GeoJoumal 17.4 5 1 3 - 5 1 6 © 1988 by Kluwer Academic Publishers

513

Variations of Existing Glaciers in the Southwestern Mountain Region of Xizang (Tibet) Wang Wenying, Academia Sinica, Lanzhou Institute for Glaciology and Cryopedologie Lanzhou, PR China

A B S T R A C T : The SW-mounta in region of Xizang in this paper is taken to extend between 27 ° 1 0 ' - 3 0 ° 10'N / 84 ° 5 0 ' - 9 1 ° 30' E, that is the vast area stretching from the Himalayas to the South Range of Xizang. The author has been in the area many t imes over 20 years surveying and conducting scientific investigations. In 1984 the author took part in the Sino- German Joint Expedit ion for further survey and the interpretation of aerial photographs and satellite images of the same area. The paper presents the data collected during this period.

Introduction

No systematic glacial survey data exist for the moun- tain regions of SW-Xizang we investigated. Nevertheless the Himalayas are a specific area and the highest peak named Qomolangma (in Nepalese called Sagarmatha) discovered by a surveying team led by Colonel Everest in 1850. After 1850 a few explorers attempted to reach the Qomolangma, but they failed. After 1921 however dozens of expeditions from more than ten countries investigate the Qomolangma region and neighbouring areas. One such team, the 1921 Mount Everest (Qomolangma) Expedition led by C. K. Howard-Bury surveyed and produced two maps, partly based on large scale photographic survey (Hinks 1922). These two maps provide the basis for further research of existing glaciers. Since the fifties, Chinese scientists have pursued many investigations in this region, and in 1974 aerial photo- graphy of the entire SW Xizang was undertaken. In 1984, Sino-German Joint Expedition worked in the above mentioned areas once more, and obtained much data of glacial changes of selected glaciers. This paper attempts to discuss the oscillations of these glaciers during the last half century.

Owing to the difficult conditions in the investigated region certain glaciers selected as representative were studied, with particular reference to oscillations.

Rongbuk Glacier in the Northern Slope of Mt. Qomolangma

Rongbuk glacier has a length of 22.2 km with a total area about 86.89 km 2. The glacier connects directly with the summit of Qomolangma, and its snout was covered by surface moraine to a depth of several meters. Since the Little Ice Age, the snout of Rongbuk glacier has not changed except for the unobvious changes in height. It is sensible therefore to adopt the outer limit of ice pyra- mids as a mark instead of the actual snout.

Comparing the ice pyramids in Rongbuk glacier on the Map II, Prelimnary Map, made by the Expedition of 1921, with our surveying results of 1966, 1974 and 1984, we found that the ice pyramids have been retreating from 1921 to 1984. The outer limit of the ice pyramids retreated as follows: 1921-1966 2400 m, that is 53.3 m/yr; 1966-1974 550 m, that is 68.8 m/yr; 1974-1984 450 m, that is 45.0 m/yr;

Over the last ten years the rate of retreat has ob- viously slowed.

Gyajo Glacier of Khumbu Himal on the Southern Slope of Mt. Qomolangma

The Gyajo glacier is a small glacier with a length only about 1.7 km. Hiroji Fushimi has investigated this

514 GeoJournal 17.4/1988

Fig 1 Scenery of Mt. Xixabangma

glacier and the following are his findings about changes in the position of the front from 1970 to 1978: 1970-1973 - 2 . 5 m/yr 1973-1975 - 2.0 m/yr 1975-1976 + 0 . 1 1 - 4 . 0 m/yr 1976-1978 - 0.9l - - 2.93 m/yr

