Observing Salinity Patterns
Part 1: Students measure the salinity of samples using a refractometer, and consider the units and density of these values. Part 2: Students apply concepts and reinforce what they've learned about salinity and the water cycle to interpret a salinity contour map of a transect of the Pacific Ocean using WOCE data. Another goal is to familiarize students with using contour graphs of ocean data, in general.
Activity is used in an introductory oceanography course at a community college for non-science majors.
Skills and concepts that students must have mastered
Students have some background on density, salinity, and the water cycle prior to completing this activity.
How the activity is situated in the course
Activity is used during the seawater and chemical oceanography unit as a hands-on activity in the classroom.
Content/concepts goals for this activity
Goal is to understand units of salinity, how changes in the water cycle impact salinity, and understand that both salinity and temperature have an independent effect on water density.
Higher order thinking skills goals for this activity
Activity involves a stepwise process where students learn how to read data shown as a contour graph, and then analyze the data to form an interpretation of patterns.
Other skills goals for this activity
Description and Teaching Materials
Part 1 Hand-out: classroom activity on measuring and understanding salinity. Materials: uses refractometers, saline solutions, and map of global sea surface salinity patterns (any available map will fit here). Textbook used (not required): Essentials of Oceanography, 10th ed. by Trujillo & Thurman (2011).
Part 2 Hand-out: classroom activity on interpreting a contour graph of salinity data in the Pacific Ocean from WOCE. Pairs with color contour maps of WOCE data below. Helpful materials for visualization: globes and string (to trace ship's path on the globe).
Salinity Contour Map: WOCE image of salinity data along 150 deg. W with legend (station P16)
Teaching Notes and Tips
Allow 20 min for students to complete Part 1 in small groups, and an additional 5-10 min for discussion at the end. Allow 20-30 min for students to complete Part 2. Parts 1 and 2 can be completed as independent activities from one another OR as a paired activity in class.
I check to make sure that students are on the right track while working on the assignment, and then especially evaluate their reasoning on pg. 2 of the Part 2 Hand-out on observing salinity patterns. I especially look for an understanding that temperature can independently impact water density in addition to salinity. Some students miss this or think the salty water near the surface "maybe hasn't had time to sink yet."
References and Resources