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Trois problèmes inverses en glaciologie

Abstract : Many questions of glaciological interest can be recognized as inverse problems. In this thesis, l illustrate this point through three examples: * Reconstruction of past temperatures : l try to combine the information given by ice isotopic composition and measured temperature profile at Vostok (Antarctica). This approach suggests that the temperature profile is not able to give any better estimate of surface temperature during the last glacial period than the classical isotopic thermometer (at Vostok). * Reconstruction of past atmospheres : air composition measured in bubbles of ice cores gives tremendous information about past atmospheres. However, the interpretation of these measurements is not immediate, because some natural phenomena can alter the composition of bubble air. l propose here a method to extract the atmospheric signal of ice cores, taking firn diffusion and gravitational separation into account. This method is then applied to interpret methane, CFCs and Û 13 C of CH, measurements. * Reconstruction of large-scale rheological properties of ice: ice-shelves and ice-streams are dynamic elements of the Antarctic ice sheet. Their rheology is an important parameter to predict the evolution of the Antarctic ice sheet. l present here a possible means to determine the effective viscosity of an ice-shelf using an ice-shelf flow model and velocity and thickness measurements. The results consist of a map of the effective viscosity of the Ross Ice Shelf. Inverse methods used to treat these problems are weIl known in many fields of geophysical sciences, but they have been used occasionaIly in glaciology. l try to show what can be learnt from their application in glaciology, but also their limits.
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Submitted on : Friday, May 25, 2012 - 8:36:32 AM
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  • HAL Id : tel-00701278, version 1



Vincent Rommelaere. Trois problèmes inverses en glaciologie. Glaciologie. Université Joseph-Fourier - Grenoble I, 1997. Français. ⟨tel-00701278⟩



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