Lab2_OzoneHole

Earth Science Lab Name: Natasha Woods Introduction to the Ozone Hole Objectives · Interpret atmospheric ozone data · Investigate causes of atmospheric ozone change · Write “testable” hypotheses Laboratory Materials · Computer with internet access Pre-lab Assignment Prior to lab, complete the Ozone tutorial in Blackboard. This tutorial will review what ozone is and how the ozone hole forms and ensure you are prepared to complete this lab. Exercise We will begin our look at the ozone hole by investigating the current conditions. Using your internet browser, please go to http://ozonewatch.gsfc.nasa.gov/monthly/SH.html to see the current conditions. On this webpage, you’ll see the current month projected on a globe positioned over Antarctica. You can click on this globe to see an enlarged map. The amount of ozone in this map is measured in Dobson units, and is represented by color on the map. The scale showing the amount of ozone is shown with the scale below the map. Using this scale and the enlarged map, answer the following questions: 1. Estimate the amount of ozone in Dobson units directly above the south pole (0°S). It is about 190 Degrees. I only say a little less than 200 even though that’s the closest marker because the blue area seems to skew left a little. 2. Estimate the amount of ozone in Dobson units at 60°S latitude. This is the light black line that encircles Antarctica. Your answer should be a range. I would say it’s about 150-390. There is a range of deep blue to yellow. 3. Based on this map, do you think a hole in ozone present over Antarctica at this time? Yes, there is a hole over Antarctica, but it is important to note that when we talk about there being a “hole” it just means extreme thinning. Over Antarctica there is less ozone in Dobson units than everything surrounding the area and that is typically considered a hole.

Now, we will use the Monthly images of the Antarctic Ozone Hole from 2013 to make observations and develop hypotheses about annual variations in the ozone hole. To begin, go to https://ozonewatch.gsfc.nasa.gov/monthly/monthly_2013-01_SH.html and cycle through the monthly images (use the links below the map). Then, answer the questions below: 4. Now that you’ve seen the annual variation in ozone during 2013, review your answer to question 3. Do you still agree with your answer to question 3? Explain your reasoning. Note: Do not change your answer to question 3! I think I still agree with my answer. There isn’t necessarily a complete lack of ozone in the area just thinning. Science considers this thinning a hole so yes there is a hole. It does continually fluctuate so sometimes it is worse than others. This ‘hole’ fluctuates with the Antarctic spring. 5. During which month(s) do you see the highest values of ozone over Antarctica? December 6. During which month(s) do you see the lowest values of ozone over Antarctica? September 7. How long did the ozone hole last in 2013? At its full dark blue range, it lasted about two months. From September-Mid November. 8. During which months does the southern hemisphere experience summer? December, January, February 9. Is insolation (incoming solar radiation) high or low at this time of year at the south pole? Incoming solar radiation would be high since the tilt of the earth will put this hemisphere closer to the sun more often. 10. During which months of the year does the southern hemisphere experience winter? June, July, August 11. Is insolation (incoming solar radiation) high or low at this time of year at the south pole? This isolation would be low since the sun is not hitting the area as often.

17. Write a hypothesis to explain your answer in question 16. Specifically, propose a reason to explain why the ozone hole has gotten (larger, smaller or stayed the same) since 1979. My hypothesis is that hole in the ozone got larger for about 15 years after the Montreal protocol was enacted due to the half life of CFCs in our atmosphere and the fact that they weren’t immediately phased out. I also hypothesis that in the last 20 years the hole has gotten smaller due to the now almost eliminated use of CFCs. The Montreal Protocol was established in 1989 to stop the production and use of ozone destroying chlorofluorocarbons (CFCs). The table below shows the atmospheric lifetimes for a number of CFCs. An atmospheric lifetime is the time it takes for the concentration of the compound to decrease to their naturally-occurring level in the atmosphere. Chemical Name Atmospheric Lifetime (Years) CFC-115 (C 2 F 5 Cl) Monochloropentafluoroethane 1020 CFC-13 (CF 3 Cl) Chlorotrifluoromethane 640 CFC-114 (C 2 F 4 Cl 2 ) Dichlorotetrafluoroethane 190 CFC-12 (CCl 2 F 2 ) Dichlorodifluoromethane 100 CFC-113 (C 2 F 3 Cl 3 ) 1,1,2-Trichlorotrifluoroethane 85 Halon 1301 (CF 3 Br) Bromotrifluoromethane 65 CFC-11 (CCl 3 F) Trichlorofluoromethane 45 CCl 4 Carbon tetrachloride 26 Halon 2402 (C 2 F 4 Br 2 ) Dibromotetrafluoroethane 20 Halon 1211 (CF 2 ClBr) Bromochlorodifluoromethane 16 Methyl Chloroform (C 2 H 3 Cl 3 ) 1,1,1-trichloroethane 5 18. How many years have passed since the Montreal Protocol was established? Show your work. 2023-1989= 34 years 18. Explain how the information in the table above helps you understand your answer to question 16.

There are only two types of CFCs that last less than 20 years in our atmosphere. Out of a comparative 11 that were most likely all released before the Montreal protocol was enacted, only two having died off in 10 years is likely to not show significant results. On top of that, with them not being completely phased out yet, this makes sense. 19. Does the information in the table support or nullify your hypothesis from question 17? It supports my hypothesis by proving that CFCs naturally die off in our atmosphere, but it does take time. The hypothesis about them still being used after the Montreal protocol is not mentioned. Conclusion Spend 5-10 minutes reviewing what you’ve learned about stratospheric ozone and the ozone hole centered over Antarctica and then answer the following Thought Questions in complete sentences. Remember these questions are 20-30% of the total lab grade: 1. How and why has the stratospheric ozone layer over Antarctica changed over time? The stratospheric ozone layer (not the hole, but the layer itself) decreased up until about 2000 due to the atmospheric life of CFCs and the timeline of the Montreal Protocol. The protocol was enacted in 1989 and since then four of the CFCs in the atmosphere have depreciated according to their atmospheric life. CFCs or chlorofluorocarbons are man made chemicals that are released into the atmosphere that make their way up to the ozonosphere. The chlorine atoms break down the ozone layer by separating the oxygen atom. This means the ozone layer traps less of the sun’s UV-B rays and allows more to penetrate our atmosphere and reach the earth’s surface. I believe it is also important to note that the ozone layer is slowly repairing itself and has been for the last 20 or so years. 2. How and why are the concentrations of stratospheric ozone over Antarctica expected to change in the future? Without new CFCs being released into the atmosphere we can expect another large dip in the size of the hole in the ozone in about 11 years. It will continue to decrease as each different type of CFC comes to the end of its atmospheric life. According to this table for another 1000 years we will still have some remaining CFCs in our atmosphere however, scientists have mentioned that around 2060 we will be back to the same place as we were in 1979. That doesn’t mean there won’t be a hole, but it will be significantly smaller.