GEOL106 Assignment 2 – Climate Change
GEOL 106 USYD Climate Change Questions
Assignment 2: Climate Change
GEOL 106 | Winter 2023
Instructions
Complete the activity detailed below, fill out the Answer Sheet (separate document), and submit the Answer Sheet as a PDF on OnQ.
Introduction
Climate change is not a new phenomenon; it has been occurring throughout Earth history. However, it is now occurring at a much higher rate than in the geologic past.
There are a number of ‘tools’ scientists can use to travel back in time and discover what the climate was like throughout Earth’s history. These tools are called proxies, as they are an indirect measure of historic conditions. By tracking climate change in the past, scientists gain insight into how current conditions fit or diverge from previous behavior, and how the future climate might look. We cover some examples of climate proxies in class and how they can be used to learn about past climate. This assignment focuses on ice core data, which can be used to reconstruct atmospheric composition and climate information going back at least 800,000 years. If you would like to further explore ice core data or play with data from other paleoclimate proxies (coral, tree ring, pollen, soil, etc.) you can download datasets here: https://www.ncei.noaa.gov/products/paleoclimatology Figure 1. Adapted from Alley, R. (2000) By looking at past concentrations of greenhouse gases (such as CO2 and methane) using ice core data, scientists can calculate how modern amounts of these gases compare to those of the past and can compare past concentrations of greenhouse gasses to temperature at that time. Ice cores have been collected since the 1950s from many locations throughout the world, but the majority come from the ice sheets of Greenland and Antarctica. Some cores are from near a Russian base in East Antarctica known as Vostok (see figure below). Conditions of glacial ice formation here provide excellent time resolution, and bubbles in the ice core preserve actual samples of the world’s ancient atmosphere (how cool is that). These same conditions also mean that long, continuous records (~800,00 years) of the ancient atmosphere are ‘saved’ in the thick ice sheet. Figure 2. Vostok Station (Wikipedia) Similar to tree rings, ice cores preserve annual layers which are the result in seasonal differences in snow properties. These annual layers, as well as dust trapped in the ice allow ages to be assigned – scientists can determine how old a layer of ice is. Figure 3. Summer layers (light, arrowed) and winter layers (dark) evident in a 19 cm long ice core (NOAA) Through analysis of ice cores, scientists learn about glacial-interglacial cycles, changing atmospheric carbon dioxide levels, and climate stability over the last thousands of years. The ice contains atoms of hydrogen and oxygen (H2O), and scientists use the isotopic composition of hydrogen and oxygen to estimate the global average temperature at the time the snow fell. In addition, bubbles of air became trapped in each layer of ice as the snow turned into glacial ice. Those bubbles act as tiny time capsules of Earth’s atmosphere at the time the snow fell. From these bubbles of air trapped in the layers of glacial ice, scientists measure the concentration of carbon dioxide (CO2) that was in the air at that time. From these measurements, scientists analyze whether or not variations in the amount of CO2 in the atmosphere correlates with changes in the average temperature of Earth’s atmosphere. Higher CO2 concentrations correlate with higher global temperature, and lower CO2 concentrations correlate with lower global temperatures.
Exercise
In this part of the assignment, you will analyze ice core data from the East Antarctic Ice Sheet, the biggest, thickest glacier in the modern world. The ice core is from the Vostok research station, and was drilled to a depth of 3.2 km. At this depth in the ice sheet, the drill has reached layers of ice about 420,000 years old. Use the data to answer the questions.
1. Explain what the red axis represents.
2. How many glacial periods are present in the data? How many interglacial periods are present?
3. Consider -3° C as the cutoff between glacial and interglacial periods. According to these data, which period seems to last longer: glacial periods or interglacial periods?
4. Describe the rate at which the earth cools into glacial periods and the rate at which the earth warms into interglacial periods.
5. Explain what the blue axis represents.
6. What does 1 ppm refer to as a percentage?
7.
a. What was the approximate atmospheric CO2 concentration 150, 000 years ago?
b. Was this a glacial or interglacial period? Checkout modern CO2 levels reported at Mauna Loa: https://gml.noaa.gov/ccgg/trends/mlo.html
8. What does the red line represent and what does the black line represent? What causes the fluctuations in the red line?
9. What is the most recent value reported?
10. How does this value compare to the trends observed in the paleoclimatic data and how does this relate to modern day climate-change?
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