Two airborne surveys of atmospheric carbon dioxide (CO2) concentration have been conducted over the Gulf Stream off the east coast of Virginia and North Carolina on September 7--8, 1983. In-situ CO2 data were acquired at an aircraft altitude over 300 m on trajectories that transected the Gulf Stream near 36¿N 73¿W. Data show evidence of a CO2 concentration increase by 4 ppm to 15 ppm above the nominal atmospheric background value of 345 pp. These enhanced vcalues were associated with the physical location of the Gulf Stream prior to the passage of a weak cold front.