(Its high resolution dust records can reflect details of environmental variation on centennial scale.)
Through research on the ingredient of snow and ice in the center and north of the Tibetan Plateau, professors of ITP Yao Tandong and Wu Guangjian et al found that the main positive icon in soluble gasoloid---continental Calcium icon is closely related to the PH value of atmospheric precipitation and the snow and ice, which can be counted as a good index in atmospheric ingredient and environmental variation reflected by mountain ice cores around arid areas of medium and low latitudes. Details of the variation can be reflected on centennial scale through reconstruction of the environmental evolution of Asian arid areas with this index.
According to professor Yao Tandong, dust plays an important role in global climatic change as the main impurity in the atmosphere. Firstly, the gasoloid in the atmosphere can not only be “direct radiation drive” through its scattering, reflection and imbibition of solar radiation, but also can be “indirect radiation drive” as it helps form cloud drop as the nucleus of condensation. Secondly, the ferruginous dust transported to the ocean from arid and semi-arid areas can control the production capacity of sea-plants and planktons, and then affect the CO2 density in the atmosphere. At the same time, the abundant dust generated in the capacious arid deserts can restrain local atmospheric precipitation and make the local soil even more arid. The impact of atmospheric dust on global change has drawn great attention of the scientists concerned in this field.
Professor Tan indicated that researchers concerned are making an endeavor to obtain records of high resolution and authenticity in their attempt of restoring past dust variation. Among them, polar and mountain ice cores of medium and low latitudes are one of the best historical records of atmospheric dust evolution. He said that there are two paths for global dust transport, one from northern Africa to southwest Europe, the Atlantic, and the American continent, the other form Middle East Asia to north Pacific and Greenland. The Middle East area including mainland China is an important source for global atmospheric dust, and has been attached much importance to in construction of relative climatic models due to its vastitude and its huge dust production. In order to understand the response and impact of Asian dust to and upon global climate, especially climate of Northern Hemisphere, we should get to know variation of the source regions first.
In order to get characteristics of the dust transport in various periods on the Tibetan Plateau, and to explore its role in global change, professor Yao and his collaborators used an ice core of 308.6 m thick attained from Guliya in western Tibet in 1992, and conducted profound research on its impurity variation. According to the researchers, the Guliya Ice Core is 6200 m high, and around the drill spot are mainly source regions for dust. Owing to its high sedimentary position and short transport distance, it can reflect directly variation of the source regions to a great extent, and is therefore a perfect spot for research on atmospheric dust evolution in arid areas of the middle Asia.
The research group found that density of Ca2+ in Guliya Ice Core has undergone radical changes during the past 100,000 years, including two periods of intense increase and two of slight increase. As these variations are directly related to changes in temperature on great scale, the Guliya Ca2+ can be a good index in reflecting variations of atmospheric dust and the environment, whose high resolution record reflects details of the variation on centennial scale. However, the density of Ca2+ doesn’t always get lower in warm periods and higher in cold periods, and it’s not absolutely consistent with records of temperature in phase and amplitude of variation. Variation in atmospheric circumfluence, the plateau’s underlying surface, atmospheric humidity, and other unstable climatic factors, may be other key influential factors besides temperature.
At last, professor Yao indicated that this research further testifies that the Tibetan Plateau ice cores are nice vehicles for understanding modern release and historical evolution of dusts in arid area in Asia. The present research only achieved initial results, and research in this field should be enhanced.