Volcanoes and climate: the triggering of preboreal Jökulhlaups in Iceland

• Published in: International Journal of Earth Sciences
• Main Authors: van Vliet-Lanoë, Brigitte, Knudsen, Oskar, Guðmundsson, Agust, Guillou, Hervé, Chazot, Gilles, Langlade, Jessica, Liorzou, Céline, Nonnotte, Philippe
• Other Authors: Laboratoire Géosciences Océan (LGO), Université de Bretagne Sud (UBS)-Institut Français de Recherche pour l'Exploitation de la Mer (IFREMER)-Université de Brest (UBO)-Centre National de la Recherche Scientifique (CNRS), Reykjavík University, Laboratoire des Sciences du Climat et de l'Environnement Gif-sur-Yvette (LSCE), Université de Versailles Saint-Quentin-en-Yvelines (UVSQ)-Institut national des sciences de l'Univers (INSU - CNRS)-Université Paris-Saclay-Centre National de la Recherche Scientifique (CNRS)-Direction de Recherche Fondamentale (CEA) (DRF (CEA)), Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Commissariat à l'énergie atomique et aux énergies alternatives (CEA), Paléocéanographie (PALEOCEAN), Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Université de Versailles Saint-Quentin-en-Yvelines (UVSQ)-Institut national des sciences de l'Univers (INSU - CNRS)-Université Paris-Saclay-Centre National de la Recherche Scientifique (CNRS)-Direction de Recherche Fondamentale (CEA) (DRF (CEA)), Institut Français de Recherche pour l'Exploitation de la Mer (IFREMER)
• Format: Article in Journal/Newspaper
• Language: English
• Published: HAL CCSD 2020
• Subjects: Holocene; Deglaciation; Iceland; Geomorphology; Glacial; Flood; Sedimentology; Tephra; Glacio-isostatic rebound; Permafrost; Saksunarvatn event; Askja S; [SDU.OCEAN]Sciences of the Universe [physics]/Ocean; Atmosphere; [SDU.ENVI]Sciences of the Universe [physics]/Continental interfaces; environment; Askja; Saksunarvatn; Vatnajökull; Ice; Ice cap; permafrost
• Online Access: https://hal.science/hal-02938576; https://hal.science/hal-02938576/document; https://hal.science/hal-02938576/file/74845.pdf; https://doi.org/10.1007/s00531-020-01833-9

International audience The Early Holocene (12-8.2 cal ka) deglaciation and pulsed warming was associated in Iceland with two major generations of jökulhlaups around the Vatna ice-cap (Vatnajökull), at ca 11.4-11.2 cal ka and ca 10.4-9.9 cal ka, and major tephra emissions from the Grímsvötn and Bárðarbunga subglacial volcanoes. The earliest flood events were recorded inland during the Middle Younger Dryas and their deposits were overlain by the Early Preboreal Vedde Ash (11.8 cal ka). The first Holocene flood events (ca 11.4-11.2 cal ka) are issued from a glacial advance. The second, and major, set of floods was partly driven by the Erdalen cold events and advances (10.1-9.7 10Be ka) initially issued from the Bárðarbunga (10.4, 10.1-9.9 ka) and Grímsvötn volcanoes (Saksunarvatn tephra complex, ca. 10.2-9.9 cal ka). These floods were also fed by the residual glacio-isostatic depressions below the Vatnajökull that enabled the storage of meltwaters in large subglacial lakes or aquifers until ca. 9.3 cal ka. This storage was enhanced by icedamming and permafrost, especially during the twinned Erdalen events. Due to the glacio-isostatic rebound, the general slope was nearly flat, and the valley was partly filled with sediments until ca 10.8 cal ka. Temporary lacustrine deposits in this valley resulted from the very broad splay of waters as for the ca 11.2 cal ka and ca 10.1-9.9 cal ka flood, due to regional permafrost. These floods had a potential duration of several months as they were mostly fed by climate-driven meltwater. The maximal volume evacuated by these events did not greatly exceed 1 × 106 m3 s−1 from the flood-affected transverse profile of the valleys that remain partly filled with sediments.