Absolute Production of Radiocarbon and the Long-Term Trend of Atmospheric Radiocarbon

Goslar, Tomasz

doi:10.1017/s0033822200041400

Cited by 14 publications

(16 citation statements)

References 34 publications

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“…[10] The reconstruction starts from the decadal 14 C production rate Q computed by Usoskin and Kromer [2005] from the INTCAL98 compilation series [Stuiver et al, 1998] of D 14 C data in tree rings. This Q-series is consistent with other estimates of the 14 C production rate obtained by other groups [Stuiver, 1980;Stuiver and Quay, 1980;Goslar, 2001]. The used time series Q is shown in Figure 1b together with its long term trend (the best fit 4th order polynomial).…”

Section: Solar Activity Reconstructionsupporting

confidence: 88%

Solar activity reconstructed over the last 7000 years: The influence of geomagnetic field changes

Usoskin¹,

Solanki²,

Korte³

2006

Geophysical Research Letters

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The long‐term solar activity, as manifested by sunspot number, has been recently reconstructed on multi‐millennium time scales by S. K. Solanki et al. (2004) from the measured concentration of 14C in tree rings. The exact level of the reconstructed solar activity depends, however, on independently evaluated data of the geomagnetic dipole strength variations. Recently, a new series of the palaeomagnetic dipole moment reconstruction for the last 7000 years has been presented by M. Korte and C. G. Constable (2005a) on the basis of a thorough analysis of global samples. The new palaeomagnetic series yields a systematically lower dipole moment in the past, compared to the earlier geomagnetic reconstructions. We have revised the earlier sunspot activity reconstruction since 5000 BC, using the new geomagnetic data series, and found that it is roughly consistent with the previous results during most of the period, although the revised sunspot number values are in general higher. Nonetheless, it is confirmed with the new palaeomagnetic series that the Sun spends only 2–3% of the time in a state of high activity, similar to the modern episode. This strengthens the conclusion that the modern high activity level is very unusual during the last 7000 years.

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Section: Solar Activity Reconstructionsupporting

confidence: 88%

Solar activity reconstructed over the last 7000 years: The influence of geomagnetic field changes

Usoskin¹,

Solanki²,

Korte³

2006

Geophysical Research Letters

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“…This corresponds to an average value of different suggestions for the mean global pre-industrial production rate of 14 C ranging from 1.6 (ref. 51) to 2.02 atoms cm −2 s −1 (ref. 23).…”

Section: Methodsmentioning

confidence: 99%

Multiradionuclide evidence for the solar origin of the cosmic-ray events of AD 774/5 and 993/4

et al. 2015

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The origin of two large peaks in the atmospheric radiocarbon (14C) concentration at AD 774/5 and 993/4 is still debated. There is consensus, however, that these features can only be explained by an increase in the atmospheric 14C production rate due to an extraterrestrial event. Here we provide evidence that these peaks were most likely produced by extreme solar events, based on several new annually resolved 10Be measurements from both Arctic and Antarctic ice cores. Using ice core 36Cl data in pair with 10Be, we further show that these solar events were characterized by a very hard energy spectrum with high fluxes of solar protons with energy above 100 MeV. These results imply that the larger of the two events (AD 774/5) was at least five times stronger than any instrumentally recorded solar event. Our findings highlight the importance of studying the possibility of severe solar energetic particle events.

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“…To do this, we had to account for contributions to the latitudinal gradient from cosmogenic production, fossil fuel burning, and terrestrial biosphere respiration. We assumed that long‐term cosmogenic production averages 6.2 kg 14 C/yr, balancing decay in short‐term carbon pools (Goslar, 2001) and consistent with observed 14 CO concentrations (Quay et al, 2000), and that interannual variability in production is proportional to the sunspot number (Lingenfelter, 1963). Carbon from fossil fuels contains no 14 C, and so the concentration of fossil fuel burning in the northern mid‐latitudes results in Δ 14 CO 2 depletion in the northern hemisphere (Levin et al, 2003).…”

Section: Methodsmentioning

confidence: 99%

Carbon isotope evidence for the latitudinal distribution and wind speed dependence of the air–sea gas transfer velocity

Krakauer

Randerson²,

Primeau³

et al. 2006

Tellus B: Chemical and Physical Meteorology

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A B S T R A C TThe air-sea gas transfer velocity is an important determinant of the exchange of gases, including CO 2 , between the atmosphere and ocean, but the magnitude of the transfer velocity and what factors control it remains poorly known. Here, we use oceanic and atmospheric observations of 14 C and 13 C to constrain the global mean gas transfer velocity as well as the exponent of its wind speed dependence, utilizing the distinct signatures left by the air-sea exchange of 14 CO 2 and 13 CO 2 . While the atmosphere and ocean inventories of 14 CO 2 and 13 CO 2 constrain the mean gas transfer velocity, the latitudinal pattern in the atmospheric and oceanic 14 C and 13 C distributions contain information about the wind speed dependence. We computed the uptake of bomb 14 C by the ocean for different transfer velocity patterns using pulse response functions from an ocean general circulation model, and evaluated the match between the predicted bomb 14 C concentrations and observationally based estimates for the 1970s-1990s. Using a wind speed climatology based on satellite measurements, we solved either for the best-fit global relationship between gas exchange and mean wind speed or for the mean gas transfer velocity over each of 11 ocean regions. We also compared the predicted consequences of different gas exchange relationships on the rate of change and interhemisphere gradient of 14 C in atmospheric CO 2 with tree-ring and atmospheric measurements. Our results suggest that globally, the dependence of the air-sea gas transfer velocity on wind speed is close to linear, with an exponent of 0.5 ± 0.4, and that the global mean gas transfer velocity at a Schmidt number of 660 is 20 ± 3 cm/hr, similar to the results of previous analyses. We find that the air-sea flux of 13 C estimated from atmosphere and ocean observations also suggests a lower than quadratic dependence of gas exchange on wind speed.

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Absolute Production of Radiocarbon and the Long-Term Trend of Atmospheric Radiocarbon

Cited by 14 publications

References 34 publications

Solar activity reconstructed over the last 7000 years: The influence of geomagnetic field changes

Solar activity reconstructed over the last 7000 years: The influence of geomagnetic field changes

Multiradionuclide evidence for the solar origin of the cosmic-ray events of AD 774/5 and 993/4

Carbon isotope evidence for the latitudinal distribution and wind speed dependence of the air–sea gas transfer velocity

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