Measurements of 36Cl during the 1950s bomb-pulse in ice at Law Dome, Antarctica

The fallout of the radioisotope 36Cl produced by nuclear weapons testing has been measured as a function of time in an ice core from a high-accumulation site in Antarctica. These measurements complement an earlier study of this 36Cl ‘bomb pulse’ in an Arctic ice core. The measurements are compared with a box model developed to describe simultaneously the data from both the Arctic and Antarctic sites. Using an up to date catalogue of the various tests, including their yields and location, the 36Cl production of the individual tests has been estimated and used as input to the box model. Exchange times for gaseous exchange between stratosphere and troposphere, and for gaseous exchange between the stratospheres of the two hemispheres are deduced. The present work also yields an improved understanding of the inclusion of aerosols and gases into ice sheets, and better constraints on the amount of 36Cl produced by nuclear weapons testing.