contribution of the "east bowl" to be negligible. steady state equilibrium line altitude (ELA) is estimated to lie in the range 300-1000 m a.s.1. The glacier was chosen for detailed study because the sequence of late- and Neo-glacial moraine systems in this area appeared to provide suitable information for modelling present and paleoclimatic influences on the glacierization of northern Cumberland Peninsula Il]. Subsequent analysis indicates that the Boas Glacier is in fact truly representative of the small cirque glaciers that lie seaward of the Penny Ice Cap l2], in factors of orientation, elevation, and receipt of global radiation. The glacier was also satisfactory from a logistics standpoint.

Preliminary studies began in 1968 and continued through 1971 with the major research effort being concentrated in 1970. Three Hoinkes precipitation storage gauges were installed in 1969 (in addi- tion to the one erected in 1968) and an initial stake network was drilled on the adjoining Akudlermuit Glacier (Fig. 1). In 1970 a micro-meteorological station was established at 1140 m a.s.1. on the

The

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Boas Glacier with subsidiary weather stations installed at six loca- tions to give information on local (meso-scale) climatic patterns. The DEW-Line weather station at Broughton Island (Fig. 1) (581 m a.s.1.) provides some possibility of correlating our data with the longer (13-year) record available from this site. The glaciological program consisted of regular stake and pit observation readings at a series of thermistor strings drilled in along the glacier, the establishment of a velocity and strain net, and the setting up of a rating curve for meltwater streams off the glaciers. The regional setting of the Boas Glacier has also been examined in terms of pre- sent and past glaciation limits from topographic maps for the region 131 and by an analysis of all available weather records for Baffin Island and West Greenland 143. The purpose of this was to relate our years of study to the longer climatic history, with a view to predicting future glaciological trends.

studies for 1969 through 1971 and relates these to the synoptic weather conditions.

This paper presents the results of the mass and energy balance

MASS BALANCE

Six stakes were established on the upper Akudlermuit Glacier in 1969 and an additional 21 stakes were installed on the Boas Glacier in early June 1970. suggested density of 20 stakes ~ I U - ~ . Results 1969-70

Extensive probe surveys were conducted from the stake system at the beginning of the 1970 ablation season. A total of thirteen snow- pits was dug at the beginning of the 1970 summer to provide specific data on density, structure, and temperature in the snowpack. All pits indicated that the 1969-1970 snowpack lay on hard ice. thirty-five snow density determinations was 0.321 + 0.007 g cm-3. The average snow depth, measured at 240 probes, was 1.22 i 0.2 E, with a rangc from 0.58 to 1.93 m. determined from these data was 0.391 0.01 m H20.

intervals and the computed water equivalent snowpack for each inter- val based on snowpit and probe measurements. ter balance (bw) derived from these data was 0.38 f m H20 with a net winter balance Bw of 0.551 x lo6 m3 H20.

Glacier at no time lay within the ablation zone but was confined within the wet snow and percolation facies 161. 1969-70 snowpack were only isothermal for 2-4 weeks. Snowpits were dug at seven sites on a weekly/bi-weekly basis and surface lowering was noted on a network of twenty stakes. Final mass balance compu- tations were based on eleven snowpits dug down to the 1969 summer surface between August 15 and 18th, 1970. At the twenty stakes the surface lowering was measured directly and the accumulation of super- imposed ice C

This number is in accord with Schytt's IS]

The mean of

The net specific winter balance (bli)

