The Evolving AMOC Multidecadal Variability in a Warming Climate.

Xiaofan Ma, Institute of Atmospheric Sciences, Chinese Academy of Sciences, Beijing, China; University of California, Riverside, Riverside, CA, United States, Wei Liu, University of California Riverside, Riverside, CA, United States, Changlin Chen, Fudan University, Shanghai, China, Jun Cheng, NUIST Nanjing University of Information Science and Technology, School of Marine Sciences, Nanjing, China, Gang Huang, IAP Insititute of Atmospheric Physics, Chinese Academy of Sciences, Beijing, China and Xichen Li, Institute of Atmospheric Physics, CAS, Beijing, China
Abstract:
Variability of the Atlantic Meridional Overturning Circulation (AMOC) plays a vital role in decadal to multidecadal climate variability. How will AMOC multidecadal variability change in a warming climate and why will this change happen are two critical scientific questions for climate projections. Here we use NCAR CESM1 to investigate the change and the physical mechanism of AMOC multidecadal variability under different CO2 levels: from Last Glacial Maximum to preindustrial level, and then to four times preindustrial level. We find that, with increasing atmospheric CO2, the AMOC multidecadal variability shows shortened period and reduced magnitude. The period change is associated with the alteration in the westward propagation of thermal Rossby waves in the subpolar Atlantic while the amplitude change is due to stochastic atmospheric forcing. The lagged phase structures between AMOC streamfunction and temperature anomalies manifest the oscillation feature of the AMOC multidecadal variability.
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