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Myles Bradford
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320 300 280 [CO2] 2 ] 2 ppm/year 1850 1870 1890 1910 1930 1950 1970 1990 2010 1970 1979: 1.

1 Atmospheric CO 2 Concentration Year 2006 Atmospheric CO 2 concentration: 381 ppm 35% above pre-industrial Atmoapheric [CO2] (ppmv) [CO2] 2 ] 2 ppm/year : 1.3 ppm y : 1.6 ppm y : 1.5 ppm y : 1.9 ppm y -1 NOAA 2007; Canadell et al. 2007, PNAS

2 Perturbation of Global Carbon Budget ( ) CO 2 flux (Pg C y -1 ) Sink Source extra-tropics deforestation tropics 1.5 Time (y) Le Quéré, unpublished; Canadell et al. 2007, PNAS

3 Perturbation of Global Carbon Budget ( ) CO 2 flux (Pg C y -1 ) Sink Source fossil fuel emissions deforestation Time (y) Le Quéré, unpublished; Canadell et al. 2007, PNAS

4 Perturbation of Global Carbon Budget ( ) CO 2 flux (Pg C y -1 ) Sink Source fossil fuel emissions deforestation Time (y) Le Quéré, unpublished; Canadell et al. 2007, PNAS

5 Perturbation of Global Carbon Budget ( ) CO 2 flux (Pg C y -1 ) Sink Source fossil fuel emissions deforestation atmospheric CO Time (y) Le Quéré, unpublished; Canadell et al. 2007, PNAS

6 Perturbation of Global Carbon Budget ( ) CO 2 flux (Pg C y -1 ) Sink Source fossil fuel emissions deforestation atmospheric CO ocean 2.2 Time (y) Le Quéré, unpublished; Canadell et al. 2007, PNAS

7 Perturbation of Global Carbon Budget ( ) fossil fuel emissions CO 2 flux (Pg C y -1 ) Sink Source deforestation atmospheric CO 2 land ocean Time (y) Le Quéré, unpublished; Canadell et al. 2007, PNAS

Partition of Anthropogenic Carbon Emissions into Sinks

atmosphere Atmosphere 55% were removed by natural sinks

$Fraction The fraction of the annual anthropogenic$

8 Partition of Anthropogenic Carbon Emissions into Sinks [ ] 45% of all CO 2 emissions accumulated in the atmosphere Atmosphere 55% were removed by natural sinks Ocean removes _ 24% Land removes _ 30% The Airborne Fraction The fraction of the annual anthropogenic emissions that remains in the atmosphere Canadell et al. 2007, PNAS

9 Factors that Influence the Airborne Fraction 1. The rate of CO 2 emissions. 2. The rate of CO 2 uptake and ultimately the total amount of C that can be stored by land and oceans: Land: CO 2 fertilization effect, soil respiration, N deposition fertilization, forest regrowth, woody encroachment, Oceans: CO 2 solubility (temperature, salinity),, ocean currents, stratification, winds, biological activity, acidification, Canadell et al. 2007, Springer; Gruber et al. 2004, Island Press

10 Time Dynamics of the Airborne Fraction Distribution (fraction) time The observed trend in Airborne Fraction was +0.25% per year (p = 0.89) from to 2006, implying a decline in the efficiency of natural sinks of 10% Canadell et al. 2007, PNAS

12 The Efficiency of Natural Sinks: Land and Ocean Fractions Land Ocean Canadell et al. 2007, PNAS

Anthropogenic CO 2 Interaction with Seawater Total inventories: (1) ΣCO 2, A = 0.350 X 10-3 l CO2 l air -1 (10 7 l air ) / 22.414 l CO2 mol -1 = 156.2 moles CO 2 (2) DIC O = 2.

13 Anthropogenic CO 2 Interaction with Seawater Total inventories: (1) ΣCO 2, A = X 10-3 l CO2 l air -1 (10 7 l air ) / l CO2 mol -1 = moles CO 2 (2) DIC O = 2.0 X 10-3 mol kg -1 (10 5 l) kg l -1 = 200 moles C (2) Σ[CO 2 ] O = 11.3 X 10-6 mol kg -1 (10 5 l) kg l -1 = 1.3 moles CO 2 (4) ΣC = DIC O + ΣCO 2,A Perturbation: The fraction, f, of the total added CO 2 that ends up in the seawater (5) f = DIC O / ΣC = DIC O / ( DIC O + ΣCO 2,A )

