日 峯 雪 氷 学 会 誌 雪 氷 45巻3号(1983年9月) 125-132頁
Glacial-meteorlogical observations of Biafo Glacier, Karakorum in 1977
Kouichi Nishimura*, Hiroshi Nishimura** and Shigeo Suizu***
Abstract: The Biafo Glacier, located at about 35.8•‹N and 75.7°E, is one of the largest glaciers in the Karakorum region, and 59 km long and 3.4•~102 km2 in area. The snowline lies at about
4600 m above sea level. For about one month in the summer of 1977, glacial-meteorological ob-
servations were carried out on the ablation area (4100 m a.s.l.) and accumulation area (4900 m a.s.l.). The results on the ablation area showed that the air temperature on moraine-covered
ice was about 7•Ž higher than that on the bare ice. A glacier wind originating from the upper
part of the glacier blows down the glacier without changing wind direction the whole day. The weather on the glacier varied with a period of about 10 days, which corresponds to the fluctu-
ations of the westerly wave. The summer weather in the Karakorum is considered to be influ- enced largely by westerly wave rather than the monsoon which is pronounced in the Nepal
Himalaya.
1. Introduction et al. (1961) measured the surface velocity of the
The Karakorum lies in the north of the Hima- Kuthiah Glacier (where surging 12 km in advance
laya region and is characterized by extreme of the front was found) and the Baltoro Glacier.
ruggedness, great height, and extensive ice cover. Their results showed fairly rapid movements with
The total area of Karakorum glaciers is about a velocity of 216 m/a on the Kuthiah Glacier
15,000 km2, which consists of 37% of the whole and 90 m/a on the Baltoro Glacier in each abla-
area of the range, while in the Himalaya the tion zone. They also estimated the depth of glacier coverage is 17% (Wissman, 1959). The Baltoro Glacier by the gravimetric method. For areas in lower altitudes in the Karakorum consist Chogo-Lungma Glacier, Kick (1956, 1964) ob-
largely of semi-arid and dry valleys. The mon- tained a surface velocity of 137 m/a and an abla-
soon which brings much precipitation in summer tion rate of bare ice of 3 to 6 cm/day. Unter-
in the Himalaya only affects the Karakorum to steiner (1957) measured radiation on the ablation
a small degree. area of the Chogo-Lungma Glacier. However, as Several authors have reported on geographical Hewitt (1969) pointed out, these studies left and glaciological research in the Karakorum re- much to be learned even about the elementary gion. Hewitt (1969) collated glaciological infor- characteristics of Karakorum glaciers. It can be mation for the Karakorum and recognized eleven said that the glaciological and meteorological
instances of glacier surges. Desio (1954) and Desio characteristics of Karakorum glaciers are virtually
unknown. * Japan Weather Association , Hokkaido Office, Sap- poro 060 In the summer of 1977, the present authors ** The Institute of Low Temperature Science , Hok- carried out glaciological and meteorological ob- kaido University, Sapporo 060 * * * Environmental Research and Technology Insti- servations on the Biafo Glacier (35•‹50'N, 75•‹40'E). tute, Shinjuku-ku, Tokyo 162 The Biafo Glacier lies in the central part of the
125 126 Kouichi Nishimura, et al. 1983 年
Karakorum and is about 59 km long. The object side of the borderline between Pakistan and of the present observations was to investigate the China, and is surrounded by mountains with ele- characteristics of a large glacier in the Karakorum vations from 6000 to 7000 m (Fig. 1.). The Biafo surrounded by arid areas. These observations Glacier is the major water source of the Braldu were made in the period from 15 July to 20 River which is a tributary of the Indus River. August 1977. This paper describes the geomor- The accumulation area of the Biafo Glacier lies phorogical feature of the Biafo Glacier and the mainly in the Lukpe-Lawo (Snow-Lake) and the results of meteorological observations. Ablation Sim-Gang Glacier. The width of the Biafo and flow of the Biafo Glacier were also measured Glacier is about 3 km at the point of confluence during this period but the results will be reported (4700 m in elevation) with the Sim-Gang Glacier, in separate papers. and is about 1 km at a point (3500 m in ele- 2. Geographical aspects of Biafo Glacier vation) 10 km distant from the terminus which The Biafo Glacier is located on the southern protrudes to the Braldu Valley of 3100 m in ele-
Fig. 1 Map of the Biafo Glacier. Thick lines indicate mountain ridge. (From the map of Mott (1950).) 9 月 Glacial-meteorological observations of Biafo Glacier, Karakorum 127
Fig. 2 View of the Biafo Glacier. The flow direction is from left to right.
vation above sea level.
