Regional Radiocarbon Effect Due to Thawing of Frozen Earth

Abstract

ABSTRACT. Accelerator mass spectrometry (AMS) measurement of 25 single-year tree rings from AD 1861-1885 at ca. ±3.5% precision shows no evidence of an anomalous 11-yr cycle of 14C near the Arctic Circle in the Mackenzie River area.However, the A14C measurements are lower on average by 2.7 ± 0.9 (v)% relative to 14C measurements on tree rings from the Pacific Northwest (Stuiver and Braziunas 1993). We attribute this depression of &4C to thawing of the ice and snow cover followed by melting of frozen earth that releases trapped 14C-depleted CO2 to the atmosphere during the short growing season from May through August. Correlation of O14C with May-August estimated temperatures yields a correlation index of r = 0.60. The reduction in el4C is dominated by seven years of anomalous depletion. These years are 1861,1867-1869,1879-1880 and 1883. The years 1867-1869 are coincident with a very strong ENSO event.

Radiocarbon Calibration and Application to Geophysics, Solar Physics, and Astrophysics

“…Three processes have been reported to produce a measurable regional change in the 14 C/C ratio of the atmosphere. There is a latitude effect (Braziunas et al 1995), costal upwelling (Damon et al 1989 and thawing of frozen earth (Damon et al 1996). The latitude effect is negligible from the Equator to the Arctic Circle but increases from the equator to around 65°S where it has been calculated to be −6‰ (50 yr too old) (Braziunas et al 1995).…”

Influence of atmospheric circulation on regional 14CO2 differences

“…Intrahemispheric 14 C offsets for the Northern Hemisphere for the prenuclear era have been investigated by a number of researchers. The magnitudes of these 14 C offsets are about several per mil and their uncertainties are of similar levels for the prebomb period [ Damon et al , 1989; Hua et al , 2004a], and for earlier periods [ Damon et al , 1996; Stuiver and Braziunas , 1998; Kromer et al , 2001; Hua et al , 2004b]. Because of measurement uncertainties it has sometimes been difficult to determine the magnitudes of intrahemispheric 14 C offsets.…”

INTCAL98 Radiocarbon Age Calibration, 24,000–0 cal BP

“…Such differences are at the limit of 14C dating and difficult to measure. The fine structure in ocean circulation (e.g., in coastal waters) and differences in regional carbon cycle sources and sinks (e.g., permafrost areas, Damon et al 1996) increase Northern Hemispheric &4C variability. The location-dependent &4C offsets also need not be constant over time.…”