Carbon cycling and climate: the CO 2. connection

Transcription

1 Carbon cycling and climate: the C 2 connection Gasses in the ocean The carbonate system (and buffering in the ocean) Carbon dioxide and the climate connection.

2 Importance of C 2 to climate C 2 acts like a blanket to trap the heat. More C 2 traps more heat. like a thicker blanket

3 All this man made C 2 really comes from.. Photosynthesis is the process

4 The ocean breathes for us: taking up C 2 C 2 biomass

5 il and coal are the products of photosynthesis.. After long storage. SINK

6 Levels of C 2 in the atmosphere are increasing.

7 Industrial C 2 in the atmosphere

8 Much of the industrial C 2 is missing! 450 ppm

9 Much of the industrial C 2 is in the ocean? 450 ppm Why?

10 Dissolution of gas in water Dissolution for any gas is controlled by partial pressure and temperature: Gas dissolution increases with decreasing temperature: CLD water holds MRE gas.

11 Dissolved gasses in the ocean 78% 21% 1% 0.035% Gasses dissolve in the ocean in proportion to their amounts in the atmosphere (mostly..)

12 xygen has a source within the ocean Photosynthesis can cause oxygen to be super saturated

13 elow the euphotic zone is the oxygen minimum why is the concentration of oxygen in deeper waters more than in surface waters?

14 .Thermohaline circulation

15 Carbon dioxide concentration in the ocean is not just controlled by the biological pump and thermohaline circulation Emerson and Hedges (2008)

16 Carbon dioxide concentration in the ocean Is not just controlled by partial pressure and respiration..

17 Carbon Dioxide (C 2 ) =C= C

18 Water (H 2 ) H H H--H

19 C 2 Reacts with H 2 C H H

20 C 2 Reacts with H 2 and makes carbonic acid H C H H 2 C 3

21 The carbonic acid gives up its H + and makes bicarbonate H C - H+ HC 3 -

22 If it gives up two H + it makes carbonate H+ - C - H+ C 3 =

23 Carbon dioxide reacts with water producing the carbonate family H C H H C - Carbonic acid Bicarbonate - C - Carbonate

24 The carbonate system in the ocean is a case of buffered acid-base chemistry Absorption of C 2 by the ocean involves 3 equilibria 1 C 2(aq) + H 2 0 H 2 C 3(aq) (carbonic acid) 2 H 2 C 3(aq) H + + HC - 3 (bicarbonate ion) 3 HC - 3 H + + C -2 3 (carbonate ion) 4 Ca ++ + C -2 3 CaC 3 (calcium carbonate mineral) Equation 4 is ignored in the dissolved system, and one and 2 are shortened to: 5 C C 2(aq) + H 2 0 2HC H +

25 The buffering of the carbonate system in the ocean pushes these reactions to the center To summarize these 3 equilibria; C 2(aq) H 2 C 3 H + + HC 3- H + + C 3-2 or the governing equation: HC H + C C 2(aq) + H 2 0

26 Carbonic acid titration..

27 Seltzer is not buffered.. But lets look at the carbonate carbon dioxide dissociation in a simple system

28 The ocean is buffered making the practical result of adding C 2 Because the ph of the ocean is fixed at about 7.8 to 8 it pushes the reaction to bicarbonate: C 2(aq) 2HC 3 - C 3-2 (The reaction runs to the middle) The combination of C 2 and C 3-2 must balance and this causes CaC 3 to be less saturated. Result: if carbon dioxide is added to the water calcium carbonate dissolves or is harder to precipitate.

29 The ocean is buffered

30 Carbonate system equilibrium Carbonate equilibrium constant in water: K = [C 2(aq) ][ C 3-2 ] [HC 3 - ] 2 the governing equation: 2HC H + C C 2(aq) + H 2 0 If the reaction is NT at equilibrium then the activities quotient, Q describes the system :

31 Carbonate system equilibrium Carbonate equilibrium constant in water: Q = [C 2(aq) ][ C -2 3 ] [HC - 3 ] 2 The reaction quotient reaction can occur. =Q/K numerically describes if the is the commonly used saturation state The governing equation: 2HC H + C C 2(aq) + H 2 0 If we add C 2, the reaction is not at equilibrium which way will it proceed? What does this mean?

32 It causes this dissociation reaction which proceeds until equilibrium is reached Carbonate system equilibrium Q = [C 2(aq) ][ C 3-2 ] [HC 3 - ] 2 the governing equation: 2HC H + C C 2(aq) + H 2 0 CaC 3 The more C 2 added to the water, the more C 3-2 is undersaturated at the same ph. if the ph drops the proportion of C 3-2 decreases Both result in it becoming harder to calcify Adding more C 2 added to the water doesn t saturate the system relative to partial pressure.

33 Adding C 2 makes the ocean more acid The ph determines which member of the family is most abundant H+ The more acidic a solution is the more hydrogen ions are running around.. That s lower ph

34 H + makes C 3 = hard to form H+ H C - H+ H+ H+ H+ H+ H+ carbonate only forms easily when the solution is slightly basic

35 C 2 acts as an acid the more you put in the water the lower the ph becomes Adapted from Wolf-Gladrow et al., 1999

36 The biological pump and C 2 The biological pump moves C 2 from the surface ocean to the deep water masses

37 .The deep conveyor belt

38 The ocean holds 50 times more C 2 than the atmosphere

39 Controls on the distribution of C 2 Water downwells: Low nutrients High 2 low C 2 content C C 2 2 C 2 C 2 C C 2 2 Corg DIC Corg DIC Corg DIC Corg DIC DIC DIC DIC content of Water increases with increasing age DIC DIC Corg Corg Corg DIC Corg DIC Corg DIC DIC Corg Carbonate Sediments are a source and sink of carbon, both Corg and C 2

40 .The deep conveyor belt

41 Pacific cean DIC

42 The biological pump interacts with the excess C 2 we are putting into the atmosphere. The marine system is taking up C 2 in surface waters and Putting it into the deep ocean. Because most of the deep ocean is capped by the thermocline, the C 2 remains there.. Until the water upwells. Question: how long does water remain deep? And how long have we been putting C 2 into the atmosphere?

43 The ocean is both a source and sink for C 2. In different places and at different times

44 cean-biosphere- atmosphere C 2 exchange drives the system Seasonal fluctuations in the concentration of atmospheric carbon dioxide are controlled by the fluctuations in photosynthesis

45 Marine biogeochemical processes affect C 2 uptake El niño

46 To be continued