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Ocean Science An interactive open-access journal of the European Geosciences Union

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doi:10.5194/osd-12-983-2015
© Author(s) 2015. This work is distributed
under the Creative Commons Attribution 3.0 License.
Research article
03 Jun 2015
Review status
A revision of this discussion paper for further review has not been submitted.
Regime changes in global sea surface salinity trend
A. L. Aretxabaleta1,*, K. W. Smith2, and J. Ballabrera-Poy1 1Institut 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
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.

Citation: 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.
A. L. Aretxabaleta et al.
A. L. Aretxabaleta et al.
A. L. Aretxabaleta et al.

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Short summary
We estimate global surface salinity means and trends using historical (1950-2014) monthly fields and recent SMOS satellite data. We separate the regimes by fitting a Gaussian Mixture Model with a non-subjective method. There are three separate regimes: A (1950-1990) with small trends; B (1990-2009) with enhanced trends; and C (2009-2014) with significantly larger trends. The trend acceleration could be related to an enhanced hydrological cycle or to changes in sampling methodology.
We estimate global surface salinity means and trends using historical (1950-2014) monthly fields...
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