Propagation of subsurface North Pacific interdecadal variations is investigated with an ocean general circulation model forced by observed sea surface temperature anomalies. Subsurface temperature anomalies subducted in the central subtropical North Pacific take a more westward pathway than a passive “temperature” tracer and reach the western boundary to the north of the bifurcation latitude. This prevents them from extending into the equator. On the boundary between the subtropical and the subarctic gyres, on the other hand, the upper 500 m heat content anomaly is found to propagate eastward as high vertical modes of Rossby waves advected by the mean eastward current. This notion is supported by a sign reversal in temperature anomaly underneath.