A Probabilistic Method to Construct an Optimal Ice Chronology for Ice Cores

• Main Authors: Lemieux-Dudon, Benedicte, Frederic, Parrenin, Blayo, Eric
• Format: Article in Journal/Newspaper
• Language: English
• Published: Institute of Low Temperature Science, Hokkaido University
• Subjects: Inverse Methods; Ice Core Chronology; Paleo-climate; 400; EPICA; ice core
• Online Access: http://hdl.handle.net/2115/45451

Accurate ice chronologies are needed for the interpretation of paleoclimate reconstructions inferred from ice cores. Several methods are used to provide chronological information: identification of dated horizons along the cores, synchronization to other dated paleoclimatic records, counting of annual layers or modelling of the ice flow. These methods are relevant for different parts of the core and enable to reach various levels of accuracy. We present a probabilistic approach based on inverse techniques which aims at building an optimal ice core chronology by using all the available chronological information. It consists in identifying the accumulation rate and the thinning function along the core 1) which are as close as possible to the flow model simulations and 2) so that the corresponding ice chronology is as close as possible to independent dating information. This probabilistic approach enables to evaluate confidence intervals on the optimal age scale as well as on the accumulation and the thinning estimates. We test the new method on the EPICA Dome C ice core. The necessary prior accumulation rate and thinning function as well as a set of dated horizons are provided by a previous work aiming at the EDC3 age scale reconstruction. We further discuss the sensitivity of the obtaincd optimal solution with respect to the necessary prior information. This probabilistic approach could be used in the future to build a common and optimal chronology for several ice cores simultaneously. III. Firn densification, close-off and chronology