Bomb Produced¹⁴C Content in Tree Rings Grown at Different Latitudes

Abstract

The 14C content in 1961–1967 rings of each of three spruce pines grown at (68° N, 130° W), (47° 30' N, 129° 16' E) and (27° 13' N, 100° 20' E) were measured. Δ14C values of the three specimens rise dramatically from a common level (∼250‰) in 1961 to their respective maxima, 964‰, 909‰, and 743‰ in 1964 and then fall to a common level ∼680‰ in 1967. The observed Δ14C increase comes most likely from the nuclear bomb test of the USSR at 75° N in 1961, although there were many other tests since the 1950s. The different effects at different latitudes reflect the atmospheric circulation patterns in the stratosphere and the transport of 14C nuclei from the stratosphere to the troposphere.

Bomb-Produced 14C in Tree Rings

“…We also noted that the Mackenzie spruce responded quickly to bomb-produced 14C, the Dailing spruce responded with a slight delay, and the Mingyin spruce responded even later; these differences presumably reflect the mechanism of meridional mixing in the troposphere. These results were reported at the 12th International Radiocarbon Conference (Dai & Fan 1986). …”

14C Activity in Different Sections and Chemical Fractions of Oak Tree Rings, AD 1938–1981

“…These authors offer an alternative explanation, that lignin remains after the AAA treatment, and it formed later in the year than cellulose. Dai and Fan (1986) studied the excess 14C at different latitudes (68°N, 47°N and 27°N) using tree rings from 1962 to 1967. The samples were said to have been repeatedly treated according to routine HCl-NaOH-HCl procedure.…”

Crossdating Juniperus procera from North Gondar, Ethiopia

“…In the Northern Hemisphere, the radiocarbon calibration curve displays a 'plateau' in the period AD 1650-1955, which limits the potential to obtain accurate radiocarbon dates during this period (Stuiver et al 1998). However, a high peak occurs after AD 1955, related to atmospheric nuclear bomb tests in the period AD 1945-1963(Dai and Fan 1986. After AD 1963 the atmospheric radiocarbon concentration declined sharply due to the incorporation of radiocarbon in other reservoirs of the carbon cycle (Nydal et al 1979).…”

“…After AD 1963 the atmospheric radiocarbon concentration declined sharply due to the incorporation of radiocarbon in other reservoirs of the carbon cycle (Nydal et al 1979). As the largest nuclear bomb tests were performed at Novaya Zemlya, Russia (72°N, 53°E) (Dai and Fan 1986), the peak varies with latitude. Therefore, a local or regional dataset of atmospheric radiocarbon concentration measurements is required to allow highly accurate dating after AD 1955.…”