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Decoupled freshwater transport and meridional overturning in the South Atlantic

Mignac, D., Ferreira, D. and Haines, K. (2019) Decoupled freshwater transport and meridional overturning in the South Atlantic. Geophysical Research Letters. ISSN 0094-8276 (In Press)

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Abstract/Summary

Freshwater transports (F_ov) 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 F_ov 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 (AAIW) layer eliminates salinity differences across the AMOC branches at ~1200 m, ∆S_1200m, which decouples F_ov from the AMOC south of ~10˚N. As AAIW disappears north of ~10˚N, a large ∆S_1200m allows the AMOC to drive substantial southward F_ov in the North Atlantic. In the South Atlantic the 0-300 m zonal salinity contrasts control the gyre freshwater transports F_gyre, which also determine the total freshwater transports. This decoupling makes the southern F_ov unlikely to play any role in AMOC stability, leaving indirect F_gyre feedbacks or F_ov in the north, as more relevant factors.

Item Type:Article
Refereed:Yes
Divisions:Faculty of Science > School of Mathematical, Physical and Computational Sciences > National Centre for Earth Observation (NCEO)
Faculty of Science > School of Mathematical, Physical and Computational Sciences > Department of Meteorology
ID Code:82184
Publisher:American Geophysical Union

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