Using radioactive krypton to find ancient glacial ice

Taylor Glacier in Antarctica.

NASA/Earth Observatory/Robert Simmon

There’s a reason that one ice core drilled from the Greenland Ice Sheet has been referred to as The Two-Mile Time Machine—the annual layers of snow (compressed to ice) provide remarkable records of Earth’s climate and atmosphere. Studying past changes in atmospheric gases is just so much easier when you can pluck a bubble of air dutifully archived by the ice, which acts like a relative with an inconveniently large collection of National Geographics. The only problem with the “Two-Mile Time Machine” is that it’s only two miles long. Ice cores in Greenland can only go back about 130,000 years, and the oldest (so far) core from Antarctica goes back about 800,000 years.

If we could go a little further back in time, about 1.2 million years ago, we'd be able to examine a terribly interesting climatic transition. Prior to that time, glacial cycles were roughly 40,000 years long; after, we've experienced 100,000 year ones. We can study that period with some ocean sediment cores, but they can’t provide the same detail.

There could, however, be Antarctic ice still around from that particular interval of antiquity. The hard part is finding it, which requires recognizing it. Now, some researchers in Oregon State have used radioactive krypton to figure out the age of ice, a technique that may help us spot older samples.