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Geomagnetic intensity and 14 C abundance in the atmosphere and ocean during the past 50 kyr
Author(s) -
Laj Carlo,
Mazaud Alain,
Duplessy JeanClaude
Publication year - 1996
Publication title -
geophysical research letters
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 2.007
H-Index - 273
eISSN - 1944-8007
pISSN - 0094-8276
DOI - 10.1029/96gl02152
Subject(s) - earth's magnetic field , geology , radiocarbon dating , volcano , intensity (physics) , atmosphere (unit) , geomagnetic secular variation , atmospheric sciences , climatology , paleontology , magnetic field , meteorology , physics , geomagnetic storm , quantum mechanics
We have used a new sedimentary record of geomagnetic field intensity, combined with published volcanic data, to examine the extent to which geomagnetic changes have affected 14 C production in the past. The production record was then converted into an atmospheric Δ 14 C signal using a 4‐box model of past oceanic circulation. The results indicate that changes in geomagnetic field intensity account for at least 80% of the Δ 14 C shift documented by published U‐Th data, which are of the order of 500 per mil with respect to a constant production hypothesis. Model simulations show that changes in past oceanic circulation account for only ±100 per mil of Δ 14 C variation, which is within the uncertainty of the geomagnetic correction. In terms of dating, these results show that the radiocarbon ages have to be shifted by 2 to 3.5 kyr towards older ages during the 20–40 ka interval.