Decoupled Freshwater Transport and Meridional Overturning in the South Atlantic

Abstract Freshwater transports (Fov) by the Atlantic meridional overturning circulation (AMOC) are sensitive to salinity distributions and may determine AMOC stability. However, climate models show large salinity biases, distorting the relation between Fov and the AMOC. Using free‐running models and...

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Bibliographic Details
Published in:Geophysical Research Letters
Main Authors: D. Mignac, D. Ferreira, K. Haines
Format: Article in Journal/Newspaper
Language:English
Published: Wiley 2019
Subjects:
AMOC
overturning
gyre
AAIW
ocean reanalyses
bistability
Geophysics. Cosmic physics
QC801-809
Antarc*
Antarctic
North Atlantic
Online Access:https://doi.org/10.1029/2018GL081328
https://doaj.org/article/a545cbcfa66548d39b078427182df1a7
Description
Summary:Abstract Freshwater transports (Fov) by the Atlantic meridional overturning circulation (AMOC) are sensitive to salinity distributions and may determine AMOC stability. However, climate models show large salinity biases, distorting the relation between Fov and the AMOC. Using free‐running models and ocean reanalyses with realistic salinities but quite different AMOCs, we show that the fresh Antarctic Intermediate Water layer eliminates salinity differences across the AMOC branches at ~1,200 m, ∆S1200m, which decouples Fov from the AMOC south of ~10°N. As the Antarctic Intermediate Water disappears north of ~10°N, a large ∆S1200m allows the AMOC to drive substantial southward Fov in the North Atlantic. In the South Atlantic the 0–300 m zonal salinity contrasts control the gyre freshwater transports Fgyre, which also determine the total freshwater transports. This decoupling makes the southern Fov unlikely to play any role in AMOC stability, leaving indirect Fgyre feedbacks or Fov in the north, as more relevant factors.

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