Teachers
Active Inquiry Questions

Key Concept
How do we understand the dynamics of the atmosphere and the ocean? Though the earth is a water planet, there are still many unanswered questions concerning the characteristics of the ocean and its relationship to the atmosphere.

In order to more fully understand the formation of storms, scientists study the role of the Gulf Stream in the surface circulation of heat energy. Through the use of satellite imagry, they are able to examine the relationship between air, sea, and land and can form a more integrated picture of our planet.

Synopsis
Students will use satellite composite maps of sea surface temperature and altimetry measurements to locate the outstanding features of the Gulf Stream. They will monitor the formation and migration of cold core and warm core rings (eddys) that develop off the Gulf Stream. They will also study the correlation between sea surface temperatures, sea surface height, and the location of mesoscale eddys can be studied in relation to the track of tropical storms.

Background Scenario
Historically, scientists have studied the Gulf Stream as a pathway from the tropics to the northern latitudes. As part of the global, wind-driven circulation model, the Gulf Stream is of particular interest because of its role in heat transport to the North Atlantic. As the Gulf Stream meanders, mesoscale eddys that are 50 - 200 km in diameter develop and become separated as distinct water masses. These parcels of water with their special characteristics are part of the dynamics of the North Atlantic gyre. While eddys off the Southeast coast of the United States and in the Gulf of Mexico influence local weather and major storm development, other surface current eddys around the world also affect climate conditions. An understanding of this complex air/sea relationship helps oceanographers and climatologists more accurately forecast changes and patterns in the global weather and the development of tropical storms.

See Background Scenario page for more specific content.

Goals
In the Gulf Stream Lesson, students will:

  • Monitor changes in North Atlantic temperature using SST satellite images
  • Learn how to read satellite-derived map of Sea Surface Heights (SSH)
  • Determine position of eddies using SST and SSH images
  • Analyze case studies of warm core ring interactions during the formation of a hurricane
  • Investigate the relationship of eddys to the development of Atlantic coastal storms and other coastal events

Science Process Skills
Observing, documenting, analyzing, comparing, interpreting, predicting and communicating

Concept Connections
heat transport, physical and chemical properties of water, ocean topography, velocity, global wind patterns

Vocabulary
Anticyclone, anomaly, altimetry, eddy (warm core rings or cold core rings), Coriolis Effect, cyclone, cyclonogenesis, geostrophic flow, geoid, gyre, hurricane, mean sea level, meander, North wall, Sargasso Sea, Western Boundary current, western intensification

Materials
Computer and internet access
Color Printer
Overhead projector for reinforcement transparencies
Optional - GIS ArcVoyager software
Background Powerpoint

Grade Level: grades 9-12

Key Question
How do we understand the dynamics of the atmosphere and the ocean?

Teacher Preparation
Begin the lesson by asking the Key Question. The students’ answers will help you become familiar with their knowledge of the gulf stream. The PowerPoint presentation is provided to give the students the necessary background information to complete this lesson.

Begin the inquiry by generating student questions relating to the gulf stream and sea surface temperatures data provided in the PowerPoint presentation.  As the students generate questions, record those questions on the board.

Once the students have all the necessary background information, you may begin asking them the "Active Inquiry Questions". Guide the students with this series of questions, provided on the student page, to get them started on the inquiry part of the lesson. These questions are designed to guide your students through their study of the gulf stream data. Their inquiries and subsequent findings will lead them to more complex questions that they can record for further investigation. Your goal is to help the students generate questions that can later be used in a hypothesis for research. Also available is a Guidelines for a Good Research Question link. This link will help students become familiar with the process of creating a good scientific question that can be answered using the data provided by the NOAA/NESDIS website.

Once the students have generated enough questions, split them up into groups of three or four. Each group is assigned a different question to investigate. Lead each group through the Researching a Hypothesis link to help guide them in researching a hypothesis. It should take a 90-minute class period to provide background, generate questions, look at data, assign groups, and go over methodology. The following day, the students can use the class time to investigate their hypotheses and present their results. It is important that you not feel like you have to have all the answers. Remember this is inquiry – let the students teach you!

