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Education: Student Outcomes

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Outcome: Explain the effect of solar energy heat on ocean circulation.
Grade level: 5-8
Theme: ocean circulation
Activity: http://www.tos.org/hands-on/teaching_phys_concepts.pdf

Activity 4.3: Convection (p. 36-37). A good grasp of the underlying principles of thermal physics is essential for understanding how the ocean functions and how it impacts climate. Thermal physics is one of the science subjects that students are familiar with and experience on a daily basis, but intertwined with the experiential knowledge they bring to class comes a mixed bag of misconceptions that must be identified and addressed. Example misconceptions include an inability to differentiate between heat and temperature, the notion that transfer of heat will always result in a temperature rise, and a misunderstanding of the concept of latent heat.

The purpose of this activity is to review basic concepts of thermal physics and highlight applications to ocean processes by focusing on the concept of convection. Convection and advection are the major modes of heat transfer in the ocean and atmosphere. Convection occurs only in fluids and involves vertical motion of fluid, or flow, rather than interactions at the molecular level. It results from differences in densities - hence buoyancy - of fluids. Examples of convective processes include: currents in Earth's mantle, which drive the tectonic system and result from heating and cooling of magma; atmospheric circulation resulting from uneven solar heating (e.g., between the poles and the equator); the global ocean conveyor belt and formation of deep water masses, resulting from cooling of surface water at high latitudes; and vertical mixing in the ocean's upper layer due to variations in heating between day and night. Advection usually refers to horizontal transfer of heat with the flow of water (e.g., the Gulf Stream).

Read the following sections of Chapter 4 (Heat and Temperature) in preparation for this activity:

  •  Background (p. 32)
  •  Mechanisms of Heat Transfer (p. 33)

Videos
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Grade level: 5-8
Theme: ocean circulation
Activity: http://www.tos.org/hands-on/teaching_phys_concepts.pdf

Activity 1.4: Effects of Temperature & Salinity on Density & Stratification (Steps 5-7; p. 9). Stratification refers to the arrangement of water masses in layers according to their densities. Water density increases with depth, but not at a constant rate. In open ocean regions (with the exception of polar seas), the water column is generally characterized by three distinct layers: an upper mixed layer (a layer of warm, less-dense water with temperature constant as a function of depth), the thermocline (a region in which the temperature decreases and density increases rapidly with increasing depth), and a deep zone of dense, colder water in which density increases slowly with depth.

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, nutrientrich waters. Stratification therefore has important implications for biological and biogeochemical processes in the ocean. For example, periods of increased ocean stratification have been associated with decreases in surface phytoplankton biomass. In coastal waters, prolonged periods of stratification can lead to hypoxia (low oxygen), causing mortality of fish, crabs, and other marine organisms.

This activity compares warm and cold water, demonstrating that fluids arrange into layers according to their densities. Students in grades 9-12 should read the Background section (p. 4-5) of Chapter 1 (Density) in preparation for this activity.

Videos
Flash Video | QuickTime Movie