Exercise 2: The topography of the ocean floor.

The ridge system of the Indian Ocean has a profound effect on the circulation below 4000 m depth.

In the west, Antarctic Bottom Water can enter the deep basins from the south and proceed across the equator.

The only access point for Antarctic Bottom Water in the east is the Australian-Antarctic Discordance (1).

The Central Indian Basin (2) is blocked in the south by the Southeast Indian Ridge (3), and the 90 East Ridge (4) prevents Antarctic Bottom Water from entering from the south east. This basin is therefore ventilated from the north, through a depression in the 90 East ridge near the equator.

(Map based on the GEBCO97 database, produced with GEBCO97 software and modified.)