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How warm is the water? Grade Level: Secondary National Science Education Standards Physical Science: Interactions of energy and matter Objectives 1. Describe how the sea surface temperature (SST) changes with the seasons. Concepts In the ocean, almost all the energy from sunlight is absorbed in the top few meters of the water. During the long days of summer, when the sun is almost directly overhead, the ocean surface soaks up a lot of energy from sunlight and warms up. During the shorter, cooler days of winter, the ocean surface soaks up less solar energy and cools down. Wind from storms also cools the surface waters during winter by mixing colder water from below. Deep waters remain dark and cold throughout the year because the surface waters absorb nearly all the solar energy. Seasonal changes in sea-surface temperature affect climate on a global scale. For instance, without the warm surface waters of the North Atlantic, much of Europe would be as cold as Alaska. Water temperatures also influence the abundance and distribution of marine animals and plants. The temperature of surface sea water also helps determine whether the water column is "stable." That´s because the density of water varies with temperature (and salinity). Warm summer water is less dense than the cold water below, so it remains floating at the surface. During the fall and winter, when shorter days, less direct sunlight, and wind from storms cool the surface waters, their density increases, and they sink. Sinking or "downwelling" of water helps drive global ocean currents. Activities/Procedure 1. Introduce the relationship between water temperature and heat input by asking your students to describe the changes in water temperature that they have experienced while swimming or diving in a lake, the ocean, or a pool. Also discuss how water temperatures in these water bodies vary from season to season. 2. Ask your students to draw a time series of the sea-surface temperature (i.e., upper 5 meters) for each month of the year (in the Northern Hemisphere). Stress that the ocean covers 70% of the Earth's surface, so that seasonal changes in sea-surface temperature affect climate on a global scale. Now ask them to draw a temperature time series of the deep-water zone (i.e., below 3000 meters) for each month of the year (again in the Northern Hemisphere). Students can draw their time series plots using the OceanExplorer TimeSeries tool. 3. Have your students draw a depth profile of sea water temperature for a summer month and a winter month using the OceanExplorer Profiler tool 4. Discuss the similarities and differences among the time series plots and depth profiles that your students have drawn. 5. Compare student time-series temperature plots and depth profiles against temperature data from BATS. Discuss the similarities and differences. You can use the BATS time-series plots (Fig. 1) and depth profiles (Fig. 2) shown below, present the students with a plot that you've constructed using OceanExplorer, or let the students use OceanExplorer to create their own plots.
You can explore changes in the duration and intensity (angle) of sunlight through the year by constructing and monitoring a sun dial. You can also monitor temperature changes in a local lake or in the ocean if you live in a coastal community. Materials OceanExplorer interactive worksheet Assignments Ask your students to record and graph changes in day length by using the information on time of sunrise and sunset found in many daily papers. Evaluation You can evaluate your students´ preconceptions about ocean temperature and how it changes throughout the year by examining the graphs that they draw using the OceanExplorer TimeSeries and Profiler tools. You can then examine the graphs they draw following the activities in this lesson plan to gauge how their understanding of seasonal ocean temperature changes has altered. |
