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What causes diff in chem distributions between the Atlantic and Pacific? Pathway of Pacific (4) What is the period of Pacific deep water cycle and how does this affect its nutrient content?
- Pacific deep water is older (b/c of new deep water formation coming into Atlantic) and has spent more time as bottom water. It goes from N to S Atlantic Current --> Indian --> Pacific.
- 1800 years --> has more time to accumulate N, P, silicate, CO2
What is the role of the carbonate system in ocean pH? Why is ocean pH ca. 8.1?
Carbonate equilibrium = strong buffer system
Bc seawater has a high concentration of bicarbonate, which is slightly basic.
What are diff between acidbase & redox reactions?
Do redox rxns require energy? Which elemetn cycles are redox rxns? (3)
Acid-base (carbonate eq) exchange protons
Redox rxns (photosyn and microbial respiration) transfer electrons (oxidation + reduction)
No, they can use or release energy. C, N, S.
What is the link between atmospheric CO2 concentration and temperature?
What would happen w/o greenhouse gases?
- 1. Incoming solar radiation is trapped by CO2
- 2. More CO2 in atmosphere = more sun's heat trapped
- 3. Without greenhouse gases, our earth's average temp would be -18C, but with them, it's averaged at 15 C.
What are the sources (2) and sinks (3) of anthropogenic CO2
sources: burning of fossil fuels and deforestation
sinks: atmosphere, ocean, forests.
How does global conveyor belt affect earth's climate? (4 steps)
Supplies heat from warm, salty tropical waters to poles for release from Earth. Affects radiation budget by bringing warm waters to polar regions, melting glaciers, reducing albedo effect, further increasing temps
Describe the processes leading to onset of ice ages and to interglacial intervals? (6)
- 1. During onset of glacial periods, changes in earth's orbit/tilt leads to unusually cool summers in N
- 2. Seawater (global conveyor belt)moving up N atlantic doesn't get warmed/evaporated/does not become more saline
- 3. Since its not as dense, cannot sink down as far, becomes blocked or slows deepwater themohaline circulation or forms midwater formation.
- 4.Increased wind strength leads to input of iron rich clay --> boosts primary productivity/
- 5. Boosted phytoplankton productivity draws down atmospheric CO2
This is reversed by earth tilting back and warming N hemisphere again.
How do ice sheet/glacial dynamics affect sea level?
Sea ice melting won't affect sea level, whereas glacial ice melting will. Can ruin infrastructure built on coast/
What are examples of evidence for anthropogenic influences on climate; projections for future global temperature and sea level?
- 1. Decreasing 13C:12C in atmosphere
- 2. Looking at ice cores air pockets to look at CO2 levels then
- 3. Exponential increase in global fossil fuels carbon emissions
2-4 degrees C; 0.1-0.8 m
How does global warming lead to ice ages?
If ice sheet is broken through and freshwater is released slowing thermohaline circulation (warm water to N atlantic)
What are major sources of N - 4? Major sinks - 2? How does it enter ocean? From where is it biologically fixated
Sources: lightning, bacteria (biological fixation), human activities (fertilizer, pollution) --> rivers --> ocean.
What is weird about P cycle? (2)
Major source: 1 Major sink: 1 Where is there extensive internal cycling?
No redox chem and no major atmospheric component
Riverine inflow (human impact) burial in sediments. In ocean.
Why are ionic comp between riverwater and seawater diff? What is seen as a sink
Depends on ability of elements to precipitate out. There is generally a high conc of last precipitated element out of ocean. Also, residence times in oceans are much longer than residence times in rivers which give little time for these elements to mix.
What are primary removal mechanisms (sinks) for elements delivered to sea? 5
- N - sedimentation, microbial denitrification
- S - hydrothermal processes
- P- sedimentation
- C - burial
What are nutrients? How do biological/chemical processes affect conc of biolimiting & biointermediate elements?
How do marine organisms influence chemical compositoin of seawater? 4
Particle formation and destruction helps determine element distribution in ocean --> reformation of calcium carbonate, photosynthesis (requires nitrates), etc.
Also think about depth vs concentration graphs and bulges.
What processes control salinity of ocean waters?
In areas of ice formation, salty/dense waters and sinks to bottom.
Also, evaporation and precipitation.
What is meant by ocean acidification and how can organisms be limited by carbonate ion concentration when CO2 is being added to the ocean?
CO2 increases total carbon concentration in ocean, but decreases contribution of CO32-, therefore decreasing carbonate ion concentration that's available for organisms to use.
What sources of data do we have about sea level and atmospheric composition in the geologic past?
Isotopes of oxygen from ice cores. High O16:O18 will be evaporated first because its lighter and is incorporated into glaciers and pockets from ice core --> low sea level.
What distinguishes currently observed changes in atmospheric CO2 concentrations from observations of changing CO2 in geologic past?
By looking at ice cores and 13C:12C data, we can tell that there is a high level of 12C vs. 13C and we see huge increase since industrial revolution
How is organic carbon synthesized by phoytoplankton transformed in the upper ocean?
Why is hydrothermal circulation so important? Highest ion in ocean? What is highest particle?
About 25% of total heat loss from earth's center is believed to be via hydrothermal circulation - important for ocean chem and heat balance.
Rxn for chemosynthesis? vs. photosynthesis?
- Photosyn: CO2 + H2O --sunlight --> CH2O + O2
- Chemosyn: CO2 + H2S + O2 + H2O --> Ch2O + sulfate + 2H+
How is organic carbon (biosyn by phytoplankton) transformed in upper ocean? Why is the fact that particulate organic C sinks to the deep ocean important in terms of nutrient cycling? How does it affect the composition of deep ocean waters.
It is decayed by microbial bacteria releasing CO2 and other nutrients, making them available to be used again by phtyoplankton UNTIL ultimately deposition locks away the carbon/nitrogen/sulfur/phoshorus in ocean sediments
Important bc nutrients can still reach bottomdwellers (stingrays, lobster, crabs, etc). Also, increases chance for nutrients to be buried/mineralized into sediment as sink taking it out from the cycle.
Makes deep ocean waters slightly more nutritious/
What is the relative relationship of inventories of CO2 in atmosphere and ocean and why ist his relationship important for udnerstanding global climate (past and present?)
Way more CO2 in oceans vs. atmosphere. Important for understanding periodicity of ice ages (170 ppm to 270 ppm). Important to predict when next ice age is coming/
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