Lamont Radiocarbon Measurements VI

Abstract

In contrast to previous radiocarbon measurement lists, this list contains only known-age samples, most of which formed during the past ten years. The measurements were made largely in order to gain an understanding of the distribution of radiocarbon within the dynamic carbon reservoir both today and at times in the past. Since all materials forming in this reservoir today do not have the same C14/C12 ratio, such an understanding is necessary in order to arrive at the most accurate possible estimate of the age of samples submitted for dating. This is particularly important when high accuracy (i.e., <100 years error) is required on subaerially grown samples and also when attempting to extend the method to samples which formed in reservoirs other than the atmosphere (for example, the ocean and freshwater systems).

Sinking particle flux in the sea ice zone of the Amundsen Shelf, Antarctica

“…The resultant CO 2 samples were analyzed for radiocarbon and stable carbon isotopes at the National Ocean Sciences Accelerator Mass Spectrometry Facility at Woods Hole Oceanographic Institution (NOSAMS WHOI) following standard techniques (McNichol et al, 1994). The uncertainty for this type of sample determined by multiple duplicate-analyses in our lab is less than 10‰ for Δ 14 C (a fractionation-corrected value of 14 C/ 12 C relative to a standard (Broecker and Olson, 1959;Stuiver and Polach, 1977)) and 0.1‰ for δ 13 C. A subset of samples was analyzed for δ 15 N values at KOPRI, using an elemental analyzer (Flash HT 2000) aligned with an isotope ratio mass spectrometer (Delta V plus).…”

Interhemispheric gradient of atmospheric radiocarbon reveals natural variability of Southern Ocean winds

“…As long as one assumes that δ 13 C is not affected by wind-driven changes in ocean dynamics and gas exchange, the variability of atmospheric 14 C can be identified approximately with changes in the 14 C-to-12 C ratio in the model atmosphere. The zero level for 14 C is chosen to correspond to the 14 C of the absolute radiocarbon standard, which is 1890 wood (Broecker and Olson, 1959). For the preanthropogenic climate system, one usually assumes a "mean state" with 14 C = 0 ‰ in the atmosphere where decay is balanced by production of 14 C in the upper atmosphere through the effect of cosmic rays (spallation).…”

The Effect of Fossil Fuel and Biogenic CO2 on the 13C and 14C Content of Atmospheric Carbon Dioxide

“…By international agreement (Broecker and Olson, 1959), the 14G correction is related to the deviation of the measured 613 from a standard value (6513) of -25% (vs (1) where 814 is defined by:…”