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Is the Surface Salinity Difference between the Atlantic and Indo-Pacific a Signature of the Atlantic Meridional Overturning Circulation?

Nilsson, Johan and Ferreira, David and Schneider, Tapio and Wills, Robert C. J. (2021) Is the Surface Salinity Difference between the Atlantic and Indo-Pacific a Signature of the Atlantic Meridional Overturning Circulation? Journal of Physical Oceanography, 51 (3). pp. 769-787. ISSN 0022-3670. doi:10.1175/jpo-d-20-0126.1. https://resolver.caltech.edu/CaltechAUTHORS:20210611-122858735

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Abstract

The high Atlantic surface salinity has sometimes been interpreted as a signature of the Atlantic meridional overturning circulation and an associated salt advection feedback. Here, the role of oceanic and atmospheric processes for creating the surface salinity difference between the Atlantic and Indo-Pacific is examined using observations and a conceptual model. In each basin, zonally averaged data are represented in diagrams relating net evaporation ˜E and surface salinity S. The data-pair curves in the ˜E–S plane share common features in both basins. However, the slopes of the curves are generally smaller in the Atlantic than in the Indo-Pacific, indicating a weaker sensitivity of the Atlantic surface salinity to net evaporation variations. To interpret these observations, a conceptual advective–diffusive model of the upper-ocean salinity is constructed. Notably, the ˜E–S relations can be qualitatively reproduced with only meridional diffusive salt transport. In this limit, the interbasin difference in salinity is caused by the spatial structure of net evaporation, which in the Indo-Pacific oceans contains lower meridional wavenumbers that are weakly damped by the diffusive transport. The observed Atlantic ˜E–Srelationship at the surface reveals no clear influence of northward advection associated with the meridional overturning circulation; however, a signature of northward advection emerges in the relationship when the salinity is vertically averaged over the upper kilometer. The results indicate that the zonal-mean near-surface salinity is shaped primarily by the spatial pattern of net evaporation and the diffusive meridional salt transport due to wind-driven gyres and mesoscale ocean eddies, rather than by salt advection within the meridional overturning circulation.


Item Type:Article
Related URLs:
URLURL TypeDescription
https://doi.org/10.1175/jpo-d-20-0126.1DOIArticle
ORCID:
AuthorORCID
Ferreira, David0000-0003-3243-9774
Schneider, Tapio0000-0001-5687-2287
Wills, Robert C. J.0000-0002-7776-2076
Additional Information:© 2021 American Meteorological Society. Received: 12 Jun 2020; Final Form: 13 Nov 2020; Published Online: 18 Feb 2021. We thank Paola Cessi for interesting discussions and valuable comments on this work. We also thank two anonymous reviewers for providing constructive suggestions. Data availability statement: All data used here are available from the references given in the text.
Subject Keywords:Atmosphere-ocean interaction; Hydrologic cycle; Meridional overturning circulation
Issue or Number:3
DOI:10.1175/jpo-d-20-0126.1
Record Number:CaltechAUTHORS:20210611-122858735
Persistent URL:https://resolver.caltech.edu/CaltechAUTHORS:20210611-122858735
Official Citation:Nilsson, J., Ferreira, D., Schneider, T., & Wills, R. C. J. (2021). Is the Surface Salinity Difference between the Atlantic and Indo-Pacific a Signature of the Atlantic Meridional Overturning Circulation?, Journal of Physical Oceanography, 51(3), 769-787; DOI: 10.1175/jpo-d-20-0126.1
Usage Policy:No commercial reproduction, distribution, display or performance rights in this work are provided.
ID Code:109484
Collection:CaltechAUTHORS
Deposited By: Tony Diaz
Deposited On:11 Jun 2021 21:09
Last Modified:11 Jun 2021 21:09

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