Ocean Water: Density

Judy Robinson, Nova Southeastern University

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This page first made public: Jun 3, 2013

Summary

In regions throughout the world oceans, water moves vertically to or down away from the surface and is set in motion by atmospheric winds, salinity and temperature differences. Cold water is much denser than warm and seawater has a higher density that fresh water and will sink below the less dense layer of water. Furthermore, vertical mixing powered by atmospheric winds can affect stratification and the rate of growth of the surface boundary layer. This lab activity is a simulation of the processes that create density stratification in ocean environments. It exposes students to concepts of temperature, salinity and wind and the role each plays in the development of water stratification.

Oceanography | High School (9-12), College Lower (13-14)

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Context

Audience

Undergraduate oceanography course with lab requirement for Marine Biology Majors curriculum.

Skills and concepts that students must have mastered

To prepare for this lab exercise, students read about the function of temperature, salinity and wind in creating distinct regions of ocean stratification. During the week the reading information and details of the assignment is available online; students have to access their Blackboard account where the information is posted.

How the activity is situated in the course

This activity is a lab exercise that is assigned about 7 weeks within the lab curriculum.

Goals

Content/concepts goals for this activity

This lab exercise is a hands-on activity that provides a visual image summarizing the functions of temperature, salinity and wind in creating water density layers reflective of those in the ocean environment.

Higher order thinking skills goals for this activity

Integral components in the hydrodynamics of ocean stratification are intuitively better understood. Students correlate visually observed patterns created by temperature, salinity and wind on water density with those inferred from a basic understanding of ocean stratification.

Other skills goals for this activity

Student collaborates with other classmates in a group experimentation activity. Student interprets observations through open discussion and written lab report.

Description and Teaching Materials

Teaching Notes and Tips

Usually the lab consists of 20 students and is divided into 4 groups of which 2 groups perform an aquarium activity while the other 2 groups do the other activity. Students will use graph paper to prepare a chart for temperatures at depths of 1,3,5,9,13,17 and 23cm.

Assessment

Students complete a graph of the results and write a lab report on the exercise. Questions concerning the results of the activity are presented on a subsequent exam.