​Marine sediment analysis indicates that nearly a million years before our time, the length of climate cycles fell from 100,000 to 40,000 years. What caused the sudden slowdown in glaciation rhythms? In order to solve this mystery, paleoclimatologists want to analyze even older ice core samples, those over 800,000 years old.

With this in mind, the Subglacior probe will undergo its first tests in Antarctica during the 2016-2017 austral summer. Entirely unprecedented, the probe has an embedded laser instrument capable of continuously recording geochemical signals, making it possible to determine the age of ice and verify its stratigraphic continuity.  The following season, the probe will be deployed at the Franco-Italian station Concordia, considered by geophysicists to be the most promising site.

Besides the European consortium Beyond Epica—Oldest Icecore, which includes CNRS and Institut Paul-Emile Victor, the search for the oldest ice mobilizes teams from the United States, China, Japan, Russia and Australia, overseen by the International Partnerships in Ice Core Sciences program. LSCE is preparing for this challenge by developing a technique for the absolute dating of very ancient ice.