On the stability of the Atlantic meridional overturning circulation during the last deglaciation

• Published in: Climate Dynamics
• Main Authors: Liu, Wei, Liu, Zhengyu, Cheng, Jun, Hu, Haibo
• Other Authors: Liu, W (reprint author), Univ Calif San Diego, Scripps Inst Oceanog, CASPO, La Jolla, CA 92093 USA., N Carolina State Univ, Cooperat Inst Climate & Satellites, Raleigh, NC 27695 USA., NOAA, Natl Climat Data Ctr, Asheville, NC USA., Univ Calif San Diego, Scripps Inst Oceanog, CASPO, La Jolla, CA 92093 USA., Peking Univ, Lab Climate Ocean & Atmosphere Studies, Beijing 100871, Peoples R China., Univ Wisconsin, Ctr Climat Res, Madison, WI USA., Nanjing Univ Informat Sci & Technol, Sch Marine Sci, Minist Educ, Key Lab Meteorol Disaster, Nanjing, Jiangsu, Peoples R China., Nanjing Univ, Sch Atmospher Sci, Nanjing 210008, Jiangsu, Peoples R China.
• Format: Journal/Newspaper
• Language: English
• Published: climate dynamics 2015
• Subjects: AMOC; Stability indicator; Freshwater transport; Feedback; The last deglaciation; OCEAN-ATMOSPHERE MODEL; MULTIPLE EQUILIBRIA REGIME; AIR-SEA INTERACTIONS; PAST 20,000 YEARS; THERMOHALINE CIRCULATION; GLACIAL MAXIMUM; SOUTH-ATLANTIC; CENTRAL GREENLAND; CLIMATE CHANGES; BERING STRAIT; Bering Strait; Greenland
• Online Access: https://hdl.handle.net/20.500.11897/206108; https://doi.org/10.1007/s00382-014-2153-1

Using a generalized stability indicator L, we explore the stability of the Atlantic meridional overturning circulation (AMOC) during the last deglaciation based on a paleoclimate simulation. From the last glacial maximum, as forced by various external climate forcings, notably the meltwater forcing, the AMOC experiences a collapse and a subsequent rapid recovery in the early stage of deglaciation. This change of the AMOC induces an anomalous freshwater divergence and later convergence across the Atlantic and therefore leads to a positive L, suggesting a negative basin-scale salinity advection feedback and, in turn, a mono-stable deglacial AMOC. Further analyses show that most anomalous freshwater is induced by the AMOC via the southern boundary of the Atlantic at 34 degrees S where the freshwater transport (M-ovS) is about equally controlled by the upper branch of the AMOC and the upper ocean salinity along 34 degrees S. From 19 to 17 ka, as a result of multiple climate feedbacks associated with the AMOC change, the upper ocean at 34 degrees S is largely salinified, which helps to induce a switch in M-ovS, from import to export. Our study has important implications to the deglacial simulations by climate models. A decomposition of L shows that the AMOC stability is mostly determined by two terms, the salinity stratification at 34 degrees S and the change of stratification with the AMOC. Both terms appear positive in model. However, the former is likely to be distorted towards positive, as associated with a common bias existing over the South Atlantic in climate models. Therefore, the AMOC is potentially biased towards mono-stability in most paleoclimate simulations. Meteorology & Atmospheric Sciences SCI(E) 2 ARTICLE [e-mail] 5-6 1257-1275 44