No. 111/2020

In autumn 2019, he spent two months in the middle of nowhere: Mathieu Casado studies Antarctic ice in order to reconstruct cli- mate change over Earth’s history. To this end, researchers use a drill to take samples from the permanent ice – the deeper they pen- etrate, the older the ice layer. Formed over hundreds of thousands of years, the ice stores infor- mation from those past ages. Pollen, salts, cosmic dust and trapped air bubbles reveal, for example, which gases were contained in the atmosphere at a given time, what vegetation there was and when mas- sive volcanic eruptions occurred. Mathieu Casado analyses the composition of the oxygen and hydrogen isotopes in the ice. “The proportion of these in a layer reveals what the air temperature was at the time,” says Casado. The ice thus delivers pre-historic temperature recordings. And that’s not all: “I have discovered that the isotopes also tell us something about the structure of the snow back then and its albedo, or pot­ ential to reflect solar radiation.” The Earth’s albedo also plays an important role in climate change today. Casado’s research seeks to examine climate history to derive knowledge about changes hap- pening now. So far, the oldest samples go back some 800,000 years. The new- est sample could reveal secrets going back more than 1.5 million years. The Antarctic climate archive is constantly expanding. Text JAN BERNDORFF The French Humboldt Research Fellow, DR MATHIEU CASADO , is currently working at the Alfred Wegener Institute’s research centre in Potsdam. Photo: Humboldt Foundation/private WHAT DOES ANTARCTIC ICE TELL US ABOUT CLIMATE CHANGE, MR CASADO? 9 HUMBOLDT KOSMOS 111/2020