Transport of Antarctic Bottom Water Entering the Brazil Basin in a Planetary Geostrophic Inverse Model

The abyssal circulation in the interior portions of the Brazil Basin and northern Argentine Basin were estimated using an overdetermined inverse method conserving neutral surface planetary potential vorticity and salinity. Antarctic Bottom Water (AABW) flows with a northward component through 30 degrees S west of the Rio Grande Rise (RGR), as expected. However, in the area east of the RGR, the model shows southward transport in the upper part of the AABW across 30 degrees S. This finding suggests that previous calculations of northward transport through Hunter Channel reaching the broader Brazil Basin may be overestimates. Reduced northward transport through the Hunter Channel has significant implications for the heat budget, implying less diapycnal mixing across the warmer AABW classes, compared to earlier studies.