A Korean research team used radioactive material left in the polar regions from atmospheric nuclear tests conducted in the Pacific in the 1950s to identify the seasonal characteristics of global atmospheric transport.
Korea Polar Research Institute (KOPRI) said on the 27th that, using faint traces of plutonium-239 left in Antarctic and Greenland ice sheets as clues, it reconstructed how air moves from the stratosphere through the troposphere to the poles.
The study began by checking how fallout from atmospheric nuclear tests spread globally over time and reached the polar regions. The team led by senior researcher Han Yeong-cheol at Korea Polar Research Institute (KOPRI) analyzed ice cores collected from four sites, including Antarctica and Greenland, and precisely measured the amount of plutonium-239 accumulated in the ice sheets between the 1950s and the 1980s.
The results showed distinct differences in the traces of the 1952 "Ivy Mike" and 1954 "Castle" atmospheric nuclear tests. Although both tests were conducted on adjacent atolls (coral islands) in the Marshall Islands in the Pacific, the traces of "Castle" were clearly preserved in Antarctic ice, whereas the traces of "Ivy Mike" were very weak or recorded later.
The researchers found the difference in the atmosphere's seasonal changes. After the fine radioactive material generated by the nuclear tests rose to the stratosphere, the timing of its descent back to the troposphere or movement toward the poles varied greatly by season.
In particular, during the Southern Hemisphere summer, exchange between the stratosphere and troposphere becomes more active, increasing the likelihood that material at higher altitudes will move faster or head toward the poles. The findings are the first case to demonstrate with observational data that stratosphere-troposphere exchange actually varies by season, providing evidence that supports existing theoretical models.
The amounts of plutonium-239 analyzed in this study were extremely small, and the team, using world-class precision analytical techniques, distinguished changes not only by year but also by season.
At the same time, it was proven that nuclear test fallout recorded in polar ice is a "natural archive" that shows a temporal cross-section of atmospheric circulation. This is expected to improve the accuracy of atmospheric transport models and enhance predictive power across various fields, including volcanic ash dispersion, climate change, and geoengineering material injection simulations.
Shin Jin-hwa, the first author of the paper and a research fellow, said, "Traces left by past nuclear tests were used in today's atmospheric science research," adding, "This study presents a new way to track the 'invisible paths' of the global atmosphere."
The findings were published on the 15th (local time) in the international journal Science Advances.
References
Science Advances (2025), DOI: https://doi.org/10.1126/sciadv.adv1172