Table 1 lists the area on the glacier within 150-m vertical

The net specific win-

The 1970 summer was remarkable for the fact that the Boas

Temperatures in the

was derived from: /

(i) \

where X is the distance from the face at times to and tl and Y is the probed depth to the ice surface

top of the stake to the snow sur-

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over the same time interval. As the glacier showed no ice during the 1970 summer, the change in net winter balance can be computed as the difference between the volume of water that moved into the pack (shown by the surface lowering) and the volume of superimposed ice formed during the 1970 sumer. The volume of superimposed ice at the end of the ablation season was calculated for the different elevation intervals using a densi.Ly of 0.82 g ~ m - ~ . ice thickened down glacier from 0.1 to 0.21 m. The total volume of 1970 superimposed ice was 0.156 x lo6 m3 H20 or a specific value of 0.107 m H20. snout to 0.15 m in the upper accumulation zone. resulted in the refreezing of the crust with a density of about 0.5 g If this density is used the surface lowering (which results in water entering the pack and either being stored or lost to the glacier) gives a mass exchange of 0,1262 x lo6 m3 or a specific "apparent" loss of 0.09 m H20.

The net balance for 1969-70 was also computed on the basis of pit and stake data for the 150-m contour intervals (Table 1). The "balance" was strongly positive and the glacier added nearly 1% to its then total mass. H,O. The net ablation during the 1970 summer was, therefore, very limited. the specific summer ablation was about 0.08 m H20.

Superimposed

Net surface lowering varied between 0.32 m at the Cooling at night

This amounted to 0.565 x lo6 m3 or 6, = 0.39 m

As approximately 0.08 m H20 fell in the form of snow/rain,

Table 1

Mass balance data, Boas Glacier, 1969-70 (m H20)

Area gw 6, 'Superimposed Surface Altitude(m) (km2) ice lowering

750-900 .13 .47 .31 .17 .22

900-1050 .194 .41 .40 .18 .20

1050-1200 .405 .43 .52 .10 . O8

west bowl 1200-1350 .414 .26 .39 . O8 .11

east bowl 1200-1350 .307 .34 .33 . O8 .11

ResuZts 1970-71

Pit, stake, and probe surveys were carried out in early June,

snow density was rather similar (0.314 g ~ m - ~ ) 1971. average of 0.83 m. giving an estimated bw =0.26 m H20. vertical zones gave a value of 0.244 m H20. The glacier was revis- ited toward mid-August, when most of the exposed surface consisted of ice. Examination of the stake network indicated that the 1970-71 cover had been totally removed although much of the previous year's large mass gain was still present as superimposed ice. For the interval 1969-71, positive mass gains were recorded above 1000 m and mass losses below it. However, the specific mass balance for 1970-71 season was -0.20 m H20.

Snow depths were notably less than the previous year with an

Computations using the 150-m

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Long-tem VaZues

An estimate of the long-term mass turnover of the glacier was attempted by calculating the mass being transferred through the Equilibrium Line Altitude (ELA). This was accomplished by establish- ing a velocity profile at about 1000 m. Annual movement is slow and averages 1 to 2 m yr-l. The depth at the ELA is estimated to be 70 m and the east bowl of the glacier is excluded from the analysis as it seems to have a very limited drainage into the main glacier at pre- sent. accumulation zone 6n = + 0.08 m H20; ablation zone bn = -0.16 m

Results-are as follows: I-I2O

METEOROLOGICAL STUDIES

The immediate objectives of the meteorological program were: (1) to determine the characteristics of the regional climate and its local variability; (2) to establish the energy budget of the Boas Glacier for summer 1970; (3) to analyze the observed characteristics in terms of the synoptic-scale circulation regimes.

GLACIAL METEOROLOGY

A micrometeorological program was operated from 9 June through 7 August at 1140 m a.s.1. on the Boas Glacier. The site was on a loo slope of NW aspect and the only significant obstructions on the horizon were in the NE quadrant where a ridge rises to 18’ elevation angle. Snow cover was present all summer, and, at the end of the measurement period (which was almost certainly the end of the ab1.a- tion season), 0.5 m of snow still remained.

fluxes; their accuracy is estimated to be 10% for global radiation, 20% for net radiation. Profiles of temperature and vapour pressure were determined near the surface, but uncertainties in these data make the computation of the turbulent heat fluxes approximate at best. The energy budget at the site is given ìn Table 2. Little variation is expected over this relatively uniform and small glacier.

