CO$_2$ and O$_2$/N$_2$ variations in and just below the bubble–clathrate transformation zone of Antarctic ice cores

• Published in: Earth and Planetary Science Letters
• Main Authors: Lüthi, Dieter, Bereiter, Bernhard, Stauffer, Bernhard, Winkler, Renato, Schwander, Jakob, Kindler, Philippe, Leuenberger, Markus, Kipfstuhl, Sepp, Capron, Emilie, LANDAIS, AMAELLE, Fischer, Hubertus, Stocker, Thomas
• Other Authors: Climate and Environmental Physics Bern (CEP), Physikalisches Institut Bern, Universität Bern Bern -Universität Bern Bern, Oeschger Centre for Climate Change Research (OCCR), University of Bern, Alfred Wegener Institute for Polar and Marine Research (AWI), Laboratoire des Sciences du Climat et de l'Environnement Gif-sur-Yvette (LSCE), Institut national des sciences de l'Univers (INSU - CNRS)-Université Paris-Saclay-Centre National de la Recherche Scientifique (CNRS)-Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Université de Versailles Saint-Quentin-en-Yvelines (UVSQ), Glaces et Continents, Climats et Isotopes Stables (GLACCIOS), Institut national des sciences de l'Univers (INSU - CNRS)-Université Paris-Saclay-Centre National de la Recherche Scientifique (CNRS)-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)-Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Université de Versailles Saint-Quentin-en-Yvelines (UVSQ), European Project: EVK2-CT-2000-00077,EPICA
• Format: Article in Journal/Newspaper
• Language: English
• Published: HAL CCSD 2010
• Subjects: [SDU.OCEAN]Sciences of the Universe [physics]/Ocean; Atmosphere; [SDU.ENVI]Sciences of the Universe [physics]/Continental interfaces; environment; Antarctic; Talos Dome; Antarc*; Antarctica; DML; EPICA; ice core
• Online Access: https://hal.archives-ouvertes.fr/hal-03200967; https://doi.org/10.1016/j.epsl.2010.06.023

International audience CO$_2$ measurements on the EPICA (European Project for Ice Coring in Antarctica) DML ice core in depth levels just below the bubble ice–clathrate ice transformation zone (1230–2240 m depth) were performed. In the youngest part (1230–1600 m), they reveal variations of up to 25 ppmv around the mean atmospheric concentration within centimetres, corresponding to a snow deposition interval of a few years. Similar results are found at corresponding depth regions of the Dome C and the Talos Dome ice cores. Since we can exclude all hitherto known processes altering the concentration of CO$_2$ in ice cores, we present a hypothesis about spatial fractionation of air components related to episodically increasing clathrate formation followed by diffusion processes from bubbles to clathrates. This hypothesis is supported by optical line-scan observations and by O$_2$/N$_2$ measurements at the same depth where strong CO$_2$ variations are detected. Below the clathrate formation zone, this small-scale fractionation process is slowly smoothed out, most likely by diffusion, regaining the initial mean atmospheric concentration. Although this process compromises the representativeness of a single CO$_2$ measurement on small ice samples in the clathrate formation zone of an ice core, it does not affect the mean atmospheric CO$_2$ concentration if CO$_2$ values are averaged over a sufficiently long depth scale (> 10 cm in case of the EPICA DML ice core).