West Greenland and global in situ14C production‐rate calibrations

Abstract

ABSTRACTThe in situ cosmogenic nuclide 14C is unique compared with other nuclides because of its short half‐life, and when combined with longer‐lived isotopes (e.g. 10Be), in situ 14C can be a powerful tool for deciphering recent and complex surface exposure histories. Like all in situ cosmogenic nuclides, quantifying earth surface processes with in situ 14C requires a well‐constrained in situ 14C production rate. We present a production‐rate calibration from an independently dated moraine in West Greenland, previously used as an in situ 10Be production‐rate calibration site. The local in situ 14C production rate is 22.8 ± 1.4 atoms g−1 a−1 (69.28°N, 50.76°W; 350 m asl) and when scaled to sea level/high latitude using time‐dependent Lal/Stone scaling (Lm), we calculate a spallation‐only in situ 14C production rate of 12.0 ± 0.9 atoms g−1 a−1 and a 14C/10Be production rate ratio of 3.1 ± 0.2. The West Greenland in situ 14C production rate is indistinguishable from the New Zealand, Promontory Point and Scottish Highlands in situ 14C production rates. When combined, we calculate a global production rate of 12.1 ± 0.5 atoms g−1 a−1 (Lm).