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masc 401 test 3 take 2
Terms in this set (21)
Is the chemical composition of sea water salts constant over long geological time scales? Why or why not?
The chemical composition of seawater is relatively constant over geological time scales due to constant composition, which states that the input and output are essentially equal for the chemical composition
Which geological processes are the principal sources and sinks of sea salts that control the salinity of the ocean
Geological processes such as volcanoes, weathering, hydrothermialism control sinks. Evaporation and precipitation also control sinks. The more precipitation the less salty (more diluted) the water. The more evaporation makes less water making the ocean saltier. Seafloor spreading
List eight dominant ions that are dissolved in seawater
Na+, Ca2+, Mg2+, Br-, SO4 2-, Cl, K, I, HCO3, F
River water typically contains about twice as much Ca as Na. Seawater however, contains about fifty times more Na that Ca. Explain why Na rather than Ca is the major cation in seawater?
Seawater has a much higher salt concentration than calcium in the water because the ocean contain biological organisms that take up calcium and use it (shells)
-Ca2+ (biological control) vs Na+ (geological control)
-Na+ has longer residence time
Define pH and seawater alkalinity
Alkalinity determines how much carbonate is in the sea water
-Ocean Alkalinity refers to the Carbonate Alkalinity which expresses the amount of carbonate in the ocean as a molar concentration. The amount of carbonate correlates to the buffering
-Sea water alkalinity is the basic/ alkaline measure of the ocean. It has a pH ~ 8.1 because it uses the carbonate equilibrium as a buffer
Explain in general outline the carbonate buffer system that stabilizes the pH of the oceans, and write down the equilibrium equation of all reactants, from CO2 to carbonate
-CO2 (g) + CO2 (aq) ←> CO2 (aq) + H2O < -- > H2CO3 < -- > H+ + HCO3- < -- > H+ + (CO3)2-
-Co enters the ocean and reacts with water to form H2Co3. Then it further breaks down to H and HCO3 until it finally reaches 2H + Co3. the resulting Co3 can later bind with calcium to form calcium carbonate that is the structure for many organisms shells
-Keeps the pH to a very narrow rename so that organisms in the ocean are able to survive
Reaction is able to go forward and backwards
Explain the buffering capacity of seawater by writing down the four most important chemical equations within the carbonate equilibrium that buffer protons (H+) and hydroxide (OH-) ions
H+ + HCO3- H2CO3
H+ + CO3-2 HCO3-
OH- + HCO3- H2O + CO3-2
OH- + H2CO3 H2O + HCO3-
Why are freshwater lakes generally more sensitive to acid rain (rain water with low pH, due to dissolved acidic gases) than the ocean? Give geographic examples for acidified lakes and their host rock
Because they do not have a buffering system like the ocean . acidified lakes are due to chemical weathering when water hydrolysis the granite and erodes it a little at a time
Ocean has a large amount of volume to disperse the acid in
Freshwater (around 7) has a lower pH than seawater (around 8)
Draw water column profiles typical of (a) biounlimited, (b) biointermediate and © biolimiting elements. Your scale on the concentration axis can be arbitrary, but should reflect the essential differences between biounlimited biointermediate and biolimiting elements. Give two examples of each type of element.
Biolimiting: NO3, PO4, Si(OH), O,N,P, Fe
Bio intermediate: CO2, Ca
Bio unlimited: Cl, Na, Mg, SO4, K, Br
How do the water column profiles of biolimiting elements differ in the Atlantic and pacific ocean and why?
Pacific deep water is older and holds more nutrients than Atlantic deep water because it has circulated around the earth using deep water currents
Nitrogen is dissolved as an atmospheric gas everywhere in the ocean;why is nitrogen then an extremely biolimiting element for phytoplankton growth?
N2 is limiting because it is only attained in the top level of the ocean where there is an abundance of light. The plankton fix the atmospheric nitrogen and use it as energy to grow
Nitrogen gets fixed by a lot of organisms in the ocean and once in use is not available until the organisms undergoes decay
Aolian transport (by wind) is an essential supply route for which biolimiting element?
What evidence demonstrates that atmospheric CO2 levels have been changing during the geologic past, and in recent times up to the present day? Where does the evidence come from?
Observations at Mauna Loa and Vostok dome C deposits
Calcifying organisms in bubbles in ice cores (found in Greenland and Antarctic)
He made a note on my test to mention the keeling curve
Describe the major driving forces that have cause changes in the earth's climate (ice age- interglactial times) during the geologic past
Based off of the Milankovitch cycle.
This cycle states that based off of the earth's orbit and tilt the earth will experience different types of weather patterns .
when the tilt is at tits max the summer will be extremely hot and the winters will be extremely cold.
When the orbit is at its max there will be long seasons. This along with the global conveyor belt cause the the ice age. The belt transfers heat around the oceans. If it slows down/ stops not enough heat will be transferred and the oceans will cool.
Wobble at maximum reroutes oceanic conveyor belts
Increased wind = increased iron levels = increased phytoplankton activity = decreased atmospheric CO2 levels
Burning of fossil fuels
Why is the melting of glaciers on Greenland, and shelf ice and glaciers in Antarctica of particular concern with respect to sea level change, in comparison to melting of arctic sea ice?
Since greenland and other shelf ice and glaciers are not part of the ocean originally the ice melts and flows into the ocean making it rise. Arctic ice is already in the water so as the ice melts it displaces the space it was originally occupying
Imagine a parallel planet, similar to earth in almost all aspects, except that the biological pump that exports organic carbon into the deep sea does not work and all of primary productivity is recycled to CO2 in the surface ocean. If the rate of primary productivity was doubled, what would the effect be on atmospheric CO2 concentrations, and why? What would be the effect on atmospheric oxygen concentrations, and why?
The CO2 and O2 concentrations in the atmosphere are controlled by burial of carbon in the sediments. If the burial of sediments were to increase due to the increased production, then you would see a draw down of CO2. Since the burial rates are the same, there is no change. That said, it is very likely that there is more biomass on the parallel planet.
Describe the function of hydrothermal vents as chemical sources in the ocean, starting with at least three examples for chemicals that originate in the hydrothermal vent subsurface, a short description of how each compound is produced in the hydrothermal subsurface and a short description of what happens to each compound after they emerge from the vent orifice
Sulfate is reduced to sulfide
Bicarbonate turns into Co2 and reduced to methane
Metals are leached out and emerge back to the seafloor and water column
Describe the function of hydrothermal vents as chemical sink (choose two examples), and explain how dissolved ions in seawater are retainer transformed in the hydrothermal vent subsurface
Oceans circulate through hydrothermal vents every 5-11 million years
NEED MORE INFO
Name two carbon-based greenhouse gases and name for each gs its sources and sinks
CO2 - fossil fuels, respiration, photosynthesis, phytoplankton
Chlorofluorocarbons - old appliances
Methane - cow manure, melting permafrost, farts, nitrogen fixing bacteria, hydrothermal vents, agriculture
How does the warming of the Arctic affect the release of greenhouse gases that are entering the ocean and the atmosphere from arctic sources?
Less ice = less albedo so less sunlight gets reflected back into space = increased temperature which fuels the greenhouse effect and increases CO2 levels
Permafrost melting contributes to the release of greenhouse gasses because as it melts, it exposes organic carbon that begins to decompose, releasing a lot of CO2
Microbial decomposition of biomass to CO2 and CH4
What are specific challenges in monitoring the flow of greenhouse gases in the Arctic?
Very cold climate
Being eaten by wild animals
Looking for "bubbles" in arctic lakes when they are frozen over can be difficult
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