Active Inquiry Questions
Here are a few examples the teacher can give the students to get them started. Following each question is a link to data that will help answer the question. All external links open in a new window. The maps below show experimental NOAA/NESDIS data and should be interpreted with caution.

Start the inquiry lesson with the question "How do we understand the dynamics of the atmosphere and the ocean?" The following questions come after the investigations in Part I and are included in the student section in order to guide their inquiry.

A. Where is the Gulf Stream? What features can you identify from the satellite imagery?
B. How has the position of the Gulf Stream, relative to the coastline and to the cold North Atlantic waters, changed over time?
C. What are the seasonal and yearly differences in SST for the North Atlantic waters?
D. Why are some years better than others for the development of tropical storms?
E. Where do the eddies form?
F. How does SSH help predict the position of Gulf Stream and eddies? In what direction do the eddies flow? What is the SST temperature of the eddies?

Students can examine the classic pictures of the North Atlantic Gulf Stream using SST maps and altimetry readings. Students will recognize special features such as the North wall, the eddies and the circulation patterns. Compare seasonal changes in the position and heat capacity of the Gulf Stream.

A. Where is the Gulf Stream? What features can you identify from the satellite imagery?

  • View daily SST pictures from the current month of the North Atlantic.

    http://coastwatch.noaa.gov/interface/interface.html

    Instructions: On the side bar, select View Results as Images. Select Region as the Northeast. Select Product as SST. Select Sensor as Imager, and select Satellite as GOES-8. Try selecting several dates from the last month.

Additional Teacher Questions:

  1. Can you identify areas that are much warmer than the surrounding water?
  2. What is the position (range of latitude and longitude) of the warmest water?
  3. What is the position (range of latitude and longitude) of the coldest water?
  4. At what latitude does the contrast of colors on the SST diagram become the greatest?
  5. At this location, what is the difference in the temperature between the warm and cold waters?
  6. Trace the positions on your map of the areas with the highest temperature gradient in surface waters.

B. How has the position of the Gulf Stream, relative to the coastline and to the cold North Atlantic waters, changed over time?

  • From the same site, examine daily SST imagery for several consecutive months of the North Atlantic. Compare your observations for each image.

C. What are the seasonal and yearly differences in SST for the North Atlantic waters?

Additional Teacher Questions
  1. What eastern states in the US are influenced by 20o Celsius water temperatures. At what latitude is the southern-most position of this 20o Celsius water?
  2. In Western Europe, what is the northern-most latitude that is warmed by the influence of the Gulf Stream and the North Atlantic gyre?
  3. Compare the temperature and general location of the Gulf Stream in September 1995 and September 1997.
  4. Seasonal variations in the position of the Gulf Stream may also influence land mass temperatures. In Western Europe, how much cooler is the winter-water temperature than the summer-water temperature?

D. Why are some years better than others for the development of tropical storms?

  • Anomalies of temperature chart the difference from the norm (or long term average for an area).
    Use the link below to study the anomalies in temperature for the North Atlantic basin and the Gulf Stream. Select STATIC DATA from the archives. Compare Mid - August dates for 1999 and 2000.
    http://www.osdpd.noaa.gov/PSB/EPS/SST/climo&hot.html

  • The year 1999 was a very active hurricane year for the eastern United States. What approximate percentage of the North Atlantic Basin had temperatures above normal during this year?

E. Where do the eddies form?

  • See the Gulf Stream current in a movie clip of the last ten days. The last ten days of the Gulf Stream motion can be seen via the GOES satellite imagery at: http://140.90.191.231/oppt/loops/goes_sst/gstream_ge_10.html

  • Watch for the formation loops in the current. What is happening to the current at these locations? In which direction relative to the Gulf Stream, are the loops forming? What is the temperature of the water that is caught in these loops?

