Description: Three deep anticyclonic eddies of a species only reported once before [ Gordon and Greengrove, 1986 ] were intersected by hydrographic lines of the World Ocean Circulation Experiment (WOCE) and South Atlantic Ventilation Experiment (SAVE) programs in the Argentine Basin. The vortices are centered near 3500 m depth at the interface between North Atlantic Deep Water and Bottom Water. They have ∼1500-m-thick cores containing Lower Circumpolar Deep Water and a dynamic influence that may span up to two thirds of the water column. As one eddy was observed just downstream of the western termination of the Falkland Escarpment, a destabilization of the deep boundary current by the sudden slope relaxation is suggested as a potential cause of eddy formation. Besides isopycnal interleaving at the eddy perimeters, strongly eroded core properties in the upper parts of the lenses, associated with low density ratios, hint at double diffusion at the top of the structures as another major decay mechanism. The presence of an eddy in the northern Argentine Basin shows the possibility for a northward drift of the vortices, in this basin at least. Deep events in recent current measurements from the Vema Channel are presented that raise the question of further equatorward motion to the Brazil Basin.

Description: The data from six zonal sections in the World Ocean Circulation Experiment (WOCE) in the tropical and southem Atlantic are used to describe the distribution of water masses. Due to the high spatial resolution, the structure oftemperature, salinity, oxygen, silicate and nitrate displays details related to transport and mixing in this region. Temperature-salinity diagrams are also presented which indicate the effects ofbranching and recirculation loops in the water mass flow.

Description: Abstract:Five hydrographic transects at nominal longitudes 0°E and 30°E, and fourteen expendablebathythermograph (XBT) sections near the former longitude are used to study the baroclinictransport of the Antarctic Circumpolar Current (ACC) between Africa and Antarctica. Thebottom-referenced geostrophic transport between the Subtropical Front and the ACC SouthernBoundary is 147±10 Sv. Estimating the transport from the XBTs using a technique previouslyemployed south of Australia proves delicate because of an irregular bathymetry and watermass variations. It nevertheless confirms ACC transports around 150 Sv. Gathering these andother estimates from the Atlantic sector suggests that, while North Atlantic Deep Water isinjected in the current west of 35°W, a partially compensating loss of Deep CircumpolarWater occurs east of this longitude. Another transport increase from 0°E to 30°E might reflectsouthward transfer across the Subtropical Front south of the Agulhas retroflection.

Description: Hydrographic and lowered acoustic Doppler current profiler data along a line from the Falkland Islands to South Georgia via the Maurice Ewing Bank are used to estimate the flow of circumpolar water into the Argentine Basin, and to study the interaction of the Antarctic Circumpolar Current with the Falkland Plateau. The estimated net transport of 129  21 Sv (Sv  106 m3 s1 ) across the section is shared between three major current bands. One is associated with the Subantarctic Front (SAF; 52  6 Sv), and the other two with branches of the Polar Front (PF) over the sill of the Falkland Plateau (44  9 Sv) and in the northwestern Georgia Basin (45  9 Sv). The latter includes a local reinforcement (20 Sv) by a deep anticyclonic recirculation around the Maurice Ewing Bank. While the classical hydrographic signature of the PF stands out in this eastbound branch, it is less distinguishable in the northbound branch over the plateau. Other circulation features are a southward entrainment of diluted North Atlantic Deep Water from the Argentine Basin over the eastern part of the Falkland Plateau, and an abyssal anticyclonic flow in the western Georgia Basin, opposite to what was generally assumed. The different behavior of the SAF and PF at the Falkland Plateau (no structural modification of the former and partitioning of the latter) is attributed to the PF being deeper than the sill depth on the upstream side of the plateau, unlike the SAF. It is suggested that the partitioning takes place at a location where the 2500-m and 3000-m isobaths diverge at the southern edge of the plateau. The western branch of the PF crosses the plateau at a distance of 250 km to the east of the SAF. Comparison with a section across the Falkland Current farther downstream shows that its deep part subsequently joins the SAF on the northern side of the plateau where the 2000–3000 m isobaths converge in the steep Falkland Escarpment. The result of this two-stage bathymetric effect is a net transfer of at least 10 Sv from the PF to the SAF at the crossing of the Falkland Plateau.

Description: Published