Results reveal that the East Shetland Atlantic Inflow is a persistent feature of North Sea circulation during the summer months. This inflow may form the western boundary of a cyclonic gyre in the bottom waters east of Shetland. It is evident that there have been substantial changes in the salinity of the northern North Sea, and of the adjacent oceanic waters during the past decades. Observations suggest that these changes are related to decadal variability of the two western North Sea inflows.