Direct measurements were made of the short and net radiation

Table 2

Energy budget of the Boas Glacier, 1140 m, 9 June-7 August, 1970 (cal cm-’)

Sources Sinks

Warming of snowpack Net radiation 3700 and glacier 1300

Melting 0.15 mH20 of Sensible heat 1100 snowpack 1200

Latent heat (condensation)

Evaporation and 500 sublimation 3650

Latent heat (superimposed ice) __ 850

6150 - 6150

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The estimate of heat of evaporation and sublimation is derived as a residual from the energy balance equation. Support for this high value is evidenced by the fact that small but definite negative vapour pressure gradients were measured for 65% of those synoptic intervals when melting was observed. Melting occurred on 30 out of 60 days. Also, direct measurements of evaporation from porous cup atmometers indicated a high evaporation potential. Further calibra- tion of these atmometers is in progress to provide firmer estimates of evaporation rates.

energy input, its relationship to mass balance has been examined. For comparison purposes, daily data were available on surface lower- ing, as determined with an ablatometer, and on runoff measured with a stream gauge at the base of the glacier. Figure 2 shows a high correlation between net radiation and surface lowering, with some 50% of the variance of the latter accounted for. better measure of conditions over the glacier as a whole. wise Tegression on daily records for 13 days during the ablation peak shows that 66% of the variance in runoff is accounted for by net radiation, mean daily temperature, and global radiation, of which the first two are of greatest importance.

made for summer, 1971, using temperature data from an unmanned station at ßase Camp (490 m) near the glacier. Using the regression of daily minimum temperature between ßase Camp and Glacier Camp for 1970, it is estimated that there were almost twice as many melting degree-days in 1971 as 1970 (Table 3). Greater ablation should therefore have oc- curred in 1971 and surveys of the glacier at the beginning and end of the summer showed that this was indeed the case.

In view of the fact that net radiation contributes 60% of the

Runoff provides a A step-

On the basis of these results an estimate of ablation has been

Table 3

Temperatures and ablation, Boas Glacier, 9 June-4 August

Me1 t ing Estimated Meas ur ed Mean temp . deg. -days ab 1 at ion ab1 at ion

("Cl (>O°C) Im H,O) Im HZ01

- 1970 -1.7 43 .15 i.03

1971 -1.1 (est.) 83 (est.) .29 i. 06 .39 +.O4

In future it should be possible to refine such extrapolations A system of cloud-day with reference to radiation and cloud data.

types (Fig. 3) developed from the 1970 observations (Table 4) shows that net radiation varies primarily in response to cloud amount and height. The use of cloud-day types makes it feasible to estimate the seasonal net-radiation from calculated clear-sky global radiation, estimated long-wave flux, and cloud cover data. This approach is being developed with respect to a combination of satellite, synoptic, and upper-air data in conjunction with field measurements at sea- level at Broughton Island some 50 km to the east.

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Table 4

C1 oud-Day Ana lys is

N SS(1y) c1 S(1-a)(ly) Rn(1y) Ln(1y) Cloud Day type (tenths)

A 10 L1 19 425 .77 98 49 -49

B 0-2 13 595 .71 173 57 -116

C 6-8 M 11 482 .76 116 70 -46

D 9-10 M 2 253 .77 58 71 14

E 6-10 H 2 534 .68 170 62 -108

L, M, and H - Low, Middle and High cloud. N - number of cases. SS - direct 6 diffuse solar radiation. ci, - albedo. Rn - net radiation. Ln - net longwave flux.

Table 5

Characteristics of summers 1970 and 1971

Mean temperature Precipitation departures (OC) departures %

June July August June July August

1970 Broughton Is. 581 m -1.5 -3.4 -2.2 +28 -94 +7 Cape Dyer 368 m -1.7 -3.3 -2.0 i42 +16 -15

1971 Broughton Is. +0.5 +0.6 -1.1 -64 +180 -64 Cape Dyer +0.4 -0.4 -0.9 -68 +190 -40

Departures based on 8-9 year means.

