A century old record of lead-210 fallout on the Greenland ice sheet

Systematic measurements of the stable oxygen isotope ratio (δ¹⁸O) and artifical radioactivity (total β) on a 77 m ice core from the DYE 3 location in S.E. Greenland provided precise age indices to study the fallout of lead-210 during the last century. The results obtained on the Dye 3 core and those of similar studies conducted on two other ice cores from the Greenland locations, Camp Century and North Central, are discussed in relation to the average fallout of ²¹⁰Pb and the probable contributions made by natural and artificial sources in the atmosphere. The results indicate that: (i) the fallout of ²¹⁰Pb observed over a period of 100 years has not remained constant, an assumption usually made in geochronological studies; (ii) the fallout of ²¹⁰Pb over the period 1886—1930 is observed to be higher at least by a factor of two than that observed in the period 1930—1975; (iii) the higher ²¹⁰Pb fallout observed over the period 1886—1930 coincides with high volcanic activity in this period; (iv) there is no evidence for significant production of ²¹⁰Pb due to testing of nuclear weapons in the three decades: 1950s to 1970s.