Chlorine-36 and cesium-137 in ice-core samples from mid-latitude glacial sites in the Northern Hemisphere

Abstract

Chlorine-36 ( 36Cl) concentrations, 36Cl/Cl ratios, and 36Cl fluxes in ice-core samples collected from the Upper Fremont Glacier (UFG) in the Wind River Mountain Range, Wyoming, United States, and the Nangpai Gosum Glacier (NGG) in the Himalayan Mountains, Nepal, were determined and compared with published results from the Dye-3 ice-core drilling site on the Greenland Ice Sheet. Cesium-137 ( 137Cs) concentrations in the NGG also were determined. The background fluxes for 36Cl for each glacial site were similar: (1.6±0.3) × 10 −2 atoms/cm 2 s for the UFG samples, (0.7±0.1) × 10 −2 atoms/cm 2 s for the NGG samples, and (0.4±0.1) × 10 −2 atoms/cm 2 s for the Dye-3 samples. The 36Cl fluxes in ice that was deposited as snow during peak atmospheric nuclear weapon test (1957–1958) were (33±1) × 10 −2 atoms/cm 2 s for the UFG site, (291±3) × 10 −2 atoms/cm 2 s for the NGG site, and (124±5) × 10 −2 atoms/cm 2 s for the Dye-3 site. A weapon test period 137Cs concentration of 0.79±0.05 Bq/kg in the NGG ice core also was detected in the same section of ice that contained the largest 36Cl concentration.