Regime changes in global sea surface salinity trend
A. L. Aretxabaleta1,*, K. W. Smith2, and J. Ballabrera-Poy11Institut de Ciències del Mar – CSIC, Barcelona, Spain 2Independent Research, West Tisbury, MA, USA *now at: US Geological Survey and Integrated Statistics, Woods Hole, MA, USA
Received: 09 Apr 2015 – Accepted for review: 11 May 2015 – Discussion started: 03 Jun 2015
Abstract. Recent studies have shown significant sea surface salinity (SSS) changes at scales ranging from regional to global. In this study, we estimate global salinity means and trends using historical (1950–2014) SSS data from the UK Met. Office Hadley Centre objectively analyzed monthly fields and recent data from the SMOS satellite (2010–2014). We separate the different components (regimes) of the global surface salinity by fitting a Gaussian Mixture Model to the data and using Expectation–Maximization to distinguish the means and trends of the data. The procedure uses a non-subjective method (Bayesian Information Criterion) to extract the optimal number of means and trends. The results show the presence of three separate regimes: Regime A (1950–1990) is characterized by small trend magnitudes; Regime B (1990–2009) exhibited enhanced trends; and Regime C (2009–2014) with significantly larger trend magnitudes. The salinity differences between regime means were around 0.01. The trend acceleration could be related to an enhanced global hydrological cycle or to a change in the sampling methodology.
Aretxabaleta, A. L., Smith, K. W., and Ballabrera-Poy, J.: Regime changes in global sea surface salinity trend, Ocean Sci. Discuss., 12, 983-1011, doi:10.5194/osd-12-983-2015, 2015.