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ETH Zurich (2017)

The role of surface sublimation in the summer mass balance of glaciers in the subtropical semiarid Andes

Ayala Ramos, Alvaro Ignacio

Titre : The role of surface sublimation in the summer mass balance of glaciers in the subtropical semiarid Andes

Auteur : Ayala Ramos, Alvaro Ignacio

Université de soutenance : ETH Zurich

Grade : Doctoral Thesis 2017

Résumé partiel
The role of glaciers as storages of water resources is of primary importance in arid and semiarid mountain regions characterised by pronounced seasonality and long melting periods without significant precipitation. A robust understanding of the physical processes controlling the energy and mass balance of glaciers in these areas is thus crucial for estimation of water resources and their seasonal variability, long term trends and future changes. It has been suggested that glaciers in dry regions are strongly affected by mass and energy losses associated to surface sublimation, but few studies provide a quantification of its influence at the glacier or catchment scales. _The main objective of this thesis is to understand and quantify the role of surface sublimation in the energy and mass balance of glaciers in dry environments, by means of point-scale and distributed physically-based energy and mass balance models. Complementary to this objective, this thesis also addresses three relevant topics in semiarid catchments related to the hydrological role of debris-free glaciers and the modelling of glacier ablation.These topics are the runoff contribution of debris-free glaciers in comparison to that of the seasonal snowpack and debris-covered glaciers, the use of temperature-index models under sublimation-favourable conditions and the spatial distribution of near-surface air temperature over mountain glaciers during the ablation season.
As study region, the subtropical semiarid Andes of North-Central Chile (29-34°S) is selected. This region is characterized by elevations up to almost 7000 m a.s.l., a dry environment, a large number of debris-free and debris-covered glaciers and a strong dependence of ecosystems and human activities on fresh water resources originated from snow and ice melt. In this region, it has been suggested that distributed, physically-based models at the glacier and catchment scales can bridge the gap between regional studies based on remote sensing products and specific studies focused on point-scale process understanding. The presented analyses are conducted on seven glaciers for which a unique dataset of meteorological, glaciological and hydrological variables has been collected in the period 2008-2015. The study sites are grouped in two clusters, one in North Chile (29-30°S), in which climatic conditions are particularly dry, and another one in Central Chile (32-34°S), where the climate is more Mediterranean.

Mots clés  : Glaciers ; Snow ; Semiarid Andes ; Hydrology ; Surface energy balance ; Surface sublimation

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Page publiée le 17 décembre 2017