Seasonal variability in the ¹⁴C/¹²C ratio for surface ocean water

Evidence is provided for seasonality in the bomb 14 C content of surface ocean water in temperate and polar regions. The GEOSECS results show that the surface waters in the north temperate Atlantic had 14 C/ 12 C ratio 35‰ higher just before late fall deepening of the mixed layer than just before the reestablishment of the summer mixed layer six months later. This is the difference expected from the summer exchange of CO 2 between the atmosphere and the surface mixed layer.