Download Lab 5: It`s All Connected: Global Circulation

It's All Connected: Global Circulation
The lab activity described here was adapted by Erin Bardar of TERC for the EarthLabs project.
Summary and Learning Objectives
Students are introduced to the global circulation patterns of the atmosphere and the oceans, and investigate how those circulation patterns
might influence their local region. Students use computer models to test predictions of ocean currents.
After completing this investigation, students should be able to:
trace pathways of wind and water on a world map to and from their region, and across an ocean to other parts of the Earth;
describe specifically how their region is connected as a system to others across the Earth by identifying what their wind and water
carry and where the wind and water go; and
write about what activities in their region might affect other regions, and what activities in other regions might affect theirs
Open the Student Lab »
Hurricane tracks are an indication of circulation patterns.
Activity Overview and Teaching Materials
In Part A: Students are introduced to the global circulation patterns of the atmosphere and the oceans, and investigate how those circulation
patterns might influence their local region.
In Part B: Students study surface ocean currents and then predict the pathway of a floating object dropped into the ocean at a particular
point, maybe one closest to their own region. Then, using a computer model of ocean currents, they test their predictions.
Printable Materials
To download one of the PDF or Word files below, right-click (control-click on a Mac) the link and choose "Save File As" or "Save Link
As."
Work Sheet 1: Black Outline Map of the World (Acrobat (PDF) 94kB Jan7 10)
World Map of Average Ocean Currents (Acrobat (PDF) 168kB Jan7 10)
World Map of Average Winds in January (Acrobat (PDF) 127kB Jan7 10)
World Map of Average Winds in July (Acrobat (PDF) 119kB Jan7 10)
Stop and Think Questions (PDF (Acrobat (PDF) 38kB Sep13 10) and Word (Microsoft Word 35kB Sep13 10))
For more information about circulation of the atmosphere and the oceans , read the section titled Background Information under
Additional Resources below.
Teaching Notes and Tips
In Part A: Students move back and forth between learning about global circulation patterns of air and water, and looking for connections
between the local area and those global circulations. Part of this work involves tracing the path of a local stream until it joins the global
ocean circulation. Resources that allow you to investigate the local-to-global connections are not provided in this Lab. You'll need to gather
those resources and explore the possibilities. What pathways do your local streams follow as they wind their way toward the ocean? (Or
might a local stream actually terminate at an endorheic body of water, which has no outflow, such as the Great Salt Lake?)
In Part B: The Ship Drift model is an engaging tool that makes the topic of ocean currents become very concrete and alive; it's interesting
and fun to use.
Here are some notes about using the model:
To see a map of ocean currents in a particular month, select the month in the drop-down menu and then click the PopUp Map button.
The map of ocean currents on the home page is interactive but it does not change when you change the month. The PopUp maps are
the maps that students use to make their predictions about the path along which ocean currents may carry an object during a
particular time of year. You can open multiple PopUp maps on your computer screen to compare ocean currents across the seasons.
To see the probable paths that a set of five drifters (buoyant objects that remain near the ocean surface) might follow over the course
of five years, select a month in the drop-down menu and click on the map of ocean currents on the home page. A new window will
open showing the probable paths of the 5 drifters. You can open multiple drifter path maps on your computer screen to see how
dropping a drifter in the same spot* can vary across the seasons.
* The latitude and longitude you select on the home page map may not be identical to the coordinates that appear at the bottom of the drifter
path map that opens, but they will be very close. The home page map displays latitude and longitude in 5 degree increments.
For more information about the Ship Drift model, visit Navigating the Ocean on NASA's Ocean Motion Web page.
Assessment
You can assess student understanding of topics addressed in this Investigation by grading their responses to the Stop and Think questions.
State and National Science Teaching Standards
Lab 5 activities have been correlated to Texas Essential Knowledge and Skills (TEKS) standards.
(1) Scientific processes. The student conducts laboratory and field investigations for at least 40% of instructional time using safe,
environmentally appropriate, and ethical practices. The student is expected to:
(A) demonstrate safe practices during laboratory and field investigations.
(2) Scientific processes. The student uses scientific methods during laboratory and field investigations. The student is expected to:
(E) demonstrate the use of course equipment, techniques, and procedures, including computers and web-based computer
applications;
(F) use a wide variety of additional course apparatuses, equipment, techniques, and procedures as appropriate such as
satellite imagery and other remote sensing data, Geographic Information Systems (GIS), Global Positioning System (GPS),
scientific probes, microscopes, telescopes, modern video and image libraries, weather stations, fossil and rock kits, bar
magnets, coiled springs, wave simulators, tectonic plate models, and planetary globes;
(G) organize, analyze, evaluate, make inferences, and predict trends from data;
(I) communicate valid conclusions supported by data using several formats such as technical reports, lab reports, labeled
drawings, graphic organizers, journals, presentations, and technical posters.
