Scientist-Educator Collaborative Workshop
Workshop Theme: Ocean-Climate Connections
Held at the NASA/Jet Propulsion Laboratory in Pasadena, CA
Thursday, June 2, 2011 through Saturday, June 4, 2011

Hands-On Activities

On the last day of the workshop, COSEE-OS Facilitators demonstrated hands-on activities that can be used in the classroom to teach students about salinity and temperature, which help govern the density of seawater - a major factor controlling the ocean's vertical movements and layered circulation. These activities can be found in the COSEE-OS publication Teaching Physical Concepts in Oceanography: An Inquiry-Based Approach (Karp-Boss et al., 2009). Click here for videos.

  A hands-on activity demonstrating how density and stratification are affected by salinity and temperature
Effects of Temperature and Salinity on Density and Stratification
This activity demonstrates that fluids arrange into layers according to their densities. The two "water masses" - salt (blue or green) vs. fresh (yellow), or cold (blue or green) vs. warm (yellow) - are initially separated by the tank's divider. When the divider is removed, the denser water (salt water or cold water) sinks to the bottom of the container and the less-dense water (fresh or warm water) floats above, forming a stratified column. In the process, an internal wave is formed in the tank.

Stratification forms an effective barrier for the exchange of nutrients and dissolved gases between the top, illuminated surface layer where phytoplankton can thrive, and the deep, nutrient-rich waters. Stratification therefore has important implications for biological and biogeochemical processes in the ocean.

  A convection apparatus used to illustrate convection due to density differences generated by fluids of dissimilar temperature
When one column of the apparatus shown at right is warmed and the other is cooled, density differences are created between the bottom of the vertical tubes, causing a pressure gradient to develop. Density differences cause water masses to sink or rise until they reach their density equilibrium level; once a water mass reaches its equilibrium density level, it begins to move horizontally in response to a pressure gradient. (Note: Pressure gradients result from differences in the vertical distributions of density, and hence hydrostatic pressure, between regions where water is denser or lighter.) Because the cold water is denser, it will move along the lower connecting tube; the hot water will move along the upper connecting tube. This activity provides a good illustration of density driven ocean circulation - for example, the global conveyor belt.