In the northern reaches of the Atlantic Ocean, warm, salty waters—delivered from the tropics by prevailing winds—cool and sink before flowing back toward the Southern Hemisphere. This process, known as the Atlantic Meridional Overturning Circulation (AMOC), transports heat and nutrients and plays a key role in Earth’s climate system.
Decades of research have deepened scientists’ understanding of the AMOC and its importance. Now a study by Johnson et al. synthesizes recent advancements in modeling the fundamental processes that drive and maintain this powerful circulation system.
The new review focuses on theoretical models that deal with pared-down conceptual perspectives on the AMOC, rather than on more complex attempts at realistic simulations. The authors discuss progress in modeling the many large- and small-scale factors that influence the AMOC, from Southern Hemisphere wind patterns and intermediate-sized eddies to the shape of continents and the bathymetry of ocean basins.
Recent theoretical models have also explored variability and anomalies in the AMOC, not just its average patterns. Some have explored why the AMOC exists in the first place, instead of a Pacific meridional circulation system. And other theoretical studies have aided interpretation of real-world observations, such as those made by the ongoing Rapid Climate Change–Meridional Overturning Circulation and Heatflux Array project, which uses an array of sensors to continuously measure AMOC dynamics at 26.5°N latitude.
In addition to compiling recent advancements, the study addresses what is on the horizon for continuing research in this field. For instance, theoretical approaches may help researchers interpret measurements from ongoing observational projects, such as the Overturning in the Subpolar North Atlantic Program (OSNAP), and may generate hypotheses that could be tested using the newly collected data.
The authors emphasize the critical role of theoretical modeling in understanding the AMOC and in linking that understanding to ocean and climate models, which could improve understanding of how the AMOC influences and is influenced by climate change. (Journal of Geophysical Research: Oceans, https://doi.org/10.1029/2019JC015330, 2019)
—Sarah Stanley, Freelance Writer