Regional 14CO2 offsets in the troposphere:: Magnitude, mechanisms, and consequences

Radiocarbon dating methods typically assume that there are no significant tropospheric (CO2)-C-14 gradients within the low- to mid-latitude zone of the Northern Hemisphere. Comparison of tree ring C-14 data from southern Germany and Anatolia supports this assumption in general but also documents episodes of significant short-term regional (CO2)-C-14 offsets. We suggest that the offset is caused by an enhanced seasonal (CO2)-C-14. cycle, with seasonally peaked flux of stratospheric C-14 into the troposphere during periods of low solar magnetic activity, coinciding with substantial atmospheric cooling. Short-term episodes of regional (CO2)-C-14, offsets are important to palaeoclimate studies and to high-resolution archaeological dating.