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

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

Figure 4-11 North-South Air Flow.

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

Figure 4-12 (a) The Coriolis Effect.

Figure 4-12 (b) The Coriolis Effect.

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)

Figure 4-12 (c) The Coriolis Effect.

Figure 4-13 Surface Wind Patterns.

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

Figure 4-14 (a) Gyres.

Figure 4-14 (b) Gyres.

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

Figure 4-15 Major Ocean Currents.

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

Figure 4-16 Ekman Spiral.

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 = 1.0270 g/cm3 Density increases when salinity increases Density increases when temperature decreases

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