Ruprecht-Karls-Universität Heidelberg

A new Alpine ice core recovered for long term climate reconstructions (October, 2005)

After a series of substantial delays ALP-IMP was eventually successful in drilling a new ice core to bedrock on Colle Gnifetti (Monte Rosa summit range), which is specifically dedicated to the reconstruction of long-term climate records. Based on various GPR (ground penetrating radar) campaigns performed in advance mostly by the Geographical Institute of University Zürich, extensive efforts were made to prospect the particularly appropriate drill position for this purpose. We decided to drill in that part of Colle Gnifetti, which experiences a relatively low net snow accumulation at a reasonable surface and bedrock topography, and offers a useful up stream flow line as well. As illustrated by Figure 1, the Colle Gnifetti drill place, meeting more or less all these terms at the same time was found to be rather exposed to the south-east ice cliff. The upper part of this particular site will thus certainly disappear not too far in the future in an ice-slide going down by 2500m or so to the Italian Anza valley. In the real drilling and supplementary sampling campaign, colleagues and friends from Physical Institute (University Berne), LGGE (CRNS-Grenoble), Geographical Institute (University Zürich), VAW (ETH Zürich) and IUP participated over one week in September 2005 (see gallery below). During that time a 60m core down to bedrock as well as a supplementary 21m core could be recovered using the drill of the Physical Institute in Berne, which has been updated to a 4- inches core diameter. First dating attempts revealed indeed a a quite low annual surface accumulation of about 15 cm water, which is comparable to the mimimum values seen in Greenland. Hence for glaciological reasons, a much better time resolution as well as a less disturbed stratigraphy may be expected for the relatively old part of this core (i.e. the near bedrock section going back into medival times and beyond). In this context, continuous analyses of water isotopomeres, which are currently on the way will specifically supplement the alrady accomplished array of isotope records, obtained from the Monte Rosa and Mt.Blanc drilling areas.




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