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The Ice Caps By boring the continental glaciers, for a quarter of a century already, scientists have climbed aboard a formidable machine for going back in time. At a depth of 400 metres, (these figures given for information purposes only, are not valid throughout the whole of Antarctica as the accumulation rates of the ice vary from one place to another), a leap of 10,000 years back in time has already been made (1) - this period marks the beginning of the interglacial period that characterises our current period. 200 metres further down, one arrives 20,000 year earlier, the time of the Last Ice Age.
The adventure is all the more fascinating as, from time to time, it is shaken up by disconcerting discoveries. So it was with the bore-hole in the middle of the Greenland continental glacier in which the Belgian glaciologist Roland Souchez took part in the context of the European GRIP programme (Greenland Ice-Core Project). Scientists discovered, in effect, that in the course of the period being studied, the Eemian Interglacial Stage (nearly 110,000 years), there were on several occasions and within only a few hundred years, drops in temperature of approximately 10 degrees. However, there is no indication, no scientific evidence produced from the Greenland samples - nor any model either - that can provide any explanation for this change of climate. Science is nonplussed. "Although we know", writes Roland Souchez (2), "that major climatic changes can occur during the cold periods of the glacial-interglacial cycle, the oscillations observed during a warm period are new." At the time of the report in the International Weekly Journal of Science, Nature (July 1993), there was consternation. Firstly, because the article was signed by 40 world-renowned glaciologists including Claude Lorius, Willy Dansgaard and Hans Oeschger, all three winners of the 1996 Tyler Prize (the Tyler Prize For Environmental Achievement); there was therefore no doubt as to the seriousness of the information. Then, because the Eemian Stage is an interglacial period that is markedly similar to our own and because the few additional degrees that there were on Earth at that time furiously resemble the least alarmist predictions concerning the progressive warming of our terrestrial atmosphere. Researchers were wondering, all the more seriously in view of this discovery, why an American borehole, drilled just 30 kilometres away from the European borehole, had not for its part obtained the same patterns. The searching and the boring therefore had to continue. In the context of the prosecution of this work, the European Union, alerted by the international EPICA was supposed to be able to answer the question posed by this discovery: as the current climatological conditions are practically the same as they were then and as the difference of two degrees is slowly being eroded, could it be that we too are moving towards similar climatological upheavals? It is difficult to image the economic repercussions that would ensue from such instability, if only in terms of fuel consumption, as just one example…
(1) These figures concern only the Antarctic for even though boring also took place in Greenland and sometimes ended up with the same results as those carried out on the southern continent, glaciologists insist that the underlying deformation of the Antarctic in the deep layers - which naturally influence the results - is not the same in Antarctica as in Greenland. (2) Climate instability during the last interglacial period recorded in the GRIP ice core, by members of the Greenland Ice-Core Project (GRIP). Nature, International Weekly Journal of Science, Volume 364, N° 6434, 15 July 1993.
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