Ocean Color: Currents and Productivity

Transcription

1 Ocean Color: Currents and Productivity Name This assignment is worth 20 points! Your textbook describes the basic properties of light and its interaction with water and the oceans (p ). What is not discussed is how light provides one of the basic tools for studying many ocean processes, including biological productivity and ocean circulation. Information gained in the following assignment therefore crosses over into many of the topics that will be covered in the class throughout the rest of the semester. Light and the Color of Water Click on the Light and the Color of Water link above. Read the information and do the experiment to answer the following questions: 1. In the color spectrum, red is considered a wavelength; blue and violet are considered short wavelengths. 2. Two processes responsible for rapidly weakening light penetration in the ocean are scattering and absorption. Describe how each process affects light in seawater. 3. Test Your Understanding. Write down the correct multiple-choice answer. Ocean Color: Overview 1. What determines the color of the ocean? 2. Describe ocean color data. What is the major type of information that can be derived from ocean color data? Classic CZCS Scenes The Coastal Zone Color Scanner (CZCS), an instrument carried on the NIMBUS-7 satellite, produced images of surface ocean color. These images allowed scientists to, for the first time, see details of the ocean over large areas. Today, other instruments have replaced the CZCS, however, its initial Classic Scenes have been integrated into a tutorial to help the public understand how measurements of ocean color can be used.

2 Note: You can return to this page to navigate to Chapters for this assignment. Also note the map at the bottom of the page to see the locations of images. Chapter 1: Tasmania. 1. Look at the image. Read the entire description. Why are the currents in this region so complex? 2. What types of measurements were made by the CZCS? What do they indicate? 3. What are phytoplankton? How does their presence affect the light being absorbed? 4. What is a "false color" image? 5. For this image of Tasmania reds and yellows indicate phytoplankton productivity; blues and purples indicate phytoplankton productivity. 6. Which coastal area of Tasmania has the lowest productivity? (circle) north / south / east / west 7. Explain why traditional (shipboard) methods of surveying these waters would result in an inaccurate map of productivity. Chapter 2: Southwest Africa--The Benguela Upwelling Zone. 1. On the blank map (last page), use a colored pencil to shade in the area depicted in this image and label it. See the image on page 378 in your text for a bigger view. 2. Explain why coastal areas usually have higher productivity than the open ocean.

3 3. Explain how the deeper waters of the ocean become enriched in nutrients. 4. What did Ekman discover about the movement of surface water in response to the wind? 5. Scroll down find a link to an animation of the Benguela upwelling system. Draw a sketch of the Benguela upwelling system. 6. On your map, draw one arrow representing the typical wind direction (label it W) and one arrow representing the actual movement of the surface water (label it E). See the image on page 378 in your text for a bigger view. Chapter 4: The Arabian Sea See Fig on page 214 and Fig on page 215 for reference. 1. Describe the change in direction of the monsoon winds in this region. 2. Compare the two CZCS images. Which image (months of year) indicates the highest productivity? Explain the wind dynamics that produce this pattern. 3. On your map, use a colored pencil to shade in the area of high productivity in the Arabian Sea. Use another pencil to draw one arrow representing the typical monsoon wind direction (label it W) that produces this condition. 4. Use both images to compare the productivity levels in the Red Sea and Persian Gulf. Which has overall higher productivity?

4 Chapter 6: The Gulf Stream (Western Boundary Current) 1. Check out Fig.7.17 on page 213 of your textbook. a. The Gulf Stream Current is shown as (what colors?) due to its temperatures. This water from Tropical regions. b. North of Cape Hatteras the temperature of the water along the coast is as indicated by (what color?) on the image. This water comes from the North Atlantic. 2. The Gulf Stream marks the dividing line between warm, low-productivity waters to the south and colder, more productive waters near the North American continental shelf. How is the Gulf Stream recognized on the CZCS image (what color is it...careful here!)? 3. Explain why the Gulf Stream is shown differently from the textbook image referred to above. Chapter 7: Gulf Stream Rings 1. The image shows a distinct "warm core" ring. a. How does a warm core ring form? b. Describe the apparent productivity in warm core rings. Explain. 2. Eddies are km in diameter and they extend to considerable depths. They should be visualized as rather than surface features. Chapter 9: The Agulhas Retroflection 1. The Agulhas Retroflection is formed because the Agulhas Current runs into the eastward flow of the and the northeastward flow of the. 2. On your map, use arrows to draw the position and direction of the currents involved in the "Agulhas Retroflection." Label the arrows (BC, ACC, and AC). (Hint: you may want to look at the diagram of worldwide ocean currents on page 198 in your text.)

5 3. What is the result of this "collision of currents?" 4. The image shows that the interaction of the currents with the plateau creates immense undulations in the current that are evident almost km east of the Retroflection. What simple experiment could you do to produce this effect? 5. Why is this area "familiar to the captains and crews of ships?"