Image Description – Bubbles of Ancient Air from Greenland Ice

Bubbles of ancient air from Greenland Ice Sheet ice… These bubble were trapped in Greenland snow tens of thousands if not a hundred thousand or more years ago. They have been preserved since, buried by eons of snow and retrieved from the depths of the ice sheet in ice cores so the air can be studied to understand what our climate and Earth systems were like when the air was preserved. One of the most meaningful things we know with certainty from this study is how much fossil fuel carbon dioxide has been emitted by humans. This can be done by evaluating the radioactive carbon carbon content of the preserved air.

Carbon 14 (C14) dating looks at the concentration of this rare radioactive isotope of carbon that decays at a very known rate. This means that carbon 14 loses a neutron and changes to the more abundant form of carbon (carbon 13) very predictably. When cosmic rays strike a nitrogen atom, its nuclease emits a neutron which strike another nitrogen atom creating the rare radioactive carbon 14 isotope.  This carbon then combines with oxygen to produce carbon dioxide, which is absorbed by living things and transformed into tissue. When the living thing dies, the C14 begins to decay with a half life of about 5,730 years.

After about 57,000 years, there is not enough C14 remaining to date. Therefore we can tell very accurately when human’s began emitted fossil carbon because there is no C14 in it as it has all completely decayed.

This sample was collected on the beach at Ilulissat, Greenland.