Student Activity

Overview
In this activity, you will use satellite composite maps of Sea Surface Temperature (SST) and altimetry measurements to locate the outstanding features of the Gulf Stream. You will monitor the formation and migration of cold core and warm core rings (eddys) that develop off the Gulf Stream. You will also study the correlation between sea surface temperatures, sea surface height, and the location of mesoscale eddys in relation to the track of tropical storms.

Goals
In this lesson you will:

  • Monitor changes in North Atlantic temperature using SST satellite images
  • Learn how to read satellite-derived mapd 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 eddies to the development of Atlantic coastal storms and other coastal events

Explanation of Questions
This lesson is designed to help you create a hypothesis, research it, and make a conclusion about effects of the gulf stream. You can do this by using the NOAA/NESDIS website to help you find data for research. Your teacher will help to guide you in the appropriate direction by helping your group create a valid hypothesis, discover the best methods to research your hypothesis, and show you ways to find appropriate data to support your hypothesis. This lesson will give you a few examples of questions and supporting data so that you can come up with questions and supporting data of your own.

Questions
All external links open in a new window.

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.

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?

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:

  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?