High frequency water isotopes records during glacial/interglacial cycles on EPICA Dome C ice core.

Abstract

<p>The iconic curve of D in water showing the 8 glacial/interglacial cycles from the EPICA Dome C ice<br>core is now a reference in paleoclimate. It shows past temperature variability back to 800 ka over the<br>3200 m deep ice core with a 55 cm resolution. However, the millennial and centennial scale<br>variability gets more challenging to observe in the deepest part of the core. Indeed, the time<br>resolution worsens when going deeper in the ice because of the ice thinning: it is larger than 200<br>years at 2500 m depth. Furthermore, isotopic diffusion affects the signal at the bottom of the ice<br>core. Pol et al., (2010) have thus shown that the sub-millennial MIS (Marine Isotopic Stage) 19 signal<br>(3157-3181 m deep) is erased because of diffusion and high resolution doesn’t add any further<br>information at this depth. In this study we want to better characterize the increase of the isotopic<br>diffusion with depth by providing new high resolution water isotopes at several intervals over the<br>EPICA ice core (EDC).<br>We present here published high resolution (11 cm) d18O measurements over the EDC ice core as<br>well as new records of high resolution (11 cm) D over MIS 7;13 and 14). We use spectral analyses to<br>determine at which depth the isotopic diffusion erases the sub-millennial variability. We also show<br>that cold periods exhibit a larger variability of water isotopes than interglacial periods.<br>The information obtained here is crucial for the new project Beyond EPICA oldest ice core, which has<br>the goal of analyzing a 1.5 Ma old ice core. In the deepest part, 1 m of ice core could represent<br>10 000 years of climate archive.</p>