The northern North Atlantic is an important region of deep water formation and an essential component of the Atlantic Meridional Overturning Circulation (AMOC). Salinity in the northern North Atlantic controls stratification and, therefore, deep water formation. Characterizing, quantifying, and understanding the distribution of sea surface salinity (SSS) and its variability is therefore crucial for understanding changes in the regional and global climate and for climate monitoring and prediction.

To characterize spatiotemporal patterns of SSS variability in the region we use satellite observations of SSS from 2011 to 2023. The dominant signal in the northern North Atlantic is the seasonal cycle accounting for more than 45% of the total SSS variance. The seasonal cycle can generally be described as a standing oscillation (the first mode from the Empirical Orthogonal Function (EOF) decomposition describes ~85% of the seasonal SSS variance) with maximum SSS in March and minimum SSS in September. The seasonal cycle in the Greenland Sea, Labrador Sea and Irminger Sea is controlled, in significant part, by freshwater flux from the Arctic. The inter-annual SSS signal is very complex. The dominant signal (~33% of non-seasonal SSS variance) consists of several "centers of action". They are in the western Greenland Sea and Iceland Sea, on the periphery of the Labrador Sea (West Greenland Current and Labrador Current) and around the Grand Banks of Newfoundland, essentially in the same areas as the "centers of action" of the seasonal cycle. The amplitude of this inter-annual signal appears to correlate relatively well with the ENSO index (surprisingly), although the time series are too short for a statistically significant inference. There is also a sequence of apparently not related events and we discuss the origin and fate of unusually fresh SSS anomaly in the Iceland Sea in late summer of 2021.