Revisiting Effect of Ocean Diapycnal Mixing on Atlantic Meridional Overturning Circulation Recovery in a Freshwater Perturbation Simulation

• Main Authors: Yu Lei, Gao Yongqi, Helge Drange
• Other Authors: The Pennsylvania State University CiteSeerX Archives
• Format: Text
• Language: English
• Published: 2007
• Subjects: Arctic; Arctic Ocean; Bergen; Greenland; Iceland; North Atlantic
• Online Access: http://citeseerx.ist.psu.edu/viewdoc/summary?doi=10.1.1.612.1829; http://nzc.iap.ac.cn/uploadpdf/254yl.pdf

The effects of ocean density vertical stratification and related ocean mixing on the transient response of the Atlantic meridional overturning circulation (AMOC) are examined in a freshwater perturbation simula-tion using the Bergen Climate Model (BCM). The results presented here are based on the model outputs of a previous freshwater experiment: a 300-year control integration (CTRL), a freshwater integration (FW1) which started after 100 years of running the CTRL with an artificially and continuously threefold increase in the freshwater flux to the Greenland-Iceland-Norwegian (GIN) Seas and the Arctic Ocean throughout the following 150-year simulation. In FW1, the transient response of the AMOC exhibits an initial decreasing of about 6 Sv (1 Sv=106 m3 s−1) over the first 50-year integration and followed a gradual recovery during the last 100-year integration. Our results show that the vertical density stratification as the crucial property of the interior ocean plays an important role for the transient responses of AMOC by regulating the convective and diapycnal mixings under the enhanced freshwater input to northern high latitudes in BCM in which the ocean diapycnal mixing is stratification-dependent. The possible mechanism is also investigated in this paper. Key words: North Atlantic meridional overturning circulation, enhanced freshwater forcing, diapycnal mix-ing DOI:10.1007/s00376-008-0597-0 1.