Use of 10Be to predict atmospheric 14C variations during the laschamp excursion: High sensitivity to cosmogenic isotope production calculations

• Published in: Radiocarbon
• Main Authors: Cauquoin, Alexandre, Raisbeck, G., Jouzel, Jean, Paillard, D.
• Other Authors: 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), Centre de Sciences Nucléaires et de Sciences de la Matière (CSNSM), Université Paris-Sud - Paris 11 (UP11)-Institut National de Physique Nucléaire et de Physique des Particules du CNRS (IN2P3)-Centre National de la Recherche Scientifique (CNRS), 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)), Modélisation du climat (CLIM)
• Format: Article in Journal/Newspaper
• Language: English
• Published: HAL CCSD 2014
• Subjects: [SDU.STU.GP]Sciences of the Universe [physics]/Earth Sciences/Geophysics [physics.geo-ph]; [PHYS.PHYS.PHYS-AO-PH]Physics [physics]/Physics [physics]/Atmospheric and Oceanic Physics [physics.ao-ph]; Greenland; Antarc*; Antarctica; GRIP; NGRIP
• Online Access: https://hal.science/hal-01088887; https://hal.science/hal-01088887/document; https://hal.science/hal-01088887/file/USE%20OF%2010Be%20TO%20PREDICT%20ATMOSPHERIC.pdf; https://doi.org/10.2458/56.16478

International audience The Laschamp excursion is a period of reduced geomagnetic field intensity occurring 40.7 ± 1.0 kyr ago. As a consequence, cosmogenic isotope production increased dramatically and its sensitivity to solar activity was enhanced during this period. The latter occurs because a larger fraction of the lower-energy interstellar galactic cosmic-ray particles, normally excluded by the geomagnetic field, is able to reach Earth's atmosphere. This produces a cosmogenic isotope production signal with a significant structure. As high-resolution 10Be profiles from both Antarctica (EDC) and Greenland (NGRIP-GRIP) during this crucial period are now available, one can use them as input into a box carbon cycle model in order to predict atmospheric 14C variations due to the Laschamp excursion. For this purpose, 10Be data are converted into 14C, using production calculations for the 10Be-14C conversion, after correction for the estimated difference of sensitivity between polar and global 10Be deposition. Several scenarios of carbon cycle state are simulated, from preindustrial to glacial conditions. Applying two recent cosmogenic isotope production calculations for the 10Be to 14C conversion, we found that the resulting atmospheric ?14C variations are very sensitive to which of these two are employed. For example, ?14C amplitude under glacial conditions varies from 260‰ (EDC) and 320‰ (Greenland) to 430‰ (EDC) and 510‰ (Greenland) depending on the formulation used for 10Be-14C conversion. ©2014 by the Arizona Board of Regents on behalf of the University of Arizona.