SMIRAGLIA C., MAGGI V., ROSSI GC. & JOHNSTON P.
Preliminary results of two ice core drillings on Monte Rosa (Colle Gnifetti and Colle del Lys), Italian Alps
Pages 165-172
Abstract
Two boreholes were drilled in the ice on Monte Rosa in 1995 and in 1996, at Colle Gnifetti (4480 m) and Colle del Lys (4240 m), respectively, with the recovery of two cores measuring 24 and 80 m in length. Physical and chemical analyses were performed on the cores, the preliminary results of which are illustrated here. Bore hole temperature and bulk visual stratigraphy and density profiles of the cores were performed directly in the field. At Colle Gnifetti, core bottom temperature proved to be –13.4 °C, whereas density showed values ranging between 0.38 g cm?³ and 0.84 g cm?³ . The levels of visible Saharan dust from well-known events and peak levels of tritium permitted a determination of the mean annual accumulation at 27.8 cm of water equivalent. At Colle del Lys the temperature measurements made at the bottom of the drilling hole showed a mean of –11,2 °C, whereas density ranged between 0.32 g cm?³ and 0.91 g cm?³, with the close-off at around 40 m depth. A mean annual accumulation of about 170 cm of water equivalent was calculated on the basis of 1963 tritium peak, from thermonuclear bomb tests, and well known 1977 Saharan dust level, as reference horizons.