(1) Laboratoire des Sciences du Climat et de l'Environnement, CEA-IPSL/CNRS, Gif-Sur-Yvette, France (2) Laboratoire de Météorologie Dynamique, Jussieu, Paris, France (3) Department of Mathematics and Geosciences, University of Trieste, Italy

During four summer seasons (2009-2012), we have monitored continuously the water vapor isotopic composition at the surface of the Greenland Ice Sheet as part of the NEEM deep ice core-drilling project (77.45 N 51.06 W, 2484 m a.s.l). Our data depict large seasonal variations from spring to summer, as well as synoptic and diurnal variability. Water stable isotopes from Greenland ice cores can provide seasonally resolved, well-dated climate information. The archived climate signal is however an integrated signal of the precipitation isotopic composition, which itself is controlled by variations in moisture origin and condensation history. Furthermore, the original precipitation signal is smoothed by diffusion in snow and ice. For instance, sublimation and condensation processes related to snow metamorphism alter the high frequency precipitation isotopic composition signal. Therefore, in order to correctly interpret ice core isotope records it is of great importance to understand the underlying physical processes in the atmospheric hydrological cycle and the interactions between the snow surface and the water vapor.