Investigation 2 - Weather and Circulation Systems
| Class Time Required | 5 class periods |
| Materials Needed |
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| Teacher Preparation | 1-2 hours to read instructions and assemble materials, print and copy images for student notebooks |
| Prior Student Knowledge |
Students will need to have a basic knowledge that low pressure is usually indicative of stormy weather , and high pressure is usually indicative of fair weather. Prior knowledge of ocean currents and weather systems would be helpful. |
| Vocabulary | climate, current, hydrological, meteorological, pressure, semipermanent, Coriolis effect |
| Science GLEs Addressed |
6th grade GLEs: SA.1.1 7th grade GLEs: SA1.1, SD3.1, SE2.2 8th grade GLEs: SE2.2 |
Overview: In this 5-day investigation, students develop an understanding that the large ocean circulations affecting Alaska mimic major weather patterns. They begin by creating and observing wave and riffle patterns and motions of objects in a tub. They plot possible current patterns on their map and organize meteorological data to determine how well wind patterns match their predictions. After a lecture/discussion to learn more about currents and weather patterns, they role-play shipping captains who must consider wind and current patterns to find the quickest route from Seattle to Anchorage. They finish up with a discussion that takes them back to the question about the toys’ movements.
Focus Question:
What causes surface ocean currents?
Engagement: (50 minutes)
Students begin this discovery of ocean currents with the world maps from Investigation 1 that show the locations and dates of the spill where the rubber bath toys washed up. Briefly discuss the specifics of the spill again and focus on the idea that toys washed up not only in Alaska, but also in Maine, and Scotland. To generate curiosity and gauge prior knowledge, ask the students how they think the toys ended up on beaches so far apart.
Tell students that they are going to learn about one of the many causes of the toys’ movements. Start with a discussion of the setting of the spill and then lead into the activity below. Ask questions to engage students and focus on the purpose of this investigation:
- What causes the surface ocean currents? (primarily wind)
- What direction do you think the wind was blowing during the time of the spill?
- Do winds always blow the same direction in a particular place?
Help the students develop hands-on knowledge of water, wind, and currents. Using a tub of water, demonstrate that wind blowing over a body of water causes riffles and waves, and eventually objects floating in the water can be transported by wind blowing across water:
Set up a tub that is large enough for the whole class to gather around and observe. Fill it halfway with water, and begin by asking students to observe the tub. Is it calm? Why is it calm? Next, make riffles and waves in the water by blowing through a straw onto the water surface. Eventually multiple students can be blowing through straws in different locations in the tub to cause a current (a continuous, directed movement of water). Drops of food coloring can be used at certain times to better display how the water is moving. Notice the waves that appear on the surface. What happens when the wind hits an object floating in the water? Place a ping-pong ball or any other lightweight, high-profile floater in the tub and observe its movement. Also place a low-profile floater (partially filled water bottle or unopened Coke can) in the tub and blow on it.
Use the following discussion questions with the entire class, or ask students to respond to them in their science notebooks:
- Do the riffles/waves move across the water in a uniform direction or are they multidirectional as when a rock is thrown into water?
- Does the object move through the water at the same speed of the wind?
- Do the objects move in response to blowing on the surface?
- Which object (high/low profile floater) moves more? Why? Apply student knowledge of sailboat masts (capture as much wind as possible) and sleek race boats (low drag).
- What might this say about winds causing ocean currents? We now know wind causes objects to move in the water; does the water itself move in response to wind?
- Help students define ocean currents as moving rivers of water in the oceans.
Exploration: (50 - 90 minutes)
This exploration will guide the students in discovering the weather and current patterns in the Gulf of Alaska. Ask students to lay a piece of tracing paper or an overhead transparency over their maps from Investigation 1, or use a pencil to write lightly on their original map. Ask them to draw possible ocean currents, using arrows, to help explain how the toys made landfall where they did (Alaska, Hawaii, Maine, and Scotland). Keep in mind that this is being done without any prior knowledge about currents. The current showing the Alaska landfall location should be fairly straightforward (an arrow from the spill site to the landfall location in Southeast Alaska), but the students should use some creative thinking in coming up with ocean currents responsible for the Scotland and Maine landfalls. The Think/Share/Pair technique is a useful method for this exercise.
