Antarctica’s ice sheets are still releasing radioactive chlorine from marine nuclear weapons tests in the 1950s, a new study finds.
This suggests regions in Antarctica store and vent the radioactive element differently than previously thought. The results also improve scientists’ ability to use chlorine to learn more about Earth’s atmosphere.
Scientists commonly use the radioactive isotopes chlorine-36 and beryllium-10 to determine the ages of ice in ice cores, which are barrels of ice obtained by drilling into ice sheets. Chlorine-36 is a naturally occurring radioactive isotope, meaning it has a different atomic mass than regular chlorine. Some chlorine-36 forms naturally when argon gas reacts with cosmic rays in Earth’s atmosphere, but it can also be produced during nuclear explosions when neutrons react with chlorine in seawater.
Nuclear weapons tests in the United States carried out in the Pacific Ocean during the 1950s and the 1960s caused reactions that generated high concentrations of isotopes like chlorine-36. The radioactive isotope reached the stratosphere, where it traveled around the globe. Some of the gas made it to Antarctica, where it was deposited on Antarctica’s ice and has remained ever since.
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Image via NASA
