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Changing Phases of Atlantic Meridional Overturning Circulation and its Impact on Global Climate
陈显尧
中国海洋大学
In the presence of top-of-atmosphere (TOA) radiative imbalance, earth’s surface would have warmed much more rapidly were it not for the buffering role of the deeper oceans. Here we describe and quantify one of the effective mechanisms for ocean heat sequestration and its variability: the Atlantic meridional overturning circulation (AMOC) that spans both hemispheres, responsible for sequestering about half of the excess heat globally during one of its phases. A picture of how AMOC varies through one complete cycle emerges: After a relatively stable low phase 1975-1998, AMOC sped up rapidly, and then declined rapidly from the 2005 peak to present. During that stable low phase Atlantic did not sequester additional heat, and the TOA radiative imbalance manifested itself mainly at the surface as rapid global warming for 25 years. This concept of rapid surface warming during a period of low AMOC runs counter to the common perception based on preindustrial data, which becomes inapplicable when there is TOA forcing.