Use data from the NOAA National Data Buoy Center to explore the current wind conditions in the Gulf of Alaska. The array of buoys deployed in the gulf and all nearshore waters of the United States are stationary and record a whole litany of meteorological and hydrological data. If the class does not have access to the Internet, distribute the Wind Data Table. If the class does have access to the Internet, use the NOAA National Data Buoy Center. Encourage the students to make their own data table to organize the information, thinking about what data to record and how to organize the data. An example of a blank data table is provided as one example of how students can set up their data collection table in their science notebooks if they’re using real-time data from the Internet.
Be sure that you clarify that when meteorologists say wind direction they are specifying that the wind is from the direction they specify—so when a meteorologist says a south wind—they mean a wind from the south to the north. Oceanographers will typically say a wind from the south (meaning a wind blowing from the south to the north).
Using the completed table, ask students to plot the location of the buoys in the Gulf of Alaska with the wind directions on their maps or map overlays.
Does the wind direction match well with the currents the students drew?
Do the current wind directions jibe well with the wind directions that would be necessary to transport objects to Alaska? Maine? Scotland?
Discuss the idea that the winds on any given day around the world may not match the average wind direction of that area. Generate student ideas about how the average wind direction might be determined. Show the class the Wind Driven Surface Currents map, representing the “long term average pattern” of surface currents around the world. Students can then compare their hypothetical currents drawn at the beginning of the exploration with the actual flow.
At this point, it should start becoming clear that the surface ocean currents are largely a product of the wind/weather patterns of the lower atmosphere. At the same time, students will start to realize that there are traditional weather regimes with an average wind direction but that winds can always shift.
Ask students why the current might move in a different direction than the wind is blowing or pushing it. An important factor in ocean surface currents is the Coriolis effect. The Earth's rotation causes circulating air to deflect. In the Northern hemisphere, the air deflects to the right, and in the Southern hemisphere, it deflects to the left.
To help increase student awareness of this concept, share one or more of the following:
NOAA Surface Ocean Currents Tutorial
Short video of a merry-go-round illustrating the Coriolis effect
Earth Education Online animation and explanation of Coriolis effect
Explanation: (1 hour)
Share and discuss the following with students: When we compare maps of wind and ocean currents on a global scale, we see that they share many of the same features. Show the animated global surface currents map to the students. Note the locations of the warm and cool currents. Next, move the cursor over the map to show the direction of global winds along with the currents. Ask students to try to find the areas where gyres might form in both the wind and the water in each of the world's large ocean basins. The similarity arises from the fact that the wind is the fundamental driver of surface ocean currents. Ask them to compare the wind patterns to the ocean circulations. Are they roughly the same? This should be further evidence that winds help cause the surface currents. Alaska is situated at the crossroads of many weather systems that traverse the subpolar and polar regions. It is for this reason that the storm track across Alaska tends to be quite active, especially in the spring and fall when warm air masses from the south mix with cold air down off the north pole.
Where do the winds come from and are they always blowing in the same directions? "Semipermanent" seasonal weather patterns exist on the earth; Alaska is affected by these semipermanent systems as well.
Share the image that depicts the average winds over a 1-year period from 2007 to 2008 for the world. Once again it can be seen in the surface wind image how the winds have a tendency to blow in a certain direction on a large-scale basis around the world.
Alaska is characterized by "semipermanent" patterns of high and low pressure. (Pressure is the variable by which weather patterns are characterized, either high or low, and is defined roughly as the weight of the atmosphere above a certain location). These patterns are semipermanent because they appear in charts of long-term average surface pressure. Because of the earth’s spin, the orientation of oceans and landmasses, and the tilt of the earth certain weather regimes are often found in certain places. They can be considered to largely represent the most common location of high and low systems. However, this does not imply that these weather features are always there; rather, they are the average weather systems and thus drive the currents.
Show the image of average pressure systems and their locations around the world. The green areas show areas of higher pressure. In the Northern Hemisphere winds circulate clockwise around high pressure systems and counterclockwise around low pressure systems. Specifically around Alaska, a semipermanent Gulf of Alaska Low is found centered over the Gulf of Alaska and the Aleutian Low is centered in the Bering Sea. The North Pacific Subtropical Gyre acts to enhance the Gulf of Alaska gyre. The trade winds and the westerlies are responsible for maintaining the position and strength of the North Pacific Subtropical Gyre. This gyre is believed to have been in existence for millennia.
