IWRA Proceedings

AbstractIntroduction: Tropical glaciers shrinkage is generalised and has been accelerating since the end of the 1970s, especially during warm phases of El Nino events. Several authors have shown the links between the Andean climate, the glaciers retreat and the global climate variations. Locally, ice loss processes (melting and sublimation) are complex and dependent on several variables like temperature, air humidity, wind, cloud cover, incident and reflected radiations on the glacier surface (thus of albedo), while its maintenance depends upon precipitation influence. But direct measurements upon glaciers are scarce and we shall try to replace them by data from meteorological station located in similar climatic situation. Objectives: • Set up models showing the links and the respective influence of climatic parameters upon glaciers variations. • Use and calibrate these models to reproduce the past glacier and climate variations. • Use these models to project future glaciers and water resources evolution, according to the main IPPC climate scenarios. Methods Establish the links and the models between local (data collected close to the glacier), regional (data collected in Ecuador by the meteorological network or by remote sensing) and global (i.e. ENSO index) climatic information at daily and monthly time scale. Select the most pertinent models considering data availability to realise the long term calibration and simulation Results Using twelve years of mass balance, meteorology, precipitation and runoff data on two glaciers located on the Antizana volcano (Ecuador) very close to equator, we studied the relations of daily and monthly melting of the glaciers with 50 variables chosen to represent the global, regional and local climate. Various models were produced. One of them explains 58% of the melt variance. This model implicates the Niño3+4 index as well as precipitation anomalies at the foot of the Antizana. Excess (lack) of precipitation during the 9 previous months will incite a decrease (increase) of melting. A warm (cool) anomaly of the ENSO oscillation will incite an increase (decrease) 4 months later. Another model explains 54% of the melt variance using only temperature data from the oldest Ecuadorian meteorological station ("Quito Observatorio", observed since 1892) Conclusions These models constitute now one of the tools that suggest and facilitate the comprehension of the links between several climatic mechanisms. They permit generate future glacier and water resources evolutions according to the main IPPC climate scenarios.