Figure 1 The origins of deep freshening in the Labrador Sea. a, Rapid and long-term freshening throughout the water column of the Labrador Sea. Shown are salinity changes since 1950 in the central part of the basin, with values >34.87 shaded. The data set was selected to lie within the 3,300-m isobath of the Labrador Sea, and the plot represents the median values of vertical property profiles, binned according to 2 density intervals. b, The two main overflows across the Greenland–Scotland ridge and their spreading pathways to the Labrador Sea (heavy dashed lines). Letters identify the locations of time series used in Fig. 2 to describe their changing characteristics en route.