Oceans, Currents, and Weather Dynamics Science 1206

Lesson Objectives identify  why oceans are important in weather dynamics identify factors that are responsible for causing ocean currents

Oceans Nearly 70% of the Earth is covered by oceans, and because the equatorial region of the Earth is mostly ocean (most land is located in the Northern Hemisphere)

Oceans The major oceans of the Earth include the Arctic Ocean around the North Pole, the Antarctic Ocean around the South Pole, the Pacific Ocean (which is the largest of all the oceans), the Atlantic Ocean, and the Indian Ocean.

Causes of the Ocean Currents: The ocean currents are a result of the interaction between several factors. 1.The Earth's eastward rotation affects ocean currents. Near the equator, the rotation of the earth causes the surface waters of the ocean to move in a westward direction.

Causes of the Ocean Currents: The Earth's rotation and resulting Coriolis effect tends to rotate waters of the northern hemisphere in a clockwise direction. At the same time, waters of the southern hemisphere rotate in a counterclockwise direction.

Causes of the Ocean Currents: 2.The tides and resulting tidal currents have a minimal effect on the open ocean currents as a whole, but do have an effect on currents near the continental shelves. The continents will redirect water movement along its edge. When the Sun and Moon are on the same side of the Earth, high tides reach their highest point. When the Sun and the Moon are on opposite sides of the Earth, the high tides are at their lowest point.

Causes of the Ocean Currents: 3. Sunlight striking the water in the equatorial region tends to warm the water causing the water to become less dense. As the water moves away from the equatorial region it is replaced by more dense colder water from below. As a result, sunlight striking the equatorial waters result in the formation of a large convection current.  

4. Another factor involved in affecting ocean circulation is the change in density as water evaporates into the atmosphere. This phase change results in the cooling of the ocean water as the water vapour moves into the atmosphere.

Loss of water from the ocean increases it salinity (saltiness). Both of these factors cause the sea water to become more dense and as a result the sea water tends to sink downward creating deep water ocean currents.

As a result of these forces on the general pattern of circulation, water from the equator generally moves toward the pole, and polar water is moved toward the equator.

Effects of Ocean Currents: The evaporation of water transfers large quantities of energy from the water of the ocean to the atmosphere above. The warming of the atmosphere above then causes the pressure and density of the air to decrease and as a result the air begins to rise.

Effects of Ocean Currents: This greatly affects the energy distribution over the Earth. Needless to say this has an influence on the winds of the Earth and an influence on global and local weather conditions.

1. Which best describe the nature of currents on the eastern part of an ocean in the northern hemisphere? a. cold and rapidly moving toward the equator b. warm and rapidly moving toward the pole c. cold and slowly moving toward the equator d. warm and slowly moving toward the pole ANSWER C

2. Which the only current to circulate around the entire earth? a. Gulf Stream b. Antarctic Circumpolar Current c. Kuroshio Current d. Canaries Current ANSWER B

3. How does the Gulf stream affect weather conditions in St 3. How does the Gulf stream affect weather conditions in St. John's compared to a city located at the same latitude but in central Canada?   a. Winter is warmer and summer is cooler in St. John's. b. Winter is colder and summer is hotter in St. John's. c. Winter is warmer and summer is warmer in St. John's. d. Winter is cooler and summer is cooler in St. John's. ANSWER A

4. When a cold dry current around 30o latitude reaches the west coast of a continent, it tends to produce a. desert b. grassland c. tropical rain forest d. temperate deciduous forest ANSWER A

5. How does the rotation of Earth act on currents on the west sides of oceans?   a. It causes them to be narrow and rapid moving. b. It causes them to be wide and rapid moving. c. It causes them to be narrow and slow moving. d. It causes them to be wide and slow moving. ANSWER A

6. What is the general effect of El Niño? a. The surface temperatures of the Pacific Ocean increases, the trade winds travel westward, and rainfall increases along the coast of Peru b. The surface temperatures of the Pacific Ocean increases, the trade winds travel eastward, and rainfall decreases along the coast of Peru. c. The surface temperatures of the Pacific Ocean decreases, the trade winds travel westward, and rainfall increases along the coast of Peru. d. The surface temperatures of the Pacific Ocean increases, the trade winds travel eastward, and rainfall increases along the coast of Peru. ANSWER D

7. What causes El Niño? a. a reversal of the Pacific trade winds, while the ocean currents remain the same b. a reversal of the Pacific ocean currents, while the trade winds remain the same c. an increase in the strength of the Pacific trade winds and ocean currents, which still travel in the same directions d. a reversal of both the Pacific trade winds and the ocean currents ANSWER D