SYNOPTIC ASPECTS

The summers 1970 and 1971 are clearly differentiated in their climatic characteristics in eastern Baffin Island (Table 5). The summer of 1970 was markedly cooler than average and June precipi.- tation was well above average with a slightly above normal total for the summer. In 1971, temperatures were near average. Precipitation was well above average in July, but below in June and August, 1971. Most of this probably fell as rain on the glacier compared with July, 1970 when 22% was snow. most critical. Above-average snowfall in this month maintains a high albedo which greatly impedes the ablation process, particularly if the month is also cloudy.

However, the month of June appears to be

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The circulation regimes, described in terms of a classification developed for Baffin Island and neighbouring areas 171, were almost identical in July-August, 1970 and 1971 and were also close to the 1961-70 average.

1970 - 197i 1961-70 - Cyclonic situations 45 47 49 %

Anticyclonic situations 55 53 51

In comparison, in July-August, 1969 there was a 68% frequency of anticyclonic situations including 32% with a dominant anticyclone cell over Baffin Island. Field reconnaissance during that summer found much exposed ice Akudlermuit Glacier, a condition which was repeated in 1971. It is significant that in June 1971, 2/3 of days were anticyclonic, where- as in June 1970, 2/3 of days were cyclonic with frequent depressions centred over Baffin Island. (Lows in the Davis Strait tend to advect warmer air masses over eastern Baffin Island.)

conditions that favour low summer ablation in this area: (1) June snowfall above average, in association with cloudy, cyclonic situ- ations (maintaining a high albedo and low global radiation receipts) ; (2) July temperatures below normal (causing some of the precipitation to fall as snow at higher elevations, slowing the melt of the snow- pack, and probably increasing the contribution of sublimation); (3) average or above-average frequency of cyclonic situations in July, especially those with lows centred over Baffin Island (maintaining thick cloud cover). These conditions are stated in what is thought to be their relative order of importance. Continuation of at least some limited surveys in subsequent seasons should help to refine and, where necessary, revise these results.

on the Boas Glacier and its neighbour, the

The following provisional conclusions can be drawn regarding

ACKNOWLEDGMENTS

This research was supported by grants from the Army Research Office, Durham (DA-ARO-D-31-124-61163 and DA-ARO-D-31-124-71-G80) and the National Science Foundation (GA-10992). The National Air Guards of Wyoming and Minnesota provided invaluable support in transporting the party between Denver and Frobisher Bay, N.W.T. Officials of the Department of Indian Affairs and Northern Develop- ment were most helpful in the arrangements on Broughton Island. The research projects involved personnel (S. Boyer, P. Carrara, J. Clark, R.E. Dugdale) and equipment from INSTAAR and the Department of Geo- logical Sciences and Geography.

REFERENCES

[l] ANDREWS, J.T., BARRY, R.G., and DRAPIER, L. (1970). An inven- tory of the present and past glacierisation of Home Bay and Okoa Bay, east Baffin Island, N.W.T., Canada, and some climatic and palaeoclimatic considerations. J. Glaciol., 9, 337-362.

glacierisation on the Okoa Bay, Padloping Island and Cape Dyer map sheets. MSc thesis, Univ. of Colorado.

[2] WILLIAMS, L.D. (1971). Radiation and elevation controls on

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131 ANDREWS, J.T. and MILLER, G.H. (1972). The Quaternary history of northern Cumberland Peninsula, Baffin Island, N.W.T. : Part IV: Maps of the present glaciation limit and lowest equilibrium line altitude for north and south Baffin Island. Arctic and Alpine Res., 4 (in press).

recorded at weather stations. [4] BRADLEY, R. (In prep.) Climatic trends for Baffin Island as

[5] SCHYTT, V. (1962). blass balance studies in Kebnekajse.