Figure 2 shows a view of the middle part of
the Biafo Glacier. The slope is very gentle, as
small as 1.7•‹ in the middle and 3•‹ in the lower
part. Crevasses were found only near the con-
fluence with the Sim-Gang Glacier and at an ele-
vation of 3800 m, running mostly near the right bank area. Figure 3 shows a transverse surface
profile and the distribution of moraine-covered Fig. 3 Transverse profile and distribution of parts of the glacier at 4100 m a.s.l. The surface moraines on the Biafo Glacier at 4100 m of the central part was about 40 m higher than in elevation. No. 1, No.2, No.3 show the both sides and the moraine-covered parts were locations of the observation stations.
about 15 m higher than the bare ice parts. A number of medial moraines lay below 4600 m; is known in some glaciers with thick moraines in
and two of them were quite wide at lower than Nepal does not exist in the Biafo Glacier.
4100 m; two side moraines were about 400 m in The snowline is defined as the boundary be-
width. At the area lower than 3400 m, rather tween firn and ice on a glacier surface at the end thin moraines cover the entire glacier surface, of the melt season. The snowline of the Biafo
whereas thick moraines cover glaciers in the Glacier was found at about 4600 m in elevation;
Nepal Himalaya such as the Khumbu and G2 this value is reliable because our observation
Glaciers (Fushimi, 1977; Nakawo, 1979). Accord- period covered the end of the melt season. The ingly, it can be said that the stagnant ice which accumulation area above 4600 m was estimated 128 Kouichi Nishimura, et al. 1983 年 .
to be about 2.2 •~ 102 km2 and the ablation area with a handy pressure anemometer, wind direc-
about 1.2 •~ 102 km2. tions with a wind sleeve. Air pressure was meas-
3. Methods of meteorological observations ured with an aneroid type altimeter, and water
At the observation site on the ablation area precipitation with a can (8 cm in diameter) in-
(4100 m) of the Biafo Glacier (Fig. 1), meteoro- stalled on the grass field. In addition, cloud forms logical stations were established: Station No. I and amounts and other weather phenomena were was located on the bare ice about 700 m from also observed.
the right bank (Fig. 4); Station No. 2 was set on 4. Results of meteorological observations a moraine-covered ice field where the surface 4.1 Ablation area at 4100 m in elevation
undulation was about 10 m in height (Fig. 5); Figure 6 shows meteorological data at three
and Station No. 3 was set in a grass field on the stations obtained at 0900 local time (0400 G.M.T.). right bank. The observation period at these three The atmospheric pressure changed periodically stations was from 17 July to 7 August; addition- in the range from 615 mb to 625 mb with a period ally, we observed at Lukpe-Lawo (4900 m) in the accumulation area from 10 to 15 August.
Observation height was about 1.2 m above the surface: air temperature and humidity with an
Assmann ventilated psychrometer, wind speed
Fig. 4 Station No. 1 on bare icc.
Fig. 6 Meteorological elements at 4100 m eleva- tion. Observations were carried out at 0900LT. No. 1: bare icc, No. 2: moraine- covered ice, No. 3: grass field on the right bank. The letter C in the wind direction Fig. 5 Station No. 2 on moraine-covered ice. indicates calm weather. 9 月 Glacial-meteorological observations of Biafo Glacier, Karakorum 129
of about 10 days; when the pressure decreased, the cloud amount increased. Rainfall was not heavy but sometimes continued weakly during a whole day; the total precipitation in the 22 days was 63 mm, and the daily maximum of 13 mm was observed on 26 July. The air temperature at Station No. 1 on the bare ice was always lower than those at other stations, and the daily fluctuation was smaller. But the overall variations of air temperature at the three stations showed a nearly similar tendency. Wind speeds at Station No. 3 in the grass field and at Station No. 1 were high as compared with those at Station No. 2 in the rough moraine- covered ice field where the wind direction was variable. To study the diurnal variation of meteorologi- cal conditions on the glacier, hourly observations Fig. 7 Hourly measurements at No. 1 station.
