1. Ocean circulation Two types of ocean currents: • surface currents
• deep ocean circulation

2. Surface Waters Circulate Horizontally, Pushed By
Surface Winds Of Hadley, Ferrel, Polar Cells
Called gyres

3. N
W E S
The Gulf Stream flows north, pushed by the trade winds of the tropics, warming the SE coast
Florida
Gulf Stream

4. N
W E S
The California Current flows south, pushed by the Westerlies, keeping the western Pacific ocean cool
Florida
Gulf Stream

5. Surface Currents = Gyres
5 Gyres exist • Caused by winds
• 1 Cycle takes ~ 10 yrs • Turned by Continents, Coriolis

6. The center of gyres have become giant whirling collections of garbage
• All 5 gyres
• Pacific’s is huge!

7. Breaks into small pieces
Animals ingest it
6x more plastic than plankton

8. Deep Water Circulation
Coldest, saltiest water at Arctic sinks
• A continuous deep current slowly
drains one ocean
into another
• All the water is turned over in the
process
Antarctica recharges cold water

9. Recall: Angle of Solar Radiation Heats Earth’s Surface Unequally
Sunlight
Ocean currents are ultimately powered by energy from the sun, but how the oceans are affected by the sun depends on latitude. The intensity of sunlight is highest in the tropics and decreases as you go towards the poles. Here, the yellow bars represent the same amount of sunlight hitting the earth at different parts of the globe. At 60° north (click), the approximate latitude of Anchorage, Alaska, the same amount of sunlight would only have about half the intensity of sunlight as that at the equator. To think about it another way (click), if you took the sun that was hitting a square this big at the equator, it would be spread out over a square this big at 60° north. Because of differences in sunlight intensity, the average annual temperature in the Galapagos Islands on the equator is about 76°F while it is only 36°F in Anchorage, Alaska. This difference in sunlight intensity causes the oceans to heat differently. (click)
Image based on:
Modified image from Windows to the Universe, 9

10. Ocean Surface Temperature is Varied as a Result10
Radiation affects temp, density, evaporation
This image shows temperatures of the ocean surface across the world. Temperature is color-coded where red colors indicate warmer temperatures, and blue and violet indicate colder temperatures. For example, the reddish area in the middle of the map shows that the oceans are warmer in the tropics. The heat absorbed in the tropics is transported north and south to higher latitudes by atmospheric and oceanic circulation. (click)
Image source:
Cold, dense; sinking water
oceanworld.tamu.edu 10

11. Salinity is Another Factor
the amount of salt dissolved in water
evaporation,
freezing act to increase salinity
rain, runoff, & thawing of ice decrease salinity
Higher salt = greater density

12. Factors influencing seawater density

13. All these density differences creates the Great Ocean Conveyor Belt
Takes 1000 years for a complete cycle

14. Normal
El Nino

15. Warmer than normal : El Nino Colder than normal : La Nina
Oceans temps measured via buoys

16. El Nino affects local
weather, westerlies
(jet stream), fisheries