Abstract

The eastern subpolar North Atlantic upper ocean salinity undergoes decadal fluctuations. A large fresh anomaly event occurred during 2012--2016. Using the ECCO state estimate, we diagnose and compare mechanisms of this low salinity event with that of the 1990s fresh anomaly event. To avoid erroneous interpretations of physical mechanisms due to reference salinity values in the freshwater budget, we perform a salt mass content budget analysis of the eastern subpolar North Atlantic. It shows that the recent fresh anomaly occurs due to the circulation of anomalous salinity by mean currents entering the eastern subpolar basin from its western boundary via the North Atlantic Current. This is in contrast to the early 1990s, when the dominant mechanism governing the fresh anomaly was the transport of the mean salinity field by anomalous currents across the southern boundary of the subpolar North Atlantic.