(3) Scientific processes. The student uses critical thinking, scientific reasoning, and problem solving to make informed decisions
within and outside the classroom. The student is expected to:
(A) in all fields of science, analyze, evaluate, and critique scientific explanations by using empirical evidence, logical
reasoning, and experimental and observational testing, including examining all sides of scientific evidence of those scientific
explanations, so as to encourage critical thinking by the student;
(B) communicate and apply scientific information extracted from various sources such as current events, news reports,
published journal articles, and marketing materials.
(11) Science Concepts. Solid Earth. The student knows that Earth's surface continuously changes over long and short time scales in
ways involving dynamic and complex interactions among Earth's subsystems. The student is expected to:
(A) compare the roles of erosion, deposition, and igneous activity by lava, water, wind, ice, and gravity in constantly
reshaping Earth's surface;
(C) describe and interpret Earth surface features using a variety of methods including satellite imagery, aerial photography,
topographic and geologic maps, and apply appropriate technologies such as Geographic Positioning Satellite (GPS)
receivers and Geographic Information Science (GIS) software.
(13) Science concepts. Fluid Earth. The student knows that the Fluid Earth is composed of the hydrosphere and atmosphere
subsystems that interact on various time scales with the biosphere and geosphere. The student is expected to:
(D) discuss mechanisms, such as atmospheric carbon dioxide concentration, major volcanic eruptions, changes in solar
luminance, giant meteorite impacts, and human activities that result in significant changes in Earth's climate.
(14) Science concepts. FluidEarth. The student knows that Earth's global ocean, powered by the Sun, is a major driving force for
weather and climate through complex atmospheric interactions. The student is expected to:
(C) explain how thermal energy transfer between the ocean and atmosphere drives surface currents, thermohaline currents,
and evaporation that influence climate.
(15) Fluid Earth. The student knows that interactions among Earth's five subsystems influence climate and resource availability,
which affect Earth's habitability. The student is expected to:
(A) describe how changing surface-ocean conditions, including El Niño-Southern Oscillation, affect global weather and
climate patterns.
Lab 5 activities have been correlated to the following National Science Education Standards.
Science as Inquiry (12ASI)
Abilities necessary to do scientific inquiry
12ASI1.3 Use technology and mathematics to improve investigations and communications. A variety of technologies, such
as hand tools, measuring instruments, and calculators, should be an integral component of scientific investigations. The use
of computers for the collection, analysis, and display of data is also a part of this standard. Mathematics plays an essential
role in all aspects of an inquiry. For example, measurement is used for posing questions, formulas are used for developing
explanations, and charts and graphs are used for communicating results.
12ASI1.6 Communicate and defend a scientific argument. Students in school science programs should develop the abilities
associated with accurate and effective communication. These include writing and following procedures, expressing
concepts, reviewing information, summarizing data, using language appropriately, developing diagrams and charts,
explaining statistical analysis, speaking clearly and logically, constructing a reasoned argument, and responding
appropriately to critical comments.
Physical Science (12BPS)
Interactions of energy and matter
12BPS6.1 Waves, including sound and seismic waves, waves on water, and light waves, have energy and can transfer
energy when they interact with matter.
Earth and Space Science (12DESS)
Energy in the earth system
12DESS1.3 Heating of earth's surface and atmosphere by the sun drives convection within the atmosphere and oceans,
producing winds and ocean currents.
12DESS1.4 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.
Additional Resources
Background Information
Atmospheric Circulation
The global circulation of air drives some of the Earth's ocean currents and helps to redistribute the solar energy that reaches Earth,
moderating climate and impacting environments for all life on Earth. Without that circulation and redistribution of solar energy, the
equatorial regions would be hotter and the polar regions colder.
What drives this atmospheric circulation? It's not simply solar energy; it's solar energy interacting with the rotating sphere that is our planet.
The differential heating that occurs when the sun heats a sphere (the earth) plays a significant role. Another factor is the Coriolis effect,
which results from the fact that the rotational speed of our spherical planet varies with latitude.
Differential Heating
Earth's solar energy is most concentrated in the region of the equator. This heating causes warm air to rise, which creates a general area of
low pressure at the equator. As the rising air cools and starts to fall back toward Earth it spreads into both the northern and southern
hemispheres (see figure) and returns to the surface of Earth at approximately 30 degrees north and south of the equator. That cooled air is
then drawn back towards the low-pressure area at the equator and repeats the circulation. This circulation creates what are known as the
Hadley Cells. (See figure.)
