Salinity Processes Upper-ocean Regional Study (SPURS): Diagnosing the Oceanic Response to a Changing Water Cycle (Invited Presentation)

Strong trends in ocean salinity have been documented over the past 50 years that suggest an intensification of the water cycle is underway. That is, saltier areas are getting saltier and fresh areas fresher. The rates of change are well above those estimated by models (Durack, Wijffels and Matear, 2012, Science 336(6080) 455-458). Since the oceanic water cycle is an order of magnitude larger than the terrestrial water cycle, these trends could have serious consequences for society. SPURS is designed to investigate the ocean's mixing and advective processes that serve to dissipate the salinity variance generated by surface water fluxes, in order to understand if salinity is hypersensitive to changes in the water cycle. The first SPURS field program was focused on the salinity maximum of the North Atlantic in 2012-2013. A large array of autonomous instruments and moorings monitored surface fluxes and water properties for over a year in concert with the Aquarius salinity satellite and five US and European research cruises. We initially found the surface salinity in the region to be higher than ever observed before, consistent with the reported global trends. We also documented the lateral eddies and vertical mixing processes that serve to disperse the high salinity of this strongly evaporative region. Both point balances and iso-haline control volume approaches are being used to diagnose the physics of this salinity maximum, which should be applicable to the other subtropical salinity maxima around the globe. In addition, plans will be presented for a second SPURS field study in a low salinity region under the ITCZ of the eastern tropical Pacific in 2016-2017.