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Argo observations revealed dramatic sea surface salinity (SSS) changes in the northeastern tropical Pacific Ocean (NETPO) during the past one and half decades, with a steady increase during 2004–2012 and a sharp decrease during 2013–2016. These changes mainly result from anomalous precipitation associated with the Walker Circulation through moisture transport across Central America. The anomalous Walker Circulation is caused by changes in trans-basin sea surface temperature (SST) gradients, especially those in the eastern tropical Pacific. Results using a longer reanalysis indicate that the upward trend of SSS in the NETPO started from the mid-1990s as the moisture transport across Central America decreased in response to reduced trans-basin SST gradients associated with the Interdecadal Pacific Oscillation and Atlantic Multidecadal Oscillation. [ABSTRACT FROM AUTHOR]