| The uptake and spreading of Chlorofluorocarbons (CFCs) in the North Atlantic from 1948 to 1997 are studied using a three-dimensional ocean circulation model known as FLAME and a novel data-assimilation scheme known as the semi-prognostic method (Sheng et al., 2001; Eden et al., 2004). The use of the semi-prognostic method leads to a better representation of the Deep Western Boundary Current and the associated distribution of model-simulated CFC concentration near the western boundary (Zhao et al., 2004). The simulated net surface flux and inventory of CFCs in the Labrador Sea region have significant interannual variability and are highly correlated with the winter NAO index. We estimate an equatorward spreading rate of the Labrador Sea Water (LSW) based on the model-estimated effective pCFC11 age. The estimated spreading rate of LSW is about 1.32 cm/s, which indicates slow spreading of climate anomalies from the source region in the subpolar North Atlantic to the equator. |
