El Niño and Ocean-Atmosphere Interactions in the Tropical Pacific
This activity investigates the oceanographic and climatic characteristics of El Niño/La Niña (ENSO) events using observational data from moored ocean buoys in the tropical Pacific Ocean. Data are obtained from NOAA's Tropical Atmosphere Ocean (TAO) project website which provides a web-based interface for accessing and displaying oceanographic data. In addition to providing an introduction to ENSO, this activity is designed to give students practice interpreting real oceanographic observations by emphasizing the description and identification of patterns in large data-sets. Students first describe patterns in sea-surface and cross-sectional transects of ocean temperatures and surface winds associated with "normal", El Niño, and La Niña years and then use this as a basis for classifying observations from unknown years and interpreting connections between oceanographic and atmospheric processes occurring in the tropical Pacific.
This activity is used in a 200-level undergraduate oceanography course and is a required core course for Geography majors. The course is considered an intermediate level course in that students are required to have taken at least one of the following courses as a prerequisite: Physical Geography, Physical Geology, or Meteorology. While skills and concepts are geared towards students with some background in the geosciences and those that are expected to take additional courses in the major, the content is an introduction to ocean science.
Skills and concepts that students must have mastered
Students should be familiar with the basics of vertical and horizontal variations in temperature and salinity in the ocean and the connection between temperature, salinity, density, and water movement. In addition, some background in the relationship between atmospheric circulation and ocean circulation is assumed. Students should know what the thermocline is and how to identify it in contoured cross-sections. They should also have some context for understanding upwelling and downwelling and the causes of vertical water movements in the ocean. No background in El Niño is required. In fact, I intentionally have students do this activity prior to any discussion of El Niño because I want students to focus on their own observations of the data and not any preconceived ideas.
How the activity is situated in the course
This activity is assigned as a stand-alone exercise completed independently, outside of class. However, it likely could be completed as a lab activity where the instructor is able to provide greater feedback to students while they are in the process of interpreting the data.
Content/concepts goals for this activity
The goals of this activity are:
- To develop observational and descriptive skills relevant to the interpretation and communication of complex (real) oceanographic data sets.
- To identify and interpret evidence of the connection between the atmosphere and the ocean
- To provide an introduction to some of the fundamental oceanographic features associated with ENSO events.
Higher order thinking skills goals for this activity
Students are forced to recognize and describe patterns in oceanographic data sets that they can then use to classify different situations. Students are asked to synthesize their observations within the context of their general understanding of ocean-atmosphere interactions. Students are asked to pose questions related to what they have observed in this activity and describe an approach that could be used to solve these questions.
Other skills goals for this activity
Description and Teaching Materials
Teaching Notes and Tips
I have found that students are frequently confused by the fact the western Pacific is a region described by longitude degrees east whereas the eastern Pacific is a region described by longitude degrees west. I have tried to emphasize this in the activity description provided to students, but it is something that needs reinforcing.
The other common pitfall is that students tend to dive right into an interpretation of the data without describing the evidence for their interpretations - which is why I try to emphasize that the first part of the written assignment should be purely descriptive.
Students are assessed according to the thoroughness of their descriptions of the data, their ability to accurately classify the unknown data sets, and their ability to draw connections between their observations and their general understanding of oceanographic processes and ocean-atmosphere interactions.
References and Resources
Homepage of the Tropical Atmosphere Ocean (TAO) project
. This site provides excellent background information on El Niño and provides data access and visualization tools that are used for this activity.