Geoscience Semester 2 Final Practice - Module 4

Carbon dioxide is naturally present in the atmosphere as part of the Earth's carbon cycle. Human activities are altering the carbon cycle, by adding more CO2 to the atmosphere and by influencing the ability of natural sinks, like forests, to remove CO2 from the atmosphere. While CO2 emissions come from a variety of natural sources, human-related emissions are responsible for the increase that has occurred in the atmosphere since the industrial revolution.

Consider the graph above. Notice the trend in atmospheric carbon dioxide as recorded at recording stations over Antarctica. Hypothesize how the schematic of the carbon cycle might change if urbanization and deforestation continue unchecked.

• Both the carbon dioxide sinks and the carbon dioxide outputs will increase so the numbers should reach equilibrium.

• The photosynthesis carbon sink will decrease in gigatons; the carbon dioxide output due to combustion will increase.

• All of the carbon dioxide sinks will decrease in gigaton amounts; the carbon dioxide output due to combustion will increase

• Carbon dioxide outputs due to combustion of fossil fuels continues to increase; the rate of photosynthesis will also continue to increase to accommodate this.

The ocean's biological carbon pump is driven by organisms that live in there. Just like the terrestrial carbon cycle, the oceanic biological carbon pump is all about photosynthesizing, respiring, eating, producing waste products, dying and decomposing. The biological pump plays a major role in all BUT ONE of the processes involved in oceanic carbon cycling.

• moving carbon throughout the ocean via food webbing.

• moving carbon down to sea floor sediments via the processes of death and decomposition.

• transforming carbon compounds into new forms of carbon compounds like calcium carbonate in shells.

• upwelling currents bringing deep, cold ocean water to the surface to warm and release carbon back to the atmosphere.

The oceans absorb carbon through three processes that draw atmospheric carbon dioxide into the oceans: the physical carbon pump, the biological carbon pump, and the carbonate pump. Molecules of CO2 enter the ocean by diffusing into the sea surface waters and dissolving as part of the physical carbon pump. Select the variable influences how much CO2 will diffuse in any given location.

• wind

• salinity

• water temperature

• geographic location

The Great Lakes ecosystem contains various types of habitats: forests, marshes, wetlands, and dune communities. These communities allow for more than 3,500 species of plants and animals to inhabit the basin. The many varieties of mammals, amphibians, reptiles, birds, and fish make the Great Lakes basin a unique and complicated ecosystem. The northern parts of the Great Lakes region are home to dense coniferous and northern hardwood forests, while largely grasslands and prairies cover the southern areas of the region. The marshes, wetlands, and dune communities are located near and along the many lake shores. Yet the Great Lakes ecosystem is in a state of change. Climatologists have determined that the climate of the Great Lakes basin will increase by 2 to 4 degrees Celsius. Warmer air temperatures affect lake levels by reducing runoff and increasing evaporation from the lake surface. Studies have shown that the predicted increase in air temperature will drop lake levels by half a meter to two meters

• Photosynthesis would increase; so would respiration. Arrows A and B, over the land, would enlarge

• Warmer temperatures will result in an increase in the levels of atmospheric carbon dioxide; arrows B, D, and F will enlarge.

• Warmer temperatures may cause an initial increase in photosynthesis as well as cellular respiration until a point is reached where the temperatures are too hot. During this initial time, the arrows will remain reciprocal, but may enlarge.

• Increased carbon dioxide causes the increased temperatures. The Output arrows would be larger and the input arrows would be smaller.

Carbon dioxide diffuses into the ocean carbon cycle via the air-sea surface exchange. Molecules of CO2 enter the ocean by diffusing into the surface waters and dissolving. The amount of CO2 that diffuses and dissolves in the surface water depends on several variables. Scientists have noted that sea more CO2 diffuses and dissolves in colder sea surface water and less CO2 diffuses and dissolves in warmer water. Let's assume the predictions of scientists predicting a warming climate are true. Can you predict the outcome if average ocean temperatures increase as well? Include the effects on appropriate components of the biosphere as well as the hydrosphere.

• Warmer oceans would result in an increase in dissolved CO2. That in turn would result in a shift in the oceans to more photosynthesis, respiration, and decomposition.

• Warmer oceans would result in an increase in dissolved gases in the oceans. An increase in the CO2 would result in an increase in the rate of photosynthesis of autotrophs found in the oceans.

• Warmer oceans would mean less dissolved CO2 as well as other gases such as oxygen in the global ocean. Lower CO2 would result in a decrease in photosynthesis of autotrophs living in the oceans....Answer 3Click to enter comments, if the student chooses this answer

• Warmer oceans result in less dissolved CO2 in the oceans and more CO2 diffusing into the atmosphere. The extra CO2 would cause increased global warming, eventually causing a spike in temperatures around the Earth and massive extinctions.

Carbon is a major component of all organic compounds, including carbohydrates, lipids, proteins, and nucleic acids. Carbon dioxide is continually exchanged between the atmosphere and oceans. What geological process returns carbon to the atmosphere in the form of carbon dioxide?

• respiration

• transpiration

• volcanic activity

• decomposition of marine sediments

Large volcanic eruptions can have an almost immediate effect on Earth's climate. Rather than warming the climate volcanic eruptions helps to cool the climate. During the 1900's there were three large eruptions that caused the entire planet to cool down by as much as 1oC. Volcanic coolings persist for only 2 to 3 years because the released aerosols fall out of the stratosphere and enter the lower atmosphere where rain and wind quickly wash them away. Using the model, can you elaborate on the reason a volcanic eruption might cool the climate?

• A dark lava flow absorbs more of the solar energy than even a desert soil, so a large enough lava flow could warm a local region.

• Aerosol gases released by the eruption move into the upper atmosphere. These gases disrupt the ozone, widening the hole that already exists. As a result, there is more incoming solar radiation, causing the Earth to become warmer.

• Sulfur dioxide emitted into the stratosphere combines with water to form sulfuric acid aerosols. This makes a haze of tiny droplets in the stratosphere that reflects incoming solar radiation, causing cooling of the Earth’s surface.

• The by-products of combustion, water vapor and carbon dioxide, remain in the atmosphere after an eruption. The result is a greater build-up than normal of the greenhouse gas, carbon dioxide, results in the warming of the Earth's climate.

The rain forests of the world trap a large amount of carbon dioxide, a greenhouse gas. Every year, however, more rain forest is cut down and burned, releasing huge amounts of carbon dioxide. Which graph BEST shows the likely effect on climate?

• A

• B

• C

• D

If Earth's atmosphere did NOT contain any water vapor, the temperature of the earth's surface would

• be about the same.

• be unable to fluctuate.

• be significantly lower.

• be significantly hotter.

The climate of a place also depends upon the amount of water in the air. How do the rising temperatures around Earth affect the amount of water in the air?

• The water in the air evaporates because the temperature of air is rising.

• There is more water in the air because the rate of evaporation increases.

• The water in the air decreases because the water on Earth starts evaporating.

• There is less water in the air because the evaporated water falls down as rain.