CHAPTER 7 Ocean Circulation 2011 Pearson Education, Inc.
Types of Ocean Currents Surface currents Deep currents 2011 Pearson Education, Inc.
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.
Measuring Surface Currents Highly sophisticated equipment:
Measuring Surface Currents ADCP Acoustic Doppler Current Profiler
Global Surface Current Flow
Measuring Deep Currents Chemical tracers Tritium Chlorofluorocarbons Argo
Argo
Surface Currents: Subtropical Gyres Northern or Southern Boundary Currents Western Boundary Currents Equatorial Currents Eastern Boundary Currents 2011 Pearson Education, Inc.
Subtropical Gyres and Currents
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.
Ekman Spiral
Ekman Transport
Geostrophic flow balance of Coriolis Effect and gravitational forces Geostrophic Flow
Fig. 9.7
Western Intensification Western Boundary Current Eastern Boundary Current
Eastern and Western Boundary Currents
Ocean Currents and Climate
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.
Diverging Surface Water Equatorial upwelling
Coastal Upwelling
Other Types of Upwelling Offshore winds Seafloor obstruction Coastal geometry change 2011 Pearson Education, Inc.
Converging Surface Water
Coastal Downwelling
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
Atlantic Ocean Circulation North Atlantic Subtropical Gyre North Equatorial Current Gulf Stream North Atlantic Current Canary Current South Equatorial Current Atlantic Equatorial Counter Current
Atlantic Ocean Circulation South Atlantic Subtropical Gyre Brazil Current Antarctic Circumpolar Current Benguela Current South Equatorial Current
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.
Gulf Stream Meanders or loops may cause loss of water volume and generate: Warm-core rings Cold-core rings Unique biological populations
Indian Ocean Circulation
Affects seasonal land weather Affects seasonal Indian Ocean current circulation Affects phytoplankton productivity Indian Ocean Monsoon
Pacific Ocean Circulation
Atmospheric-Ocean Connections in the Pacific Ocean Normal Conditions: Walker Circulation 2011 Pearson Education, Inc.
El Nin o Southern Oscillation (ENSO)
La Nin a ENSO Cool Phase
ENSO Occurrences
ENSO has Global Impacts
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.
Thermohaline Circulation
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
Density Structure Water mass Water type A B H 2 O Mass
T S Diagram
Conveyor Belt Circulation 2011 Pearson Education, Inc.
End of CHAPTER 7 Ocean Circulation 2011 Pearson Education, Inc.