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- Muscheler, Raimund, et al.
(författare)
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Changes in the carbon cycle during the last deglaciation as indicated by the comparison of Be-10 and C-14 records
- 2004
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Ingår i: Earth and Planetary Science Letters. - 1385-013X. ; 219:3-4, s. 325-340
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Tidskriftsartikel (refereegranskat)abstract
- The variations in atmospheric radiocarbon (C-14) concentration during the last 50 000 years can be attributed to changes in the C-14 production rate (due to changes in solar activity, the geomagnetic field and/or interstellar galactic cosmic ray flux) and to changes in the global carbon cycle. The relative contributions of these processes is the subject of current debate. Although the discrepancies between the various reconstructions of the past atmospheric radiocarbon concentration increase with age, the relatively good agreement over the last 25 000 years allows a quantitative discussion of the causes of the observed C-14 variations for this period. Using Be-10 measurements from Greenland Summit ice cores, we show that, in addition to solar and geomagnetically induced production rate changes, significant changes in the carbon cycle have to be considered to explain the measured C-14 concentrations. There is evidence that these changes are connected to: (1) global deglaciation and (2) climate changes in the North Atlantic region on centennial to millennial time scales related to changes in the ocean circulation. Differences between Be-10 and geomagnetic field records, however, suggest that uncertainties of about 20% still exist in determinations of past changes in the C-14 production rate. (C) 2004 Elsevier B.V. All rights reserved.
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| 2. |
- O'Hare, Paschal, et al.
(författare)
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Multiradionuclide evidence for an extreme solar proton event around 2,610 BP (similar to 660 BC)
- 2019
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Ingår i: Proceedings of the National Academy of Sciences of the United States of America. - : NATL ACAD SCIENCES. - 0027-8424 .- 1091-6490. ; 116:13, s. 5961-5966
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Tidskriftsartikel (refereegranskat)abstract
- Recently, it has been confirmed that extreme solar proton events can lead to significantly increased atmospheric production rates of cosmogenic radionuclides. Evidence of such events is recorded in annually resolved natural archives, such as tree rings [carbon-14 (C-14)] and ice cores [beryllium-10 (Be-10), chlorine-36 (Cl-36)]. Here, we show evidence for an extreme solar event around 2,610 years B.P. (similar to 660 BC) based on high-resolution Be-10 data from two Greenland ice cores. Our conclusions are supported by modeled C-14 production rates for the same period. Using existing Cl-36 ice core data in conjunction with Be-10, we further show that this solar event was characterized by a very hard energy spectrum. These results indicate that the 2,610-years B.P. event was an order of magnitude stronger than any solar event recorded during the instrumental period and comparable with the solar proton event of AD 774/775, the largest solar event known to date. The results illustrate the importance of multiple ice core radionuclide measurements for the reliable identification of short-term production rate increases and the assessment of their origins.
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