Radiokrypton Dating Identifies Ancient Antarctic Ice

Researchers count the number of radioactive krypton-81 atoms remaining in ice using a laser trap.

Image courtesy of Vasilii Petrenko
Vasilii Petrenko of the University of Rochester processing ice cores on Taylor Glacier, Antarctica.

The Science

A new method of measuring the age of ancient glacial ice is demonstrated by counting the radioactive krypton-81 atoms with a laser-based atom trap. Every krypton-81 atom is mixed with more than one trillion krypton atoms of other isotopes. Yet the atom trap provides the means to detect these extremely rare atoms, and perform radiokrypton dating on samples of 40-80 kg of ice.

The Impact

Radiokrypton dating allows scientists to determine the age of ice ranging from 50 thousand years to 1.5 million years, thus increasing the age span covered by the current technologies. Old ice provides a unique archive of Earth’s climate history, and may lead to an understanding of the mechanisms that cause the planet to shift into and out of ice ages.


Past variations in Earth’s climate and atmospheric composition are recorded in accumulating polar meteoric ice and the air trapped within it. As new ice piles on year after year, old ice at the bottom is slowly pushed out towards the edge of the ice dome.  Eventually, some re-emerge at the surface forming ice outcrops. These near-surface archives, however, are difficult to date reliably. The first successful radiokrypton dating on polar ice was demonstrated using Atom Trap Trace Analysis (ATTA), a method developed at DOE’s Argonne National Laboratory. This work was carried out by a collaboration of nuclear physicists from Argonne and glaciologists from Oregon State University and other institutions. The collaboration recently demonstrated 81Kr radiometric dating of ice, allowing accurate dating of up to 1.5 million-year-old ice. The technique successfully identified valuable ice from the previous interglacial period at Taylor Glacier, Antarctica. This method will enhance the scientific value of outcropping sites as archives of old ice needed for paleoclimatic reconstructions and can aid efforts to extend the ice core record further back in time. This work was recently published in the Proceedings of the National Academy of Sciences (PNAS), along with a commentary titled “Radiokrypton dating finally takes off”.


Wei Jiang
Argonne National Laboratory

Zheng-Tian Lu
Argonne National Laboratory


The Laboratory for Radiokrypton Dating is supported by the Department of Energy, Office of Nuclear Physics, under contract DE-AC02-06CH11357. Development of the ATTA-3 instrument was supported in part by NSF EAR-0651161. This work was also supported by two collaborative awards 0838936 and 0839031 made by the Division of Polar Programs in NSF's Geosciences Directorate, and the National Oceanic and Atmospheric Administration Climate and Global Change Fellowship Program.


C. Buizert, et al., “Radiometric 81Kr dating identifies 120,000-year-old ice at Taylor Glacier, Antarctica “, Proceedings of the National Academy of Sciences, 111, 6876 (2014) [DOI: 10.1073/pnas.132032911]

Related Links

“Radiometric 81Kr dating identifies 120,000-year-old ice at Taylor Glacier, Antarctica”

“Radiokrypton dating finally takes off”

“Using krypton gas to date the age of ancient ice cores”

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Program: NP

Additional: Collaborations , Non-DOE Interagency Collaboration