Yebokangjal Glacier on the Northern Slope of Mt. Xixabangma

In 1964 the Mountaineering Team of the People's Republic of China climbed Xixabangma, the last un- climbed mountain of more than 8000 m (Fig 1). The Scientific Expedition working together with the Moun- taineering Team produced a complete map of Yebokangjal Glacier which is 14 km in length. In 1974 Chinese aerial photography covered the Xixabangma area, and in 1984 the Sino-German Joint Expedition surveyed the area and endeavoured to interpret the aerial photographs on the spot. The results are: The outer limit of ice pyramids as an indicator: 1964-1974 - 2 0 0 m, that is - 20 .0 m/yr 1974-1984 +550 m, that is +55.0 m/yr

Tab 1 Oscillations in the fronts of gaciers of Fuqu river in the SE slope of Mt. Xixabangma during 1974-84

N a m e Length (km) Changes of glacier in 1974 of terminals (m)

1974-84 Advance

Fu-No. 34 14.1 0 Fu-No. 40 9.5 4- 750 Fu-No. 27 5.8 + 200 Fu-No. 25 5.5 -4- 150 Fu-No. 23 3.1 + 650 Fu-No. 26 1.3 ~ 125 Fu-No. 38 1.2 ~ 700

Fig 2 Zhangzangpu Glacier No. 4 on the aerial photograph of November 1974

Glaciers of the Fuqu River Catchment on the Southeastern Slope of Mt. Xixabangma

Professor Zheng Benxing, member of the 1984 Sino- German Joint Expedition with assistants Jiao Keqen and Sheng Yungping, investigated the glaciers of the Fuqu river. My own measurements of the above-mentioned glaciers showed six glacier fronts out of the seven have been advancing to varying degrees over the last ten years, except glacier Fu-No. 34 which, with a length of 14.1 km, is stable. The extent of the oscillations is shown in Tab 1.

Zhangzangpu Glacier No. 4 on the Eastern Slope of Xixabangma

Zhangzangpu Glacier No. 4 (Fig 2) has a total area about 3.31 km 2, with a length of 3.7 km and is connect- ed directly with Mt. Quemobamare , 6109 m in height, the main peak of the Bamarekangri spur of the Hima- layas. Comparison of the aerial photographs of

GeoJournal 17 .4 /1988 515

Fig 3 191o 20 90 Fluctuations of selected glaciers in the SW Xizang (Tibet) from 1921 to "- "" ' " i " ' " 1984 ' I

+ 1 0 0 ~ + 5 0 m a d v a n c i n g

- -- 50 m r e t r e a t i n g - - I 0 0

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1920 50

1960

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i

1960

64 66

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6 4

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i

i 66 6J9 70

8 4

Rongbuk

~--275 -- .0 "--179 -

~/ / / ' /~ / J ' / /~ / J~ ' ,+55 .0~/ ' / ' /L ~/'/YL~. Y e b o k a n g j a l

0 F u - N o . 34

~ / / / / 2 ~ / / / / / 2 + 7 5 . 0 r / / / / 1 ~ Y/'/J.~ F u - N o 40

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1 I I I 73 74 76 78 1980 84

November 1974 and the present position shows that the Glacier No. 4 has advanced about 500 m.

There was a glacial lake, which held about 30 mil- lion m3 water at the front of Glacier No. 4. On July 10, 1981, that lake burst with a huge debris-flow and caused enormous loss of life and property along the Boqu/Bhote Kosi river. The resulting traffic disruption persists. The burst produced great changes in the frontal relief of the Zhangzangpu Glacier No. 4, and the water level of the lake has fallen about 22 m.

The Southern Glaciers

Glaciers of the S range in Nagarze area, Nagarze county of Xixang Autonomous Region, located on the W shore of Yamzho lake, about the mainpass on the route from Lhasa to Xigaze. The S range of Xizang, where existing glaciers are developing forms natural block on the SW flank of Nagarze county. Chinese

glaciologists and surveyors have been surveying and mapping part of the glaciers since 1966.

Recent variations of several representative glaciers are listed in Tab 2.

To facilitate comparison these values are shown as annual average (Fig 3).

