Changes in the Seasonal Cycle of Sea Surface Salinity during the Argo-era (2004-2013)

The Argo program has provided the scientific community with near-global, seasonally uniform coverage of hydrographic profiles over the past decade. Recent launches of the SAC-D/Aquarius and SMOS satellites have provided near real-time snapshots of global ocean sea surface salinity (SSS). Changes in SSS over time and space have shown to be a direct reflection of changes in our global hydrological cycle. In addition, salinity is an important component of ocean circulation. This study attempts to advance our understanding of interannual changes in SSS by looking at year to year changes in the seasonal cycle over the past decade. We utilize near-surface salinity data from the World Ocean Database (WOD) to compute gridded monthly SSS fields from January 2004 through December 2013. The WOD includes Argo salinities along with other salinity profile data which augment Argo data. In addition to in situ derived monthly analyses, level-3 monthly data from SMOS and Aquarius are also utilized for the 2010-2013 and 2012-2013 calendar years, respectively. For each calendar year (2004-2013), a Fourier decomposition is applied and the first and second harmonics are examined for year to year changes in salinity. Additionally, interannual SSS variability is correlated to multiple climate indices (ENSO, NAO, etc.) over the past decade.