Geological Sciences 101 Lab #13 - Records of and Present Change

INTRODUCTION This lab has several parts. First, we will access paleoclimate data sets acquired by drilling into layers of ice preserved in Antarctic ice sheets. We will plot them with Excel and examine the changes in and atmospheric composition that occurred during the last . We’ll compare these data with similar data gathered in . We will also examine changes in recorded by tropical reefs. After graphing the data to understand their temporal changes will use ArcView to examine these changes spatially. Finally, we will explore modern changes in atmospheric composition that are due to anthropogenic influence.

PART I - GATHERING DATA ON PAST First we will work with data collected by researchers who have drilled into Arctic and Antarctic ice caps to learn about Earth's past climate changes. Just as layers of preserve the record of conditions on the ancient Earth, layers of ice preserve a great deal of information about conditions over the last 200,000 years. Especially important are the tiny samples of ancient preserved in bubbles trapped in the ice, as well as the chemical composition of the ice itself, which contains a record of temperature variation. You will gather data from the Vostok site in , where a joint French-Russian team drilled a 2000 meter long , containing paleoclimate information back almost 250 thousand years before present. We will also look at sea level data from part of this time interval. The record of ancient sea level is obtained from dating found in the world's coral reefs. Since many corals must live just below the surface of the ocean they provide a good measure of ancient sea levels. Getting & Graphing the Data You will use your browser to visit the National Geophysical Data Center in order to download data on . These data are posted and utilized by the world's leading researchers in order to study how climate has changed in the geologic past, and to predict how it might change in the near future. Use your browser to go to: • http://www.ngdc.noaa.gov • Once there, click on the "Paleoclimatology" link. • On the Paleoclimate page, choose the "Paleoclimate Data" link. • In the section titled, "Obtaining Data by Discipline," choose "Ice Cores." • On the ice core page, click on the map of Antactica • Mouse over the red dots until you find one labeled "Vostok" (its on the right-hand side of the map). Click on it.

1 When you click on the Vostok site, you should see a window with information about the site, and a drop-down menu that allows you to choose data sets to download. • Select Data 125-2077m • Use the "Save As" command to store the file on the Z drive in the Geo101/Excel Files folder (note--make sure you don't save the file in HTML format, save it as text). Open your file with Excel: • Find Excel under the Start button (-> Programs -> Office -> Excel). Start Excel. • Use the open command to import the file CO2.txt. You may have to switch to "All Files (*.*)" in the "Files of Type" box, if you don't see your files listed in the Open window. • In the Text Import Wizard window, choose "Delimited" from the Original Data Type window. Click Next. • Choose "Space" in the Delimiters box. Click Finish. We only need two columns from this data set. Delete everything except the column that begins with 1700 and the column that begins with 274.5. • Label the 1700 column "Age (yr)." This is the age of the sample in years before present. • Label the 274.5 column "CO2 (ppm)." These data are measurements of the amount of carbon dioxide gas in the atmosphere throughout the past 150,000 years. Ppm stands for "parts per million." A measurement of 274 ppm means that for every million molecules of atmosphere, 274 of those are carbon dioxide. We have prepared a spread sheet (101_climate.xls) with a variety of data sets for this lab. You should paste your new CO2 data into this file. Look for Geo101/Paleoclimate/101_climate.xls. Open the 101_climate.xls file. • Copy the two columns of CO2 data and paste them into the first page of the 101_climate.xls spreadsheet (Vostok temp data) beside the two columns of temperature data. There is one small inconsistency between these two data sets: the temperature data is given in thousands of years while the CO2 data is given in years. We want to plot both data sets on a single graph, so we'll have to adjust the age of the CO2 data to be consistent with the temperature data. • Insert a column between the Age (yr) and CO2 (ppm) columns. • Divide the age data by 1000 so that it is in ka (thousands of years). Do this by typing an equals sign, then click on the first age value, then type "/1000" and hit enter. You may then drag this formula down to fill all the cells below. Label this column "Age (kyr)." • Save your work. Graph the data: • Begin with temperature. Use the cursor to select the two columns of temperature data, "Age (kyr)" and "Temp (C) +/- present."

2 • Use the graph tool to insert a graph on this page of your Excel spreadsheet. Choose a scatter plot. • Label the graph "Vostok Ice Core," label the X-axis "Age (kyr)," label the Y-axis "Temp (C) +/- present." • Re-scale the X-axis so that is has a minimum value of 0 and a maximum values of 250, in increments of 10 ka. • Now add the CO2 data to the temperature graph. Under the Chart menu choose Add Data. Use the cursor to select the new data to add (Age (kyr) and CO2). A dialog box will appear. Make sure the following boxes are checked: Add cells as : New Series Values (Y) in : Columns Categories (X values) in First Column Depending on how you have “grabbed” your data you may or may not want to also check the box labeled: Series Names in First Row (did you highlight the names of the columns or not?) Note that this squashes all of your temperature measurements (because the range of values in the two data sets is very different). We'll fix this by switching the CO2 data to a "secondary axis." • Double-click on any CO2 data point on your graph in order to access the "Format Data Series" screen. • Choose "Axis," and tell it to plot the series on the secondary axis. • Once this is done, double-click on the secondary axis and re-scale the CO2 data from 150 - 300. • Make your graph "look pretty," and print it.

