Our Coasts and Climate

Transcription

1 GRADE: adaptable for all levels BY: Jill Rivero, MA Science Educator for the Wyland Foundation OBJECTIVE: Students will understand the difference between warm salty water near the ocean s surface and cold, less salty water in the ocean depths. Students will learn that when these two areas mix, a large, slow current is created, forming a thermohaline circulation. PURPOSE: To educate students on the different types of overturning in the oceans due to areas of different temperatures and salinities. VOCABULARY: ocean, density, salinity, ocean temperature (sea surface vs. deep), ocean circulation, thermohaline, ocean currents, overturning, heat flux, deep water renewal, convection TIME NEEDED: 1. 5 hours (30-45 minute class prep and background research; 45 minute lab) TEACHER PREP AND BACKGROUND RESEARCH: 1. Read the article, Melting Arctic sea ice could be disrupting the oceans circulation with major consequences on the following link: CLASS PREP AND BACKGROUND RESEARCH: 1. In a class setting or in small groups, have students view the animation at the following NASA link: 2. Ask students what they think this animation was showing? 3. Have students write their answers on a sticky note and post on a central spot in the classroom where Teacher can read off to class and discuss comments. (Allow time for students to ask questions, and to discuss possible misconceptions without correcting.) 4. Read the Introduction section below together as a class and pay particular attention to the vocab terms density, salinity, and temperature. View the NASA animation again, pausing if necessary to identify ocean current regions or to discuss any misconceptions from earlier. Now watch together as a class the video available on You Tube called Water Density -Cold vs Hot and Salt Water vs. Fresh Water : (allow time for student s reactions, as well as questions.)

2 5. At this time, read together as a class the section below called Background Information. Allow time afterwards for individual searches online or for showing video examples to the class of ocean currents. (See You Tube link below), Ocean Density Currents Demonstration 6. Finally, discuss as a class the power of ocean currents. Why are ocean currents so important to the world s climate? Break the class into small groups and have students converse about what they think would happen of the ocean currents changed in temperature, slowed down or stopped moving altogether. INTRODUCTION: Surface ocean currents are driven mostly by wind, except in Polar Regions where the colder surface water sinks due to evaporation near warmer sea ice (heat flux; due to reflection of sunlight) and to sea ice formation (sea ice is made from fresh water; the salt that is left over sinks). When the surface water becomes cold and dense enough with salt to sink, this forces deeper ocean water to move horizontally until it meets warmer waters in equatorial regions, mostly in the Pacific and Indian Oceans. These very large, slow currents are called a thermohaline circulation because they are formed through temperature and salinity (Haline) differences. The end result is major overturning of the oceans cold and warm water currents that help regulate and keep stable the world s major climate regions. Any disruption of these currents could contribute further to climactic changes. Let s take a look at some of the world s most important thermohaline circulations. Thermohaline Circulation #1: Atlantic Meridional Overturning Circulation LOCATION: North Atlantic Ocean around Greenland, Iceland, and the North Sea, FROM: South Atlantic via the Gulf Stream RETURNS: South Atlantic via the North Atlantic Deep Water current. CLIMATE RESULT: The continual influx of warm water into the North Atlantic polar ocean keeps the regions around Iceland and southern Greenland mostly free of sea ice year round. ANIMATION: To see an animation of this current, see the NASA link below: Thermohaline Circulation #2: LOCATION: Antarctic Circumpolar Current (Atlantic overturning circulation) FROM: Circumpolar motion from the Atlantic connects with the region around latitude 60 south from west to east around Antarctica (the only part of the Earth where the ocean can flow all the way around the world with no land in the way). RETURNS: Indian and Pacific Oceans and connects northward with the Atlantic flow. ANIMATION: To see an animation of this current, see the NASA link below:

3 BACKGROUND INFORMATION: *The Antarctic ice sheet that forms and melts over the ocean each year is nearly twice the size of the United States. *Combine the Antarctic and the Greenland Ice Sheet in the north and think about this: -If the Greenland Ice Sheet melted, scientists estimate that sea level would rise about 6 meters (20 feet). - If the Antarctic Ice Sheet melted, sea level would rise by about 60 meters (200 feet). *The Gulf Stream, together with its northern extension towards Europe, the North Atlantic Drift, is a powerful, warm, and swift Atlantic ocean current that originates at the tip of Florida, and follows the eastern coastlines of the United States and Newfoundland before crossing the Atlantic Ocean. *The Gulf Stream influences the climate of the east coast of North America from Florida to Newfoundland, and the west coast of Europe. *The Gulf Stream is also a significant potential source of renewable power generation.

