FY 2002

Anthropogenic chlorofluorocarbon in the Black Sea and the Sea of Marmara

Lee, B.-S., J.L. Bullister, J.W. Murray, and R.E. Sonnerup

Deep-Sea Res. Pt. I, 49(5), 895–913, doi: 10.1016/S0967-0637(02)00005-5 (2002)

Measurements of the distributions of two chlorofluorocarbons, CCl₃F (CFC-11) and CCl₂F₂ (CFC-12), made during the June/July 1988 R.V. Knorr cruise in the Black Sea indicate that CFC-11 is non-conservative relative to CFC-12 in the strongly reducing anoxic waters. A multi-layer model combining horizontal/vertical renewal and vertical diffusion processes was tuned to the distributions of CFC-12 and salinity in suboxic and anoxic waters and used to estimate the residence times of subsurface waters and first-order in situ removal rate constants for CFC-11. The model-calculated residence times were ~5 yr in the suboxic zone (80–120 m) and increased to ~625 yr at 500 m. The first-order CFC-11 in situ removal coefficients were 0.52 ± 0.19 yr⁻¹ for the depth range 160-480 m. Based on the observed CFC-12 concentrations, the residence time of cold intermediate layer water (~50–100 m) was estimated to be <5 yr. The residence time of the deep water (100–450 m) in the Sea of Marmara was estimated to be 12–19 yr using a box model tuned to CFC-12, implying an in situ oxygen utilization rate of 10–18 µmol kg⁻¹ yr⁻¹.