ATM-9310121 Stuiver, Minze University of Washington Title: Atmospheric 14C the Ocean, and the Sun The 14C/12C ratios of atmospheric CO2 are quite variable as they reflect changes in 14C cosmic-ray production rate in the upper atmosphere, as well as climate-dependent re-allocation of 14C between the various earth carbon reservoirs. This award supports high-precision 14C measurements of early Holocene wood from the German Pine chronology which will contribute to an improved definition of the 14C/12C record back to 11,400 calendar years before the present. Causal factors for 14C/12C variability such as climate and solar influences will be identified and characterized with the aid of carbon reservoir modeling. Feedback mechanisms may play a role. High-precisionSeptember 27, 1993 measurements of materials of the current millennium will also be utilized to understand climatic factors. Regional 14C/12C differences and North - South latitudinal 14C/12C gradients will be defined. Incorporating the gradients into carbon reservoir models will lead to a better definition of carbon cycle sinks and sources.