<p>The Pacific shallow meridional overturning circulations, known as Subtropical-tropical Cells (STCs), serve as oceanic channels that link the tropical and subtropical regions. Using Argo observations, here we find distinct seasonal variations in the subsurface branches of the Pacific STCs. The STCs pycnocline transports at each latitude exhibit remarkable seasonal variation, especially the interior transport. The seasonal variation differs between the near-equatorial (5–8°) and far-equatorial regions (9–15°), exhibiting an equatorward enhancement. In the near-equatorial region, the Northern STC pycnocline transports show a strong transport in spring and weak transport in summer, while in the South Pacific, there are two marked peaks in both spring and autumn, with a weakening in summer. In both hemispheres, wind stress curl perturbations in the far-equatorial regions directly drive seasonal subsurface transport perturbations of the STCs. In the Northern Hemisphere, Ekman transport plays a more important role, while equatorial upwelling is the primary mechanism in the Southern STC. The spring peak of the pycnocline transports in the South Pacific is primarily driven by equatorial upwelling, while the autumn peak results from the combined influence of upwelling and Ekman transport. Additionally, the westward propagation of Rossby waves, induced by local wind stress curl, significantly impacts sea surface height, subsequently affecting the subsurface meridional transport of the STCs. The Rossby wave signal is more pronounced in the near-equatorial region of the Northern Hemisphere, having a greater impact on the Northern STC.</p>