We went to Allan Hills to hunt for ice older than 800 thousand years, which is the current limit of deep ice cores from Antarctica. To our surprise, the oldest sample turns out to be more than 2 million years old!
Our work was selected by Science as Top 10 in "2017 Breakthrough of the Year". Also see the initial media report after our work was first presented at Goldschmidt 2017 in Paris. Click the title above to know more.
Around 1 million years ago, Earth's glacial cycles went through an intriguing and yet mysterious transition (the mid-Pleistocene Transition, or "MPT"). A decline in CO2 concentrations is one of the candidates proposed to account for the MPT. Now, with the discovery of ice older than 1 million years, we directly measured the atmospheric composition across the MPT, which could shed light on the origin of this critical climatic transition. Click the title above to know more.
3. Inferring Carbon Dioxide Concentrations in the Basal Ice
While the lower-most 7 m of the Allan Hills ice cores contains the oldest (2.7 Ma) ice samples evern retrieved thus far, its gas composition has been affected by the in situ production of CO2 from respiration. As a result, observed CO2 levels as high as 1,500 ppm do not represent the original atmospheric composition. Now I am using the triple oxygen isotopes of O2 (Δ17O) as a paleo-CO2 proxy to infer the original CO2 concentrations in the ice section affected by respiration.
Image on the right: Dr. John Higgins holding the bottom piece of a 2.7 Ma ice core. Photo courtesy of Dr. John Higgins.