Abstract
Students will investigate the motion of water currents by mapping the possible movement of messages cast into the ocean in bottles. This lesson assumes that students have been introduced to Cartesian coordinates prior to this lesson, but it does include a review. This review is taken from a math lesson called “Where are We”, which can be found at: http://pulse.pharmacy.arizona.edu/math/where_arewe.html.

Purpose - Engagement of students in the study of water currents.

Objectives
Students will be able to:
1. Accurately plot the appearance of bottles on a world map.
2. Illustrate the flow of an ocean current based upon above plots.
3. Orally propose an explanation for forces driving the currents

National Science Education Standard:
CONTENT STANDARD D: Earth and Space Science
ENERGY IN THE EARTH SYSTEM

• Earth systems have internal and external sources of energy, both of which create heat. The sun is the major external source of energy. Two primary sources of internal energy are the decay of radioactive isotopes and the gravitational energy from the earth’s original formation.

• Heating of earth’s surface and atmosphere by the sun drives convection within the atmosphere and oceans, producing winds and ocean currents.

• Global climate is determined by energy transfer from the sun at and near the earth’s surface. This energy transfer is influenced by dynamic processes such as cloud cover and the earth’s rotation, and static conditions such as the position of mountain ranges and oceans.

GEOCHEMICAL CYCLES

• Movement of matter between reservoirs is driven by the earth’s internal and external sources of energy. These movements are often accompanied by a change in the physical and chemical properties of the matter. Carbon, for example, occurs in carbonate rocks such as limestone, in the atmosphere as carbon dioxide gas, in water as dissolved carbon dioxide, and in all organisms as complex molecules that control the chemistry of life.

Teacher Background
The Equatorial currents (North, South and Counter currents) flow 3 - 6 km each day. The western boundary currents that flow from the equator to the high latitudes are warm water currents that extend 100 – 200 meters below the ocean surface. They move 40 - 120 km each day and extend up to 1000 meters below the ocean surface. Eastern boundary currents flow from the high latitudes towards the equator and are cold-water currents. They are broad shallow currents that flow 3 – 7 km per day. The remaining currents in North and South America move water from warm to cold currents and vice versa. Because there is no landmass to interfere, the Antarctic Circumpolar Current flows steadily along Antarctica and returns little water to the equator.


Related and Resource Websites
Ocean World - Currents
http://oceanworld.tamu.edu/students/currents/index.html
Surface and Subsurface Ocean Currents
http://www.physicalgeography.net/fundamentals/8q.html

.

Activity
Part One
1. If you have access to a television and VCR, begin by showing the class an excerpt from the film Message in a Bottle. (Show the part where the reporter is looking at a map showing all the sightings of the sailor’s bottled letters to his wife.) Where else have they heard of messages being sent in bottles? Do they think it is a reliable way to communicate? [If you do not have access to the above, ask students to tell you stories they have heard of where sailors are stuck on deserted islands. According to the stories what do those sailors almost always do? Why? Do they think it is a reliable way to communicate?]

2. Tell students that today they will be responsible for finding a different lost sailor using messages in bottles. Each group will be given a series of locations where the bottles were found either on a shore, or in the ocean by other vessels. Their task is to plot those locations on a map to see if they can use that data to determine where the sailor was when he or she threw the bottle into the ocean. Review with students the use of Cartesian coordinates to plot locations. Explain to the students that many world maps are laid out on a similar rectangular grid. Pass out the Mercator Projection maps. (This map can be found at http://alabamamaps.ua.edu/world/world/world2.pdf) Explain that Mercator Projection is different because the grid is rectangular and this causes distortion in the size of the countries as you move closer to the poles.

3. Have the students find and darken the lines representing the equator and Prime Meridian on the map. Tell the students that the point of intersection of these two lines is the origin from which coordinates are calculated. The darkened lines also divide the projection into four quadrants, which are labeled quadrants I, II, III, and IV in their standard positions as if on a coordinate plane. Ask the students to tell you the quadrant the following coordinates are in:

4. Tell the students that the quadrants also allow us to use positive and negative Cartesian coordinates to find locations. Ask them, “Looking at the map, which coordinates would you expect to be positive?” Which would be negative? (North latitudes and East longitudes would be positive while South latitudes and West longitudes would be negative). Discuss the importance of which direction comes first in the coordinate pairs. (Degrees of latitude come first and then degrees of longitude, which are backwards from the normal ways of plotting points as the first number gives the vertical location and the second number gives you the horizontal location). Ask the students the range of numbers valid for each coordinate. (Degrees of latitude can vary from and degrees of longitude can vary from ) Ask the students to tell you the quadrant the following coordinates are in:
i.

5. Distribute world maps and bottle locations. Allow students 15-20 minutes to plot their points and determine the direction of the current that took the bottles. Once students have finished, have them use an overhead transparency to prepare a summary of their findings for the class. Inform students that a blank overhead of the world will be available for their presentation. (If you have limited funds the overhead can be left blank and the students can write on their own overhead; if it is feasible, make sufficient copies of the map so that each group can have their own copy.)

Part Two
4. Have groups share the locations of the found bottles with the class and what they believe to be the correct location of the lost sailor. Invite other groups to question the findings or suggest possibilities the others might have overlooked. Emphasize constructive criticism to the students.

5. As students are listening to presentations, they should be sketching what they believe to be the overall picture of global ocean currents in their laboratory notebooks.

Closure
What are the similarities and what are the differences? How else might we work to determine the way the oceans move and why? What characteristics of ocean water might affect its currents?

Embedded Assessment
Students’ use of Cartesian coordinates to plot accurately can be assessed during the group practice of Cartesian coordinates and through the map that they triangulate the origin of the sailor’s bottled message. During the group presentation students’ ability to use plot data to identify which ocean currents carried the bottles can be assessed. Further are all students participating? Can they hypothesize a plausible reason why the ocean moved the bottles where they did?

The Community Outreach and Education Program is part of the Southwest Environmental Health Sciences Center: an NIEHS Award

Supported by NIEHS grant # ES06694