Presentation on theme: "Oceanography Chapter 37. 5. Heating of Earth’s surface and atmosphere by the sun drives convection within the atmosphere and oceans, producing winds and."— Presentation transcript:
5. Heating of Earth’s surface and atmosphere by the sun drives convection within the atmosphere and oceans, producing winds and ocean currents. As a basis for understanding this concept: a. Students know how differential heating of Earth results in circulation patterns in the atmosphere and oceans that globally distribute the heat. b. Students know the relationship between the rotation of Earth and the circular motions of ocean currents and air in pressure centers. d. Students know properties of ocean water, such as temperature and salinity, can be used to explain the layered structure of the oceans, the generation of horizontal and vertical ocean currents, and the geographic distribution of marine organisms.
Objectives Students will know the circulation patterns of the oceans and how the heat is distributed Students will know the properties of ocean water, the layered structure of the oceans, the generation of horizontal and vertical ocean currents.
What is oceanography? The study of Earths oceans.
Chemical Composition of water 96.5% Fresh Water 3.5% Dissolved Salts Most abundant salt sodium chloride Other salts are sulfates and chlorides. These are so dissolved called ions.
Dissolved gases Oxygen, nitrogen and carbon dioxide Dissolved Nutrients Nitrates, phosphates, and silicates Both of these greatly effect life in the oceans.
Salinity Measurement of amount of dissolved salts in seawater. Measured grams of salt per kilogram of water Average 3.5 % or.35 ppt Salinity map showing areas of high salinity in green, medium salinity in blue and low salinity in purple.
Variations in Salinity Subtropical Regions Rate of evaporation exceed precipitation Salinity is 37 ppt Equatorial Regions Precipitation is abundant Salinity is 34-35 ppt Polar regions Salinity is 32-33 ppt
Physical Properties of Seawater Seawater is denser than freshwater. Density varies depending on salinity and temperature. Cold water is denser than warm water. Variations in salinity cause the freezing point of seawater to be lower than fresh water.
Ocean Layering Temperature Profile Draw, label, explain and color figure 37.15 on page 675 Plot changing water temperature with depth The three layered ocean with the upper mixed layer (yellow), main thermocline (green), and deep (bottom) water (blue).
Ocean Layers Surface layer Warm and Sunlit layer Thermocline layer rapid decreasing temperature with depth. Bottom layer Cold and dark near freezing Theromocline and Surface layers are absent in polar seas
Important Phrases Repeat after me: Seawater is denser than freshwater. Cold water is denser than warm water.
Ocean currents Density current Differences in salinity and temperature cause this current to move slowly through deep ocean waters Surface currents Wind driven current that effects the upper few hundred meters of ocean Fast as 100 km per day See page 676 of book
Predictable Surface Currents Northern hemisphere Trade winds blow east to west therefore tropical ocean currents flow east to west Northern mid-latitudes Prevailing Westerlies and resulting ocean current travels west to east Northern Polar Regions Polar Easterly move polar currents east to west
Gyres Continents deflect ocean currents north and south this creates closed circular systems called gyres. Five main gyres North Pacific, North Atlantic, South Pacific, South Atlantic, and the Indian Ocean
When equatorial currents deflect off a continent the warm ocean current moves warm tropical waters toward the higher colder latitudes in polar regions. The warm water cools is deflected by landmasses and move back toward the equator.
How does the Coriolis effect gyres? Example- flushing toilet Northern hemisphere Gyres move clockwise Southern hemisphere Gyres move counter clock wise
Upwelling Ocean water moves vertically. Exist mainly on western coast of continents. Trade winds blow surface waters off shore and that water is replaced with upwelling deep water. These waters are rich in nutrients, which supports abundant populations of marine life.
An result of a upwelling is the richest fishing grounds due to abundant marine life. For example Peru and California
Review Sheet Define salinity. Explain how salinity varies in different areas and what effects salinity. What are the physical properties of seawater? What is a temperature profile? Describe the three different ocean layers. Fill in the blanks; Cold water is denser than _______water. Seawater is denser than ____________. What are the two most important phrases to learn? Differentiate between surface and density currents. Explain how Trade winds effect surface currents and what direction do each current travel. Clarify what are gyres. Why do currents just not travel east to west or west to east? Explain an upwelling and what are the results from an upwelling.