UNIVERSITÀ DEGLI STUDI DI MILANO Dottorato di Ricerca in Scienze della Terra Ciclo XXIX The dark side of the ice: Glaciological and biological aspects of supraglacial debris Ph.D. Thesis Roberto Sergio Azzoni Matricola R10479 Tutor Academic Year Coordinator Prof.ssa Guglielmina Diolaiuti 2015/2016 Prof. ssa Elisabetta Erba Co- Tutor Dott. Andrea Zerboni Dott. Roberto Ambrosini Dott. Andrea Franzetti Foreword PART I SUPRAGLACIAL DEBRIS: GLACIOLOGICAL ASPECTS ....................................................... 2 Introduction ............................................................................................................................................ 3 Importance of supraglacial debris in glacier system ............................................................................ 4 Importance of thin, sparse debris and dust in glacier system ............................................................... 5 Aim of this study .................................................................................................................................. 7 References ............................................................................................................................................ 8 Chapter 1 The evolution of debris mantling glaciers in the Stelvio Park (Italian Alps) over the time window 2003-2012 from high-resolution remote-sensing dataAbstract ........................................................ 15 Abstract ................................................................................................................................................. 16 1.1. Introduction ............................................................................................................................ 17 1.1.1. Study Area................................................................................................................................................................... 19 1.2. Material and methods .................................................................................................................. 20 1.2.1. Remotely-sensed data and glacier outlines ....................................................................................................... 20 1.2.2. Supervised classification of orthophotos and accuracy ................................................................................ 21 1.3. Results ......................................................................................................................................... 23 1.3.1. Definition of surface properties over the whole region ................................................................................ 23 1.3.2. The Forni Glacier tongue ....................................................................................................................................... 26 1.3.3. Error assessment........................................................................................................................................................ 26 1.4. Discussion ................................................................................................................................... 28 1.4.1. The evolution of debris cover ............................................................................................................................... 28 1.4.2. Lithology of glacial basins and its role in controlling magnitude and rates of debris production .. 37 1.5. Conclusion .................................................................................................................................. 39 1.6. Acknowledgements ..................................................................................................................... 40 1.7. References ................................................................................................................................... 40 Chapter 2 High-resolution mapping of glacier surface features. The UAV survey of the Forni Glacier (Stelvio Park, Italy) .............................................................................................................................. 47 Abstract ................................................................................................................................................. 48 2.1. Introduction ............................................................................................................................ 49 2.1.1. Study Area................................................................................................................................................................... 50 2.2. Material and methods .................................................................................................................. 51 2.2.1. Remotely-sensed data and glacier outlines ....................................................................................................... 52 2.2.2. Extraction of glacier large-scale features based on the UAV orthomosaic ............................................ 53 2.2.3. Extraction of glacier large-scale features based on Landsat imagery ...................................................... 53 2.2.4. Classification of the glacier small-scale features based on the UAV orthomosaic .............................. 54 2.3. Results and discussion ................................................................................................................. 55 2.3.1. Identification of large-scale features ................................................................................................................... 55 2.3.2. Identification of small-scale features based on the UAV orthomosaic .................................................... 60 2.4. Conclusions.................................................................................................................................. 65 2.5. Acknowledgments ....................................................................................................................... 66 2.6. References .................................................................................................................................... 67 Chapter 3 Estimating ice albedo from fine debris cover quantified by a semi-automatic method: the case study of Forni Glacier, Italian Alps .................................................................................................... 70 Abstract ................................................................................................................................................. 71 3.1. Introduction ............................................................................................................................. 72 3.1.1. Research motivation and study aims ................................................................................................................... 72 3.1.2. Previous studies and recent literature on fine debris occurring at glacier surface ................................ 73 3.1.3. Study Area ................................................................................................................................................................... 75 3.2. Methods .................................................................................................................................. 77 3.2.1. Debris cover quantification .................................................................................................................................... 78 3.2.2. Albedo .......................................................................................................................................................................... 80 3.2.3. Sedimentological analyses and debris coverage rate evaluation ................................................................ 83 3.3. Results..................................................................................................................................... 84 3.3.1. Debris coverage ratio (d) and ice albedo (α) .................................................................................................... 84 3.3.2. Debris composition and debris coverage rate (Cr) ......................................................................................... 90 3.3.3. Accuracy assessment of semi-automatic debris cover quantification ...................................................... 94 3.4. Discussion ............................................................................................................................. 100 3.5. Conclusion ............................................................................................................................ 101 3.6. Acknowledgments ................................................................................................................ 103 3.6. References ............................................................................................................................. 103 PART II SUPRAGLACIAL DEBRIS: BIOLOGICAL ASPECTS ............................................................... 109 Introduction......................................................................................................................................... 110 Life on debris-covered glaciers ........................................................................................................ 111 Life in snow .....................................................................................................................................