The North Pacific high pressure system is the region of high sea-level pressure that occurs over the eastern North Pacific Ocean in the climatological mean (climate is defined as the average weather of a location). This region of high pressure shifts north during the summer and south during the winter and is largely a result of the large-scale subsidence that occurs over the subtropical regions of the world.
Aleutian Low: This semipermanent low pressure center is located near the Aleutian Islands. Most intense in winter, the Aleutian Low is characterized by many strong cyclones. Traveling cyclones formed in the subpolar latitudes in the North Pacific usually slow down and reach maximum intensity in the area of the Aleutian Low.
The crux of this lesson is to depict how the weather/winds drive surface currents through an example in our own Alaska backyard.
Have students revisit their ocean circulation arrows, modifying their existing arrows to show the surface currents or drawing new current arrows that match the wind circulations around the semipermanent weather systems.
Prompt the students with the following question:
Do you have arrows on your map that could logically transport the toys to Alaska, Maine, and Scotland?
Elaboration (1 hour)
This next activity expands on the idea that winds cause the surface currents and starts to challenge and extend the students’ conceptual understanding. Until this point students know that weather systems with defined wind patterns create the surface ocean currents. This activity adds a level of complexity with transient weather systems producing winds in opposition to the “normal” currents that the students have already discovered. Students will be asked to test their knowledge and understanding of what creates the currents.
Divide the students into pairs or groups. They will role-play the captains of a cargo ship about to leave from Seattle, Washington, headed to the port of Anchorage, Alaska.
Background:
More than 98% of cargo shipped to and from the United States is transported by water. Students should realize that despite the prevalence of air travel and advances in aerospace technology, the earth’s oceans are still vital to freight transportation, energy production, and recreation (NOAA 2008). The port of Anchorage is the most active port in Alaska through which more than 95% of all cargo entering and leaving Alaska passes, acting as a distribution center of goods to the rest of Alaska. It serves 80% of Alaska’s population and 90% of the consumer goods entering Alaska.
The scenario:
- The goal is get to the port of Anchorage as quickly as possible; each captain is paid by how quickly they get their cargo to the port of Anchorage.
- There are currently two weather systems impacting the route, a high pressure system over the Gulf of Alaska, and a low pressure system over Bristol Bay.
Assignment: Develop the quickest route to Anchorage.
Distribute the map to have students plot their ship’s course.
Things to keep in mind:
- Students should assume that a straight line is the quickest path (disregard rhumb lines and the Great Circle methods) to get between two points with still water.
- Students should use their knowledge of the average circulation in the Gulf of Alaska (students should use their maps in their science notebooks) in this exercise.
- Students might consider how the “normal” current might be affected with the storm.
- Seattle, Washington, and Anchorage, Alaska, are 2,327 kilometers apart.
The following feedback can be offered to the students and proposed as questions to answer in their science notebooks:
Most students will direct their ship between the low and the high pressure systems where there is a direct current north into Anchorage. Probe the students to see if they understand that this route is directly opposed to the “normal” current that the Gulf of Alaska gyre produces.
Possible discussion/analysis questions could revolve around:
How much can a single weather system affect the Gulf of Alaska gyre?
How long would the weather system have to be there to direct the water against the normal current?
Which side of Kodiak Island might be quicker?
How do the magnitudes of the winds associated with the weather systems compare to the speeds of the current in the gyre?
Based on the students’ reasons for their proposed ship route, do they think it would take longer to complete the northbound trip or the southbound trip?
There isn’t necessarily a right or wrong answer to this scenario. Evaluation of this exercise hinges on the extent to which the students can justify their route.