4 NAME: Date: Period: LAB: MATERIALS: (Per group): ml Beakers, 2 Liters - Tap water, 20 grams - Salt, 10 ml - red and blue food coloring, ml Graduated Cylinder, Hot Plate and 10 Ice Cubes (for ice bath); mL or large Tupperware container or 1-10 Gallon Aquarium (students can take turns using) HYPOTHESIS: If we test two different water temperatures with the same salinity, then we predict that the hot water will (rise, sink, stay at the same level) and that the cold water will (rise, sink, stay at the same level). (Circle one answer per blank above) PROCEDURE: 1. Divide students into groups of 3 or Have students fill each 250 ml beaker with 100 ml of water, one hot and one cold. 3. Next, have students add 10 grams of salt to each beaker. 4 Have students count out and drop 5 ml of food coloring into their beakers, red for Hot, blue for Cold. 5. (*Optional) Have students time how long it takes for each beaker s color to diffuse universally throughout the water in the beaker. 6. Have students fill a Tupperware with 1000mL Room temperature tap water (or if you have access to a 10 Gallon Aquarium, have students fill with 5 gallons of water ¾ full and take turns in their groups). 7. Have students pour their Hot water into the right side of their Tupperware container. Record how long it takes for the color to finish moving (up or down, right or left). Record other observations below. 8. Have students pour their Cold water into the left side of their Tupperware container. Record how long it takes for the color to finish moving (up or down, right or left). Record other observations below. 9. Have students record the time it takes for a distinct third layer of color (oftentimes a purple layer develops) and record below:

5 DATA TABLE 1: HOT (blue) COLD (red) Time to finish moving: Observations: (Color moved up, down, left right) Time 3rd Layer forms: INTERPRETING DATA: HOT WATER: 1) How long did it take for the red-colored, hot water to stop moving? Did it move up or down, left or right? Why do you think it did this? 2) How do you think the water would react with more salt in it? Would this change your data in any way? Why or why not? COLD WATER: 3) How long did it take for the blue-colored, cold water to stop moving? Did it move up or down, left or right? Why do you think it did this? 4) How do you think the water would react with more salt in it? Would this change your data in any way? Why or why not? 3RD LAYER: 5) How long did it take for a third distinctly different colored layer to form? Why do you think this happened? 6) How do you think the water would react with more salt in it? Would this change the time it took to form? Why or why not?

6 ANALYSIS: WATER IS LIFE 7) What importance does salt play in the distribution of ocean currents? 8) What role does temperature play in the distribution of ocean currents? 9) What do you think would happen if one beaker contained more salt than the other, for instance, the Cold water? How would this impact the speed of the movement of this denser and colder ocean water current? -What do you think would happen if the Hot water beaker contained more salt than the other? How would this impact the speed of the movement of this denser and warmer ocean water current? VOCABULARY REVIEW: 10) What does the word overturning mean to you? What does this word have to do with today s Lab activity in terms of warm and cold ocean waters? 11) What does the word deep water renewal mean to you? 12) After performing this lab, is there such a phenomenon as cold, deep water current? Looking at the globe, where does the cold water come from and how does this deep water current begin? Where does the deep water travel to after forming? *BONUS QUESTION: 13) Melting sea ice happens every summer. However, some polar areas are experiencing longer and longer warmer periods, leading to more ice melting than can be reformed during the winter months that follow. 14) Why is melting sea ice a problem? 15) What continents and their climates are most affected by deep, cold water currents? 16) What solutions could human s come up with that would help control or limit global warming?

7 SUMMARY CONCLUSION: Please write a 3-5 sentence paragraph using at least 5 of the words from the word bank below. Try to describe what happened during this lab according to your data and what you learned from your data. WORD BANK: Oceania (a place), Global Warming, Greenhouse Gases, Sea-Level Rise, Ocean Warming, Glacial Melting, Carbon Cycle, Micronesia, Kiribati Islands (also known as Kiribati), Sea-wall, Erosion, Resettlement This lesson was developed with the generous support of our National Presenting Partner Toyota, and these sponsors: Fredrix, Toro, National Van Lines, Arts & Activities, Marco Fine Arts, and Michaels