Fig. 2: Changes in volume transports along 1920–2100.

Mean zonal (a) and meridional (b) velocity fields over 1920–2100, averaged over the upper 985-m of the ocean. In both panels, red represents positive (eastward/northward), while blue represents negative (westward/southward) velocities. Dotted gray contours indicate the zero zonal/meridional velocity line. The regions where zonal and meridional volume transports were derived are shown through boxes and transects, whose colors and numbers correspond to those on panels (c–e) and on Supplementary Fig. 1 (which shows the vertical profiles associated with boxes/transects). The volume transport time series (c–e) are integrated over the upper 985-m layer (slightly above 1-km) across transects and boxes (in the latter case, representing the mean transport along cross-sectional ranges of the boxes). Only MOC streamfunction time series (time series 21b-24b) are vertically integrated up to the depth of transition between north- and southward zonally integrated meridional velocities. When deriving eastward/northward (westward/southward) volume transports, only positive (negative) velocity values are taken into account, to avoid counterflow interference — with exception of MOC streamfunction time series (21b-24b). Panels c–e are standardized in length and their y-axis (positive upwards) varies in 1-Sverdrup intervals (1 Sv = 10⁶ m³.s⁻¹). The legends indicate the value corresponding to the first time-step (year of 1920) in each time series (t₁). The gray dashed vertical line marks the transition from the historical (1920–2005) to the RCP8.5 (2006–2100) period. Time series mean and trend values are displayed in Supplementary Table 1.