ANNUAL 14C TREE-RING DATA AROUND 400 AD: MID- AND HIGH-LATITUDE RECORDS

Two tree-ring series, one from a high-latitude pine tree (located in northern Scandinavia) and one from a mid-latitude oak tree (located in eastern Germany) were analyzed for radiocarbon (C-14) at annual resolution. The new records cover the calendar date ranges 290-460 AD and 382-486 AD, respectively, overlapping by 79 yr. The series show similar trends as IntCal13. However, some significant deviations around 400 AD are present with lower Delta C-14 (higher C-14 ages). An average offset between the two new series and IntCal13 of about 20 years in conventional C-14 age is observed. A latitudinal C-14 offset between the tree sites in central and northern Europe, as would be expected due to the relatively large spatial distance, is not recorded, however. Periodic changes in the C-14 records are resolved that can be attributed to the 11-year solar cycle (Schwabe cycle) with cycle length from 9 to 11 years. The magnitude of changes in Delta C-14 due to the solar cycle is between 1.5 and 3%0. Since solar cyclicity is only partially synchronous between the two new series, reasons for asynchronicity are explored.