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A review of the Atlantic Meridional Overturning Circulation: observations, inferences, and mechanisms


A recently published and thorough review of the current state of scientific knowledge regarding the Atlantic Meridional Overturning Circulation (AMOC) has been published in Reviews of Geophysics.This effort was supported by CPO’s Climate Variability and Predictability (CVP) and Modeling, Analysis, Prediction, and Projections (MAPP) programs. 
Authors Martha Buckley and John Marshall detail the important discoveries and improvements in understanding of the AMOC made through ongoing investments in science, including: 

  • understanding the relative warmth of the Northern Hemisphere versus the Southern Hemisphere, 
  • the occurrence of the Intertropical Convergence Zone (ITCZ) just north of the equator, 
  • the sequestration of heat anomalies into the ocean that affects climate change trajectories, 
  • the influence of AMOC variability on climate and weather over land, 
  • the importance of observing systems, and 
  • the potential for decadal prediction systems stemming from AMOC understanding and other improvements to models.


This is a review about the Atlantic Meridional Overturning Circulation (AMOC), its mean structure, temporal variability, controlling mechanisms, and role in the coupled climate system. The AMOC plays a central role in climate through its heat and freshwater transports. Northward ocean heat transport achieved by the AMOC is responsible for the relative warmth of the Northern Hemisphere compared to the Southern Hemisphere and is thought to play a role in setting the mean position of the Intertropical Convergence Zone north of the equator. The AMOC is a key means by which heat anomalies are sequestered into the ocean’s interior and thus modulates the trajectory of climate change. Fluctuations in the AMOC have been linked to low-frequency variability of Atlantic sea surface temperatures with a host of implications for climate variability over surrounding landmasses. On intra-annual timescales, variability in AMOC is large and primarily reflects the response to local wind forcing; meridional coherence of anomalies is limited to that of the wind field. On interannual to decadal timescales, AMOC changes are primarily geostrophic and related to buoyancy anomalies on the western boundary. A pacemaker region for decadal AMOC changes is located in a western “transition zone” along the boundary between the subtropical and subpolar gyres. Decadal AMOC anomalies are communicated meridionally from this region. AMOC observations, as well as the expanded ocean observational network provided by the Argo array and satellite altimetry, are inspiring efforts to develop decadal predictability systems using coupled atmosphere-ocean models initialized by ocean data.

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