Atlantic meridional overturning circulation and associated heat transport

Abstract

The Atlantic meridional overturning circulation (AMOC) is a key component of the ocean circu- lation system that is constantly moving water, heat, salt, carbon, nutrients, and other substances around the globe. The AMOC impacts the Atlantic Ocean in a unique way, making it the only ocean basin where heat is carried northward in both hemispheres. Recognizing the role of the AMOC in Earth’’s climate and, hence, the importance of monitoring and understanding it, several AMOC-observing systems have been established over the last two decades (e.g., Frajka-Williams et al. 2019; McCarthy et al. 2020; Fig. 3.20). This section describes the most recent findings derived from the existing observations of the volume (MOC) and the associated meridional heat transports (MHT). Because some of the key boundary current arrays have been observed for longer than the fully trans-basin arrays, key results on those boundary currents are also reviewed.

Estimates of the northward MOC and MHT transports: (a) across OSNAP array, (b) at 26.5°N, and (c) at 34.5°S. Gray curves show 12-hourly values for RAPID/MOCHA/WBTS in (b) and daily values for SAMBA in (c); black curves show MOC monthly values. The blue lines show averages during 2004–08 and 2008–12 in panel (b) and linear trends in 2009–10 and 2013–17 in panel (c). MHT estimates are shown by red curves for OSNAP and RAPID/MOCHA/WBTS arrays. The green curve in (b) shows the MOC estimate at 26.5°N from the combination of altimetry and Argo data. The blue/red crosses in (c) show MOC/ MHT estimates obtained from XBT data along AX18 transect in the South Atlantic.

Eleanor Frajka-Williams

Professor of Ocean Dynamics in a Changing Climate

I am a physical oceanographer who uses ocean observations to investigate ocean dynamics and circulation in a changing climate. I have a particular interest in problems spanning scales (from micro- to large-scale) or spheres (biogeosphere, cryosphere, atmosphere), and in methods that leverage traditional observations with new platforms and satellite data.