Single-year radiocarbon dating anchors Viking Age trade cycles in time

Recent discoveries of rapid changes in the atmospheric 14C concentration linked to solar particle events have spurred the construction of new radiocarbon annual calibration datasets1–13. With these datasets, radiocarbon dating becomes relevant for urban sites, which require dates at higher resolution than previous calibration datasets could offer. Here we use a single-year radiocarbon calibration curve to anchor the archaeological stratigraphy of a Viking Age trade centre in time. We present absolutely dated evidence for artefact finds charting the expansion of long-distance trade from as far away as Arctic Norway and the Middle East, which we linked to the beginning of the Viking Age at ad 790 ± 10. The methods developed here enable human interactions and cultural, climatic and environmental changes to be compared in archaeological stratigraphies worldwide. Disturbances in the radiocarbon record anchor a precisely dated archaeological stratigraphy of a medieval trading emporium in Denmark in time, revealing that the Viking expansion was associated with competition for trade routes rather than with raids.