In this special issue of Oceanography, we explore the results of SPURS-1, the first part of the ocean process study Salinity Processes in the Upper-ocean Regional Study (SPURS). The experiment was conducted between August 2012 and October 2013 in the subtropical North Atlantic and was the first of two experiments (SPURS come in pairs!). SPURS-2 is planned for 2016–2017 in the tropical eastern Pacific Ocean.

The scientific motivation behind SPURS arises from the desire to understand the patterns and variations of salinity at the ocean’s surface. To first order, surface salinity patterns reflect the overlying patterns of evaporation and precipitation that force the freshwater balance in the upper ocean (Wüst, 1936). Maps of the net difference between evaporation and precipitation (E–P) appear to be quite similar in pattern to surface salinity. If the surface salinity is determined only by (E–P), then the ocean itself might serve as crude “rain gauge.” In fact, it is already known that ocean circulation in the form of wind-driven surface currents must be accounted for in understanding surface salinity patterns (surface salinity maxima are offset poleward of subtropical E–P maxima due to Ekman currents induced by the trade winds). In addition, ocean mixing processes also affect the temporal evolution of surface salinity. SPURS was designed to examine the salinity balance in the upper ocean through observation of salinity and ocean circulation on a variety of scales.

Lindstrom, E., F. Bryan, and R. Schmitt. 2015. SPURS: Salinity Processes in the Upper-ocean Regional Study—The North Atlantic Experiment. Oceanography 28(1):14–19, https://doi.org/10.5670/oceanog.2015.01.

Asher, W.E., A.T. Jessup, and D. Clark. 2014. Stable near surface ocean salinity stratifications due to evaporation observed during STRASSE. Journal of Geophysical Research 119:3,219–3,233, https://doi.org/10.1002/2014JC009808.
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2. Bryan, F., and S. Bachman. 2015. Isohaline salinity budget of the North Atlantic salinity maximum. Journal of Physical Oceanography 45:724–736, https://doi.org/10.1175/JPO-D-14-0172.1.
3. Busecke, J., A.L. Gordon, Z. Li, F. Bingham, and J. Font. 2014. Subtropical surface layer salinity budget and the role of mesoscale turbulence. Journal of Geophysical Research 119:4,124–4,140, https://doi.org/10.1002/2013JC009715.
4. Gordon, A.L., and C.F. Giulivi. 2014. Ocean eddy freshwater flux convergence into the North Atlantic subtropics. Journal of Geophysical Research 119:3,327–3,335, https://doi.org/10.1002/2013JC009596.
5. Hernandez, O., J. Boutin, N. Kolodziejczyk, G. Reverdin, N. Martin, F. Gaillard, N. Reul, and J.L. Vergely. 2014. SMOS salinity in the subtropical North Atlantic salinity maximum. Part 1. Comparison with Aquarius and in situ salinity. Journal of Geophysical Research 119:8,878–8,896, https://doi.org/10.1002/2013JC009610.
6. Schanze, J.J., R.W. Schmitt, and L. Yu, 2010. The global oceanic freshwater cycle: A best estimate quantification. Journal of Marine Research 68:569–595, https://doi.org/10.1357/002224010794657164.
7. Wüst, G. 1936. Oberflächensalzgehalt, Verdunstung und Niederschlag auf dem Weltmeere. Länderkundliche Forschung, Festschrift Norbert Krebs, 347–359.

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