Krypton-81 Dating Achieved for Antarctic Ice by USTC Researchers

Antarctic and Greenland ice cores serve as critical archives of Earth's climatic history, often extending several kilometers beneath the surface. However, precisely dating the deepest layers, which can reveal significant climate transitions, has long been a challenge due to the scarcity of reliable isotopic markers. Krypton-81, a rare radioactive isotope, is particularly useful for this purpose, as it can date ice over a million years old. Yet, extracting and detecting the tiny quantities required-just a few hundred atoms per kilogram of ice-has proven exceptionally difficult.

The USTC team addressed this challenge by refining their all-optical single-atom detection method, first developed in 2021 [Phys. Rev. Lett. 127, 023201 (2021)]. Recent advancements include a high-brightness, narrow-bandwidth vacuum-ultraviolet light source that efficiently produces metastable krypton atoms, coupled with improvements that reduce cross-contamination by two orders of magnitude. These innovations dramatically lower the required sample size to just 100 nanoliters of krypton gas, equivalent to roughly 1 kilogram of ice, and extend the dating range to 1.5 million years.

The team successfully tested this approach on two ice samples from Taylor Glacier in Antarctica, dating them to approximately 130,000 years. These results closely align with independently established ice stratigraphy, confirming the method's reliability and accuracy.

Looking ahead, the USTC researchers plan to expand their collaboration with international glaciologists to apply this method to basal ice from Greenland, Antarctica, and the Tibetan Plateau. Their work promises to enhance our understanding of ancient ice dynamics, potentially shedding light on the stability of the Greenland ice sheet and the development history of Tibetan glaciers.

Research Report:81Kr dating of 1 kg Antarctic ice