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Laboratory exercise to explore water density, surface ocean currents, and ocean circulation
This is an introductory, undergraduate, oceanography laboratory course that is co-requisite with a lecture section. Most students are non-science majors and are taking the class to fulfill a science requirement. These laboratories are led by graduate student teaching assistants.
Skills and concepts that students must have mastered
Depending on the semester and the lecturer, the students have been introduced to the main concepts of circulation patterns in the ocean during the lecture portion of class. Because the information varies from semester to semester, there is a brief presentation developed for the TAs to use if necessary.
How the activity is situated in the course
This is a stand alone laboratory that is completed in a 3-hour section. The following week, the students complete a synthesis or quiz over the material covered from the lab.
Content/concepts goals for this activity
Water density, ocean circulation, thermocline, thermohaline, pycnocline
Higher order thinking skills goals for this activity
- Develop and test hypotheses and experiment with water density.
- Simple experimental design.
- Understand the main ocean circulation patterns and their controls.
Other skills goals for this activity
- Describe and design a simple experiment.
- Draw ocean circulation patterns
Description and Teaching Materials
Students conduct a simple experiment, measuring mass, volume, and temperature in order to understand what controls water density. This experiment will help students understand ocean circulation, namely deep currents driven by density contrasts in the water produced by temperature and salinity variations. Wind-driven surface currents also affect ocean circulation.
Teaching Notes and Tips
During the first part of the lab, students will develop hypotheses and design simple experiments about water density. For the experiments, we provide a big bucket of ice with water bottles in it to make water at ~0°C, tap water, and a coffee maker that we use to make water at ~80°C. We provide salt (either kitchen iodized salt, or a sea water salt mixture for aquariums) and food coloring. The students are given beakers to mix and pour water into, and a number of plastic beads (I think these are "airsoft" gun pellets, similar to plastic bb's) that will float or sink depending on the density of the water made. Students are given free range to develop hypotheses and design a way to create and test the density of the water they can create. For the second part of the lab, students are drawing graphs to develop an understanding of the physical and chemical properties of the ocean. In the third part of the lab, the students are drawing maps to understand surface ocean currents.
There is a synthesis (or quiz) that we give students the following week to test their knowledge of the material. In previous years, we gave the synthesis at the end of the lab period, and recently we have been giving it the following week. We can't decide which method is better.
References and Resources
Because the professor leading the lecture section changes frequently, there is a brief powerpoint lecture that the TAs can use to introduce the main points of the lab. I let TAs decide to use this or not. There is a vocabulary sheet that we give to the students to take notes on during this presentation. It is also a useful guide for them to use and fill out during lab.