The 41 Ca bomb pulse and atmospheric transport of radionuclides

For the first time, the 41 Ca signal from the nuclear weapon tests has been measured. Calcium 41 concentrations have been determined in alpine ice of the Fiescherhorn glacier (Switzerland) with accelerator mass spectrometry. The peak concentrations have been observed to be about 3×10 6 atoms of 41 Ca per kilogram of ice in. the 1950s. It has been found that 41 Ca is produced essentially by the atoll bombs. A universal box model, able to describe atmospheric transport of radionuclides that are in gaseous form or attached to aerosols, has been developed. The model has been applied to calculate the bomb pulses of 14 C, 36 Cl, 41 Ca, 90 Sr, and 137 Cs, For the transport of radionuclides that are attached to aerosols such as 41 Ca, 90 Sr, and 137 Cs, sedimentation (gravitational settling) in the upper stratosphere has been taken into account. It has been found that the deposition of bomb‐produced 36 Cl on the Earth's surface is delayed compared to that of 90 Sr by about 1 year because 36 Cl stays gaseous in the stratosphere. The model can also be used to calculate the deposition of cosmogenic radionuclides, e.g., 36 Cl and 10 Be, in their natural archives, such as polar ice sheets.