F. How does SSH help predict the position of Gulf Stream and eddies? In what direction do the eddies flow? What is the SST temperature of the eddies?

The use of satellite altimetry allows scientists to view the sea surface in a different way than allowed by SST diagrams. Altimetry measures the height of the sea with respect to the average sea level. Use the link to investigate differences in sea level height along the Gulf Stream and in the North Atlantic. NOTE: On this page, set your date, go to bottom of the page and send your values.

http://argo.colorado.edu/%7Erealtime/gsfc_gom-real-time_ssh/

  • The scale is based in centimeters above or below the mean sea surface level on this map. Where are the highest values of SSH located in respect to the Gulf Stream?
  • Can you trace the path of the Gulf Stream current around these different sea level heights?
  • What would be the relative temperatures of the lower SSH areas compared to the surrounding water? What would be the temperatures of the higher SSH areas?
  • Using the same date, link to the geostrophic flow viewer below and compare your traced diagram to the more obvious Gulf Stream current. Is the flow of the eddys that are higher SSH generally clockwise or counterclockwise? What is the directional flow of the lower SSH eddys? http://argo.colorado.edu/%7Erealtime/gom-real-time_velmag/

Inquiry Event Investigation
Use this section to help students design their individual, inquiry investigations after studying the information about hurricanes Opal and Bret.

What is the role of the Gulf Stream and the eddies in the development and strength of tropical storms?

A. Study the cases of rapid hurricane intensification in the southern Gulf Stream (Opal and Bret) with the corresponding maps. The Gulf of Mexico is the birthplace of some of the waters that make up the Gulf Stream off the Atlantic coast.

http://www-ccar.colorado.edu/~altimetry/applications/hurricanes/images/bret_altimetry.gif
http://www-ccar.colorado.edu/~altimetry/applications/hurricanes/images/bret_heat.gif

When researching in the area of hurricane development, scientists use satellite imagery to enhance the complex relationships between the ocean and the air above. The following study has more detailed information about the Loop Current in the Gulf of Mexico and the intensification of tropical storms. Use the data map to find out more about ocean conditions for different dates.

http://www.aoml.noaa.gov/phod/cyclone/data/

B. Investigate paths of other hurricanes and note differences in relative SST and SSH (including any eddys that may have been in the path) during each tropical season. Select different years and different storms to investigate.

http://fermi.jhuapl.edu/hurr/index.html

  1. Besides SST and SSH, what other factors may influence the development and intensification of a tropical storm?
  2. Look at the current year's satellite readings and predict the rate of strengthening of a tropical depression in the North Atlantic or the Gulf of Mexico.

How to read a Sea Surface Height map to detect height differences

Altimeters on the satellites measure the distance from the satellite to the surface of the earth. The earth's "level" surface, based on the force of gravity, is referred to as the geoid. On the waters, the geoid is the level surface that water would have if it were not acted on by outside forces (wind, tides, etc.). In reality, sea height is not the same all over the world. The satellites measure SSH relative to the geoid surface with calibration and adjustment based on local ground data (mean sea level measurements). The anomaly SSH satellite maps show the difference in measured sea height from the calculated, mean sea level. These images are color-coded and the scale is often in centimeters.

Additional Questions to Consider as students are selecting a research problem:
(Students should be able to use many of the lesson links to help them in their investigation)

  1. Do the other major surface gyres have currents similar in nature to the Gulf Stream?
  2. The return currents of the gyre circulation also have unique characteristics. Compare these currents to the Western Boundary currents.
  3. What do the currents carry with them? Is this a free ride for sea organisms, and do other marine animals follow these pathways in their movements?
  4. How does surface ocean circulation affect deep water circulation in the ocean?
  5. Satellites can monitor, with imagery, the dispersal of chemical spills. If you were a lawyer investigating a company that had toxic spill, what information would you want in addition to the satellite imagery?