Sequence of events at high resolution during deglaciations over the last 800ka from the EDC ice core

The EPICA Dome C (EDC) ice core has been drilled from 1996 to 2004. Its study revealed a unique 800 ka long continuous climatic record including 9 deglaciations. Ice cores contain numerous proxies in the ice and in the air trapped in bubbles (chronological constraints, greenhouse gases concentration, local temperature proxies, mid to low latitude climate proxies). Here, we focus on information provided by the isotopic (and elemental) composition of water and oxygen archived in both ice and gas matrix. On one hand, the water isotopic composition brings information on past temperatures and water cycle re-organizations:   d¹⁸O or dD records past temperature, whereas the combination of d¹⁸O with dD or d¹⁷O provide information on the past water cycle organization through d-excess and ¹⁷O-excess linked to climatic conditions of the evaporative regions. On the other hand, the elemental composition of oxygen expressed in the O₂/N₂ ratio provides key information for orbital dating over the last 800 ka in complement with the isotopic composition of atmospheric oxygen (d¹⁸O of O₂ or d¹⁸O_atm) which is related as well to the low latitude water cycle.

In this study, we present new high resolution records of water isotopes (d¹⁸O, d-excess and ¹⁷O-excess) as well as high resolution measurements of O₂/N₂ and d¹⁸O_atm over the last 9 deglaciations on the EDC ice core. We first use the high resolution records of O₂/N₂ and d¹⁸O_atm to improve absolute dating constrain over the glacial terminations and discuss the link between orbital forcing and climate variations recorded in the EDC ice core. In a second part, we use d-excess, ¹⁷O-excess and d¹⁸O_atm to constrain the relative chronology of high vs low latitude climatic events at sub-millennial scale over past deglaciations.