| Popis: |
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 d18Oatm) 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 d18Oatm over the last 9 deglaciations on the EDC ice core. We first use the high resolution records of O2/N2 and d18Oatm 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 d18Oatm to constrain the relative chronology of high vs low latitude climatic events at sub-millennial scale over past deglaciations. |
