Fig. 4: Components of overturning variability.

a OSNAP West Meridional Overturning Circulation (MOC) anomalies: overturning derived from the Labrador Sea array (blue; shading indicates uncertainty as shown in Fig. 2); MOC variability arising from time-varying density and velocity anomalies in the Labrador Current (LC; light gray) computed with time-mean velocities/densities at the West Greenland Current (WGC) boundary, and MOC variability arising from density and velocity anomalies in the WGC (black) computed with time-mean velocities/densities at the LC boundary. b OSNAP East MOC anomalies: overturning derived from the OSNAP East array (red; shading indicates uncertainty as shown in Fig. 2); MOC variability arising from time-varying density and velocity in the region between Greenland and mid-Iceland basin (black) computed with time-mean velocities/densities at the eastern boundary, and MOC variability arising from density and velocity anomalies in the East Greenland Current (EGC; light gray) computed with time-mean velocities/densities everywhere else. For the reconstruction based on the time-varying data at the western boundary (light gray line), the MOC is defined as the minimum of the stream function integrated from the bottom to the sea surface in density space (sign has been changed for comparisons).