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Section 24.1 Surface Currents Wind Patterns—such as—trade winds and westerly winds, cause surface currents which are continuous rivers of water flowing at the ocean surface. These flow clockwise in the Northern Hemisphere and counter-clockwise in the Southern Hemisphere.

Section 24.1 Surface Currents Describe how monsoon winds affect the behavior of surface currents. Monsoon winds change direction with the seasons, causing surface currents nearby to also change direction.

Section 24.1 Surface Currents Describe a countercurrent and contrast its flow with the other currents described in this section. A countercurrent flows in the opposite direction as wind-related currents. It develops because wind-related currents push a lot of water to one side of an ocean basin. The countercurrent then pushes it back.

Greatest Intermediate Least 1. Salinity ABW NADW AIW 2. Temperature 3. Depth 4. Density

Section 24.2 Currents Under the Surface Explain how evaporation affects density currents. Evaporation increases the salinity and therefore the density, of the sea water. Denser water sinks to form currents that flow beneath those formed by less dense water.

Section 24.2 Currents Under the Surfface Describe two types of upwellings and their effect on marine life. One kind of upwelling happens at western continental coasts when surface winds push surface water out to sea and cold water rises from below to fill the void. Another kind happens when opposing winds blow water away from a region and cold water rises to fill the void. Upwelling water brings nutrients with it that support phytoplankton and a rich array of marine life.

Section 24.3 Tides 1. Sun: Sun’s gravity causes high tides by pulling on water nearest it, and also pulling Earth away from the water on the far side of Earth; low tide results in remaining areas. When in line with moon, Sun’s gravity enhances moon’s gravity. When at odds, it minimizes the moon’s gravitational effect on tides.

Section 24.3 Tides 2. Moon – Moon’s gravity causes high tides by pulling on water nearest it, and also pulling Earth away from the water on the far side of Earth; low tide results in remaining areas. As moon orbits Earth, tidal changes advance through the day.

Section 24.3 Tides Shoreline shape: Broad, open shorelines allow high tide waters to spread out, minimizing their height. Narrow, constricted shorelines force high tide waters into confined spaces, maximizing their height.

Section 24.3 What is the tidal impact of the new moon at perigee? The new moon at perigee causes very high tides because moon is closest to Earth and sun’s gravity, which enhances the moon’s gravity.