Scientists Use Krypton Dating to Estimate Antarctic Ice's Age

Researchers have used radiometric krypton-dating to find the age of ancient Antarctic ice. The new technique can be used to hunt and date old ice samples.

Finding old ice samples is important because it helps scientists construct and fine-tune ancient climate models. The latest krypton-based dating technique shows that the ice from Taylor Glacier in Antarctica is around 120,000 years old.

Just so that we are clear, researchers here are using krypton- the noble gas and not kryptonite, which is a fictional material that weakens the otherwise invulnerable hero, Superman.

The krypton-dating method is currently the most accurate means of confirming the age of ice samples, according to a news release from National Science Foundation.

"The oldest ice found in drilled cores is around 800,000 years old and with this new technique we think we can look in other regions and successfully date polar ice back as far as 1.5 million years," said Christo Buizert, a postdoctoral researcher at Oregon State University and lead author of the study. "That is very exciting because a lot of interesting things happened with the Earth's climate prior to 800,000 years ago that we currently cannot study in the ice core record."

What is Krypton dating?

Krypton is a noble gas that doesn't interact with chemicals. It has a half-life period of around 230,000 years.

The gas is produced by cosmic radiation hitting Earth and is trapped in air bubbles in the Antarctic ice.

The technique of krypton dating is much like the popular carbon-14 dating method that measures the radioactive decay of a known isotope and compares it with a stable isotope.

Isotopes are the variants of a chemical. The versions arise due to difference in the number of neutrons in the atoms.

Krypton isotope called krypton-81 decays slowly while krypton 83 doesn't decay. The proportion of both isotopes gives researchers an estimation of the age of the ice.

Krypton-81 exists in small quantities, which is why it was never really used in scientific studies in the past. However, a breakthrough in detector technology in 2011 enabled scientists to count the number of Krypton-81 atoms with greater accuracy, paving way for its use in age-estimation studies.

The new atom counter called Atom Trap Trace Analysis, or ATTA was developed by Zheng-Tian Lu at Argonne National Laboratory near Chicago.

The research

For the current study, researchers melted about 660 pounds of ice samples obtained from the Taylor Glacier in Antarctica. The air released during the melting was trapped and stored in flasks. University of Bern, Switzerland researchers isolated the krypton gas, which was then sent to Argonne for krypton-81 counting, according to a news release.

"The atom trap is so sensitive that it can capture and count individual atoms," said Buizert, who is in OSU's College of Earth, Ocean, and Atmospheric Sciences. "The only problem is that there isn't a lot of krypton in the air, and thus there isn't much in the ice, either. That's why we need such large samples to melt down."

Researchers found that the ice sample from the glacier is about 120,000 years old. They verified their results using studies conducted on ice cores taken from the same region.

The study was published in the journal Proceedings of the National Academy of Sciences. The work was funded by the National Science Foundation and the U.S. Department of Energy.