West Greenland and global in situ 14 C production‐rate calibrations

The in situ cosmogenic nuclide 14 C is unique compared with other nuclides because of its short half‐life, and when combined with longer‐lived isotopes (e.g. 10 Be), in situ 14 C 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 14 C requires a well‐constrained in situ 14 C production rate. We present a production‐rate calibration from an independently dated moraine in West Greenland, previously used as an in situ 10 Be production‐rate calibration site. The local in situ 14 C 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 14 C production rate of 12.0 ± 0.9 atoms g −1 a −1 and a 14 C/ 10 Be production rate ratio of 3.1 ± 0.2. The West Greenland in situ 14 C production rate is indistinguishable from the New Zealand, Promontory Point and Scottish Highlands in situ 14 C production rates. When combined, we calculate a global production rate of 12.1 ± 0.5 atoms g −1 a −1 (Lm).