GLACIER RETREAT IN THE ANDES
Jordan et al. (2005) used aerial photographs of the Cotopaxi Volcano ice cap (Ecuador) to quantify the evolution of the surface area. The results show that glaciers stagnated from 1956 to 1976 and then underwent a very strong recession from 1976 to 1997, losing about 30% of their surface area (probably linked to the increase in inten- sity, duration and frequency of warm ENSO phases).
This finding corroborates the observations made on the nearby Glacier 15 (Antizana ice cap) located 10 km northeast of the Cotopaxi Volcano, which also lost about 30% of its surface area from 1956 to 1997. Slope exposure to humid fluxes from the Amazon and solar radiation at the Cotopaxi ice cap did not have any significant effect, since all the glaciers of the volcano retreated to a similar degree. It is interesting to note that the glacier recession on the Cotopaxi Volcano was particularly pronounced because of the conical form of the ice cap, resulting in exposure of the surface area below the equilibrium line altitude to strong ablation conditions.
Rivera et al. (2005) found that ice-capped volcanoes of the Chilean Lake District have undergone significant glacier retreat during recent decades, probably in response to tropospheric warming and precipitation decrease. By 2003, the shrinking glaciers of the Mocho-Choshuenco Volcano had lost 11.5 ± 2.5 km2, i.e. 40.5% of the total ice area of 28.4 km2 measured in 1976. A maximum decrease in area was observed at a rate of 0.45 km2 year-1 between 1987 and 2003.
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