Antarctic bottom and lower circumpolar deep water circulation in the eastern Indian Ocean

Net northward transport below γ n > 28.1 kg m −3 (≈3200 m) into the Perth Basin of between 4.4 and 5.8 Sv is estimated from a year‐long current meter mooring array between the Broken and Naturaliste plateaus. Northward transport of between 2.0 and 2.5 Sv of Antarctic Bottom Water (γ n > 28.2 kg m −3 ), that must upwell within the southern region of the Perth Basin, results in an area‐averaged diapycnal velocity and diffusivity of w * = 2.5–3.1 × 10 −6 m s −1 and κ = 13–15 × 10 −4 m 2 s −1 , respectively. Diffusivity estimates for the Perth Basin are several times larger than area‐averaged mixing estimates for the abyssal subtropical South Atlantic and Pacific oceans. However, the dissipation of turbulent kinetic energy required to maintain the abyssal mixing in the Perth Basin, ε = O (10 −9 W kg −1 ), is similar to that required in the South Atlantic Ocean. The area‐averaged diffusivity in the Perth Basin does not require unreasonable energy dissipation rates as this ocean basin is only weakly stratified. The abyssal diffusivity of the Perth Basin results from intense mixing at the basin boundary and in the basin interior over rough topography. The complex bathymetry and low abyssal stratification suggests that the Indian Ocean, for a given energy dissipation, may support a larger meridional overturning circulation than other subtropical basins.