The Effect of Diapycnal Mixing on the Ventilation and CFC-11 Uptake in the Southern Ocean

作     者：Helge DRANGE 

作者机构：Nansen Environmental and Remote Sensing Center Bergen Norway Nansen-Zhu International Research Centre Institute of Atmospheric Physics Chinese Academy of Sciences Beijing 100029Bjerknes Centre for Climate Research Bergen Norway Geophysical Institute University of Bergen Bergen Norway 

出 版 物：《Advances in Atmospheric Sciences》 (大气科学进展（英文版）)

年 卷 期：2004年第21卷第5期

页      面：755-766页

核心收录：

学科分类：07[理学] 070601[理学-气象学] 0706[理学-大气科学] 

基　　金：挪威资助 the project GOSAC (ENV4-CT97-0495) under the EC Environment and Climate Programme 

主　　题：chlorofluorocarbons CFC-11 diapycnal mixing ocean modelling ocean ventilation Southern Ocean transient tracers 

摘      要：The Miami Isopycnic Coordinate Ocean Model (MICOM) is used to investigate the effect of diapycnal mixing on the oceanic uptake of CFC-11 and the ventilation of the surface waters in the Southern Ocean (south of 45°S). Three model experiments are performed: one with a diapycnal mixing coefficientK d (m2 s?1) of 2 × 10?7/N (Expt. 1), one withK d = 0 (Expt. 2), and one withK d = 5 × 10?8/N (Expt. 3),N (s?1) is the Brunt-V?is?l? frequency. The model simulations indicate that the observed vertical distribution of CFC-11 along 88°W (prime meridian at 0°E) in the Southern Ocean is caused by local ventilation of the surface waters and westward-directed (eastward-directed) isopycnic transport and mixing from deeply ventilated waters in the Weddell Sea region. It is found that at the end of 1997, the simulated net ocean uptake of CFC-11 in Expt. 2 is 25% below that of Expt. 1. The decreased uptake of CFC-11 in the Southern Ocean accounts for 80% of this difference. Furthermore, Expts. 2 and 3 yield far more realistic vertical distributions of the ventilated CFC-waters than Expt. 1. The experiments clearly highlight the sensitivity of the Southern Ocean surface water ventilation to the distribution and thickness of the simulated mixed layer. It is argued that inclusion of CFCs in coupled climate models could be used as a test-bed for evaluating the decadal-scale ocean uptake of heat and CO2.