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

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