Holocene glacier fluctuations in Greenland, contribution of cosmogenic surface exposure dating

• Main Author: Biette, Melody
• Other Authors: Laboratoire de géographie physique : Environnements Quaternaires et Actuels (LGP), Université Paris 1 Panthéon-Sorbonne (UP1)-Université Paris-Est Créteil Val-de-Marne - Paris 12 (UPEC UP12)-Centre National de la Recherche Scientifique (CNRS), Université Panthéon-Sorbonne - Paris I, Vincent Jomelli, Marie Chenet
• Format: Doctoral or Postdoctoral Thesis
• Language: French
• Published: HAL CCSD 2022
• Subjects: Glacier fluctuation; Cosmogenic dating; Holocene; Greenland; Fluctuation glacière; Datation cosmogénique; Holocène; Groenland; [SHS.GEO]Humanities and Social Sciences/Geography; Clavering Island; glacier; Ice Sheet
• Online Access: https://theses.hal.science/tel-03771706; https://theses.hal.science/tel-03771706/document; https://theses.hal.science/tel-03771706/file/BIETTE.pdf

Mountain glaciers and local ice caps are particularly sensitive to changes in temperature and precipitation in Greenland. A better understanding of glacier margins fluctuations over time will help to document the regional climate evolution and contribute to the determination of the different mechanisms involved in climate variability in the Northern hemisphere. This work aims to improve our knowledge of glaciers evolution disconnected from the ice sheet in Greenland during the Holocene (i.e. the last 11.7 ka). In this end, the present study focuses on a geomorphological feature adjacent to the current glaciers: moraines. These rock accumulations were formed by erosion during past glacial extensions. In this study, 10Be cosmogenic moraines dating is used to document the evolution of seven glaciers across three parts of Greenland: Clavering Island (northeast), Tasilap valley (southeast) and Isortup valley (south). Combined to the other glacial chronologies in Greenland, this provides further evidence of a maximum glacial extension during the Early Holocene (11.7 – 8.2 ka). However, the most original results concern the identification of two new moraine stages showing glacial expansions during the Late Holocene (since 4.2 ka). These moraines were formed during the Middle of Neoglacial (~3 ka) in the three investigated sites of this thesis, and during the Dark Age Cold Period (~1.2-1.7 ka) in six of our seven glacial chronologies. By improving the spatial coverage of glacial chronologies in Greenland, it was also possible to reconsider the relationship between different climate forcing in the Northern Hemisphere. These new glacial chronologies can also contribute to the knowledge of the spatial heterogeneity of climate in the Northern Hemisphere. In parallel with the 10Be dating on moraines, a glaciological model (Degree-days) based on a pre-existing glacial chronology in Disko Island (central west) was applied to estimate temperature conditions responsible for glacial extension during the Medieval Climate Anomaly ...