Description: The flow field in the area of what was thought to be the source region of the North Brazil Current (NBC) off the northeast coast of Brazil between 5 degrees 30'S and 10 degrees S was investigated in austral spring during November 1992 and compared with observations in October 1990. The data were taken with several different instruments, including vessel-mounted ADCP, lowered-ADCP, Pegasus, CTD and XBTs. The flow was found off the coast at 5 degrees 30'S as well as at 10 degrees S as an undercurrent, the North Brazil Undercurrent (NBUC). The NBUC shows a subsurface core at about 200 m depth with velocities of up to 90.0 cm s(-1), resulting in large northward transports of more than 22 Sv in the upper 1000 m. The transport is about the same at 5 degrees 30'S and 10 degrees S, hence no net inflow from the east is required to feed the NBUC. The climatological Ekman transport is to the south between 5 degrees 30'S and 10 degrees S, and in consequence the northward flow near the surface was reduced and might be one reason for the existence of the undercurrent. The flow near the coast was to the north at 10 degrees S, therefore the Brazil Current had to start as a coastal current south of 10 degrees S. For the zonal sections at 5 degrees 30'S and 10 degrees S the geostrophic computations relative to the density surface sigma(1) = 32.15 kg m(-3) (about 1150 m depth) resulted in transports comparable to those obtained from direct measurements. The results further show that the choice of a correct level of no motion can be supported by the direct observations. A shallower reference based on water mass boundaries alone would reduce the NBUC transport to almost zero. Computations with data from the historical data base for austral fall resulted in a weaker NBUC of less than 20 Sv near 10 degrees S, indicating a possible seasonal signal in the NBUC with a stronger NBUC in austral spring.

Description: Recent results from hydrographic, chlorofluoromethane (CFM) and current measurements during an R.V. Meteor cruise in February/March 1994 underscore the importance of the Vema Fracture Zone (VFZ), located near 11°N on the Mid-Atlantic Ridge, for the transport of bottom water from the deep western basin of the equatorial Atlantic into the eastern abyss. The eastward transport in the bottom water range, of 1.8-2.0 Sv below 2.0°C, and of 2.1–2.4 Sv below the level of no motion at 3640 m, was determined by a combination of geostrophic calculations and direct current observations by a lowered ADCP. The comparison to former results indicates that the eastward flow in the VFZ is rather persistent. The water mass properties (Θ, S and CFMs) in the VFZ were compared to stations in the Guiana Basin, in the equatorial channel, and in the Brazil Basin at 10°S suggesting a significant contribution of North Atlantic Deep Water to the entire bottom water layer in the VFZ.