1. Ocean Circulation
Tyburn Marine Biology - Spring 2019

2. Ocean currents have a big effect on the weather!
The Scilly Isles – only 30 miles off the coast of Cornwall, England (lat 50o!) but in the warm Gulf Stream!
Ocean currents have a big effect on the weather!
Iceland Weather…

3. The Mediterranean Sea, seen from the Space Shuttle, looking toward the east

4. GYRE – The flow around the periphery of an ocean basin (from gyros = a circle)

5. Surface Winds drive the initial surface gyres…

6. But it’s more complicated!
Four Forces – surface winds, the Sun’s heat, Coriolis Force, and Gravity
– determine the exact patterns for ocean currents

7. North Atlantic Gyre
Coriolis Force effects

8. Coriolis Forces play an even more important role for ocean currents than for atmospheric winds – because these small but persistent forces have more time to act on slower-moving ocean currents!
Video1! Video2!

9. The Ekman “spiral”

10. Overall water column movement is about 45o to RIGHT of winds (N. Hem)

11. Wind
North
Atlantic
Water!

13. “center” of hill!

14. The Result…

15. Global Ocean SURFACE Currents

16. Western Boundary Currents – the fastest on Earth!
A Sverdrup (sv) = 1 million m3 per second!

17. The Gulf Stream

18. The Gulf Stream

19. Gulf Stream “eddies”

20. A photo mosaic of several day’s IR data

22. An eddy off the coast of Japan!

24. Transverse Currents – provide the links for the northward and southward flowing currents

25. Today will be hazy, hot, and humid in Annapolis …
Today will be hazy, hot, and humid in Annapolis ….summertime weather is affected by ocean and atmosphere currents

26. Equatorial Upwelling

28. Coastal Upwelling (or subsidence
Coastal Upwelling (or subsidence!) is caused by the Coriolis transport of water near the surface (where the angle is nearly 90 degrees)

29. Growth of phytoplankton in the nutrient-rich waters where upwelling is taking place off the California coast.

30. caused by winds that blow steadily across a wide ocean area
Langmuir Circulation
caused by winds that blow steadily across a wide ocean area

32. A “non-El Nino” year!

33. El Nino year has unusually warm eastern Pacific waters!

34. A quick return to cooler conditions
Peak El Nino

35. Thermohaline Circulation a VERTICAL, density-driven ocean circulation!
Mixing of equal-density water from points a and b would produce MORE dense water at point c – it would SINK!

37. Basin-driven vertical circulations – the Strait of Gibralter between Spain and Morocco

38. “Classic” Thermohaline circulation

39. Atlantic Ocean Water Layers and Sources

40. Convergence and Divergence of Surface Waters

42. Measuring Ocean Currents

43. 1992 “Rubber Ducky” accident
SOFAR float (11,500 ft!)

45. Current Measuring Devices
A “Woodhead” seabed drifter

46. Ekman Flow meter

47. A Slocum Glider – uses energy from gravity, buoyance, heat and batteries to “swim” for months and report info about currents from it’s GPS