Two regimes of Atlantic multidecadal oscillation: cross-basin dependent or Atlantic-intrinsic

• Published in: Science Bulletin
• Main Authors: Lin, Pengfei, Yu, Zipeng, Lü, Jianhua, Ding, Mengrong, Hu, Aixue, Liu, Hailong
• Language: unknown
• Published: 2020
• Subjects: 54 ENVIRONMENTAL SCIENCES; Greenland; Pacific; Iceland
• Online Access: http://www.osti.gov/servlets/purl/1609283; https://www.osti.gov/biblio/1609283; https://doi.org/10.1016/j.scib.2018.12.027

The Atlantic Multidedal Oscillation (AMO) is a prominent mode of sea surface temperature variability in the Atlantic and incurs significant global influence. Most coupled models failed to reproduce the observed 50-80-year AMO, but were overwhelmed by a 10-30-year AMO. Here we show that the 50-80-year AMO and 10-30-year AMO represent two different AMO regimes. The key differences are: (1) the 50-80-year AMO involves transport of warm and saline Atlantic water into the Greenland-Iceland-Norwegian (GIN) Seas prior to reaching its maximum positive phase, while such a transport is weak for the 10-30-year AMO; (2) the zonality of atmospheric variability associated with the 50-80 year AMO favors the transport of warm and saline water into the GIN Seas; (3) the disappearance of Pacific variability weakens the zonality of atmospheric variability and the transport of warm and saline water into the GIN Seas, leading to the weakening of the 50-80-year AMO. In contrast, the 10-30-year AMO does not show dependence on the variability in Pacific and in the GIN Seas and may be an Atlantic-intrinsic mode. Our results suggest that differentiating these AMO regimes and a better understanding of the cross-basin connections are essential to reconcile the current debate on the nature of AMO and hence to its reliable prediction, which is still lacking in most of coupled models.