Exploring Paleoclimate Data

In this graphing activity, students investigate Oxygen-18 data from ice cores used to investigate past climate.

Learning Goals

Overall...

• Students will have an understanding of how scientists use proxy records to infer past climates.
• Students will graph data (using Excel) to evaluate connections between oxygen isotope ratios in ice cores and temperature.

Specifically, students will understand that…

• there are different forms of elements that are known as isotopes.
• different isotopes of atoms evaporate and condense at different temperatures.
• that there are different forms of water (heavy and light) that contain isotopes of oxygen and that these forms evaporate and condense at different temperatures.
• ice core samples from arctic regions contain a nearly continuous record of atmospheric conditions.
• scientists use differential evaporation and condensation rates of water (Raleigh Distillation) that contains isotopes of oxygen to measure changes in temperature in the atmosphere.
• scientists have calculated how the change in oxygen isotopes in ice core samples can be correlated with temperature.
• scientists can use proxy records to determine past climatic conditions and that there are procedures in place which allow scientists to have a high degree of confidence in the information gained through proxy sources.

Learning Objectives

• Students will describe how evaporation and condensation rates differ based on the mass of the matter that is undergoing a phase change and that temperature controls the rate at which matter of differing mass changes phases.
• Students will be able to create charts using Excel and analyze charts for trends.
• Students will develop an understanding of how scientists use proxy records (specifically O-18:O16 ratio in ice cores) to draw conclusions about past climates.

Materials

For the Introduction Demonstration:

• Styrofoam spheres (D = 2 cm)
• Spray paint
• Large clear cylinder (app 18”)
• Box fan (Note: the cylinder or container should be the same diameter (or smaller) as fan blades)

For Learning Background Concepts:

For Exploring Ice Core Data:

• Greenland ice core and temperature data (.xls format)
• Computers with Microsoft Excel for students or pairs

Directions

• A slide presentation will be used to introduce students to the use of proxy records in understanding paleoclimates.
• A brief video showing climate scientists retrieving ice cores and explaining data that can be extracted from ice core samples.
• Students will watch a teacher demonstration that simulates the evaporation and condensation of isotopic compounds.
• Students will answer guiding questions and will be asked to make a connection between the demonstration and the water cycle.

Learning Background Concepts:

• Students will complete a brief reading on how different forms of water (heavy and light) preferentially evaporate and condense and how this relates to the O-18:O16 ratio in ice core samples.
• Students will answers questions on a Background Student Sheet to show understanding of concepts covered in demo and reading.

Exploring and Interpreting Ice Core Data:

• Students will graph actual oxygen isotope ice core data from Greenland and recorded temperatures from this region using Excel. The data comes from twenty sites in Greenland. Multiple samples of ratios between heavy and light oxygen from each site have been statistically averaged through a process known as Principal Component (PC) analysis. Students will create a graph of the isotope data compared to average temperature data collected in that region. Both the ice core and temperature data represent conditions in the winter season (November-April) for the years 1829-1970.
• By answering questions on the student sheet, students will answer synthesis/analysis questions and develop a conclusion on the relationship between O-18:O-16 ratio in ice cores and global temperatures.

Background

Scientists who study the environment often want to know what the Earth was like in the past. Often the information that they seek is from times far more distant than the written record covers. Because no recorded data exists from the distant past for measurements like temperature and precipitation, scientists use what are known as proxy records. These are indirect methods for estimating climatic conditions of the distant past. Some common proxy records that help paleoclimatologists infer the climatic conditions of the past are tree rings, layers of ocean sediments, pollen, and ice cores. In this investigation, we will be looking at how scientists use the ratio of Oxygen-18 to Oxygen-16 in ice core samples to determine past temperatures.