Studio del rapporto accumulo/ablazione in un ghiacciaio alpino di grandi dimensioni: l’esempio del Ghiacciaio del Lys

Application of the accumulation/ablation ratio to the large alpine glacier: the Lys Glacier M. Rosa

Abstract

From 1992 to 1994, the Lys Glacier was the subject of a detailed study to determine its mass balance not based on topographical methods prior to the completion of the first DTM in 1994-1995. The method employed involved comparison between the accumulation remaining at the end of the prevalent ablation period and the annual surface ablation, both measured experimentally. This required the prior investigation and interpretation of the accumulation, transport and ablation patterns. The results revealed the importance of reworking of the snow cover by wind and avalanches, which totally falsifies calculations based on climatic data, and the importance of the surface moraine as an ablation factor, especially owing to its inclusion of a groundwater body that facilitates the exchange of heat. Consideration of the many accumulation and ablation factors present in a large glacier such as the Lys, some of which had hitherto been regarded as negligible, greatly complicated the interpretation of the experimental data. On the other hand, it enabled an initial estimate to be made of its mass balance. This was certainly negative in 1993.