Ice core evidence for the thickness and character of clear facies basal ice at Glacier de Tsanfleuron, Switzerland

• Main Authors: Hubbard, Bryn, Tison, Jean-Louis, Janssens, Laurent, Spiro, B.
• Format: Article in Journal/Newspaper
• Language: English
• Published: 2000
• Subjects: Glaciologie; ice core; Journal of Glaciology
• Online Access: http://hdl.handle.net/2013/ULB-DIPOT:oai:dipot.ulb.ac.be:2013/29438

Five ice cores have been retrieved from a transect close to the terminus of Glacier de Tsanfleuron, Switzerland. The cores extend from the ice surface to the glacier bed, and are 3.5-44.8 m long. Stratigraphic logging based on bubble size and density reveals the presence of a highly metamorphosed basal ice layer, about 10 m thick, from which all traces of bubble-rich ice have been removed. This bubble-poor ice, which corresponds closely with clear-facies ice observed in cavities beneath numerous temperate-based glaciers, contrasts with the overlying bubble-rich or bubble-foliated englacial ice and the underlying debris-rich and bubble-free dispersed-facies basal ice. Down-core patterns in major-ion composition, stable-isotope composition and total gas content and composition are generally consistent with formation of clear-facies ice by deformation-related metamorphism of bubbly, englacial ice. In addition, isotopic data suggest that storage of downward-percolating meltwaters occurs close to the upper surface of the clear-facies ice layer, perhaps reflecting a local variation in ice permeability across the transition from englacial to clear-facies ice. Enrichment in crustally derived ionic species is noted in the lowermost decimetres of the debris-free, clear-facies ice that immediately overlies debris-rich dispersed-facies basal ice. This ionic enrichment in debris-free ice is interpreted in terms of active inter-granular meltwater flow within some decimetres of the glacier bed. info:eu-repo/semantics/published