Fig. 3: Difference in the interdecadal variations of the oscillation source of the westerly wave in AMO.

a The summertime SST anomalies (℃, compared to the average value of 1961–2020) in the key are of the North Atlantic and (b) the annual variation of AMO from 1961 to 2020; the transport characteristics correlated between AMO and 200 hPa wind field vortices in the summers of (c) 1961–1990 and (d) 1991–2020 (the flow field is the integration of AMO and u–v correlated vectors, and the coloring is the integrated vorticity of AMO and u–v correlated vectors). The area within the deep pink box represents the high–impact area B of North Atlantic SST changes (75°–43° W, 25°–52.5° N) in (c, d).