Long term Forecast of Glaciation and Evaluation of Glacial Resources of the Central Asia with the Use of Isotopic Methods

Transcription

1 Long term Forecast of Glaciation and Evaluation of Glacial Resources of the Central Asia with the Use of Isotopic Methods Vladimir I. SHATRAVIN, Tamara V. TUZOVA, Institute of Water Problems and Hydropower of the National Academy of Sciences of the Kyrgyz Republic, Frunze street, 533, Bishkek, Kyrgyzstan,

2 Abstract The decrease of runoff caused by climate change causes interstate contradictions on water question in the states of the Central Asia, in due course the opposition will only amplify. The glaciers of highlands quickly degrade at global climate change. In view of this, the ability to make reliable long term climate and glaciations change forecast is so important.

3 The existing models of long term glacial and climate change forecasting don t allow making reliable forecasts even for the next 100 years. Modern warming represents a part of a natural cycle of fluctuations of climate. In this connection, a pattern of natural climatic and glacial changes which had been taking place throughout long period of time at least Holocene (more than 10 thousand years) should be put in a basis of long termed forecasting of climate and glaciations. By this time, such patterns are not established due to imperfection of methods of dating of moraines (glacial deposits), which are reliable witnesses of the last glaciation.

4 Moraines are traditionally considered to be chronologically dumb formations. We have found a method for accurate radiocarbon dating of moraines with the use of autochthonous specific organic matter dispersed in them. At that the morphologically expressed pattern of disintegration of Holocene glaciation has been established. It consists of not less than seven basic stages. It

5 ) Morphologically apparent staged moraines (I-VII) in the Tez-Ter moraine glacial complex (basin of the Ala-Archa River, the Northern Tien-Shan.

6 The same - on aerophotography

7 Morphologically expressed stadial moraines (I - V) in the Holocene moraine-glacial complex. On the photo marked the places of sampling for radiocarbon dating.

8 The schematic model of long term forecasting of glacial changes is

9 Shematical model of long-term prognosis of natural glacial transformations: Horizontal axis time scale (thousands years); I - VII glaciation stages associated with morphologically articulated moraines of the Holocene glaciation; 8000, 5000, and 3400 established radiocarbon ages of stadial moraines;? anticipated next stage of the Holocene glaciation. Dating of other stadial moraines is a way to long term glacial and climate change forecast.

10 Образец текста Второй уровень Третий уровень Четвертый уровень Пятый уровень Образец текста Второй уровень Третий уровень Четвертый уровень Пятый уровень Sampling for C-14 dating of Pleistocen moraines. Sampling for C-14 dating of Holocene moraines. I, II - morphologically expressed stadial moraines. 3, 4 - mining.

11 It is necessary to combine radiocarbon dating of stadial moraines with isotope oxygen (basing on ratio of isotopes О16/О18) glaciers investigation for more detailed paleoglaciological reconstruction of the Holocene glaciation. Our method of radiocarbon dating of moraines we offer will allow to date the isotope oxygen (О16/О18) curve (that is to adhere it to a reliable age scale) received during drilling of mountain glaciers. For this purpose, it is necessary to select series of samples on contacts of glacial ice and a

12 The frontal ledge of Holocene moraine-glacial complex in one of valleys of the Northern Tien-Shan: 1 exposure of glacial ice; 2 ablative moraine; 3, 4 stadial moraine-glacial generations.

13 Outcrops of Holocene moraine and glacial ice in one of the moraine-glacier complexes of the Noth Tien-Shan.

14 The mountainous glaciers do not only retreat; they are also being shielded with surface moraines.

15 Open and shielded parts of

16 The glaciers of the Tien Shan. 1 open parts of the glaciers. 2 shielded parts of the glaciers.

17 Inilchek glacier. Shilded part of the glacier.

18 Fedchenko glacier, Central

19 Glaciers of the Central Pamir. Peak Somoni (Communism).

20 In the foreseeable future both will lead to considerable reduction of glacial drain. During the first stages of glaciers shielding (when the thickness of moraine cover is insignificant), their thawing is accelerated and the drain module is increased. Further, increase of the moraine cover thickness leads to retardation of ice thawing up to its full termination. Glaciers thus appear to be sort of preserved. It is important to forecast glaciation as well as glaciers shielding and the following reduction of glacial runoff.

21 How quickly will modern glaciers in the future "go" under moraine? What will affect glacial drain more reduction of glaciers sizes or their shielding factor? We need to answer these questions studying shielded glaciers, tendencies and speed of shielding in forecasting aspect.

22 The glacial runoff from shielded parts of glaciers is in contact with moraines depositions and as it had been shown earlier it leads to increase of isotope shift in the uranium of glacial waters, i.e. to increase not only of general content of uranium in thawed snow, but also

23 Aksay glacier 1 shielded parts of the

24 There are reports on threateningly fast degradation of glaciers in the Central Asia. Thus, in it is stated that 2/3 of glaciers of China will have disappeared by 2060, and by 2100 the glaciers will have melted down completely. The quantity of glaciers in the Tien-Shan located on the territory of the Kyrgyz Republic can be tens times reduced by 2100.

25 Certainly, in all these cases only open parts of glaciers were considered, because nobody had studied the shielded glaciers. In this connection, the forecast of glacial disaster in this sources is not wellfounded. To obtain an objective picture, it is necessary to study shielded glaciers, including historic genetic aspect.

26 We need to revalue the ice resources of the mountain areas, listed in the catalog of glaciers of the Kyrgyz Tien Shan. The shielded glaciers were not listed in this catalog. In this connection ice resources are considerably underestimated. Methodology to evaluate volumes of the shielded glaciers should be worked out.

27 Moraine-glacial complex of the Karabatkak, basin of the ChonAksuu river, the Terskey Ala-Too range. This figure shows the Holocene moraine glacial complex of a glacier and the Karabatkak lake. Not moraines, but glaciers of generations of different ages shielded with moraines are situated in the foreground (all around the lake). They (and other, similar to them in different cases) are not listed in the catalog of glaciers of Tien Shan. Only the morained glacier parts are in the catalog. (see the Fig.: number 1 within the glacier).

28 To make long term forecast of glaciers shielding and reduction of glacial runoff caused by it, it is necessary to execute uranium isotope researches on the moraine glacial complexes together with morpholitological

29 Conclusion To solve the stated tasks, we should stop endless monitoring of glaciers and glacial runoff and switch to highly productive investigations with the use of isotopic methods. In order to achieve it, it is necessary to

30 Thank you for your attention