Worksheet #19 ATOC 3600 November 2, 2000
NAME: ____________________


1. Estimate the time scale for emptying the sedimentary reservoir by geologic processes given that volcanic outgassing amounts to about 0.05 Gt C/yr and the reservoir is contains roughly 60 million Gt-C.
Volcanic outgassing is a process that depletes sedimentary carbon and would deplete a reservoir of 60 million Gt in about 1.2 billion years.

2. If the oceans were to stop absorbing carbon (due to saturation for example), what percentage increase in atmospheric carbon (per year) would initially occur?
The oceans absorb about 50 GtC per year. If this were to stop, the atmosphere would gain 50 GtC per year which is about 6.7% of the 750 GtC held by the atmosphere. If you tried to use the numbers from Table 10.10 it would be incorrect because that Table shows the net imbalance between dissolution and evaporation of carbon, not the net dissolution.

3. What carbon compounds are produced by photosynthesis and exploited by living beings for energy? What reactants are required to generate these compounds?
Carbohydrates (C-H2O) and oxygen are produced by photosynthesis from the reactants of CO2, H2O and light.

4. If the deep ocean circulation were to accelerate and thus increase the existing exchange of carbon with surface oceans, what impact might this have on the surface ocean and, eventually, the atmosphere? 
In the net, the exchange of carbon between the deep ocean and the surface ocean contributes bicarbonate ions to the surface ocean. If upwelling were to increase the surface ocean would have more bicarbonate ion and would eventually saturate, reducting the amount of CO2 that would disolve in the upper ocean and atmospheric carbon levels would eventually increase. 

5. Propose an investigation aimed at reducing the amount of carbon dioxide in the atmosphere based on what you know about the long-term or short-term carbon cycles. To do so, simply state a process relevant to atmospheric CO2 levels and suggest an hypothesis you'd like to investigate for modulating its rate.
There are many possible answers to this. For example, one might attempt to modulate the rate of carbon uptake by the surface oceans by enhancing photosynthesis in the surface oceans. Currently, experiments that contribute iron to the upper ocean are exploring this possibility. Many other experiements can be envisioned.