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We measured the Δ 14 C values in 57 rings (from AD 1824 to 1880) of a white spruce grown in Mackenzie Delta (68°N, 130°W), as part of our continuing study of the Δ 14 C variation related to solar activities. The values exhibit a 10‰ fluctuation with an 11-year periodicity anti-correlated with the solar activity cycle. We also measured the Δ 14 C values in 6 rings (from AD 1940 to 1945). The abnormally high value in the 1943 ring may be due to two large solar flares occurring in 1942.
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Fan et al. (1986) studied this question.
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