Anthropogenic Chlorofluoromethanes in the Greenland and Norwegian Seas

Abstract

The concentrations of two industrially produced chlorofluoromethanes, CCl(3)F(F-11) and CCl(2)F(2)(F-12), have been measured in the water column and in the marine atmosphere of the Greenland and Norwegian seas. Measurable concentrations of these two chlorofluoromethanes have penetrated to the deep basins of both of these regions, and the general characteristics of their vertical distributions are similar to those of the bomb-produced radioisotopes injected into the atmosphere on a similar time scale. The data have been fitted to a time-dependent box model based on deep convective mixing in the Greenland Sea and lateral exchange between the deep basins. The model calculations for the two chlorofluoromethanes in the Greenland Sea give similar results, with a time scale for deep convection of about 40 years. The time scale for lateral mixing between the deep Greenland Sea and the deep Norwegian Sea is estimated to be 20 to 30 years, although the agreement between the calculations for the two chlorofluoromethanes is limited by analytical uncertainties at the low concentrations found in the deep Norwegian Sea and by uncertainties in the model assumptions.