1. Ms. Halbohm Marine Biology
Chapter 4 Section 3
Ms. Halbohm
Marine Biology

2. Winds and Currents Winds
result from horizontal air movements caused by temperature, density, etc.
as air heats, its density decreases and it rises; as it cools, density increases and it falls toward earth
wind patterns: upper air flow from the equator towards the north and south

3. Figure 4-11 North-South Air Flow.

4. Winds and Currents Winds Coriolis effect
a point rotating at the equator moves faster than a point at a higher latitude
path of air mass appears to curve relative to the earth’s surface—to the right in the Northern Hemisphere, left in the Southern

5. Figure 4-12 (a) The Coriolis Effect.

6. Figure 4-12 (b) The Coriolis Effect.

7. Winds and Currents Surface wind patterns
3 convection cells in each hemisphere:
northeast & southeast trade winds
westerlies
polar easterlies
areas of vertical air movement between wind belts
Doldrums (at equator)
horse latitudes (at 30o N & S)

8. Figure 4-12 (c) The Coriolis Effect.

9. Figure 4-13 Surface Wind Patterns.

10. Winds and Currents Ocean currents surface currents
driven mainly by trade winds (easterlies and westerlies) in each hemisphere
Coriolis effect
currents deflected to the right of the prevailing wind direction in the Northern Hemisphere, to the left in the Southern Hemisphere
deflection can be as much as 45-degree angle from wind direction
gyres—water flow in a circular pattern around the edge of an ocean basin

11. Figure 4-14 (a) Gyres.

12. Figure 4-14 (b) Gyres.

13. Winds and Currents Classification of currents
western-boundary currents: fastest, deepest currents that move warm water toward the poles in each gyre (e.g. Gulf Stream)
eastern-boundary currents: slow moving, carry cold water toward the equator
transverse currents: connect eastern- and western-boundary currents in each gyre
biological impact
western-boundary currents not productive, carry little nutrients, but increase oxygen mixed in water
eastern-boundary currents productive, nutrient-rich

14. Figure 4-15 Major Ocean Currents.

15. Winds and Currents Currents below the surface
energy transferred from winds to surface water is transferred to deeper water
deeper-water currents are deflected by the Coriolis effect, down to about 100 m
friction causes loss of energy, so each layer moves at an angle to and more slowly than the layer above, creating an Ekman spiral
Ekman transport—net movement of water to the 100-m depth

16. Figure 4-16 Ekman Spiral.

17. Ocean Layers and Ocean Mixing
Density—the mass of a substance in a given volume, usually measured in g/cm3
density of pure water = 1 g/cm3
density of salt water = g/cm3
Density increases when salinity increases
Density increases when temperature decreases

18. Figure 4-17 Effect OF Temperature And Salinity On The Density Of Seawater.