Depth-Age relationship of the B26_2011 firn core

The firn core array of the North Greenland Traverse (NGT) provides unique climatic information for North Greenland until the mid 1990ies. In order to extend this climate record into more recent time, some of the drill sites were revisited and extension cores were drilled. The record is a composite of snow liners (from the surface to 1.29 m depth) and a consecutive firn core from 1.47 m depth to 30.00 m depth with a diameter of 75 cm. Density was measured by weighing the 55 cm long bags. Stable oxygen isotopes (δ18O) were measured at the Niels Bohr Institute, Copenhagen, Denmark. Using raw, un-calibrated dielectrical profiling (DEP) data from the field (NEEM Set-up), volcanic tie points were derived. Together with the smoothed density data and the isotopic composition the record was dated by layer counting. The annual mean values of δ18O were obtained based on this dating. Based on the density measurements and the dating, the annual accumulation rate in water equivalent depth was derived.