Something similar but opposite happens in the polar regions. The solar energy
falling on Earth's surface in the polar regions is spread over a much greater surface
area. The resulting colder air creates high-pressure areas at Earth's surface, with
cold air flowing away from the poles. As that air reaches lower latitudes it is
subject to more intense solar energy, warms, rises, and is drawn toward the lowpressure areas that are high above the poles. This circulation creates two additional
cells in the polar regions.
In between the Hadley and polar cells in each hemisphere is a third cell of air
circulation.
Coriolis Effect
What is the Coriolis Effect, and why does it occur? First think just about the solid
Earth. As the Earth rotates, a point on the equator moves in a large circle, and
travels more than 38,000 km during one full revolution, or in 24 hours. Its
rotational speed is approximately 1600 km/hr. During that same 24 hours, a point
close to one of the poles makes a much smaller circle in the course of one day, and
travels just a tiny fraction of the distance, so it's rotational speed is significantly
slower than a point on the equator. In fact, a point on Earth's equator rotates at a
greater speed than any point north or south of the equator.
This image gives a three dimensional view of the
global wind circulation patterns dues to unequal
heating at the equator and the poles.
If Earth did not rotate, air flowing from a higher latitude toward the equator would move directly south or north (depending on the
hemisphere). However, because of the rotation, air that flows toward the equator is moving from a latitude where its rotational speed is less
to a latitude where the rotational speed is more. As a result, that air rotates more slowly than the land below it, so it "falls behind" and it is
deflected toward the west (see figure below). This produces a wind at the equator that flows from east to west.
Likewise, air flowing away from the equator and towards a higher, more slowly rotating latitude will rotate more rapidly than the land below,
and will deflect towards the east to produce a west-to-east wind.
Study the figure above to draw the connections between the cells that result from differential heating of the Earth and the major patterns of
global atmospheric circulation that result from cell circulation and the Coriolis effect.
While the bands of circulating air cells and the Coriolis effect drive the general atmospheric circulation patterns, that circulation is also
influenced by local conditions and is much more complex than the simplified illustrations suggest.
This image below shows twenty years of cyclone paths in the Atlantic. Can you see evidence of the general atmospheric circulation patterns?
Cyclone paths in the Atlantic. Click image to enlarge.
Ocean Circulation
Read the National Oceanic and Atmospheric Administration's concise, well-illustrated resources that explain the driving forces behind ocean
circulation. Some of these are related to the winds described above; others have a very different driving mechanism (a combination of
temperature and salinity). The sections that address Surface Ocean Currents and The Global Conveyer Belt are just two of the topics covered
in the Currents section of this education Web site.
Work Sheet 1: Black Outline Map of the World
World Map of Average Ocean Currents Solid lines are warm currents and dashed lines are cold currents.
World Map of Average Winds in January
World Map of Average Winds in July
Earthlabs: Earth System Science – Lab 5
http://serc.carleton.edu/eslabs/climate/lab5.html
It’s All Connected: Global Circulation
PART A: Tracing Pathways
Stop and Think: Wind
1: What are the regions from which wind blows into your region? Write down real
geographic names (for example, write the name of a mountain chain, not just
"mountains").
2: What might the wind be bringing into your region? Think about the places the wind is
coming from, what happens there, what lives there. Think about dust, insects, tiny
seeds, smoke, air masses of cooler or warmer temperatures, and moisture. Be specific in
your responses.
3: When wind blows out of your region, what region does it blow into? Again, write
down real geographic names.
4: What might the wind be carrying out of your region? Is it the same as what it brought
in? Be as specific as you can about what is being carried, and where it goes.
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Earthlabs: Earth System Science – Lab 5
http://serc.carleton.edu/eslabs/climate/lab5.html
Stop and Think: Water
5: What are the regions from which water flows into your region? Write down
geographic names.
6: What might the water be bringing into your region? Be as specific as you can.
7: When water flows out of your region, what region does it flow into? Again, write down
geographic names.
8: What might the water be carrying out of your region? Be specific.
Page 2 of 3
Earthlabs: Earth System Science – Lab 5
http://serc.carleton.edu/eslabs/climate/lab5.html
PART B: Message in a Bottle
1: Imagine dropping a message in a bottle into the ocean at a given location and
observing where the object would end up as a result of surface currents. Based on the
pathways you traced in Part A, where do you think your bottle would end up?
2: How well does your prediction of where your message in a bottle would end up agree
with the computer model? Explain.
3: What events and activities in other parts of the globe could affect your region?
Describe events and activities that are caused by people (such as making dams) and
those caused by nature (such as volcanic eruptions).
4: What events and activities in your region could affect other parts of the globe?
5: Compare and contrast the paths of these drifters with those of drifters dropped into
the ocean near your study region.
6: Why do you think there are international laws for dumping waste/trash/chemicals in
the ocean, rather than just local laws? Do these laws only need to extend to nearby
neighboring countries? Explain.
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