1-10: Ocean Structure and Circulation

Pre-Class Preparation

• To understand the forces that drive the circulation patterns of the global oceans and the relation of global atmospheric circulation to global ocean circulation.
• To understand the time and space scales of flow in the global ocean, including inter-basin transport and its role in transporting heat globally.

Procedure

1. Read the learning unit.

   Class images

2. Take the learning unit quiz. Quizzes are available from your portfolio. You may access your portfolio via the list of students participating in this years course, as represented by the icon below.
   
   
3. Additional Required Reading. Although you are not ultimately responsible for content listed in this section, we encourage you to fully explore the links in order to provide a better scope on the upcoming class discussion.

   	Current Ocean Temperatures
   	How the Oceans Influence Climate. (From the United Nations Environment Programme, UNEP)
   	Oceans and the Carbon Cycle. (From the United Nations Environment Programme, UNEP)
   	The PIRATA Project

Class Discussion

• Problem to ponder...
  If we run short of food raised on land, why can't we "farm" the vast reaches of the ocean far from continents?

• Class Discussion Summary: by classmates Heather Freidhof and Dan Pulido

  We started with a discussion of the ocean's capacity to carry heat and disperse energy poleward. Ocean currents flow clockwise in the northern hemisphere and counterclockwise in the southern hemisphere. If one was to view the earth from the north pole looking downward, one would see air parcels moving toward the poles. These air parcels are subject to the Coriolis force, a force created by the rotation of the earth. Depending on the parcel's movement toward or away from the equator, its speed can be either decreased or increased respectively. Ocean circulation is also driven by density of the water. Warm water's density increases due to evaporation and increased salt content. This water will contribute to the deep ocean acting as a conveyor belt. These regions act as pulleys for the conveyor belt because the polar regions produce saline cold water. Deep mixing occurs at these polar latitudes, whereas in the regions of the intertropical convergence zone, no deep mixing occurs. In the mid latitudes, seasonal mixing occurs. Pure water has a maximum density of 4^o C. Temperatures of water below 4^o C become less dense and rise to the surface but the denser 4^o C water in the lower layers allows fish to survive the cold winters. The discussion ended with the topic of increasing temperatures in the tropical pacific. Moored buoys which were anchored to the ocean bottom, were used to collect the data. Data of temperature, salinity and wind speeds were recorded. From the data, temperatures have increased dramatically.

Post-Class Activities

• Participate in the electronic dialog. Use this forum for:
  • continuing class discussion;
  • posing new questions to students or the instructor;
  • responding to issues/questions raised by students in class/electronic dialog.

  Visitor Access (Visitors are welcome to participate in the dialog. Just click on the icon below)	Student Access (Students must post all dialog from their portfolio. Click on the icon below to access the student list.)

• Recommended Reading Materials

  	A Primer on Ocean Currents, Woods Hole Oceanographic Institution.
  	British Antarctic Survey Press Release 1/95 27 February 1995: ONE SMALL ICE SHELF DIES, ONE GIANT ICEBERG BORN
  	Gordon, A. L., 1988: The southern ocean and global climate. Oceanus 31, 39-46.
  	Houghton, J. T., L. G. Meira Filho, B. A. Callander N. Harris, A. Kattenberg, and K. Maskell, 1996: Climate Change 1995. The Science of Climate Change. Cambridge University Press, 210-216, 489-504.
  	Kerr, R., 1997: A New Driver for the Atlantic's Moods and Europe's Weather. Science, 7 February 1997.
  	Open University Course Team, 1989: Ocean Circulation. Pergamon Press, Oxford: 238 pp.
  	Perry, A.H., and J. M. Walker, 1977: The Ocean-Atmosphere System. Longman, Inc., New York: 160 pp.
  	Steele, J.H., 1989: The message from the oceans. Oceanus, 32, 5-9.
  	Tolmazin, David, 1985: Elements of Dynamic Oceanography. Allen and Unwin Publishers, Inc., Winchester, MA: 181 pp.

• References

  	Derr, R. A., 1998: Warming's unpleasant surprise: Shivering in the greenhouse? Science 281, 156-158.
  	Malakoff, David, 1998: Death by suffocation in the Gulf of Mexico. Science 281, 190-192.
  	J. A. McGowan, D. R. Cayan, and L. M. Dorman, 1998: Climate-ocean variability and ecosystem response in the northeast Pacific. Science 281, 210-217.
  	Falkowski, P. G., R. T. Barber, and V. Smetacek, 1998: Biogeochemical controls and feedbacks on ocean primary production. Science 281, 200-206.
  	Jickells, T. D., 1998: Nutrient biogeochemistry of the coastal zone. Science 281, 217-222.
  	1998 Conference of the World Ocean Circulation Experiment
  	Glossary of Oceanography
  	NOAA Oceanography Resources on the Internet
  	The Scripps Institution of Oceanography International Research Institute
  	Sea Surface Temperature from 1981 to Present
  	World Ocean Circulation Experiment Bibliography - from US WOCE office A-H, I-R, S-Z
  	Parilla, G., et al., 1994: Rising temperatures in the North Atlantic ocean over the past 35 years. Nature 369, 48-51.
  	Semtner, Albert J. 1995: Modeling ocean circulation. Science 269, 1379-1385.