Triple isotopic composition of oxygen in water and dioxygen during deglaciations recorded in the EPICA Dome C ice core to link climate, biosphere productivity and water cycle

High precision measurements of triple isotopic composition of oxygen in water is a useful tool to infer the dynamic of past hydrological cycle when measured in ice core together with δ¹⁸O and δD. In particular, the triple isotopic composition of oxygen in water provides information on the climatic conditions of the evaporative sources. In parallel, it has been shown that the triple isotopic composition of oxygen in the atmospheric dioxygen can be a useful tracer of the global biosphere productivity and hence reconstruct the dynamic of the global biosphere productivity in the past from measurements performed in the air bubbles. Measuring triple isotopic composition of oxygen both in the water and in the atmospheric dioxygen trapped in bubbles in ice cores is thus a strong added value to study the past variability of water cycle and biosphere productivity in parallel to climate change.

Here, we first present new laboratory experiments performed in closed biological chambers to show how the triple isotopic composition of oxygen in atmospheric dioxygen can be used for quantification of the biosphere productivity with determination of fractionation coefficients. Then, we present new records of triple isotopic composition of oxygen in water and O₂ trapped in bubbles from the EPICA Dome C ice core over the deglaciations of the last 800 ka.