Cosmogenic isotopes as proxies for the solar activity Edouard BARD & Mélanie BARONI CEREGE, Aix-en-Provence VolSol project
Max Planck Institute, Jena 14 C production and decay
Geo- and helio-magnetic fields modulate the arrival of protons from galactic cosmic rays Cascade of particle reactions in the atmosphere (air shower)
Anti-correlation between the solar activity and the cosmic-ray flux measured by neutron monitors Sunspot numbers 18 24 19 20 21 22 23 Cosmic rays (Oulu + Climax) Usoskin 2013 Liv. Rev. Solar Phys.
Geo- and heliomagnetic modulation geomagnetic latitude Minimum of the 11-yr sunspot cycle Production of cosmogenic nuclides ( 14 C and 10 Be ) average Maximum of the 11-yr sunspot cycle
Production ( 10 Be) as a function of altitude, the solar modulation potential Φ and the intensity of the geomagnetic dipole M/M o Kovaltsov & Usoskin 2010 EPSL
Studying the solar activity with cosmogenic nuclides from various geological archives 14 C & 10 Be in marine sediments 10 Be & 36 Cl in polar ice Stalagmites 14 C in subfossil wood 14 C in corals 14 C in stalagmites
14 C & 10 Be by accelerator mass spectrometry in Aix-en-Provence AixMICADAS ASTERisques
The most recent 14 C calibration curve prepared by the IntCal group: IntCal13 after 09, 04, 98, 93 Volume in Open Access http://www.radiocarbon.org
Atmospheric 14 CO 2 molecules diffuse in the other reservoirs of the carbon cycle
Comparing 14 C and 10 Be records requires the use of numerical models of various complexity Joos et al. 1996 Tellus Stocker et al. 1994 L. Fairhead Bard et al. 1994 EPSL Field et al. 2006 JGR
The carbon cycle acts as a low-pass filter for 14 C e.g. sinusoidal production changes on atmospheric 14 C 14 C Production Attenuation Phase lag CC model Atmospheric 14 C Bard et al. 1997 EPSL Delaygue & Bard 2011 Clim. Dyn.
Bomb tests in the early 60s provide us with the impulse response function Hua & Barbetti 2004 Radiocarbon
The bomb 14 C has diffused into other reservoirs of the carbon cycle, e.g. the ocean Presence of bomb 14 C Natural 14 C deficit linked to the age of water masses since their last equilibration with the atmosphere ( 1 in 8 years) Grottoli & Eakin 2007 Earth Sci. Rev. Jenkins et al. 2010 Radiocarbon
10 Be measured in ice cores from Antarctica! South Pole
10 Be in ice cores from Antarctica and 14 C in tree-rings (all converted in 14 C units) High 10 Be production by GCR (quiet Sun) Low 10 Be production by GCR (active Sun) Year A.D. Bard et al. 1997 EPSL, 2000 Tellus, Horiuchi et al. 2008 QG, Delaygue & Bard 2011 Clim. Dyn.
10 Be records from Greenland and Antarctica (GRIP and EDML) Steinhilber et al. 2012 PNAS
Extracting the solar activity from the IntCal 14 C curve Calendar age (years B.P.) Heliomagnetic High frequencies Geomagnetic low frequencies + carbon cycle changes + (slow solar changes?) Stuiver et al. 1998 Radiocarbon as plotted by Solanki et al. 2004 Nature
Sunspot number reconstruction over the Holocene Calendar age (years B.P) Observations since 1610 Calculations based on 14 C in tree rings Solanki et al. 2004 Nature
Sensitivity to the geomagnetic records Duration of solar minima Maunder type Spörer type Various paleomagnetic records Solar minima Usoskin et al. 2006 GRL, 2007 A&A
An unexpected and mysterious result in 14 C records with annual resolution Japanese cedar forest A rapid ( 1 yr) 15 jump in 14 C around 775 AD
The spike has been replicated in trees from Germany, California, Siberia and New-Zealand Usoskin et al. 2013 A&A, Jull et al. 2014 GRL Carbon cycle box modeling shows it is compatible with an increase of 15-20 kg of 14 C 2-3 times the average yearly production by GCR
Another spike (10 ) detected around 994 AD Miyake et al. 2013 Nat. Comm.
Previously detected in a 10 Be record from Antarctica but at low resolution Dome Fuji ice core Horiuchi et al. 2008 QG The spike is too rapid and too large for the solar modulation of galactic cosmic rays, hence:! Supernova (but no other evidence),! Strong solar energetic particle (SEP) event
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