| Summary: | [Departement_IRSTEA]EEE [TR1_IRSTEA]23 - ALTEAURISK / DYNAL From satellite remote sensing, global and repetitive measurements of the ice sheets are available. Inversion tools are necessary to get the snow mantle characteristics (snow grain size, density.) from those measurements. For modelling and for comparison with in situ data, size and shape parameters must be clearly defined. Digital image analysis is an adequate tool for providing objective (independent of operator) measurements of the snow characteristics. New methods are developped and applied to a large number of data from Antarctica mainly. Another field of research is the study of the ice core gaz content to get the past atmospheric composition. The snow mantle near rhe surface is porous and therefore there is a difference between the ages of the gaz and of the ice. Snow densification and diffusion models are then used to quantify those processes. The analysis of 2D digital images of Antarctic firn and ice at different depths provided the necessary parameters to validate the models. A third application of digital image analysis was the study of the grain growth in the deep ice. This growth depends on the temperature and the age of the ice. Grain size measurements from thin ice samples are necessary to validate the models. So far those measurements were done manually. New automatic tools were developed which give new insights to this field of study. La télédétection satellitaire est en mesure de fournir des informations globales sur les calottes polaires et d'en effectuer un suivi régulier dans le temps. Pour être facilement interprétées, afin d'en déduire des caractéristiques du manteau neigeux observé depuis l'espace (taille, forme des grains, rugosité de surface.), les données satellitaires doivent être validées et inversées à l'aide de paramétrisations simples. Il est alors indispensable de définir des paramètres robustes et simples de la taille et de la forme des grains de neige à partir de leur observation. Un moyen d'observation et de mesure ...
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