Global Change 478/578
Fall 2007
Study guide for Legal and Policy lecture (10/18), Ocean Biogeochemistry (10/23-30), and Anthropogenic CO2 wrapup (11/1).
This study guide was prepared for the review taking place 11/6. Remember to use the upcoming study guide (coming early Dec.) in addition to this one for exam review. Also remember to use homeworks and notes from student presentations.
This guide does not replace your notes in terms of studying, but we hope it will helpyou identify the major points that were covered in lecture. The best way to use this is to write out the answers to each question, and then return to your lecture notes to see if you were correct. If you have doubts or do not fully understand the question, see Julie or Scott.
Inorganic C in the Ocean
Basics:
Why does the deep ocean have a higher concentration of dissolved inorganic carbon than the surface? (describe the 2 main "pumps" that transfer ocean carbon from surface to deep waters)
What controls CO2 gas exchange between the atmosphere and ocean?
Know: forms of CO2 in the ocean (how much of each?), alkalinity, supersaturation, buffer capacity
How does temperature affect the amount of CO2 that seawater can hold?
How is ocean pH changing now (and in the future)?
What fraction of anthropogenic CO2 emitted since the 1800's is now in the ocean?
Where is CO2 flux from ocean to atmosphere strongest, and why? Where is CO2 flux from atmosphere to ocean strongest, and why?
What happens to CO2 when it enters the ocean from the atmosphere? (what does it react with, what is used, what is formed)
Study questions
What effect does calcification have on CO2 in the surface ocean?
How does an increase in alkalinity affect the surface ocean's CO2 concentration and ability to take up CO2? Explain.
How will calcification by marine organisms likely change in the future? Why?
What will be the impact of rising atmospheric CO2 on calcium carbonate saturation in the surface ocean? What evidence exists that this may be a significant ecological problem?
Basics
Marine productivity - who does it, how much do they do per year, turnover (residence) time, GPP vs NPP, where is it strongest? Recycled vs new.
Nutrients: which are important, sources, Redfield ratios, what does "limiting" mean?, where are they found in surface ocean?
Nitrogen - different forms, fixation, denitrification (who does these and under what conditions?)
Phosphate - sources and sinks
Why are nutrients and dissolved inorganic C higher in deep than shallow water? Does O2 follow te same pattern? Describe and explain its variation with depth.
What is the microbial loop?
Are new studies increasing or decreasing estimates of N fixation adn denitrification? Would you characterize these processes as very well known in terms of magnitudes and actors?
Study questions
Describe the transit of marine organic matter from the surface ocean to the sediments; include estimates of how much C passes thru the main steps in this process, and how it changes deep ocean chemistry.
Which aspects of the marine N budget have been most perturbed by human activity?
The ocean is currently a major sink for anthropogenic CO2. Describe in detail how this may change in the future, including the major processes/mechanisms that contribute to any strengthening/weakening of this sink
Is N fixation related at all to denitrification in terms of where it occurs? Why might this be?
Why does Fe stimulate NPP in some parts of the ocean and not others? What regions are particularly susceptible to this? Does increased NPP translate to increase C sequestraion? Why or why not?
What general types of processes are important for evaluating the future of the ocean carbon sink? Give examples and how they are expected to change in the future. (hint - I can think of three general types; biological, geochemical, and circulation. Examples of each are in the lecture notes)
What region is most important for the future of the ocean carbon sink and why?
What change has recently been observed in nitrogen cycling in Narragansett Bay, and what sequence of events seems to be responsible?
What is ocean stratification and why is it significant for future ocean carbon sink projections? How will stratification shcnage in the future, what drives this change, and what effect will this have on NPP in the Southern Ocean vs in the warmer (low and mid-latitude) oceans.
Ocean carbon uptake is related to ocean thermohaline circulation - describe the relationship and the likelihood of future changes to circulation and the associated carbon uptake.
Anthropogenic CO2: where does the carbon go?
Why did Svante Arrhenius, who over 100 years ago quantified the global climate’s sensitivity to elevated CO2, not think that global warming was an issue to worry about?
What is a simple, straightforward (and wrong) way to estimate the fraction of anthropogenic CO2 that will go into the ocean?
What is a “top down” method, based on concentration measurements in the earth’s atmosphere, for estimating where on the earth’s surface anthropogenic CO2 is going? How does it work? What is a consistent robust result of this kind of study?
How can measurements of oxygen in the atmosphere contribute to our understanding of how uptake of anthropogenic CO2 is partitioned between land and ocean?
Briefly describe how two “bottom up” methods – eddy flux measurements and remote sensing – can be helpful in adding to our understanding of the global and local carbon budgets.
There are now a suite of about a dozen models that have coupled the global climate system to the global carbon cycle. What is a consistent prediction, made by these models, about the future of sinks for anthropogenic carbon? (what is predicted about the ocean sink and about the land sink?)