Fig. 8 500 mb pressure chart at 1200 G.M.T. (0700 Pakistan local time) on 21 July, 1977. The weather was fine on Biafo Glacier (indicated as X). Numbers on contour lines indicate altitude of 500 mb. 130 Kouichi Nishimura, et al. 1983 年
were carried out at Station No. 1 from 29 July between the upper and lower parts of the glacier.
to 4 August. The results are shown in Fig. 7. Like the change in atmospheric pressure, the
Relatively low atmospheric pressure was observed weather changed periodically with a period of
during the periods of 29-30 July and 3-4 August, about 10 days. The cyclic variation can be at-
the variation of atmospheric pressure was similar tributed to the regular movement of upper air
to that of the cloud amount. Air temperature masses. Figures 8 and 9 are 500 mb pressure showed at diurnal variation in the range from charts of the eastern part of the northern hemi-
2•Ž to 13•Ž, with a mean of 5.4•Ž. sphere on 21 and 24 July respectively. Both
Wind on the glacier surface was from NW, charts show concentric waves with the center in namely, it blew down from the upstream part of the Arctic and global wave numbers of 7. The
the glacier. The wind speed increased on clear weather on the Biafo Glacier was fine on the nights when the air temperature difference be- 21st and rainy on the 24th, which correspond to
tween the upper and lower parts of the glacier the development of a pressure ridge and trough, was large. Accordingly, the wind can be regarded respectively. It is well known that most glaciers
as a glacier wind. The simultaneous increase in in the eastern region of the Himalaya are
the air temperature and wind speed suggests that nourished from precipitation during the mon-
the downstream motion of the air mass was ac- soon when the so-called monsoon trough extends celerated by the increased temperature difference from Pakistan to the Bengal Bay in summer
Fig. 9 500 mb pressure chart at 1200 G.M.T. on 24 July, 1977. The weather was rainy on Biafo Glacier. 9 月 Glacial-meteorological observations of Biafo Glacier, Karakorum 131
stations at 4100 m elevation. (Nakajima et al., 1976). It is considered that
Karakorum glaciers do not receive much nourish- 5. Concluding remarks ment from monsoon precipitation compared with In the summer of 1977, glacial-meteorological observations were carried out at two sites on the glaciers in the Nepal Himalaya.
4.2 Accumulation area at 4900 m in elevation Biafo Glacier in the Karakorum. Different mete-
Results of meteorological observations at Lukpe- orological conditions were observed in accordance
Lawo are shown in Fig. 10. Observations were with the surface features of the glacier. The air made every three hours from 10 to 12 August and temperature on the bare ice was lower and fluc- every hour during 13-15 August. The atmos- tuations were smaller than on the moraine- covered ice and on the bank of the glacier. The pheric pressure had no distinct variations, though the complete record was not obtained. Clear diurnal air temperature variation was large in weather was observed at night and cloudy weather the snow field on Lukpe-Ldwo at 4900 m ele- in the daytime. The diurnal variation of air vation. Steady glacier wind was found in the temperature was fairly large; the air temperature ablation area, but not on Lukpe-Ldwo in the rose about 5•Ž in the daytime and fell about accumulation area. Periodic 10-day variations of -7℃ at night. The wind was usually very weak weather were considered to be caused mainly by and had no prevailing directions, which was the large-scale disturbance of upper air masses, quite different from the wind regime at the not by the monsoon. Acknowledgments The authors are grateful to the members of the
Tethys Society and the Institute of Low Temper- ature Science, Hokkaido University for helpful suggestions on the planning of this study. The authors would also like to express their gratitude to Dr. N. Maeno and Prof. G. Wakahama of the Institute of Low Temperature Science and Prof. Kou Kusunoki of the National Institute of Polar Research for their useful comments on this paper.
References
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Kick, W., 1956: Chogo Lungma Glacier, Karakoram. in Hidden Valley, Mukut Himal, Nepal. J. Geogr. J., 122, 93-96. Glaciol., 22, 87, 273-283. Kick, W., 1964: Der Chogo-Lungma-Gletscher im Untersteiner, N., 1957: Glazial-meteorologische Un- Karakorum 2. Z. Gletscherkd. Glazialgeol., 5, 1, tersuchungen im Karakorum. Warmehaushalt. 1-59. Arch. Meteorol. Geophys. Bioklimatol., B8, 1-30. Mott, P. G., 1950: Karakoram survey, 1939; a new Wissman, H. von, 1959: Die Heutige Vergletscherung map. Geogr. J., 116, 89-95. und Schneegrenze in Hochasien, mit Hinweisen Nakajima, C., Shrestha, M. L. and Basnyat, M. B., auf die Vergletscherung der letzten Eiszeit. Abh. 1976: Synoptic analyses of the precipitation in Math.-Naturwiss. Kl., Akad. Wiss. und Lit. Mainz, Nepal in 1974. Seppyo, 38, Spec. Issue, 50-58. Jahrg. 1959, 14, 1101-1407. Nakawo, M., 1979: Supraglacial debris of G2 Glacier (Received 18 April 1983; revised manuscript accepted 29 June 1983)