CHAPTER 7 Ocean Circulation Pearson Education, Inc.

Transcription

1 CHAPTER 7 Ocean Circulation 2011 Pearson Education, Inc.

2 Types of Ocean Currents Surface currents Deep currents 2011 Pearson Education, Inc.

3 Measuring Surface Currents Direct methods Floating device tracked through time Fixed current meter Indirect methods Pressure gradients Radar altimeters Doppler flow meter 2011 Pearson Education, Inc.

4 Measuring Surface Currents Highly sophisticated equipment:

5

6

7

8 Measuring Surface Currents ADCP Acoustic Doppler Current Profiler

9

10 Global Surface Current Flow

11 Measuring Deep Currents Chemical tracers Tritium Chlorofluorocarbons Argo

12 Argo

13 Surface Currents: Subtropical Gyres Northern or Southern Boundary Currents Western Boundary Currents Equatorial Currents Eastern Boundary Currents 2011 Pearson Education, Inc.

14 Subtropical Gyres and Currents

15 Other Surface Currents Equatorial Countercurrents eastward flow between North and South Equatorial Currents Subpolar Gyres Rotate opposite subtropical gyres Smaller and fewer than subtropical gyres 2011 Pearson Education, Inc.

16 Ekman Spiral

17 Ekman Transport

18 Geostrophic flow balance of Coriolis Effect and gravitational forces Geostrophic Flow

19 Fig. 9.7

20 Western Intensification Western Boundary Current Eastern Boundary Current

21 Eastern and Western Boundary Currents

22 Ocean Currents and Climate

23 Upwelling and Downwelling Upwelling Vertical movement of cold, nutrient-rich water to surface High biological productivity Downwelling Vertical movement of surface water downward in water column 2011 Pearson Education, Inc.

24 Diverging Surface Water Equatorial upwelling

25 Coastal Upwelling

26 Other Types of Upwelling Offshore winds Seafloor obstruction Coastal geometry change 2011 Pearson Education, Inc.

27 Converging Surface Water

28 Coastal Downwelling

29 Antarctic Circumpolar Current Also called West Wind Drift and Penguin Gyre Only current to completely encircle Earth Moves more water than any other current Antarctic Circulation

30 Atlantic Ocean Circulation North Atlantic Subtropical Gyre North Equatorial Current Gulf Stream North Atlantic Current Canary Current South Equatorial Current Atlantic Equatorial Counter Current

31 Atlantic Ocean Circulation South Atlantic Subtropical Gyre Brazil Current Antarctic Circumpolar Current Benguela Current South Equatorial Current

32 Gulf Stream Best studied of all ocean currents Meanders and loops Merges with Sargasso Sea Circulates around center of North Atlantic Gyre Unique biology Sargassum 2011 Pearson Education, Inc.

33 Gulf Stream Meanders or loops may cause loss of water volume and generate: Warm-core rings Cold-core rings Unique biological populations

34 Indian Ocean Circulation

35 Affects seasonal land weather Affects seasonal Indian Ocean current circulation Affects phytoplankton productivity Indian Ocean Monsoon

36 Pacific Ocean Circulation

37 Atmospheric-Ocean Connections in the Pacific Ocean Normal Conditions: Walker Circulation 2011 Pearson Education, Inc.

38 El Nin o Southern Oscillation (ENSO)

39 La Nin a ENSO Cool Phase

40

41 ENSO Occurrences

42 ENSO has Global Impacts

43 Deep-Ocean Currents Thermohaline Circulation Originates in high latitude surface ocean Cooled, now dense surface water sinks and changes little. Deep-water masses identified on temperature salinity (T S) diagram Identifies deep water masses based on temperature, salinity, and resulting density 2011 Pearson Education, Inc.

44 Thermohaline Circulation

45 Surface Processes Temperature Salinity Pressure Plays a very small role Usually ignored T-S Diagram Isopycnal σ t = density 1000 kg/m 3 σ t = (density -1) x 1000 g/cm 3 Density Structure

46 Density Structure Water mass Water type A B H 2 O Mass

47 T S Diagram

48 Conveyor Belt Circulation 2011 Pearson Education, Inc.

49 End of CHAPTER 7 Ocean Circulation 2011 Pearson Education, Inc.