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|Epica basal ice - Eastern Antarctica|
Overkoepelend project: Research action SPSD-I: Sustainable management of the North Sea
Identifier financieringsorganisatie: A4/DD/E02 (Other contract id)
Periode: December 1996 tot November 2000
|The purpose of this research is to undertake a detailed interpretation of the composition of the basal ices from the EPICA drilling at the Dome C and the role of the possible interactions between the ice cap and the stretches of water detected at its base.
In recent years it has appeared very clearly that the composition of polar ices records key parameters of the Earth's climatic environment. Since the deeper the layers of ice, the older they are, a drilling which crosses some 3,000 m of Antarctic ice and reaches the substratum makes it possible to obtain a record extending over a several hundred thousand years. That is the primary purpose of the European project EPICA in Eastern Antarctica, which will permit an especially precise environmental reconstruction over such a time span. The methods of absolute dating of the ices do not extend back beyond 100,000 years, and the only method for assessing the age of the deepest ices remains a modelling of the flow of the ice cap.
In this context, the composition of the basal ices provides not only indications on the characteristics of the deformations which the ice cap has undergone, but it also makes it possible to understand, as has been done for the central part of Greenland, the processes which governed its development and influenced its dynamics. Such information is fundamental for a correct modelling of the flow, which alone makes to work out a chronological scale going back beyond 100,000 years.
Near the site chosen for the first deep EPICA drilling, namely Dome C in the Eastern Antarctic, radio-echo surveys have revealed the existence of stretch of sub-glacial water. It is thus highly likely that very particular dynamic conditions, different from those in the centre of Greenland, prevailed and prevail at the base of this ice cap, because of the interactions between the ice and those stretches of water. Understanding these phenomena is essential for deciphering the palaeoclimatological record going earlier than 100,000 years ago.
The following objectives will be pursued during this study :
1) A preliminary technical improvement of certain analytical methods, in order to address the particular characteristics of the basal ices rich in debris and low in gas content.
2) A better understanding of the physico-chemical processes which occur at the surface of contact between a glacier and a lake in Antarctica, thanks to the analysis of the composition of the ices formed there.
3) A better understanding of the physico-chemical processes which occur in Antarctica at the anchoring line, where the glacier detaches from the substratum at the seawater interface, via analysis of the composition of the ices formed there.
4) A better understanding of the characteristics of Eastern Antarctica fossil ices buried within the ground in areas currently not frozen, in order to be able to determine their genesis. This knowledge could prove to be important insofar as underground ices preceding the formation of the cap could exist at the base of the EPICA ice core.
5) Application of the knowledge acquired within the framework of the foregoing objectives for analysing the composition of the basal ices of the EPICA drilling at Dome C.
6) Determination of the characteristics of deformations suffered at the base by the ice cap in the region of Dome C and its implications on the chronological scale of 100,000 years.
These studies should make it possible to better determine the magnitude of the deformations present at the base of Dome C. They should result in an improvement of the chronological stratigraphy of the deep ices in light of the analysis of their composition, a stratigraphy which is indispensable for reconstituting the ancient climates going back more than 100,000 years.
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