1. Density Structure
Surface Processes
Temperature
Salinity
Pressure

2. Changes with Depth
Density
Pycnocline
σt = density – 1000 kg/m3

3. Changes with Depth
Temperature
Thermocline
Salinity
Halocline

4. Changes with Depth Stable Unstable Density increases with depth
Density decreases with depth
Leads to overturn & mixing of water column

5. Fig a

6. Fig b

7. Fig c

8. The Layered Oceans Surface Intermediate Deep Bottom 0-200m 300-2000m

9. Atlantic Ocean
NADW
AAIW
AABW
SASW

10. Pacific Ocean Layers difficult to distinguish
No large source of deep water

11. Indian Ocean
No deep water
Fairly uniform mixture

12. Arctic Ocean Density controlled more by salinity
Circulation confined to < 500m

13. Mediterranean Sea

14. Thermohaline Circulation
Ocean radiator

15. Thermohaline Circulation
Freshwater lid
Very cold freshwater runoff at high latitudes
Very low density  does not sink
Fjords and semi-enclosed bays

16. Global Currents

17. Fig. 9.25

18. Measuring the Currents
Highly sophisticated equipment:

19. Measuring the Currents

20. Measuring the Currents
Current Meters

21. Measuring the Currents
Doppler current meter
Emits sound of known frequency
Measures frequency of returning echoes