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 = University of Bern = Université de Berne (UNIBE)-Universität Bern = University of Bern = Université de Berne (UNIBE), Oeschger Centre for Climate Change Research (OCCR), Universität Bern = University of Bern = Université de Berne (UNIBE), Alfred Wegener Institute for Polar and Marine Research (AWI), 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)), 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; Antarc*; Antarctic; Antarctica; DML; EPICA; ice core
• Online Access: https://hal.science/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).