A multi-ice-core, annual-layer-counted Greenland ice-core chronology for the last 3800 years: GICC21

Abstract. Ice-core timescales are vital for the understanding of past climate; hence they should be updated whenever significant amounts new data become available. Here, Greenland ice-core chronology GICC05 was revised last 3835 years by synchronizing six deep ice cores and three shallow from central sheet. A method applied combining automated counting annual layers on multiple parallel proxies manual fine-tuning. layer bias found in all because site-specific signal disturbances; therefore comparison deemed necessary to increase timescale accuracy. After examining sources error their correlation lengths, uncertainty rate quantified 1 year per century. The is younger than about 13 at ago. most recent 800 largely unaffected revision. Between 2000 ago, offset between increases steadily, with steepest occurring 1100 Moreover, oscillations 5 around average observed 2500 3800 non-linear behavior attributed previous mismatches volcanic eruptions, much more extensive dataset available this study, finer resolution ammonium matching. By analysis common variations cosmogenic radionuclides, alignment IntCal20 curve (Reimer et al., 2020).