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

The 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; 350m 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).