Importance of the eastern Indian Ocean for the abyssal Pacific

The role of the eastern Indian Ocean in controlling the abyssal circulation in the Pacific is examined using a 1degrees x 1degrees world ocean model. Thanks to the improvement of bottom topography and the incorporation of a bottom boundary layer model, the bottom water formation off the Adelie Coast is produced. This bottom water is not only the source of the abyssal water in the eastern Indian but also has a great influence on the whole abyssal Pacific. The lower part of Circumpolar Deep Water (CDW), which enters the abyssal Pacific passing through south of New Zealand, changes its property through mixing with this bottom water flowing underneath CDW in the Australian-Antarctic Basin and the South Australia Basin. The tracer experiments show that the water ventilated off the Adelie Coast occupies about 20% of the abyssal Pacific, whereas North Atlantic Deep Water (NADW) occupies about 50%, the Weddell Sea bottom water about 20%, and the Ross Sea bottom water about 10%. The flux of the ventilated water estimated by the tracer experiments is 17.1 Sv for NADW, 6.3 Sv from the Weddell Sea, 6.2 Sv from off the Adelie Coast, and 3.5 Sv from Ross Sea in this model. The total flux of 33.1 Sv is not far from the estimate from observations, though it may overestimate by 1-4 Sv. This does not directly indicate that the real world ocean should have the large amount of the bottom water sources in the Pacific-Indian sector. However, the model offers a picture of the water properties consistent with the observation.