14 Change in DIC per change in fco 2 at chemical equilibrium: Uptake Factor, U.F. (Pilson, 1998) ΔDIC O /Δ fco 2,O = U.F. (µmol kg -1 / µatm) fractional change in fco 2 per fractional change in DIC: Revelle factor, R: R = ( fco 2,O / fco 2,O ) / ( DIC O / DIC O ) = (DIC 0 / fco 2,O ) / U.F. Equilibrium change in DIC, [CO 3 2- ], ph for increasing fco 2 (A C&B =2300 µeq kg -1, T=20, S=35)

15 F. Example Given the A C and DIC of surface seawater (25 C, S = 35), (a) determine the ph and fco 2 (b) How does the ph change if fco 2 increases by 100 ppm? (1) K H = [CO 2 ] / fco 2 = (mol kg -1 atm -1 ) (2) K 1 = [HCO - 3 ] [H + ] / [CO 2 ] = 1.41 x 10-6 (mol kg -1 ) (3) K 2 = [CO 2-3 ] [H + ] / [HCO - 3 ] = 1.07 x 10-9 (mol kg -1 ) (4) DIC = [HCO - 3 ] + [CO 2-3 ] + [CO 2 ] = 1900 x 10-6 (mol kg -1 ) (5) A C = [HCO 3 - ] + 2 [CO 3 2- ] = 2160 x 10-6 (eq kg -1 ) Assume that [CO 2 ] is only a small fraction of DIC (10 x 10-6 compared to 2000 x 10-6 ) (6) [CO 2-3 ] ~ A C DIC = 260 x 10-6 (mol kg -1 ) (7) [HCO - 3 ] ~ 2 DIC A C = 1640 x 10-6 (mol kg -1 ) (a) Initial ph and [CO 2 ]: [H + ] = K 2 [HCO 3 - ] / [CO 3 2- ] = 1.07 x 10-9 (1640 / 260) = 6.31 x 10-9 ; ph = 8.2 [CO 2 ] = [HCO 3 - ] [H + ] / K 1 = (1640 x 10-6 ) X (2.31 x 10-9 ) / 1.41 x 10-6 = 7.3 x 10-6 fco 2 = [CO 2 ] / K H = 7.3 x 10-6 / = 260 x 10-6 atm (b) Now, increase f CO 2 from 260 ppm to 360 ppm New [CO 2 ] = 360 x 10-6 X = X 10-6 Alkalinity does not Change! To calculate the ph change you have to know how DIC changes! Write an equation with AC, DIC, ph and [CO] as unknowns This example is an approximation of the Chemical Equilibrium Case U.F. = DIC / fco 2 = 23/100=.23 mol kg -1 atm -1 R= ( fco 2 /fco 2 )/ ( DIC/DIC) = ( )/(23/1900) = 25 (unitless) K 1 /K 2 = [HCO 3 - ] 2 / [CO 3 2- ] [CO 2 ] = 1.41 x 10-6 / 1.07 x 10-9 = 1318 [CO 2 ] (A C -DIC) K 1 / K 2 = 4 DIC 2 4 DIC A C + A C 2 0 = 4 DIC 2 + {[CO 2 ] K 1 /K 2 4 A C } DIC + A C 2 [CO 2 ] A C (K 1 /K 2 ) DIC = (-b + (b 2-4ac) 0.5 ) / 2a ; DIC = 1923 x 10-6 (mol kg -1 ) [H + ] = K 1 [CO 2 ] / [HCO 3 - ] = K 1 [CO 2 ] / (2DIC A C ) = 1.41 x 10-6 (10.15x10-6 ) / (2 x 1923 x x 10-6 ) = 8.49 x 10-9 ; ph = 8.07

16 Global Distribution of the Revelle Factor (Sabine et al., 2007)

17 The Factor Limiting Anthropogenic CO 2 Thermocline Uptake is Mixing Across the Ocean

18 Now the change in carbon content of the reservoirs in the tall box can be calculated using the Revelle factor. Starting with: f = DIC O / { ΣCO 2,A + DIC O } Expanding this to include the fractional changes: f = DIC O ( DIC / DIC) / { ΣCO 2,A ( fco 2 / fco 2 ) + DIC O ( DIC / DIC)} dividing by ( DIC / DIC): f = DIC O / {ΣCO 2,A [( fco 2 / fco 2 ) / ( DIC / DIC)] + DICo} using the definition of the Revelle factor: f = DIC O / {ΣCO 2,A (R) + DICo} = 200 / {156.2 (10) + 200} = 0.11

Carbon Dioxide, Alkalinity and ph

Carbon Dioxide, Alkalinity and ph OCN 623 Chemical Oceanography 15 March 2018 Reading: Libes, Chapter 15, pp. 383 389 (Remainder of chapter will be used with the classes Global Carbon Dioxide and Biogenic