[6] MüLLER, F. (1962). Zonation in the accumulation area of the J. Glaciol., 281-289.

glaciers of Axel Heiberg, N.W.T., Canada. J. Glaciol., 4,

[7] BARRY, R.G. (1972). Further climatological studies of Baffin 302-318.

Island, Northwest Territories. Inland Waters Branch, Tech. Bull. (Ottawa, Canada) (in press).

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JULY 14 20 25 I I I

30 I

AUGUST 5 I

I

-2 L NET RADIATION (ly/doy)

Fig. 2. Temporal correlation between [upper diagram] the surface lowering at the glacier meteorological station in cm dy-’

net radiation (ly dy-l) [lower diagram] at the site for the Boas Glacier, summer 1970. Elevation

of station 1140 m a.s.1.

380

IO

RADIATION DAY TYPE A Example: I July 1970

-

EST

1.0

RADIATION DAY TYPE B Example: 27 July 1970

5 05 ,. -

0.0

Fig. 3. Examples of cloud-day types (see Table 4). Data from the station at 1140 m a.s.1. on the Boas Glacier A. Radiation-day type (A) showing short-wave (S) , absorbed short-wave (S(1-a)) and net radiation (Rn) . Black and vertical lines indicate periods of positive

and negative long-wave fluxes respectively. B. Cloud-day type (B), line symbols, etc., the same as for A

381

DISCUSSION

G. WendZer [U.S.A.) - Our findings on the McCall Glacier, Brooks Range, Alaska, situated at a latitude similar to that of the Boas Glacier, do not show the high evaporation rates found by the authors. We found that in spring and early summer evaporation is relatively high there, but not as great as in Baffin Island. However in summer, during most of the ablation season, the evaporation is compensated €or by condensation and a net value mean to zero was found,

R.S. Bradley (U.S.A.) - A Russian author, V.A. Markin, reported that evaporation contributed about 67 percent to the total energy balance in W. Spitsbergen during the summer of 1965. It is the only study I am aware of that shows similar evaporation rates, but it was not clear whether Markin obtained evaporation also as the residual in a balance or not. component.

It is very difficult to record the evaporative

II. Lang (Switzerland) - Your study involves multiple stepwise regression analysis of runoff and meteorological data. the partial correlation coefficients for net radiation, temperature, and global radiation?

What were

R.S. BradZey (U.S.A.) - This information is not directly avail- able. The problem involved in this analysis was that the runoff data covered a very short period of about two weeks. The number of points in the stepwise regression is very small and therefore it is difficult to assess the significance of the relationship. But about 66 percent of the variance could be accounted for by the three variables.

H. Lang (Switzerland) - Was this analysis based on hourly or daily values?

R.S. Bradley (U.S.A.) - It was based on daily values. Midnight to midnight for radiation and noon to noon for runoff. was a twelve-hour lag between the components.

Thus there

O. H. Ldken (Canada) - The authors should be congratulated on this very interesting study which highlights the glaciological and meteorological conditions during two very different budget years. believe that such studies of strongly contrasting conditions may help our understanding of the elusive glacier-climate relationship.

data from Decade Glacier will be of interest in connection with the temperature trends that you showed on the basis of data from Clyde, where distinct changes were observed during the 1960's. studies on Decade Glacier, approximately 70 hm southwest of Clyde, show no such trends. Of the six budget years between 1964-1970, three gave a positive and three a negative mass balance. Of these years, two (1965-66 and 1968-69) had very large negative values and the glacier had a very considerable mass loss over the six-year period.

R.S. EradZey (U.S.A.) - Climatic data for all of Baffin Island

only to parts of eastern

I

We must, however, proceed with some caution; the mass balance

Mass balance

are highly correlated and synchronous in time; however, the informa- tion given in this paper may be pertinent Baffin Island. Further detailed information concerning this work is available in the report: Institute of Arctic and Alpine Research Miscellaneous Paper (No. 3, October 1972).

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