assignment

GEOG 3390 D01 Assignment #2 1 CLAYTON H. RIDDELL FACULTY OF EARTH, ENVIRONMENT, AND RESOURCES DEPARTMENT OF ENVIRONMENT AND GEOGRAPHY GEOG 3390 INTRODUCTION TO CLIMATE CHANGE AND ITS CAUSES ASSIGNMENT #2 : CURRENT CHANGE IN CONTEXT INTRODUCTION This assignment will examine the use of various proxy measures to estimate past climate change events. You will be working with real data and use the data to examine past temperature. In the final section of this assignment, students will be asked to critically examine a specific historical climate change event based on peer -reviewed literature. NOTE : the quality of your presentation (neatness, spelling, grammar, etc.) is an important component of your grade for this assignment. Make sure t o provide answers in complete answers. Failure to use complete sentences will result in a grade of 0 for that question. Provide all answers to the following questions in one document (do not submit handwritten paper assignment) ASSIGNMENT SECTION I: Paleo climate P roxies - Foram Coiling Direction (10 marks) Background: Foraminiferids (“forams”) are unicellular organisms (“protists”) that are mostly planktonic, meaning that they float in the upper (sunlit) portions of the ocean water. They are heterotrophic – th at is, they need to eat – and their food consists of phytoplankton they snag out of the water with leglike “pseudopods.” Forams have hard external skeletal material, like a snail has a shell. Technically, these skeletons are known as “tests.” They are made of calcite, CaCO 3. Forams grow by adding new chambers to their tests, like we might add newer, bigger rooms to a house. Each chamber looks a bit like a bulb or a globe (Figure 1) . Interestingly, when ocean water temperatures are cooler than 8° to 10° C, f orams add these new chambers in a counter clockwise spiral (“left -coiling”). When temperatures are warmer than 8° to 10° C, they add their new chambers in a clockwise spiral (“right -coiling”). The coiling direction of fossil forams can therefore serve as a n indication of ancient temperatures. We call this sort of evidence a “proxy” of paleotemperature. Proxies are not direct measurements of temperature, but they are evidence of ancient temperatures. Figure 1: Examples of right - and left -coiling of for am ( Photo Credits: Michael Hesemann, Foraminifera EU ) In this activity, you will calculate the proportions of left - and right -coiling individuals of one of the most common foram species, Neogloboquadrina pachyderma . The specimens were collected from seaflo or GEOG 3390 D01 Assignment #2 2 sediment samples from different periods of time over the last 160,000 years. Your calculations will make a graph. Then you will interpret that graph to arrive at an interpretation of what Earth’s climate was doing during this interval of time. Using the spreadsheet provided in UMLearn (foram_coiling_direction_activity.xlsx) , • calculate the total number of Neogloboquadrina pachyderma for each age. • calculate the percentage of left and right coiling Neogloboquadrina pachyderma for each age • once y ou have completed the table, a graph will be automatically drawn. Question 1: Provide a copy of the table and graph in your assignment (do not submit the Excel file, rather copy in the Word document ) (3 marks) Question 2: Which geological epochs are include d in your study’s sampled time period? (1 mark) Question 3: According to the coiling direction of the sampled forams, when was the temperature warmer ? When was it cooler ? (2 marks) Question 4: What are some limitations to using this data for estimating climate change events? Be specific for this proxy measure (4 marks) SECTION II: Paleo climate P roxies – Vostok Ice Core (10 marks) Background : The Vostok ice core was drilled at a Russian research station high on a dome of glacial ice in Antarctica by an international team of researchers. It provides valuable paleoclimate data going back more than 400,000 years. One way of estimating temperature from the ice core data is to examine isotopic variations in hydrogen. Water, of course, is a molecule made of two atoms of hydrogen and one atom of oxygen. Like many other elements, hydrogen comes in neutron -heavy and neutron -light versions (isotopes). Nor mal hydrogen has one proton only, but some hydrogen has a neutron as well, making 2H, also known as “deuterium,” and usually abbreviated as “D.” The signature of ancient temperature can be found in the ratio of heavier to lighter versions of hydrogen. Whe n it is warmer out, there is more energy to power evaporation of heavy (D -containing) water molecules from the ocean. This means the ocean gets isotopically “lighter” during warm times, and the water that evaporates and later condenses into clouds and fall s as precipitation (snow, in Vostok’s case) gets isotopically “heavier.” During cold times, the opposite is true: there is not enough energy to boost heavy water molecules out of the ocean as vapor, so the ocean gets isotopically heavier, and the snow (mad e from the water molecules that succeeded in evaporating) gets isotopically more “lightweight.” Researchers measure the ratio of D to H using a machine called a mass spectrometer. They can then describe the “mix” of D and : in a sample of water (or ice) with a single number, called the δD (pronounced “delta -deuterium” , using: δD = (((D/: of a sample)/ (D/: of a standard)) – 1) x 1000 (The “standard” is "Vienna Standard Mean Ocean Water" (vSMOW), which is not seawater that has salt in it, but rather water that evaporates from seawater, without any salt coming with it.) GEOG 3390 D01 Assignment #2 3 The thing to remember about δD is that when δD decreases, it means that : is increasing in proportion to D – that the overall mix of the two isotopes is getting skewed toward the lightweight isotope. So: lower δDs mean more : and less D; this indicates a lower temperature (because there was less energy available to evaporate water molecules containing D atoms from the ocean). When δD is higher, it means there is more D and less H; this indicat es a higher temperature (with more available energy to evaporate water molecules containing D atoms). The unit we use to express δD is “per mil,” which basically means “out of a thousand,” in the same way that “per cent” means “out of a hundred.” Per mil i s written ‰, which is just like the % symbol with one more “0,” just as a thousand (1000) has one more “0” than a hundred (100). Using the spreadsheet provided in UMLearn (Vostok_ice_core_data.xlsx ), calculate the temperature from δD using the equation: Temperature (° C) = -55.5 + (δD + 440) / 6 Once you have completed the table, a graph will be automatically drawn. Question 5: Provide a copy of the table and graph in your assignment (do not submit the Excel file, rather copy in the Word document (3 marks) Question 6: Which geological epochs are included in your study’s sampled time period? (1 mark) Question 7: What is the total range (maximum minus minimum) of paleotemperatures recorded by the dataset? (1 mark) Question 8: Describe the pattern of temperature in Antarctica over the time period . (2 marks) Question 9: How does this data set compare to the data set you examined for Section 1 ? (Compare the two graphs) What do they have in common? How do they differ? (3 marks) SECTION III: Historical Climate Change Event (10 marks) Using the key papers by Hoffman (1998) and Allen (2008) (available through UM Libraries) write an opinion paper either in support of or against the Snowball Earth Hypothesis. Write an opinion paper that: • briefly review the controversy (approximately a pa ge) (3 marks) , and • state your opinion regarding the support o f the Snowball Earth Hypoth esis (maximum of 3 pages) (5 marks) An additional 2 marks will be provided for style of the paper (i.e. spelling errors, referencing, etc .). This essay should be no more than 4 p ages (Arial font, double spaced, 12 -point font). You are able (but not required) to use additional resources . Remember that you must cite all references you use using APA format (see course syllabus). Allen, P. A., & Etienne, J. L. (2008). Sedimentary challenge to Snowball Earth. Nature Geoscience , 1(12), 817 -825. Hoffman, P. F., Kaufman, A. J., Halverson, G. P., & Schrag, D. P. (1998). A Neoproterozoic Snowball Earth. Science , 281 (5381), 1342 -1346.