Wind effect on the Atlantic meridional overturning circulation via sea ice and vertical diffusion

• Published in: Climate Dynamics
• Main Authors: Yang, Haijun, Wang, Kun, Dai, Haijin, Wang, Yuxing, Li, Qing
• Other Authors: Yang, HJ (reprint author), Peking Univ, Lab Climate & Ocean Atmosphere Studies LaCOAS, 209 Chengfu Rd, Beijing 100871, Peoples R China.; Yang, HJ (reprint author), Peking Univ, Sch Phys, Dept Atmospher & Ocean Sci, 209 Chengfu Rd, Beijing 100871, Peoples R China., Peking Univ, Lab Climate & Ocean Atmosphere Studies LaCOAS, 209 Chengfu Rd, Beijing 100871, Peoples R China., Peking Univ, Sch Phys, Dept Atmospher & Ocean Sci, 209 Chengfu Rd, Beijing 100871, Peoples R China., Yang, HJ (reprint author), Peking Univ, Sch Phys, Dept Atmospher & Ocean Sci, 209 Chengfu Rd, Beijing 100871, Peoples R China.
• Format: Journal/Newspaper
• Language: English
• Published: CLIMATE DYNAMICS 2016
• Subjects: AMOC; Wind effect; Freshwater flux; Sea ice; Vertical diffusion; Positive feedback; NORTH-ATLANTIC; THERMOHALINE CIRCULATION; FRESH-WATER; SOUTHERN-OCEAN; DEEP-WATER; MULTIDECADAL OSCILLATION; CLIMATE VARIABILITY; MODEL; IMPACT; TEMPERATURE; Southern Ocean; North Atlantic; North atlantic Thermohaline circulation
• Online Access: https://hdl.handle.net/20.500.11897/492194; https://doi.org/10.1007/s00382-015-2774-z

Effects of wind and fresh water on the Atlantic meridional overturning circulation (AMOC) are investigated using a fully coupled climate model. The AMOC can change significantly when perturbed by either wind stress or freshwater flux in the North Atlantic. This study focuses on wind stress effect. Our model results show that the wind forcing is crucial in maintaining the AMOC. Reducing wind forcing over the ocean can cause immediately weakening of the vertical salinity diffusion and convection in the mid-high latitudes Atlantic, resulting in an enhancement of vertical salinity stratification that restrains the deep water formation there, triggering a slowdown of the thermohaline circulation. As the thermohaline circulation weakens, the sea ice expands southward and melts, providing the upper ocean with fresh water that weakens the thermohaline circulation further. The wind perturbation experiments suggest a positive feedback between sea-ice and thermohaline circulation strength, which can eventually result in a complete shutdown of the AMOC. This study also suggests that sea-ice variability may be also important to the natural AMOC variability on decadal and longer timescales. NSF of China [91337106, 41376007, 41176002, 40976007]; National Basic Research Program of China [2012CB955200] SCI(E) ARTICLE [e-mail] 11-12 3387-3403 46