Global biosphere primary productivity changes during the past eight glacial cycles
Ji‐Woong Yang, Margaux Brandon, Amaëlle Landais, Stéphanie Duchamp‐Alphonse, Thomas Blunier, Frédéric Prié, Thomas Extier
Abstract
Global biosphere productivity is the largest uptake flux of atmospheric carbon dioxide (CO 2 ), and it plays an important role in past and future carbon cycles. However, global estimation of biosphere productivity remains a challenge. Using the ancient air enclosed in polar ice cores, we present the first 800,000-year record of triple isotopic ratios of atmospheric oxygen, which reflects past global biosphere productivity. We observe that global biosphere productivity in the past eight glacial intervals was lower than that in the preindustrial era and that, in most cases, it starts to increase millennia before deglaciations. Both variations occur concomitantly with CO 2 changes, implying a dominant control of CO 2 on global biosphere productivity that supports a pervasive negative feedback under the glacial climate.