Evidence of glacial flour in the deepest 89 m of the Vostok ice core

• Published in: Annals of Glaciology
• Main Authors: Simões, Jefferson, Petit, Jean Robert, Souchez, Roland, Lipenkov, Vladimir Ya., de Angelis, Martine, Leibao, Liu, Jouzel, Jean, Duval, Paul
• Other Authors: Laboratoire de glaciologie et géophysique de l'environnement (LGGE), Observatoire des Sciences de l'Univers de Grenoble (OSUG), Université Joseph Fourier - Grenoble 1 (UJF)-Institut polytechnique de Grenoble - Grenoble Institute of Technology (Grenoble INP )-Institut national des sciences de l'Univers (INSU - CNRS)-Institut national de recherche en sciences et technologies pour l'environnement et l'agriculture (IRSTEA)-Université Savoie Mont Blanc (USMB Université de Savoie Université de Chambéry )-Centre National de la Recherche Scientifique (CNRS)-Université Joseph Fourier - Grenoble 1 (UJF)-Institut polytechnique de Grenoble - Grenoble Institute of Technology (Grenoble INP )-Institut national des sciences de l'Univers (INSU - CNRS)-Institut national de recherche en sciences et technologies pour l'environnement et l'agriculture (IRSTEA)-Université Savoie Mont Blanc (USMB Université de Savoie Université de Chambéry )-Centre National de la Recherche Scientifique (CNRS)-Centre National de la Recherche Scientifique (CNRS), Université libre de Bruxelles (ULB), 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), Glaces et Continents, Climats et Isotopes Stables (GLACCIOS), 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))
• Format: Article in Journal/Newspaper
• Language: English
• Published: HAL CCSD 2002
• Subjects: [SDU.OCEAN]Sciences of the Universe [physics]/Ocean; Atmosphere; [SDU.ENVI]Sciences of the Universe [physics]/Continental interfaces; environment; Annals of Glaciology; ice core; Ice Sheet
• Online Access: https://hal.science/hal-03127326; https://doi.org/10.3189/172756402781816816

International audience The 3623 m long Vostok ice core is divided into two main parts: (1) from the surface to a depth of 3310m, the ice layers are undisturbed and may be used to reconstruct the climatic record over the past 420 kyr; (2) from 3538 m to the bottom, the core is made up of accreted ice formed by freezing of the lake. In between, the glacier ice is disturbed by ice dynamics, as shown, for example, by inclined volcanic-ash layers. Microparticle concentrations and distributions as well as ionic and isotopic content were used to subdivide this third section. The identification of layers with bedrock material provides clues as to the entrainment processes at sub-freezing temperatures. Dust concentration and size distribution as well as ionic content are comparable with values found in ice of glacial and interglacial periods. Below 3450 m depth, however, the mode of the volume size distribution clearly shifts from 2.1 µm to 3.4 µm in diameter. Particles as large as 30 µm in diameter are observed and cannot have an aeolian origin. From microscopic observations, we suggest that they originate from the bedrock and represent glacial flour entrained in a shear layer up to 89 m from the glacier sole. This process most likely occurred when the ice sheet was grounded before flowing over the lake.