Objectives
Students will be able to:

use real time data to locate the Gulf Stream

Materials
copies for each group of the tracking chart  Full Basin   Western Atlantic
copies for each student of the Blank Gulf Stream Map
computers with Internet access
colored pencils
Student Worksheets   Pair 1, Pair 2, Pair 3
optional: printable Lab Report Directions

Background
The use of satellite imagery is one of the most accurate ways to locate the Gulf Stream.   NOAA (National Oceanic and Atmospheric Administration) operates a Polar Orbiting Satellite (POES) with an AVHRR sensor (Advanced Very High Resolution Radiometer).  This sensor measures the amount of thermal infrared radiation given off by the surface of the ocean.  The amount of thermal infrared radiation given off by an object is related to its temperature, so by measuring the amount of radiation given off by the ocean, scientists can calculate the temperature of the sea surface.  The satellite thermal infrared radiation data is color coded to produce an image of the ocean.  The satellite image allows people to easy locate the warm current of water in the Atlantic Ocean known as the Gulf Stream by comparing the color differences to a color/temperature scale.  Sea surface height (radar altimeter data), measured by the TOPEX/Poseidon and ERS-2 satellites also is valuable information to help track down the location of the Gulf Stream.  The Radar Altimeter on ERS-2 sends radar signals to the earth and ocean surface and collects the return signal.  That information is processed to reveal the ocean wave height and wind speed (over oceans), the surface backscatter, and the height of the satellite above the surface.  This provides the possibility to monitor the global ocean circulation and regional current systems.  The satellite systems offers the advantage of daily global coverage.  Other means of  measuring sea surface temperature such as buoys (drifting and moored) are used to maintain accuracy of the satellite data, further removing sources of error.

Oceanographers use the images to visualize the Gulf Stream; the width, the number of rings and meanders, etc.  Constant monitoring is necessary because the Gulf Stream is not a stable current, it meanders North and South. Sometimes these meanders are small, taking the form of waves which appear to break backwards relative to the northeasterly flow of the current.  In some instances, the meanders become so large that a pocket of warm water is pinched off and separates from the stream into the cooler shelf water. These are called warm core rings. The warm core rings rotate clockwise for several days, eventually drifting west to southwest until they interact with the shelf or the Gulf Stream.  Most warm core rings are reabsorbed into the stream after wandering for 1 to 3 months.  The effects of warm core rings were observed by early oceanographers, but the true extent was not well understood until the availability of satellite imagery.  It is also interesting to note that just as stream meanders to the North can pinch off a warm core ring, stream meanders to the South can also pinch off, forming a cold core ring. These rings are often less visible in the satellite imagery because of the warmer water lying above, but can still be seen by the trained eye.  (Northern Gulf Stream Image  June 11, 1997)
 

Procedure 
1.  Create working groups of 6 students. Break each group of six into pairs.

Pair 1
2.  Obtain the most recent data from the following buoys.  Record the following information on the Student Worksheet:  Latitude and Longitude, Time and Date, Air Temperature (ATMP), Water Temperature (WTMP).  Scroll down the page to the Previous 24 observations.  Plot the location of the 6 buoys on the chart.

Pair 2
3.  Obtain the most recent ship data by clicking on the Ships in the North Atlantic link below.  The symbols on the chart represent the ships and buoys currently logging data in the Northern Atlantic. The red symbols are buoys and the blue symbols represent ships.  Notice the series of letters and numbers under the blue ship symbols. These are the "Ship IDs".  No two sets of letters and numbers are the same.  Locate at least four ships between 30N - 50N Latitude and 50W - 80W Longitude.  Write down the exact "Ship ID" on the Student Worksheet.

Ships in the North Atlantic 

4.  Now click on the Ships Observations Report link below.  Look through the data reported by the ships selected from the North Atlantic map.  Record the water temperature.  Record the location of the ship(s).  

Ships Database

NOTE: If the Ship ID does not show up in the current hour observations, use the drop down Time menu and get the data for the previous hours.


Pair 3
5.  Obtain the most recent satellite image of the Gulf Stream and answer the questions on the student worksheet.

Real Time Sea Surface Temperature Satellite Data 

6.  Using colored pencils, sketch the approximate current location of the Gulf Stream on the chart.  Use the appropriate colored pencil to represent the temperature of the water and label.  Use the latitude and longitude points to guide placement of the current. 


7.  After each pair of students has collected their respective data and answered their questions, have the students regroup into their group of six. Have the students compare their data and answer the Assessemtn questions on the worksheets.

Assessment
Compare the ocean water temperature data from the satellite image with the temperatures collected from the ships and buoys. 
1. How close do the data sources compare? 

2. With the availability of satellite imagery, why do you think scientists continue to collect data from ships and buoys?

Analyze satellite imagery.  Review the following archived satellite images and answer the questions on the Student Worksheet.

3. Does the position of the North Wall (the Northern boundary of the Gulf Stream) fluctuate greatly during the year?  Explain.

4.  Describe yearly sea surface temperature changes of the Northwest Atlantic Ocean.  

5.  Study the satellite image below.   Based on the information in the image, estimate the time of year.  Support your answer.

Lab Report Assessment
1. Define the following Gulf Stream terms:
North Wall
warm core eddies
cold core eddies
Gulf Stream meanders

Apply the knowledge learned working in your small group to the following activities.  Complete the activities individually and submit your question responses and completed Gulf Stream Map in your Lab Report.

What information besides sea surface temperature might illustrate the pathway of the Gulf Stream?


2.  View the example real time data image to learn how to locate the Gulf Stream, the position of the North Wall, warm-core eddies, cold core eddies and Gulf Stream meanders.


3.  Using the AVHRR Sea Surface Temperature Data, choose a recent 7-Day Composite Image for the Gulf Stream Region:

Choose the current year and month (Click on choice) Scroll down and select the most recent 7-Day Composite Image.  If there is too much cloud interference, click back and select the next day.

4.  On the Blank Gulf Stream Map, sketch in the current location of the Gulf Stream and label the following:

The Gulf Stream Current North Wall Meanders Cold-core eddies Warm-core eddies

5.  Using the Gulf Stream Velocities, choose the real time data image timeframe that best matches your sea surface temperature date.

6.  On the Gulf Stream Map, draw in the arrows that represent the direction of the water flow in the following features:

The Gulf Stream Current North Wall Meanders Cold-core eddies Warm-core eddies

7.  Answer the following questions in your lab report:
 

a.  What direction does the current flow around Cold-core      eddies? b.  What direction does the current flow around Warm-core eddies? c.  Do Cold-core eddies or Warm-core eddies have faster current velocities? d.  Where is the location of the North Wall in respect to the Gulf Stream? e.  What is the difference between a meander and an eddy? f.  What features were easily recognized on the sea surface temperature map? g.  What features were easily recognized on the velocities map? h.  If you had to choose one of these real time data to use while sailing in the Gulf Stream, which would it be? Why? i. How is the Gulf Stream identified today? j. Why is it important to know where currents are today?  k. Why is it so important to spend money on a satellite to collect this data? l. How are today's data collection methods different than from the ones identified in the previous lesson?  Better? m. Are any of the older methods still employed today?  Which ones?  Why? n.  In general, does the position of the Gulf Stream change drastically during the course of one year?  Provide support for your response.

Implementation Tips
Students will need Internet access to complete the Lab Report portion of this lesson.  Please ensure that all students will have access prior to assigning the Lab Report.  An option would be to print and photocopy the images prior to class and distribute the images to the students with limited or no Internet access to enable them to complete the assignment.