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| Titel |
A reconstruction of radiocarbon production and total solar irradiance from the Holocene 14C and CO2 records: implications of data and model uncertainties |
| VerfasserIn |
Raphael Roth, Fortunat Joos |
| Konferenz |
EGU General Assembly 2013
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| Medientyp |
Artikel
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| Sprache |
Englisch
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| Digitales Dokument |
PDF |
| Erschienen |
In: GRA - Volume 15 (2013) |
| Datensatznummer |
250076158
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| Zusammenfassung |
| Past atmospheric CO2 concentrations reconstructed from polar ice cores [Monnin et al.,
2004] combined with its Δ14C signature as conserved in tree-rings [Reimer et al., 2009]
provide important information both on the cycling of carbon as well as the production of
radiocarbon in the atmosphere. As the 14C production rate (Q) is modulated by changes in the
strength of the magnetic field enclosed in solar wind, it serves as a valuable proxy for past
changes in solar activity.
Using the Bern3D-LPX, a fully featured Earth System Model of Intermediate
Complexity (EMIC) with a 3D ocean and a dynamic vegetation model component, we
perform transient carbon-cycle simulations spanning the past 21 kyr. By solving
the atmospheric 14C budget, the radiocarbon production rate over the Holocene is
reconstructed. Applying different deglacial forcings, as well as a control-simulation
with constant climate, the sensitivity of Q to carbon-cycle changes is discussed.
The error in the terrestrial 14C record is translated into an uncertainty in Q using a
Monte-Carlo approach. In addition, uncertainties in the global carbon inventory, GPP and
air-sea gas-exchange are taken into account. The estimated modern (1950-2005)
production rate of 1.55±0.20 atoms/cm2/s is close to a recent theoretical calculations by
Kovaltsov et al. (2012) yielding a modern production rate of 1.64 atoms/cm2/s
but considerably lower than the estimated 2 atoms/cm2/s by Masarik and Beer
(2009).
The newly produced production rate record is then interpreted as a proxy for solar activity
changes in the past 10 kyrs. To do so, we use published results from particle simulations
[Masarik and Beer, 1999] together with the latest reconstruction of the geomagnetic dipole
moment [Knudsen et al., 2008] to calculate the past history of the so-called solar modulation
potential (Φ). The 14C based Φ is extended to 2005 A.D. with instrumental data [Usoskin et
al., 2011].
In a subsequent step, Φ is translated into past total solar irradiance (TSI) using a
recently published Φ-TSI relationship [Steinhilber et al., 2009]. Our TSI record
shows, besides recent solar grand solar minimas like the Maunder Minumum (MM),
numerous centennial-scale variations with deviations from the long-term mean of
only approx. 0.5 W/m2, while the millennial-scale trend in TSI is even smaller.
The frequency-spectrum of TSI reveals well known solar periodicities of different
length. Finally, our radiocarbon-based TSI record is fed back into Bern3D-LPX in
order model past changes in surfaces atmospheric temperature (SAT) caused by
solar variations, leading to relatively low transient SAT excursions of less than 0.1
K.
References:
Monnin et al., Earth Planet. Sci. Lett., 2004, 224, 45-54
Reimer et al., Radiocarbon, 2009, 51, 1111-1150
Masarik and Beer, J. Geophys. Res., 1999, 104, 12099-12111
Kovaltsov et al., Earth Planet. Sci. Lett., 2012, 337-338, 114-120
Knudsen et al., Earth Planet. Sci. Lett., 2008, 272, 319-329
Usoskin et al., J. Geophys. Res., 2011, 116, A02104-
Steinhilber at al., Geophys. Res. Lett., 2009, 36, L19704- |
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