Discussions of Glacial Variations in the Southwestern Mountain Regions in Xizang

(a) Generally, existing glaciers in the SW mountain regions of Xizang are of the normal stable type. Rapidly advancing glaciers have not been found in the investigated area. This is not true of the W sections of Himalayas. The explanation of this stability might be that the S slope in SW Xizang has much ablation but more moisture while the N slope in SW Xizang has little ablation but less moisture.

Tab 2 The terminal variations of the gla- ciers of the S range in Nagarze area

Name Length (km)

Qiangyum 4.9

Karala 4.6 Jidanjoma 1.0

Terminal variations (m) Year Retreat Stable Advance

1979 -130(1966--68) - 68(1968--69) 0 (1969-84)

1966 -550 (1966-79) +200(1979--84) 1966 - 72 (1966-79) +150(1979-84)

516 GeoJournal 17.4/1988

(b) Since the Little Ice Age until now, over the last 150 years, the large glaciers both on the S and the N slopes in this section of Himalayas have receded to the permafrost zone. Some glaciersnouts, protected by the thick surface moraine (thickness over 1.2 m) have been stable for a long time and their "retreat" is in the form of thinning. It is acceptable to repre- sent the oscillations of this type of glaciers, such as Rongbuk and Yebokangjial, by means of the outer limit of advance or retreat of ice pyramids.

(c) The small glaciers with the length shorter than 10 km and presenting bare ice in the investigated region are very sensitive. About 90% of these glaciers have been advancing since 1974.

(d) While studying the process of the frontal oscillations in high mountain regions, attention should be paid to the glacier front with lake, for lake burst and debris- flow, as at Zhangzangpu Glacier No. 4, are likely hazards. In 1984 we found that the area of glacial lake near the terminus of Fu-No. 40 was at one time larger than that shown in 1974 aerial photographs. In the meantime the glacial front had also advanced 750 m. Jarqu river, a tributary of the Boqu river, has a similar lake near the glacier front (pers.comm. M. Kuhle). These potential hazards should be noted and if necessary something can be done to lessen the conditions favouring debris flows, such as exploding the moraine bank and part-draining the lake. This would be much less expensive than the costs of future recovering after a catastrophe.

(e) Snowfall is a main cause of glacial osciaUations. Changes of snow cover are attracting increased scien- tific interest. On May 27th, 1975, a Chinese moun-

taineering team climbed to summit of Qomolangma and set up a red column 3.51 in height. The column was buried in the snow to about 0.92 m. In August of 1980, Reinhold Messner climbed the summit and reached the column but only about 0.4 m was visible. Since then, mountaineers from several countries have reached the summit in May and August, but failed to see the column, probably it is now buried in the snow. This suggests that the snow cover on the Mt. Qomolangma has been thickening by 0.4 m per year since 1975. Through aerial photographic inter- pretation and surveying on the spot, we found that the snow cover in Xixabangma area has also obvi- ously increased since 1979. This seems to add some support to the controversial opinion tha t the world climate is becoming colder.

References

Finsterwalder, R.; Rentsch, H.: Zur H6hen/inderung von Ostalpen- gletschern im Zeitraum 1969-1979. Zeitschrift f/Jr Gletscher- kunde und Glazialgeologie 16, 111-115 (1980)

Fushimi, H.; Ohata, T.: Fluctuations of glaciers from 1970 to 1978 in the Khumbu Himal, East Nepal. Seppyo 1980.

Glaciology, Division of, Lanchow Institute of Glaciology, Cryopedo- logy and Desert Research, Academia Sinica: Basic features of the glaciers of the Mr. Jomo Lungma region, southern part of the Tibet Autonomous Region, China. Scientia Sinica 18, 1, 106-130 (1975)

Hinks, A. R.: The Mt. Everest maps and photographs. Alpine Journal, pp. 228-234 (May 1922)

Wang Wenying: Glaciers in the northeastern part of the Ching- Hai-Hsitsang (Oinghai-Xizang) plateau (Tibet) and their varia- tions. Journal of Glaciology 29, 383-391 (1983)