Monitorización de glaciares y glaciares rocosos pirenaicosmás de una década aplicando técnicas geomáticas en La Paúl y Maladeta

Résumé

This doctoral thesis presents and analyzes the annual monitoring works carried out over 12 years (2008-2020) in Pyrenean glaciers and rock glaciers by the GIR PANGEA. Specifically in the glaciers of La Paúl (2009-2020) and Maladeta (2010-2020) and the rock glaciers of La Paúl (2013-2020) and Maladeta (2008-2020). This research focuses on the technical component of the monitoring works by studying different geomatic techniques applied to the in situ surface control of glaciers and rock glaciers. Thus, the suitability of geomatic studies is evaluated from data acquisition and processing to the production of surface deformation models. Periodic data acquisition was performed using Total Stations, Global Navigation Satellite Systems, Terrestrial Laser Scanners and Terrestrial and low-height Aerial Photogrammetry. Simultaneously, the analysis of surface variations and compatibility between the geomatics techniques employed was performed through coordinate subtraction (1D and 2D), elevation model comparison (2.5D), and point cloud comparison methodologies (3D) from the models obtained or derived from the different techniques. The various configurations and methods used to capture, process, and compare the geographic information obtained in the glaciers and rock glaciers of La Paúl and Maladeta have allowed us to determine the limitations of each geomatic technique as the precise and detailed evolution of the studied scenarios. Some examples include the relative compatibility of quantifying and distributing glacial deformations with total stations, terrestrial laser scanners, and drone photogrammetry is highlighted as the suitability of the aerial point of view in the survey of geometrically complex surfaces such as rock glaciers. Some difficulties encountered focused on generating accurate surveys using terrestrial photogrammetry or the reduced performance of some terrestrial laser scanners for acquiring measurements on ice and snow surfaces. Throughout the chapters of this document, multiple other cases are presented, where the efficiency of the techniques is analyzed, many of which are reflected in the scientific publications related to geomatics attached to this doctoral thesis. The application of different techniques and procedures has made it possible to determine with centimetric precision (I) the constant degradation of the Maladeta glacier tongue, (II) the significant variability of a glacier subject to topoclimatic factors, such as that of La Paúl, (III) the generalized surface activity of the La Paúl rock glacier, and (IV) the localized and limited activity of the Maladeta rock glacier. The geomatics work of the GIR PANGEA for more than a decade has shown the need to adapt to the landforms deformation rates and for a correct interpretation of their surface dynamics, in addition to exposing the usefulness of reviewing and merging the geospatial information captured by traditional and the most recent geomatics techniques for a complete and detailed analysis. This doctoral thesis has provided data on the surface evolution of glaciers and rock glaciers of Maladeta and La Paúl with unprecedented temporal and spatial resolutions in these locations. Data about the landforms are accompanied by valuable information about the applicability of geomatics techniques in these environments. Aspects that, besides improving future geomatic works in La Paúl and Maladeta, as well as in other similar scenarios, provide invaluable information for the study and understanding of the cryosphere in the high Pyrenean Mountains.