While memories of the beach are still fresh in students’ minds, ocean science offers many hooks for seasonal lessons in all of the sciences. Oceans cover more than 70 percent of Earth’s surface and contain 97 percent of all water on the planet. But according to the National Oceanographic and Atmospheric Administration (NOAA), the lead federal agency for protecting and managing the ocean, more than 95 percent of the underwater world has yet to be explored. Ocean scientists often point out that we know more about the surface of the moon than of the ocean floor. That’s true even though the ocean produces much of the air we breathe (from photosynthetic plankton, kelp and algae) and much of the food on our plates.
Many ocean life forms and events that are most familiar to students occur at the surface or in waters relatively near the surface, which are the focus of this post. Next month’s post, “Ocean Science: Start Shallow, Go Deep (Part II),” will explore science concepts in deep waters and on the ocean floor.
For biology classes, fall is a prime season to study migrations. Gray whales make one of the longest migrations of any mammal: roughly 5,000 miles each way between waters off Mexico in winter and the Arctic in summer. Currently the whales are still feeding in the Arctic, but soon they will start moving south to their winter breeding grounds. Learn about gray whales’ feeding habits and track their progress south on the Journey North web site. For more species consult Ocean Tracks, which shows the movement of elephant seals, white sharks, Bluefin tuna and albatrosses in the Pacific Ocean.
Fall is also high season for hurricanes, which are driven by heat transfer from warm ocean waters to the atmosphere. The U.S. National Weather Service’s official hurricane seasons for the Atlantic and Eastern Pacific oceans extend through November 30, and many major hurricanes have struck in September. Physics teachers can use hurricanes to illustrate basic concepts, including zones of high and low pressure, vacuums and energy transfers. Unit 3, section 5 of The Habitable Planet explains how ocean circulation patterns help to generate hurricanes and monsoons, another form of seasonal tropical storm.
To extend the lesson, ask students to consider how warmer ocean temperatures as a result of climate change may affect the frequency and strength of hurricanes. This is a complex question that has generated much debate among climate scientists. But according to a 2013 study by MIT professor Kerry Emmanuel, a leading expert on this issue (and featured scientist in the video for The Habitable Planet’s unit 2 on Earth’s atmosphere), climate change could make hurricanes both more frequent and more intense. For advanced students, the scientific debate over Emmanuel’s position shows how difficult it can be to show causal connections between climate change and complex weather events.
Oceans are also key links in broader climate patterns such as the El Niño Southern Oscillation, an event that occurs every three to seven years when trade winds across the Pacific weaken and warm water piles up against the coast of South America. El Niño events cause far-reaching impacts on weather, including heavy rains and landslides in North and South America and droughts in Asia. The National Weather Service is currently predicting a 60-65 percent chance of El Niño occurring during the fall of 2014 and winter of 2015. For details about El Niño, see Annenberg’s Weather interactive on the water cycle. Then look at NWS monthly weather forecasts for the United States to see how temperatures and precipitation in your area may be affected.
Oceans also can serve as a frame for chemistry lessons. Many ocean scientists are strongly concerned about acidification – changes in ocean chemistry that are driven by climate change, as seawater absorbs rising amounts of carbon dioxide from the atmosphere. According to NOAA, the acidity of surface ocean waters has increased by about 30 percent since the start of the Industrial Revolution, and could be 150 percent more acidic by the year 2100. This would represent a fall in pH value from approximately 8.2 to 7.8 or lower.
Acidification is already having harmful impacts on marine life. For example, shellfish farmers in the Pacific Northwest have reported that some organisms’ shells are thinning or are pitted and damaged. For an applied chemistry lesson focusing on ocean acidification, start with unit 10 of Chemistry: Challenges and Solutions, an overview of acids and bases. Then dive into “Sea Change: The Pacific’s Perilous Turn,” an award-winning multi-media series by the Seattle Times that examines how acidification could alter life in the world’s oceans.
Ultimately acidification can only be reversed by reducing carbon emissions into the atmosphere. In the short run, however, other strategies could help to mitigate the impact on ocean life. NOAA is working with university and shellfish industry scientists in the Pacific Northwest to monitor ocean chemistry and develop responses, such as reducing nutrient pollution from land, which also contributes to acidification.
Next month’s science post will explore the deep oceans for more science topics, including deep ocean life forms; the geology of the ocean floor; and the chemical and biological processes slowly breaking down the Titanic at its underwater resting site.