Study of tracer distribution in the Drake Passage

In English:
R/V Hesperides occupied the World Ocean Circulation Experiment SR1b repeat
section across the Scotia Sea in February 1995, February 1996, and February
1998. On each cruise the same set of 21 hydrographic stations with
characteristic spacing <20 nautical miles was visited. The results of the three
surveys display a characteristic zonation of water masses in the region, which
is defined by four hydrographic fronts. The net geostrophic transport of the
Antarctic Circumpolar Current (ACC) across SR1b, computed with reference to the
deepest common depth of each pair of adjacent stations, is similar in all three
cruises, 144 Sv in February 1995, 131 Sv in February 1996, and 134 Sv in
February 1998, and compares well with earlier computations of the ACC transport
across Drake Passage. A close comparison of the vertical distributions of water
properties on SR1b reveals changes in the structure of the ACC that are linked
to undersampled current mesoscale activity, as suggested by infrared satellite
images contemporary to the cruises. The most remarkable features are several
hydrographic discontinuities observed in the Antarctic Zone south of the
Southern ACC Front (SACCF), which are believed to be signatures of eddies
produced east of the Shackleton Fracture Zone. The paper further addresses the
different contribution of each ACC zonal band to the net geostrophic transport
across SR1b on each Hesperides occupation.