Continuous estimate of Atlantic oceanic freshwater flux at 26.5°N

McDonagh, Elaine L.; King, Brian A. ORCID: https://orcid.org/0000-0003-1338-3234; Bryden, Harry L.; Courtois, Peggy; Szuts, Zoltan; Baringer, Molly; Cunningham, Stuart A.; Atkinson, Chris; McCarthy, Gerard. 2015 Continuous estimate of Atlantic oceanic freshwater flux at 26.5°N. Journal of Climate, 28 (22). 8888-8906. 10.1175/JCLI-D-14-00519.1

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Text © Copyright 2015 American Meteorological Society (AMS). Permission to use figures, tables, and brief excerpts from this work in scientific and educational works is hereby granted provided that the source is acknowledged. Any use of material in this work that is determined to be “fair use” under Section 107 of the U.S. Copyright Act September 2010 Page 2 or that satisfies the conditions specified in Section 108 of the U.S. Copyright Act (17 USC §108, as revised by P.L. 94-553) does not require the AMS’s permission. Republication, systematic reproduction, posting in electronic form, such as on a web site or in a searchable database, or other uses of this material, except as exempted by the above statement, requires written permission or a license from the AMS. Additional details are provided in the AMS Copyright Policy, available on the AMS Web site located at (http://www.ametsoc.org/) or from the AMS at 617- 227-2425 or copyrights@ametsoc.org. jcli-d-14-00519%2E1.pdf - Published Version Download (1MB) | Preview

Abstract/Summary

The first continuous estimates of freshwater flux across 26.5°N are calculated using observations from the RAPID–MOCHA–Western Boundary Time Series (WBTS) and Argo floats every 10 days between April 2004 and October 2012. The mean plus or minus the standard deviation of the freshwater flux (FW) is −1.17 ± 0.20 Sv (1 Sv ≡ 106 m3 s−1; negative flux is southward), implying a freshwater divergence of −0.37 ± 0.20 Sv between the Bering Strait and 26.5°N. This is in the sense of an input of 0.37 Sv of freshwater into the ocean, consistent with a region where precipitation dominates over evaporation. The sign and the variability of the freshwater divergence are dominated by the overturning component (−0.78 ± 0.21 Sv). The horizontal component of the freshwater divergence is smaller, associated with little variability and positive (0.35 ± 0.04 Sv). A linear relationship, describing 91% of the variance, exists between the strength of the meridional overturning circulation (MOC) and the freshwater flux (−0.37 − 0.047 Sv of FW per Sverdrups of MOC). The time series of the residual to this relationship shows a small (0.02 Sv in 8.5 yr) but detectable decrease in the freshwater flux (i.e., an increase in the southward freshwater flux) for a given MOC strength. Historical analyses of observations at 24.5°N are consistent with a more negative freshwater divergence from −0.03 to −0.37 Sv since 1974. This change is associated with an increased southward freshwater flux at this latitude due to an increase in the Florida Straits salinity (and therefore the northward salinity flux).

Item Type:	Publication - Article
Digital Object Identifier (DOI):	10.1175/JCLI-D-14-00519.1
ISSN:	0894-8755
Additional Keywords:	Circulation/ Dynamics, Meridional overturning circulation, Atm/Ocean Structure/ Phenomena, Freshwater, Physical Meteorology and Climatology, Salinity
Date made live:	07 Dec 2015 16:35 +0 (UTC)
URI:	https://nora.nerc.ac.uk/id/eprint/512366

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