Using a CFC effective age to estimate propagation and storage of climate anomalies in the deep western North Atlantic Ocean

Abstract

1990s chlorofluorocarbon (CFC) observations are used to estimate an effective age of 20 years for North Atlantic Deep Water (NADW) at the equator. The effective age is found by subtracting a “relic” age from pCFC‐11 age. The effective age is several to 10 years younger at the equator than other methods. From the effective age equatorward “effective” spreading rates of 1–2 cm/s are found, which are similar for the NADW components. Effective spreading rates take into account recirculation gyres, along‐equator flow, and mixing, which slow spreading of climate anomalies from the North Atlantic to the Southern Hemisphere. The difference between direct velocities and tracer effective spreading rates suggests that the buffering effect due to storage, in the western North Atlantic and equatorial region, is about 20 years. Even so, warming and freshening due to greenhouse gases will be first felt in the deep waters of the western North Atlantic.