Beschreibung:
Transport of the deepest water westward through a gap at 28°S in the Ninetyeast Ridge between the Central Indian Basin and the West Australia Basin is calculated from hydrographic data collected as part of WOCE Hydrographic Program section I8N. Zero reference velocity levels at mid‐depth were chosen through consideration of water masses. The small transport of 1.0 Sv westward of water denser than σ4 = 45.92 kg m−3 through the gap must all upwell in the southern Central Indian Basin. Of this, 0.7 Sv upwells between the central and western sill sections, that is, close to the sill itself. Using the areas covered by the isopycnal, we calculate an average vertical velocity of 3.3 · 10−3 cm s−1 close to the sill and of 4.2 · 10−4 cm s−1 west of the sill. Associated average vertical diffusivities are 105 cm² s−1 close to the sill and 13 cm² s−1 west of the sill, in this bottom layer.