Fig. 5: Volume transport through Drake Passage.

a Monthly values of total (red curve) and baroclinic (blue curve) transports across the repeat SR1b hydrographic section in Drake Passage computed from the HYbrid Coordinate Ocean Model (HYCOM) in comparison with baroclinic transport estimated from 24 SR1b hydrographic surveys¹⁰² (black circles) over 1993–2018 and with monthly baroclinic transport (magenta curve) estimated from the continuous cDrake observations¹⁹¹ from December 2007 to October 2011. The HYCOM transports (available between 1979–2020) are shown for the period 1993–2018 (coincident with the 24 SR1b observations). b Cumulative barotropic Antarctic Circumpolar Current (ACC) transports from south to north across Drake Passage¹⁰². The circled purple line is the cumulative barotropic transport based on cDrake observations¹⁹²; the circled and thick orange lines are the HYCOM-modeled cumulative barotropic transports calculated using velocities subsampled at the cDrake mooring locations and at the full model resolution, respectively. The dashed vertical lines and circles indicate the cDrake mooring locations. c, d Vertical profile of transport per unit depth as a function of depth at the Drake Passage repeat SADCP section and repeat hydrographic SR1b section from HYCOM and observations¹⁰². The red horizontal bars are the HYCOM-modeled total transport. In c, the black circles are SADCP observations¹⁹⁸. In d, the black circles are baroclinic transports based on the long-term SR1b hydrographic surveys. Positive transports correspond to eastward flow.