A New Method for Dating Ice Core Samples: Radiometric Krypton Dating
By Lenny Pierce on April 23, 2014
Krypton, which as it turns out is not just a planet in the DC universe, has an isotope called krypton-81, which is now being used to date Antarctic ice core samples and hopefully provide insight on the different periods of climate change throughout Earth’s history.
Krypton is a noble gas which can get locked up in air bubbles of ice and stay there as more and more layers of snow (which eventually compacts into ice) are piled on top of it over time. Just like carbon has isotopes which we can used to date things, so too does krypton. The amount of decay in krypton’s radioactive isotope krypton-81 can be calculated in a process called radiometric krypton dating. Krypton dating is slightly different from carbon dating, since the half life of krypton is 230,000 years – about 5x that of carbon. This means that this new type of dating can reach much farther back in time. Theoretically, this method could be used to date ice that is 1.5 million years old. In addition to a lengthier half life, the krypton dating is more stable than carbon dating. Both are more stable than online dating.
The Taylor glacier, where the ice core samples were taken. (National Geographic)
To examine the krypton that was trapped in the air bubbles of the Antarctic ice, 660 pounds of cylindrical ice samples were removed by researchers, placed in vacuums, and melted to unlock the ancient air. This gas then headed to Switzerland, where the krypton could be masterfully separated from the rest of the air. Chocolate and krypton isolation – that’s what Switzerland DOES. From Switzerland it headed to the Argonne National Laboratory in Lemont, Illinois, where the krypton-81 isotopes could be measured. After all those air miles, what they found was that the ice they gathered was 120,000 years old.
An important question this research may someday answer is why the intervals of major climate cycles were much smaller a million years ago. In the last 800,000 years, scientists think that Earth has moved in and out of ice ages about every 100,000 years. But prior to that 800,000 year mark, these massive climate swings happened way more frequently – about every 40,000 years. Scientists hope that more krypton dating could yield a better understanding of exactly why this rate of fluctuation may have changed.