5. Carbon

Question 1

What are the three carbon reservoirs?

Answer 1

The ocean, land and atmosphere.

Question 2

How much carbon is sequestered in the ocean?

Answer 2

~ 40000 Pg

Question 3

What chemical form does carbon take in the ocean?

Answer 3

Dissolved Inorganic Carbon

Question 4

How is carbon transferred from the surface into the intermediate and deep ocean (these have the greatest concentrations because largest ocean layers)?

Answer 4

Through the biological and physical pump.

Question 5

How does carbon dioxide dissolve into the ocean (i.e., what does ocean-atmosphere gas exchange depend on)?

Answer 5

Carbon dioxide dissolves into the ocean by diffusion (the partial pressure of carbon dioxide (pCO2) atmosphere is greater than pCO2 in the ocean).

Question 6

How does DIC form?

Answer 6

Carbon dioxide reacts with water to form carbonic acid which is a diprotic acid: it dissociates into (bi)carbonate ions.

Question 7

What is DIC?

Answer 7

The sum of carbon dioxide and (bi)carbonate ions.

Question 8

What does the equilibrium of DIC depend on?

Answer 8

The pH

Question 9

What does an ocean pH 8.1 mean for relative concentrations in DIC?

Answer 9

0. 5% CO2 (aq)
1. 5% - bicarbonate
2. 0% - carbonate

Question 10

What is the second largest carbon reservoir and how much carbon does it contain?

Answer 10

Land

4000 Pg

Question 11

What is the significance of the atmosphere in the carbon cycle, with it being the smallest repository?

Answer 11

Rapid exchanges with ocean (and land) and ocean-atmosphere coupling.

Question 12

What are the three anthropogenic influences on the carbon cycle?

Answer 12

Combustion of fossil fuels
Deforestation (land-use change)
Cement production

Question 13

What % of anthropogenic carbon emissions has the ocean sequestered?

Answer 13

~ 40% - the partial pressure of surface ocean water follows closely the trend in atmospheric CO2.

Question 14

What do cumulative carbon emissions determine?

Answer 14

Global temperature rise