Oceanography Exam 3.1
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Residence time. Provide formula?
Average length of time that a particle of any substance spends in a defined part of ocean.
[element]/(input OR output)
Define nutrients. Which are the most important to rememebr? (4)
Any organic/inorganic compound used by plants in primary production.
Most important are nitrogen and phosphorus, followed by silicic acid. Iron has been shown to help a lot too.
What are the 5 types?
Process by which organisms use organic materials (food) as a source of energy. Usually uses O2 and produces CO2.
But there is also aerobic, nitrate, iron, and sulfate reduction, as well as methanogenesis.
Define convection vs conduction
Convection - In a fluid being warmed at its bottom and/or cooled at its upper surface, process by which warmer fluid rises and cooler fluid sinks in a density driven circulation.
Conduction - transfer of heat (or electricity) through a material or between two materials in contact with each other by passing directly from one molecule to another adjacent molecule. Basically, when heat spreads through a material (heat from stove through pan).
Define chemical weathering
Breakdown of Earth's rock by chemical mechanisms, the important ones being carbonation, hydration, hydroylsis, oxidation and ion exchange.
What is the chemical reaction for carbonate equilibrium?
What is its purpose? What happens if atmospheric CO2 increases?
CO2 (g) <--> CO2 (aq) + H2O <--> H2CO3 <--> HCO3- (bicarbonate)+ H+ <--> CO32- (carbonate) + 2H+
Purpose: Acts as a buffer system in ocean against acids and bases.
If atmospheric CO2 increases, increases concentrations of carbonic acid, bicarbonate, and carbonate and therefore H+ concentrations --> lower pH. Also, the contribution of CO32- to total CO2 decreases, so less CO32- for calcifying organisms.
Principle of Constant Composition - What does the implicate?
Ratio of concentration of any particular major ion to the total is essentially constant.
Because the residence times of most major elements are long compared to mixing time of ocean, will see uniform distribution of these elements throughout ocean IF distribution is unaffected by biological/chemical processes.
This means that ionic composition of seawater is the same all across, just the concentration are different.
Define conservative behavior vs. non-conservative behavior
Conservative behavior - [ion] only changes by mixing of water masses, not by biological processes.
Non-conservative behavior - [ion] is significantly changed by biological/chemical processes
Global Conveyor Belt. How long is its period? Also called?
Starts in Norwegian Sea --> warm water from Gulf Stream heats atmosphere in cold northern latitudes. Loss of heat to the atmosphere makes the water cooler and dense, causing it to sink to the bottom of the ocean and is transpored north.Then cold bottom waters are able to rise and warm at surface. Goes west to east for cold and east to west for warm.
1000 years. Thermohaline circulation.
Tendency of atmosphere or greenhouse glass to be transparent to incoming solar radiation while absorbing/reflecting longer-wavelength heat radiation from earth.
Photosynthesis vs. Chemosynthesis
Photosynthesis: production of organic compounds from CO2 + H2O (w/ release of O2) in presence of chlorophyll by use of energy as is done by plants.
Chemosynthesis: production of organic compounds from inorganic substances via energy of substances like H2S, NH3, H2 and methane
Difference b/t biounlimited, biointermediate, and biolimiting nutrients?
Conservative or nonconservative? Variation throughout ocean?
Biounlimited - conservative - concentrations are not significantly affected by chemical/biological reactions; little or no variation throughout oceans, constant ratio to Cl- throughout oceans.
Biointermediate - nonconservative (slightly affected by chem/bio rxns) Are usually present in sufficient concentrations to not limit primary production, slight variations throughout oceans
Biolimited - nonconservative (significantly affected by chem/bio rxns), large variations throughout ocean, highly depleted in surface waters --> limit primary production.
Define alkalinity. Formula?
Opposite of acidity; measure of degree to which [OH-] > [H+] in a solution. But in a marine biology setting, it is a measure of the concentration of carbonate ions
CA = 2[CO32-]*[HCO3-]
Define albedo effect. What does a high albedo effect do vs. low albedo effect in terms of solar heat in the Arctic? What type of feedback does this lead to?