3 QUESTIONS 1) Examine the record of CO2 and temperature over the last 170,000 years. Are the trends similar or different? Describe. What can you conclude about the behavior of CO2 and temperature over time? 2) Ice ages are identified by their colder . When was the last ice age? What was the temperature difference in Antarctica at that time with respect to the present temperature? What was the atmospheric CO2 concentration during the last ice age? 3) Are there any other ice ages recorded in this data? How many? When? 4) When Earth enters an ice age does the climate cool relatively quickly or relatively slowly? When it warms is it fast or slow? 5) Calculate the rate at which atmospheric CO2 increased (in ppm/year) during the warming period that followed the last ice age (show your work).

PART II - COMPARISONS WITH OTHER DATA SETS • Examine the GRIP Ice Core data in the 101_climate.xls file. These are also temperature measurements made from and ice core in Greenland. • Examine the two graphs; the first shows the entire ice core record, the second graph shows only the last 40,000 years of the data. 6) Do the same ice ages appear in both the Greenland and Antarctic data sets? Was the temperature change in Greenland more/less/the same during the last ice age as it was in Antarctica? 7) Examine the graph of the last 40,000 years. Describe the climate from 10,000 years to the present. Describe the climate prior to 10,000 years ago. 8) Ancient switched from a hunter-gatherer style of existence to and agriculture-based existence approximately 8,000 years ago. Do the paleoclimate data suggest any environmental influence on this development? What might it be? • Switch to the Mauna Loa CO2 measurements. These are modern analyses made in the unpolluted central Pacific ocean. The data record monthly changes in CO2 from March 1958 - December 1999. • Examine the two graphs, the monthly CO2 data and the yearly average CO2 concentrations from 1958-1999. 9) Describe the monthly CO2 data. What process is responsible for the pattern you observe?

10) Calculate the rate of change in the yearly average CO2 from 1958 to 1999 (in ppm/year). Show your work. Is this rate constant across the entire period of observation, or does it change in the more recent years?

11) Compare this rate with the post-ice age change you calculated above. Outline a hypothesis that explains your result. • Switch to the Barbados Coral data. The graph here shows the magnitude of that accompanied the melting of ice caps from the last ice age.

4 12) What is the magnitude of sea level rise from the height of the last ice age to present? 13) What is the most rapid rate of change (in cm/year) recorded during this period?

PART III - SPATIAL ANALYSIS OF SEA LEVEL CHANGE In this part you will learn how to make calculations using ArcView and the digital elevation model of the world. We will examine the of the Pleistocene world, and then examine a global warming scenario. At the height of the last there were northern hemisphere ice caps extending as far south as central Pennsylvania. These large continental ice sheets sequestered a huge amount of sea , lowering sea level significantly, as seen in the Barbados coral data. At present the Earth still has large ice caps in Greenland and Antarctica. If this ice were to melt entirely, sea level would rise by approximately 90 meters. • If there is not already a shortcut on the desktop to “Sealevel.apr,” then open ArcView (under the Start button -> Programs -> Remote Sensing -> ArcView 3.2 -> ArcView 3.2). • Open existing project Sealevel.apr (Z://class/Geo101/Paleoclimate/Sealevel.apr) Calculate sea level changes: • Under the Analysis menu choose Map Calculator. • Double-click on Etopo5, then type <90 and hit "Evaluate." • A new theme is added (called Map Calculation 1) which shows all areas above 90m as "0" and areas below 90m as "1." Change the "0" color to transparent so that you can see the topography. You may want to change the color of the ocean as well. • Drag the cntry95 and cities themes to the top of the legend so that they display on top of the new sea level. • Use the i-button to identify cities and countries (make sure the theme you want to identify is selected). • Use the measuring tool to measure shoreline retreat along the east coast of North America, in Northern Europe, and in South Asia. 14) What would be the average shoreline retreat for each of these three areas, assuming an extreme 90 meter sea level rise? • Repeat the map calculation Etopo5 < -125 (the Pleistocene lowstand). 15) Cite some significant differences between Pleistocene (ice age) and modern geography.

· Use the high-resolution inset maps to raise sea level by 2 meters (in Map Calculator set E_US_1km < 2 etc.) 16) Map the effects of a modest sea level rise of 2 meters. What places will be most significantly impacted? What is the average width of coastline along the eastern US that will be inundated? Make an estimate of the number of people in the Eastern US, Europe, and Asia, who would be displaced by such a change (use the i-button with the cities theme).

5 17) Time to put it all together. Use the data you've collected in questions #1-16 as a basis for the following scenario. You have been chosen to represent the US at the next global climate change summit meeting. Using the data, graphs and insight that you have gained through this lab, present an overview of climate change past, present and future. Illustrate your remarks with the graphs/maps from this lab.

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