Within the North Atlantic subtropical gyre lies a salinity maximum region, relatively constant in time, yet forced by a seasonally varying strong evaporation zone located several degrees south and advected by wind-driven Ekman currents and geostrophic gyre currents and eddies. Large-scale calculations using in situ salinities to quantify salt divergence in the mixed layer, together with freshwater flux products, cannot account for the observed surface salinity signature. Small-scale and vertical processes must complete the budget. The Aquarius satellite system, launched in June 2011, now provides sea surface salinity observations every seven days at approximately 100 km spacing. Here, we reexamine the surface freshwater balance in the salinity maximum region, the location of the Salinity Processes in the Upper-ocean Regional Study (SPURS) campaign, from a satellite-sensed perspective. Advection of surface salinity by Ocean Surface Current Analyses Real-time (OSCAR) satellite-based surface currents is investigated for the whole region as well as within two boxes that isolate the salinity maximum and the maximum evaporation regions. Locations of imbalance, variability of surface salinity forcing terms, and areas of potential transport and redistribution are explored using satellite observations. A discussion then considers the vertical pathways by which surface waters reach and exchange salinity with the deep ocean, thus contributing to the signal seen at the surface.

Dohan, K., H.-Y. Kao, and G.S.E. Lagerloef. 2015. The freshwater balance over the North Atlantic SPURS domain from Aquarius satellite salinity, OSCAR satellite surface currents, and some simplified approaches. Oceanography 28(1):86–95, https://doi.org/10.5670/oceanog.2015.07.

de Boyer Montégut, C., G. Madec, A.S. Fisher, A. Lazar, and D. Iudicone. 2004. Mixed layer depth over the global ocean: An examination of profile data and a profile-based climatology. Journal of Geophysical Research 109, C12003, https://doi.org/10.1029/2004JC002378.

Dohan, K., and N. Maximenko. 2010. Monitoring ocean currents with satellite sensors. Oceanography 23(4):94–103, https://doi.org/10.5670/oceanog.2010.08.

Godfrey, J.S., and E.J. Lindstrom. 1989. The heat budget of the equatorial western Pacific surface mixed layer. Journal of Geophysical Research 94:8,007–8,017, https://doi.org/10.1029/JC094iC06p08007.

Joyce, R.J., J.E. Janowiak, P.A. Arkin, and P. Xie. 2004. CMORPH: A method that produces global precipitation estimates from passive microwave and infrared data at high spatial and temporal resolution. Journal of Hydrometerology 5:487–503, https://doi.org/10.1175/1525-7541(2004)005<0487:CAMTPG>2.0.CO;2.

Lagerloef, G. 2014. Sea surface salinity. Pp. 747–754 in Encyclopedia of Remote Sensing. E.G. Njoku, ed., Springer, New York, https://doi.org/10.1007/978-0-387-36699-9_165.

Lagerloef, G., R. Schmitt, J. Schanze, and H.-Y. Kao. 2010. The ocean and the global water cycle. Oceanography 23(4):82–93, https://doi.org/10.5670/oceanog.2010.07.

Lagerloef, G., F. Wentz, S. Yeuh, H.-Y. Kao, G. Johnson, and J. Lyman. 2012. Aquarius satellite mission provides new detailed view of sea surface salinity. In State of the Climate in 2011, Bulletin of the American Meteorological Society 93(7):S70–S71.

Lukas, R., and E. Lindstrom. 1991. The mixed layer of the western equatorial Pacific Ocean. Journal of Geophysical Research 96(S01):3,343–3,357, https://doi.org/10.1029/90JC01951.

Maes, C., K. Ando, T. Delcroix, W.S. Kessler, M.J. McPhaden, and D. Roemmich. 2006. Observed correlation of surface salinity, temperature and barrier layer at the eastern edge of the western Pacific warm pool. Geophysical Research Letters 33, L06,601, https://doi.org/10.1029/2005GL024772.

Reynolds, R.W., N.A. Rayner, T.M. Smith, D.C. Stokes, and W. Wang. 2002. An improved in situ and satellite SST analysis for climate. Journal of Climate 15:1,609–1,625, https://doi.org/10.1175/1520-0442(2002)015<1609:AIISAS>2.0.CO;2.

Roemmich, D., and J. Gilson. 2009. The 2004–2008 mean and annual cycle of temperature, salinity, and steric height in the global ocean from the Argo Program. Progress in Oceanography 82:81–100, https://doi.org/10.1016/j.pocean.2009.03.004.

Sato, K., T. Suga, and K. Hanawa. 2004. Barrier layer in the North Pacific subtropical gyre. Geophysical Research Letters 31, L05,301, https://doi.org/10.1029/2003GL018590.

Schanze, J., R. Schmitt, and L. Yu. 2010. The global oceanic freshwater cycle: A state-of-the-art quantification. Journal of Marine Research 68:569–595, https://doi.org/10.1357/002224010794657164.

Schmitt, R.W., and A.Blair. 2015. A river of salt. Oceanography 28(1):40–45, https://doi.org/10.5670/oceanog.2015.04.

Stevenson, J.W., and P.P. Niiler. 1983. Upper ocean heat budget during the Hawaii-to-Tahiti shuttle experiment. Journal of Physical Oceanography 13:1,894–1,907, https://doi.org/10.1175/1520-0485(1983)013<1894:UOHBDT>2.0.CO;2.

Stommel, H., and K.N. Fedorov. 1967. Small scale structure in temperature and salinity near Timor and Mindanao. Tellus 19:306–325, https://doi.org/10.1111/j.2153-3490.1967.tb01484.x.

Talley, L.D., G.L. Pickard, W.J. Emery, and J.H. Swift. 2011. Section 9.8.2.2 in Descriptive Physical Oceanography: An Introduction, sixth ed. Elsevier Science, Boston.

Tang, W., S.H. Yueh, A.G. Fore, and A. Hayashi. 2014. Validation of Aquarius sea surface salinity with in situ measurements from Argo floats and moored buoys. Journal of Geophysical Research 119:6,171–6,189, https://doi.org/10.1002/2014JC010101.

Yeager, S.G., and W.G. Large. 2004. Late-winter generation of spiciness on subducted isopycnals. Journal of Physical Oceanography 34:1,528–1,547, https://doi.org/10.1175/1520-0485(2004)034<1528:LGOSOS>2.0.CO;2.

Yeager, S.G., and W.G. Large. 2007. Observational evidence of winter spice injection. Journal of Physical Oceanography 37:2,895–2,919, https://doi.org/10.1175/2007JPO3629.1.

Yu, L., X. Jin, and R. Weller. 2008. Multidecade global flux datasets from the objectively analyzed air-sea fluxes (OAFlux) project: Latent and sensible heat fluxes, ocean evaporation, and related surface meteorological variables. OAFlux Project Technical Report (OA-2008-01), Woods Hole Oceanographic Institution.

This is an open access article made available under the terms of the Creative Commons Attribution 4.0 International License (https://creativecommons.org/licenses/by/4.0/), which permits use, sharing, adaptation, distribution, and reproduction in any medium or format as long as users cite the materials appropriately, provide a link to the Creative Commons license, and indicate the changes that were made to the original content. Images, animations, videos, or other third-party material used in articles are included in the Creative Commons license unless indicated otherwise in a credit line to the material. If the material is not included in the article’s Creative Commons license, users will need to obtain permission directly from the license holder to reproduce the material.