- It is the reflecting power of a surface. Measures ability to reflect sunlight. If albedo effect of poles decreases, less able to reflect sunlight, more solar heat is taken up into ocean (as in case of Arctic) --> melting glaciers/snow.
- Leads to negative effect.
Define the biological pump. What does it power? Draw picture
Sum of processes that transport carbon from atm --> surface waters --> ocean's interior. Powers biology of ocean.
Describe the role of the biological pump with increase of atmospheric CO2
How would increasingly high temperatures in climate change affect the bio pump?
Since bio pump in ocean is limited by availability of light and nutrients and not by carbon, does not play significant role in elevation of CO2.
However, climate change may affect bio pump by warming & stratifying surface ocean --> decreasing supply of nutrients to euphotic zone --> decreasing primary production.
Define ocean acidification. What is it caused by?
Ongoing decrease in pH in Earth's oceans caused by uptake of anthropogenic carbon dioxide from the atmosphere.
Increased CO2 increases total CO2 = combined concentrations of H2CO3, HCO3-, CO32-. As a result, more H+ is formed too. This also limits amount of CO32- available for organisms to use
Is iron biolimiting?
Yes. Bc scientists dumped a bunch of bioavailable iron in open ocean (far from land) and saw a increase in phytoplankton growth.
Would increasing efficiency of bacteria that degrade organic C affect CO2 balance in atmosphere?
What is the only way to decrease CO2 in atmosphere? How would adding iron decrease CO2 in atmosphere?
No, bc its compensated for by efficient bacterial degradation of organic matter (releases CO2 in respiration).
By organic matter sinking all the way to the bottom before oxidizing via respiration.. Burial of organic matter keeps Earth from reaching thermodynamic chemical equilibrium.
General rxn describing chemical weathering
General rxn for rainfall?
Rocks + acid --> Dissolved ions + Clay
CO2+ H2O <--> H2CO3 <--> H+ + HCO3-
What is vent water comprised of: What is its pH like? What is it rich in? (4) What ions does it not have? What is the temperature
- 3.5-4.5 --> acidic
- Rich in Zn, Fe, Mn, H2S
Does not have Mg2+ or sulfate SO42-
350 deg C
Draw chemical reactions of hydrothermal vents:
Seawater (3 ions) forms 3 things combines with 5 hot basalt rock ions and expelled as? What are vent chimneys made of? (3) What is not found and where do they go?
What are factors controlling chemical composition of seawater? (3)
What is the predominant removal mechanism of dissolved ions?
- 1. If the element is conservative or nonconservative (biological/chemical rxns)
- 2. Evaporite sequence
- 3. Principle of constant composition
Authigenic mineral formation
What is the sequence of reactions occurring when CO2 is added to water?
Specific pkas? 2
CO2 + H2O <--> H2CO3 <--> H+ HCO3- <--> 2H+ + CO32-
- pka1 = 6.38 (H2CO3 --> HCO3- + H+)
- pka 2 = 10.31
What are processes that affect cycling of elmeents in ocean? For C (3) N (3) S (2)? Name 3 biological processes
- C: photosynthesis, respiration, sedimentation
- N: biological fixation, denitrification, sedimentation
- S: Volcanic activity, hydrothermal processes
Excretion, respiration, photosynthesis
What are the four pieces of evidence leading to discovery of deep-sea hydrothermal activity?
- 1. Fe-Mn rich sediments near ridges (volcanic activity)
- 2. 3He anomaly - mantle/ocean interactions (3He from inside earth has been trapped there since formation)
- 3. Heat flow measurements --> convective heat flow: younger crust = approximate same teperature as older crust (should be hotter).
- 4. Lab experiments: basalt-water interaction at high temperature results in Mg removal.
What are the implications of principle of constant composition?
What's the caveat?
Bc residence times of most elements are long compared to mixing time of ocean, there's generally uniform distribution of these elements in ocean IF distribution isn't affected by bio/chem processes
What does biogeochemical zonation lead to? In what order from top to bottom (6)
Distinct reducing environments in sediments depending on oxidizing agent
What is cut off between POM and DOM?
What keeps Earth from reaching thermodynamic/chemical equilibrium since O2 is a strong oxidant and CH2O is a strong reductant?
O2 and CH2O are kept separate by burial of organic carbon.
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