Transports and pathways of the tropical AMOC return flow from Argo data and shipboard velocity measurements


The upper-ocean circulation of the tropical Atlantic is a complex superposition of thermohaline and wind-driven flow components. The resulting zonally- and vertically-integrated upper-ocean meridional flow is referred to as the upper branch of the Atlantic Meridional Overturning Circulation (AMOC) - a major component and potential tipping element of the global climate system. We investigate the tropical part of the northward AMOC branch, i.e. the return flow covering the upper 1,200 m, based on Argo data and repeated shipboard velocity measurements. The western boundary mean circulation at 11°S is realistically reproduced from high-resolution Argo data showing a remarkably good representation of the vertical structure of meridional velocity and the volume transport of water mass layers when compared to results from direct velocity measurements along a repeated ship section. Thus, we extend the analysis to the inner tropical Atlantic. Within the AMOC return flow, a diapycnal upwelling of central water into the thermocline layer of ~2 Sv is derived between 11°S and 10°N which is about half the magnitude of previous estimates, likely due to improved horizontal resolution. The mean strength of the AMOC return flow is ~16 Sv across 11°S and 10°N. At 11°S, northward transport is concentrated at the western boundary where the AMOC return flow enters the tropics at all vertical layers above 1,200 m. At 10°N, northward transport is observed both at the western boundary and in the interior predominantly in the surface and intermediate layer indicating recirculation and transformation of thermocline and central water within the tropics.

Related Identifier
Metadata Access
Creator Tuchen, Franz Philip (Ed.); Brandt, Peter (Ed.); Lübbecke, Joke (Ed.); Hummels, Rebecca (Ed.)
Publisher PANGAEA - Data Publisher for Earth & Environmental Science
Publication Year 2021
Funding Reference European Commission, 817578
Rights Creative Commons Attribution 4.0 International;
OpenAccess true
Language English
Resource Type Collection of Datasets; Collection
Size 46 datasets
Discipline Geosciences; Natural Sciences; Oceanography/Marine Science; Physical Oceanography
Spatial Coverage (-70.909W, -53.145S, 18.435E, 53.564N)
Temporal Coverage Begin 1990-10-06T16:05:00Z
Temporal Coverage End 2019-11-19T00:00:00Z