3.1 Bathymetry and circulation

Fig. 2 Sandwell and Smith bathymetry of the Crozet Plateau

East of the South West Indian Ridge at about 45°S 40°E lies the Del Caño Rise (Fig. 2), which drops down to 3000 m depth at its eastern terminus (46°S 48°E) before rising again to what we shall refer to as the Crozet Plateau between 49°E and 53°E. The Crozet Plateau itself is split into two halves by the Indivat Basin (Recq, 1998) which is closed to the south by a ridge 300 - 400 m deep. The western plateau is a wide shelf area with a few small islands and treacherous shoals. The eastern part of Crozet consists of two islands, Ile de la Possession and Ile de l´Est, volcanic in origin with mountains rising to over 1000 m. Pollard and Read (2001) have shown that a major branch (bold S shaped curves on SeaWIFS figs) of the Antarctic Circumpolar Current (ACC) runs along the south side of the Del Caño Rise then turns north into the Crozet Basin through the 3000 m deep gap between the Del Caño Rise and the Crozet Plateau. This is the major pathway by which the ACC enters the Crozet Basin north of Crozet. This pathway follows the bathymetry of the Del Caño Rise towards the northwest but has to turn sharply back east when it meets the Agulhas Return Current along 42°S. East of the Crozet Plateau the bathymetry drops steeply down to the 4000 m abyssal plain which extends east to the Kerguelen Plateau. The remnants of Antarctic Bottom Water can enter the Crozet Basin just east of the Crozet Plateau therefore (e.g. Swallow and Pollard, 1988).

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