Extensions
Local Expert. Bring science into your classroom by inviting a local meteorologist to talk to the students about their job of forecasting, weather patterns in Alaska, and how they use technology to do their job. In Alaska there are National Weather Service offices with meteorologists in Anchorage, Fairbanks, Juneau, Annette, Barrow, Bethel, Cold Bay, King Salmon, Kodiak, Kotzebue, McGrath, Nome, St. Paul, Valdez, and Yakutat. If a visit is not possible, it might be possible to bring the scientist into your classroom with Skype software. Skype allows you to “call” another person computer-to-computer and have a conversation replete with audio and video free over the Internet. It is available as a free download on the Internet and is used to network with anyone else who also has Skype free of charge.
Quikscat Images. A possible sidebar activity with a foray into technology would be to explore QUIKSCAT data, showing current satellite-derived ocean surface winds. QUIKSCAT images are derived from an instrument called a scatterometer, mounted on polar orbiting satellites that calculate wind speed and directions based on ocean surface roughness algorithms. You can use an archived image if you don’t have Internet access.
Do the winds from the QuikScat image match well with the ocean currents the students sketched in their science notebooks? If so, why? If not, why not?
Coriolis Effect. Examine the Coriolis Effect, which is responsible for the “spin” of a weather system. You might also want to use a lesson plan for a hands-on activity.
Evaluation
Evaluation takes the form of a classroom discussion that immediately follows the ship route exercise above, allowing formative assessment of student knowledge and understanding about how weather determines surface currents.
A Socratic Seminar format would be well suited to this discussion. The questions don’t necessarily have right or wrong answers but rather encourage divergent solutions with logical arguments.
The following questions can guide the seminar/discussion and lead into the investigations that follow:
Based on all knowledge and understandings to date of weather systems and their effects on surface ocean currents, why and how did many of the toys wash ashore in Southeast Alaska?
If the toys all spilled in the same location, how did some of the toys wash up thousands of ocean miles away from other toys?
What further information would you like to know about the spill and time period following the spill, to better ascertain the route the toys took through the Gulf of Alaska and beyond?
Possible Answers:
The weather on the day of the spill and the weeks and months following it.
Gulf of Alaska buoy data during the time the toys were afloat.
How fast do the toys move in response to a given wind speed?
Teacher Preparation
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Tips from Teachers |
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No tips are currently available. |
Read all of the materials and background information, gather materials and practice simulating wind in the tub, make copies of handouts, print and copy images for student notebooks, and work through the shipping exercise that students will be doing. Make sure the links to the animations and maps work, and if possible, download them so they will be easily accessible.
Curricular Connections
This investigation provides many connections to math, especially calculations of distance, time, and speed.
A Language Arts connection is provided through communication in class, especially the Socratic Seminar.Ideas for adapting to different local environment or context:
Relate the discussion of currents and how wind blows across the water to any local water body with which the students are familiar: a river or lake close to the community, a nearby bay, etc.
| Student Handouts |
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| Items for Group Displa |
Images: buoy, Gulf of Alaska gyre image, Weather systems, Average winds, Average pressure systems, North Pacific Subtropical Gyre |
| Material Items |
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| Facility/Equipment Requirements |
Internet access for student pairs or groups is desirable but not mandatory |
Alaska Science Standards and Grade Level Expectations Addressed:
6th Grade:
The student demonstrates an understanding of the processes of science by
SA1.1 asking questions, predicting, observing, describing, measuring, classifying, making generalizations, inferring, and communicating.*
7th Grade:
The student demonstrates an understanding of the processes of science by
SA1.1 asking questions, predicting, observing, describing, measuring, classifying, making generalizations, inferring, and communicating.*
The student demonstrates an understanding of cycles influenced by energy from the sun and by the earth’s position and motion in our solar system by
SD3.1 describing the weather using accepted meteorological terms (e.g., pressure systems, fonts, precipitation).
The student demonstrates an understanding that solving problems involves different ways of thinking by
SE2.2 comparing the student’s work to the work of peers in order to identify multiple paths that can be used to investigate a question or problem.* (L)
8th Grade:
The student demonstrates an understanding of the processes of science by
SA1.1 asking questions, predicting, observing, describing, measuring, classifying, making generalizations, inferring, and communicating.*
The student demonstrates an understanding that solving problems involves different ways of thinking by
SE2.2 comparing the student’s work to the work of peers in order to identify multiple paths that can be used to investigate and evaluate potential solutions to a question or problem. (L)
Essential Questions:
Enduring Understandings:
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