A team led by Prof. Zheng-Tian Lu and Prof. Wei Jiang from the University of Science and Technology of China (USTC), have developed a novel technique known as All-Optical Atom Trap Trace Analysis. In collaboration with American glaciologists, they have successfully performed krypton-81 dating on 1-kilogram samples of ancient Antarctic ice using this method. This advance provides a powerful new tool for studying paleoclimate changes on million-year timescales. The findings were published in the Nature Communications .
Deep ice cores drilled from the Antarctic continent and the Greenland ice sheet—often extending a couple of kilometers in depth—serve as invaluable archives of Earth's past climate and ice sheet evolution. The basal ice at the bottom of these cores may preserve records of major climatic transitions, but accurately dating this ice has long been a challenge due to stratigraphic disturbances. Krypton-81, a rare radioactive isotope, is an ideal tracer for dating ice. However, only a few hundred krypton-81 atoms are present in each kilogram of ancient ice, making their detection an extreme technical challenge.
To tackle this, the USTC team developed an all-optical single-atom detection technique in 2021 [Phys. Rev. Lett. 127, 023201 (2021)]. Over the past four years, the team has further advanced the method to handle real ice core samples. By developing a high-brightness, narrow-bandwidth vacuum-ultraviolet light source, they efficiently produced metastable krypton atoms and dramatically reduced sample cross-contamination by two orders of magnitude—all while enabling non-destructive measurement. This breakthrough reduces the required sample size to just 100 nanoliters of krypton gas (equivalent to about 1 kg of ice) and extends the upper dating limit to 1.5 million years.
Using this technology, the USTC team collaborated with glaciologists including Professor Michael Bender and Dr. Sarah Shackleton from Princeton University to date two 1-kg ice samples from Taylor Glacier, Antarctica. The results—approximately 130,000 years old—closely match the independently established ice stratigraphy, confirming the accuracy and reliability of krypton-81 dating.
This work makes krypton-81 dating feasible for small ice core samples. The USTC team is now working with glaciologists both in China and abroad to systematically apply the method to basal ice from Greenland, Antarctica, and the Tibetan Plateau. The new dating approach opens exciting research avenues for investigating Greenland ice sheet stability, the development timeline of Tibetan glaciers, and identifying ancient ice that spans the Mid-Pleistocene Transition—advancing both glaciology and paleoclimate science.
This achievement marks a successful collaboration between Chinese physicists and American earth scientists, uniting expertise in quantum physics and glaciology to advance global climate science.
