Earth/Environmental Science Oceanography

Transcription

1 Earth/Environmental Science Oceanography Name Part I. Modeling Deep Ocean Currents LAB: Ocean Circulation and Climate DIRECTIONS DO NOT RINSE the container between solutions! A. Effect of Temperature 1. Fill a shoebox about halfway with tap water and tilt the box so that no more than a thin layer of water covers the elevated end of the box. 2. Use a funnel so that the bottom of the funnel is just above (or in) the level of the water at the elevated end in the box.(see picture below) Funnel Earth Science Textbook Water 3. Obtain BLUE water and pour 25ml of blue ice water into a beaker. DO NOT POUR YET! Make a prediction about what will happen when you pour the cold blue water through the funnel into the box. 4. Pour the cold blue water into the funnel slowly and describe your observations. 5. Obtain RED water and pour 25ml of red hot water into a beaker. DO NOT POUR YET! Make a prediction about what will happen when you pour the hot red water through the funnel into the box. 6. Pour the hot red water into the funnel slowly and describe your observations. Water Density Page 1

2 B. Effect of Salinity 1. Pour 25ml of room temperature YELLOW water which contains SALT into a beaker. DO NOT POUR YET! Make a prediction about what will happen when you pour the yellow salt water through the funnel into the box. 2. Pour the room temperature saline water into the funnel slowly and describe your observations. 3. Pour 25ml of ice cold GREEN water which contains SALT into a beaker. DO NOT POUR YET! Make a prediction about what will happen when you pour the yellow salt water through the funnel into the box. 4. Pour the ice cold saline water into the funnel slowly and describe your observations. Use colored pencils to fill in the diagram of your completed experiment below, showing the relative positions of each of the colored solutions used in the lab. Earth Science Textbook Questions 1. What is density? 2. Which has a higher density, salty water or fresh water? Water Density Page 2

3 3. Which has a higher density, cold water or warm water? 4. How would an increase in evaporation affect the density of ocean water? 5. Which would contain more water molecules? EXPLAIN your answers! A beaker containing 100 ml of hot water A beaker containing 100 ml of cold water 6. When seawater freezes in Polar Regions, most of the salt is left behind. How does this affect the density of the water that is left unfrozen? Part II. Oceans and Climate: How Could Warming Cause Cooling? Refer to the attached article to answer the questions below. 1. What is the Great Ocean Conveyor Belt and what drives it? Explain how the Conveyor Belt works. 2. What keeps Europe's winters relatively mild? Water Density Page 3

4 3. Where on Earth is the coldest and saltiest water found? 4. How long does dense water remain on the ocean floor? 5. How might global warming shut down the Conveyor? 6. How could the collapse of the Great Ocean Conveyor Belt due to global warming lead to cooler temperatures in Europe? The Great Ocean Conveyor Belt Source: El Niño has strong effects on weather and climate measured on a scale of months. But broad circulation patterns in the world's oceans also control climate patterns on a scale of decades to centuries. In fact, Europeans may owe their very existence to heat transported to the North Atlantic by a global system of currents known as the Great Ocean Conveyor Belt. Water Density Page 4

5 Unlike most ocean currents, which are driven by surface winds, the flow of the Conveyor Belt is driven by differences in the temperature and salinity of seawater. Cold, salty water sinks; warm, less salty water stays on the surface. This sets up a system of interconnected deep and shallow currents that transport heat from the tropics to higher latitudes. The Gulf Stream, for instance, is part of the Conveyor Belt. It helps to ferry heat to the North Atlantic that keeps Europe's winters relatively mild. Without the Conveyor Belt, the city of Dublin would have an Arctic climate and much of the rest of Europe would be too frigid for trees to grow. The Conveyor Belt begins in the North Atlantic. There the water grows colder and saltier and sinks. This feeds a sluggish mass called the North Atlantic Deep Water. With a flow 20 times that of all the world's rivers combined, the deep water flows southward over the ocean floor. The flow is vast, but not swift: Once deep water forms, it may not touch the open air again for 1000 years. The flow surfaces again around Antarctica, where it is chilled again. Ultimately, it surfaces in the Indian and Pacific Oceans and then flows back north into the South Atlantic and eventually into the North Atlantic. The heat it carries warms the frigid, eastward moving air masses from Canada, Greenland, and Iceland. This flow of oceanwarmed air helps keep the winter climate of Europe balmier than at equivalent latitudes in North America. The Great Conveyor Crash? Some scientists are concerned that polar ice will melt, with potentially disastrous effects across the globe. The Great Ocean Conveyor Belt is mighty, but it is not invincible. Some scientists believe that it may be vulnerable to the effects of global climate change, whether natural or manmade. Computer simulations suggest that if the North Atlantic warmed just slightly, or were diluted by freshwater from increased rainfall or melting continental glaciers, the formation of deep water might decrease enough to shut down the conveyor. Both effects -- warming or dilution -- are possible consequences of global warming. Global average temperatures are now on the rise. Scientists are still struggling to figure out how much of the rise is natural -- part of the ceaseless cycles of climate on Earth -- and how much is the result of the burning of fossil fuels and other human activities. Either way, scientists are closely watching the polar regions for signs of trouble. The trouble could show up as a decline in the amount of sea ice in the Arctic or crumbling ice sheets in the Antarctic -- both could prove to be the early warning signs of harmful global warming, like the proverbial canary in a coal mine. -- By Daniel Pendick Water Density Page 5