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12. Western Boundary Currents and Climate

 

 

 

 

 

 

 

Expedition Menu

1. Introduction
2. Tracking Drifters
3. Drifters Pacific
4. Drifters Atlantic
5. Drifters Indian
6. Velocity Pacific
7. Velocity Atlantic
8. Velocity Indian
9. Global Circulation
10. Counter Currents
11. Boundary Currents
12. Western Boundary
Currents
13. Typhoons & Hurricanes
14. Eastern Currents


 

Seaweb LogoOcean Report Logo

The ocean controls climate and vice versa -- listen to this report on the connection between the ocean and global climate from Seaweb's Ocean Report.
  • Transcript:
  • Most scientists agree that the climate is changing, but the question is how fast is this change occurring and what is the ocean's role in this change?
  • The ocean and the earth's atmosphere interact, when the atmosphere changes, the oceans follow closely, and the oceans play an important role in controlling the world's climate and the patterns of weather.
  • But if we change the atmosphere, as we are now doing by adding carbon dioxide and other gases, we may change ocean currents, which will lead to a major change in climate, says Dr. James Baker, formerly the head admisntrator of the National Oceanic and Atmospheric Administration (NOAA).
  • Dr Baker says some scientists believe that the temprature may rise 4 to 5 degrees Farenheit in the next 100 years.
  • So that is why he is very concerned about climate change as it is a very important thing to worry about.
  • If we change the atmosphere's chemistry, and hence change the climate and the ocean as well and that could have an impact on all of us.
  • Let's examine the major boundary currents, which have drastically different climatic effects depending if it is the eastern or western boundary current (remember each ocean has these boundary currents, so it is global influence as well).
  • First review the chart showing characteristics of surface water flow, especially the boundary currents, that you created earlier.

Image Provided by Rosenstiel School of Marine and Atmospheric Science of the University of Miami


Warm air holds more moisture (humidity) than cold air.

Remember that the ocean's temperature, be it warm or cold, strongly influences the temperature in the overlying mass of air.  You can see this in the diagram below by noting the difference in the width of the red color band, representing air temperatures between 20 and 30oC on the western and eastern sides of the ocean basins.  

  • Note how the band of warm air temperatures is contracted on the east side and expanded on the west side of each ocean, especially the Pacific and Atlantic -- scroll up to the see how this pattern mimics the distribution of sea surface water temperature in the diagram above. 

We shall first examine the impact of western boundary currents -------

Let's Listen to Seaweb Ocean Report about the western boundary current known as the Gulf Stream (along the east coast of U.S.) -- remember western refers to its position in the ocean -- the west side of the ocean.

Why is the ocean water warm at the beach south of Cape Cod, in Nantucket, but north of Cape Cod in Gloucester Massachusetts it is "freezing?"asks Laura. a listener of the Ocean Report.

The answer has to do with the Gulf Stream, which is the warm current that flows northward from the Gulf of Mexico along the U.S. east coast.

At first the Gulf SAtream flows close to shore, but by around Cape Hatteras, North Carolina, the prevailing winds push the Gulf Stream offshore. By the Massachusets, the Gulf Stream has been pushed far out to sea by the wind.

The very western edge of the Gulf Stream warms the water off Nantucket's beaches, but now by Cape Cod, the current heads northeast towards Europe, so that there is no way its warming effect can extend back west around Cape Cod to Boston or Gloucester.

Meanwhile, another major ocean current, called the Labrador current flows south from the Arctic and brings extra cold water to New England, including the beaches in Gloucester. .

Trace the Gulf Stream on this Map of Sea Surface Temperature

Image provided by the Rosenstiel School of Marine and Atmospheric Science of the University of Miami

The Gulf Stream shows up as the band of warm water extending northwards along the east side of Florida
(in orange) and continues northwards (in yellow) off eastern U.S. 
Use the temperature scale along the right each of diagram, in degrees Celcius, to estimate the range of water temperature carried by the Gulf Stream.

As mentioned in the previous expedition, the term "eddy current" refers to localised areas of turbulence that give rise to persistent vortices (for example, smaller-scale circular currents around the edges of the major surface currents). Watch the animation showing eddy currents along the edges of the Gulf Stream, one of the major surface currents on the western side of the Atlantic Ocean.

Here is an animation of the Gulf Stream over the past 26 weeks by Remko Scharroo of Department of Earth Observation and Space Systems at Delft University
Last Updated on
July 1, 2011
Send to Don Reed
Department of Geology
San José State University

look.gif (2305 bytes) Given this relationship, which one of the following statements describes the temperature and water vapor content of the air over the western boundary currents, such as the Gulf Stream.