Chapter 13 - Deep Circulation in the Ocean

13.5 Important Concepts

1. The deep circulation of the ocean is very important because it determines the vertical stratification of the oceans and because it modulates climate.



2. The cold, deep water in the ocean absorbs CO₂ from the atmosphere, therefore temporarily reducing atmospheric CO₂.



3. Eventually, however, most of the CO₂ must be released back to the ocean. (Some is used by plants, some is used to make sea shells).



4. The production of deep bottom waters in the north Atlantic causes a transport of one petawatt of heat into the northern hemisphere which warms Europe.



5. Variability of deep water formation in the north Atlantic has been tied to large fluctuations of northern hemisphere temperature during the last ice ages.



6. The theory for the deep circulation was worked out by Stommel and Arons in a series of papers published from 1958 to 1960. They showed that vertical velocities are needed nearly everywhere in the ocean to maintain the thermocline, and the vertical velocity drives the deep circulation.



7. The deep circulation is driven by vertical mixing, which is largest above mid-ocean ridges, near seamounts, and in strong boundary currents.



8. The deep circulation is too weak to measure directly. It is inferred from observations of water masses de ned by their temperature and salinity and from observation of tracers.



9. The Antarctic Circumpolar Current mixes deep water from all oceans and redistributes it back to each ocean. The current is deep and slow with a transport of 125Sv.

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