FIGURE 2. SST restoring forces robust multidecadal fluctuations in the Atlantic Ocean meridional overturning circulation, Labrador Sea convection and the North Atlantic Oscillation.

a, Annual mean meridional overturning circulation (MOC) at 30° N from the SST-restored simulations. Grey shading indicates ensemble spread in all panels. b, Simulated wintertime (December–February) Labrador Sea (60–50° W, 55–65° N) mixed-layer depth and observed annual mean Labrador Sea Water (LSW) thickness²⁶. The latter is defined between isopycnals _1.5 = 34.72–34.62, and is closely related to wintertime Labrador Sea convection. Simulated Labrador Sea convection precedes MOC variations at 30° N, with a maximum correlation (0.71) when the MOC lags by three years. c, Observed²⁹ and simulated ensemble mean wintertime North Atlantic Oscillation (NAO) indices. Solid lines indicate the seven-year running mean. The NAO index is defined as the sea-level-pressure (SLP) difference between Lisbon and Stykkisholmur. Observed NAO variations precede MOC variations at 30° N, with a maximum correlation (0.52) when the MOC lags by 3–4 years, but are not closely related to simulated Labrador Sea convection (r < 0.4 at any lag).