Lecture 12- Carbon cycles and elevated CO2 Flashcards Preview

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Flashcards in Lecture 12- Carbon cycles and elevated CO2 Deck (40):
1

How many gigatons of Carbon are there in the deep ocean?

-38 100 -by far the most

2

How many gigatons of Carbon are there in the vegetation on land and in the marine biota? What does this mean for photosynthesis?

-610 in land vegetation -3 in marine biota -almost as much photosynthesis takes place in the sea as on land, means the photosynthetic life in the sea turns over quickly and is more efficient

3

How many gigatons of Carbon are released by humans into the atmosphere via fossil fuel burning etc?

-4000 -significant amount

4

What does the ocean carbon cycle look like?

-

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5

What is the equation for the ocean carbon cycle?

-

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6

What is H2CO3?

-carbonic acid

7

What is HCO3-?

-bicarbonate

8

What is CO3 2-?

-carbonate

9

What is the most abundant form of carbon in the sea?

HCO3- = bicarbonate, 98% -CO2=around 1% -CO3 2-= around 1%

10

What are the two things carbon can do when it gets into the sea?

-can either sink (100 gigatonnes)

-or exchange with the atmosphere (about 92 gigatonnes do that)

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11

How much of dissolved organic carbon is there in the sea?

-700 gigatonnes

12

What are the two processes that drive C into the deep ocean?

1) Solubility Pump 2) Biological Pump

13

How does the solubility pump work?

-CO2 is more soluble in cold water and cold water is deeper, CO2 follows the solubility gradient

-moves passively

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14

How does the biological pump work? (2)

1.-all living organisms have lot of C, they due and their remains/shells sink deeper into the ocean

2.-lot of predators hide at night in the deep sea, come out during the day to feed, eat other organisms and retreat back, taking the C with them

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15

How much C of the biological pump is coccolith sedimentation responsible for?

-Coccolith sedimentation ~25% of C transport to deep ocean

16

How much of the ocean floor is covered by calcareous ooze?

-Calcareous ooze covers 48% of oceans sea floor -comes from Calcium carbonate so driven by haptophytes

17

How much of the ocean floor is covered by siliceous ooze?

-Siliceous ooze covers 15% of oceans sea floor

18

What are the current levels of atmospheric CO2?

-Atmospheric CO2 has fluctuated over geological time, however we are entering unprecedented high levels (>100ppm higher than ever before)

19

What may happen as more C is deposited in the ocean (solubility pump)?

-as temperatures rise -the solubility gradient may be disrupted -more C on top

20

How can the biological pump be affected by the increased atmospheric CO2?

-not clear, need to consider: 1.-What factors increase primary productivity? a) available nutrients (upwellings/mixing/dust),storms 2.What factors decrease primary productivity? a) nutrient deprivation (water column stratification)

21

Can increased C in the sea increase productivity?

-it can -but it is not usually limiting, mostly P, Ni and Fe are needed

22

Has primary production increased or decreased since 1998-2006?

- 1998-2000 increased - 2000-2006 decreased

23

How have the Arctic phytoplankton blooms been affected by the elevated CO2?

-some occur up to 50 days earlier -may last only 14 days -some delayed -potential impacts for down-stream food chain as very seasonal life in the Arctic

24

What will happen to the ocean pH as the CO2 increases?

-it will acidify (decrease)

25

How much of the anthropogenic CO2 enters the oceans?

25%

26

What happens to carbonate as CO2 increases in the sea?

-more CO2 means less carbonate

-carbonate ions decrease quickly as more CO2 is added

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27

What is calcium carbonate used for?

- (CaCO3) is used for shells, scales and skeletons of many organisms

28

What are the two polymorphs of calcium carbonate that exist in the sea?

1: Calcite 2. Aragonite (less stable) -have different crystal lattice structure

29

Which organisms use Calcite to build their shells?

-haptophytes -forams(also single-celled organisms, heterotrophic)

30

Which organisms use Aragonite to build their shells?

-hard coral -molluscs -pteropods

31

What do you have to have in the sea to precipitate calcium carbonate?

-Calcium -and carbonate

32

What is the equation for saturation state of calcium and carbonate?

-

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33

What must omega equal at saturation?

1

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34

What values of omega do Calcite and Aragonite need to form?

-Calcite= 1 -Aragonite= more than 3

35

What is the current omega value?

-about 3.3 -predicted to be less than 3 by 2050

36

What does the decrease in omega value mean for marine life?

-corals will not be able to form -catastrophic

37

What happens to haptophytes grown in very high CO2 concentrations?

-their scales look different and there are fewer, at first the primary productivity increases but the calcification decreases= slows down the deposition of C on the sea floor

38

What were the two experiments used to test if Iron fertilisation could increase the primary productivity?

-have tried 2 experiments -first had 450kg (40 fold Fe increase)of Fe dumped into the ocean, 4 fold increase in primary production, effect lasted 4 days -second 10-20 fold Fe increase (released in successive infusions) triggered bloom for 3 weeks, 30 fold increase in production, 60% decrease in surface CO2

39

Why is the Iron fertilization unlikely to work?

-Uncertainties of light, dilution of iron by currents, variability of sequestration into deep ocean, change in phytoplankton diversity and impact on downstream food web -Modelling suggests 100 years of fertilisation of Southern Ocean could lower CO2 by 50 +/- 25 ppm at best -Ocean acidification is also decreasing Fe bio-availability, so Fe stress might further reduce ocean productivity.

40

How much of the ocean is Fe limited?

20-30%