The study of glaciers is intimately connected to the study of Earth's climate variability over time. Geoscientists have been intrigued for decades by the geologic record of climate variations throughout Earth's history. This is especially true of the evidence for repeated"ice ages" during the last 2 million years of Earth history.

For this exercise, you will have an opportunity to access and download one of the most important records of Earth's climate variability - the record of atmospheric carbon dioxide concentrations during the last 420,000 years.

In order to access these data, you will need to acquire some new skills using the spreadsheet software, Excel by Microsoft.

1. Go to the website ofNational Geophysical Data Center. Once at the site, locate the"Paleoclimate" link on the menu at the left side of the screen and click on the link.

2. At the Paleoclimate page, choose the"Paleoclimatic Data" link. Choose"Ice Cores" from the menu of selections on the left side of the page.

3. Click on the map of Antarctica on the right side of the Ice Core page and wait for the application to load. When the map loads, move your cursor over the red dots until you have located the Vostok Station (see Fig. 12.10 of your textbook). Click on the"Vostok" dot.

4. When the data availability module loads, use the pull down menu to locate"CO2 Data, 420KyrBP" and select it, then click on the"DATA" button to view the data on your computer screen.

5. You will see two columns of data. One is labeled"Gas Age" and the other is CO2 (ppmv). Use your cursor to select these data by clicking at the beginning of the first column and dragging your mouse down the page until you reach the end of the data.

6. Once you have selected all the data, copy the data to your computer's clipboard by using the Edit Copy command from the menu bar.

7. Next, locate Microsoft Excel on your computer and start the program. When the program begins, click in the upper left cell on the page, then select Edit and"Paste Special" then"Text" from the menu. If your data did not paste into separate columns, you will need to select column A, then under the"Data" tab on the menu bar, select"Text to Columns" option. You should also choose"Space delimited" for your data.

8. You should now have your ice core data in two separate columns in the spreadsheet. Next you will create a graph of the data. Note that the first column of data represents age in years before present and the second column is the concentration of atmospheric carbon dioxide gas.

9. To create a graph, first select the data in both columns. Next, choose"Insert" then"Chart" from the menu at the top of the page. When the dialogue box appears, choose the"XY (Scatter)" option for our graph. To help visualize the data, choose one of the scatter plots that connects each point with a line.

10. Now click"Finish" and a graph of the data will be pasted onto your screen. Examine the data and answer the questions below by searching the Ice Core Data website for information. Good Luck!

a. What does your graph represent? What are the data that you have plotted?

b. Why do the graphed data go up and down? What does this represent?

c. On the horizontal axis, where is the youngest age and where is the oldest?

d. What do the peaks on the graph represent? What was Earth's climate like during these intervals?

e. What do the valleys represent? What was Earth's climate like during these intervals?

f. How were these data obtained? How is it that geoscientists were able to obtain a sample of Earth's atmosphere from our ancient past?

g. Describe what you see on this graph. Do you find anything interesting about it? What do you suppose causes the graphed data to rise and fall? Can you relate this graph to your knowledge or experience in geology? Can you relate this graph to your knowledge or experience with the concept of glaciers?