The Oceanic Sink Uptake in the mixed layer Fate of atmospheric increases Feedbacks

Oceans: Dissolved Inorganic Carbon (DIC) 0.7% 9.7% carbonate ion 89.6% bicarbonate ion

(pCO2)a (pCO2)ML atmosphere ocean surface layer Chemical equilibrium (DIC) deep ocean

(pCO2)a (pCO2)ML atmosphere ocean surface layer Chemical equilibrium Photosynthesis Skeleton construction BioPump deep ocean

BioPump: depletes surface nutrients dissolved phosphate

Why atmospheric CO2 conc. is low: Most oceanic carbon is not dissolved CO2 DIC in surface ocean layer is low

(pCO2)a (pCO2)ML atmosphere ocean surface layer Chemical equilibrium Photosynthesis Skeleton construction turbulent mixing BioPump deep ocean upwelling downwelling

What happens when atmospheric CO2 increases? Ocean plants do not respond as land plants (no greater uptake unless BioPump increases)

Preindustrial atmosphere 594 Gt C 594 Gt C ocean surface layer atm. mass of CO2 (Gt C) atmosphere 594 Gt C 594 Gt C ocean surface layer ~67 m CO2 CO32- HCO3- CO2 concentration in mixed layer Partial pressure of CO2 in mixed layer solubility deep ocean

Equilibrium Preindustrial atmosphere 594 Gt C 594 Gt C ocean surface layer ~67 m CO2 CO32- HCO3- 0.46% 11.8% 87.7% 2.7 Gt 70 Gt 521 Gt Assume, deep ocean

Add 10 Gt C to atmosphere……

Ocean uptake without chemical reactions

Ocean uptake with chemical reactions (pCO2)a atmosphere (pCO2)ML Chemical equilibrium ocean surface layer deep ocean

All fossil fuels preindustrial today burned Changes in the 3 chemical species constituting dissolved inorganic carbon (DIC) Changes in the concentrations of the three different chemical species constituting dissolved inorganic carbon (DIC). As the influx of extra CO2 acidifies the surface ocean and raises DIC, the carbonate ion concentration (dark grey) falls strongly, the concentration of dissolved CO2 gas (black) increases strongly and the bicarbonate ion concentration (light grey) increases slightly. Surface ocean pH was on average about 8.2 in the pre-industrial ocean, is about 8.1 on average today and could drop to as low as about 7.4 if all available fossil fuels are burnt. Graph calculated for an average surface ocean of temperature 15°C, salinity 35 and alkalinity 2310 μmol kg−1. Black-shaded region, [CO2(aq.)]; light grey-shaded region, [HCO−3]; dark grey-shaded region, [CO2−3]. All fossil fuels burned preindustrial today Tyrrell T Phil. Trans. R. Soc. A 2011;369:887-908

Ocean uptake with chemical reactions Increase total dissolved inorganic carbon content of mixed layer by 1%.... Component Pre-industrial carbon (Gt) Pre-industrial pCO2/conc. Change in pCO2 ( atm) or concentration ( mol/kg) Atmosphere 593.6 278.4 atm 27 atm (+9.7%) ML HCO3- 521.1 1737 mol/kg 31.8 mol/kg (+1.8%) ML CO32- 69.8 234 mol/kg -12.83 mol/kg (-5.5%) ML CO2 2.7 9 mol/kg 0.88 mol/kg (+9.7%) ML Total 1980 mol/kg 19.80 mol/kg (1%)

10 Gt C increase: Ocean uptake: 0.9 Gt C Fractional change in sea-water partial pressure (Harvey: Equation 8.6) Fractional change in DIC 10 Gt C increase: atmospheric uptake Ocean uptake: 0.9 Gt C

Over time: CO2 uptake depletes carbonate ion CO2 builds up in mixed layer Buffering factor increases, slowing uptake

Deeper ocean uptake? Downward flux with sudden 10 Gt C into atmosphere Tranfer process Steady-state flux (Gt C yr-1) Perturbation flux (Gt C yr-1) Advection 0.07 0.002 Upwelling/ downwelling -2.48↑ 0.033 Turbulent mixing -7.97 ↑ 0.425 Bio pump 10.38 0.000 atmosphere (pCO2)a ocean surface layer (pCO2)ML Chemical equilibrium Photosynthesis Skeleton construction BioPump turbulent mixing Downward flux with sudden 10 Gt C into atmosphere deep ocean upwelling downwelling

1.45-2.25 Gt C yr-1 Source: Sabine et al., 2004. The Oceanic Sink for Anthropogenic CO2. Science 305: 367-371.

Anthropogenic CO2 in ocean (mol m-2); vertically integrated Fig. 1. Column inventory of anthropogenic CO2 in the ocean (mol m–2). High inventories are associated with deep water formation in the North Atlantic and intermediate and mode water formation between 30° and 50°S. Total inventory of shaded regions is 106 ± 17 Pg C. Source: Sabine et al., 2004. The Oceanic Sink for Anthropogenic CO2. Science 305: 367-371.

Anthropogenic CO2 ( mol kg-1) Representative sections of anthropogenic CO2 (μmol kg–1) from (A) the Atlantic, (B) Pacific, and Indian (C) oceans. Gray hatched regions and numbers indicate distribution of intermediate water masses (and North Atlantic Deep Water) on the given section and the total inventory of anthropogenic CO2 (Pg C) within these water masses. The southern water masses in each ocean represent Antarctic Intermediate Water. The northern water masses represent the North Atlantic Deep Water (A), North Pacific Intermediate Water (B), and Red Sea/Persian Gulf Intermediate Water (C). The two bold lines in each panel give the potential density [σθ = (density – 1) × 1000] contours for the surfaces shown in Fig. 4. Insets show maps of the cruise tracks used. Note that the depth scale for (A) is twice that of the other figures, reflecting the deeper penetration in the North Atlantic. Source: Sabine et al., 2004. The Oceanic Sink for Anthropogenic CO2. Science 305: 367-371.

warmer ocean temps. → decreased solubility Feedbacks: warmer ocean temps. → decreased solubility pCO2 increases by 4.3% per 1°C Long-term positive feedback Biological pump: to what degree would climate change alter thermohaline overturning?

Could incorporate new readings in “oceans” folder. Also, see: Get Long et al. 2013 Journal of Climate Twentieth-Century Oceanic Carbon Uptake and Storage in CESM1(BGC)

Fraction of the total emissions (FFoss + FLUC) that remains in the atmosphere (A), the land biosphere (B), and the ocean (C). Fraction of the total emissions (FFoss + FLUC) that remains in the atmosphere (A), the land biosphere (B), and the ocean (C). Canadell J G et al. PNAS 2007;104:18866-18870 ©2007 by National Academy of Sciences

Fossil-fuel intensity of the GWP from 1970 to 2006 (A) and the CO2 budget from 1959 to 2006 (B). Fossil-fuel intensity of the GWP from 1970 to 2006 (A) and the CO2 budget from 1959 to 2006 (B). Fossil-fuel intensity uses GWP data based on market exchange rates, expressed in U.S. dollars (referenced to 1990, with inflation removed). (B Upper) CO2 emissions to the atmosphere (sources) as the sum of fossil fuel combustion, land-use change, and other emissions, which are primarily from cement production. (Lower) The fate of the emitted CO2, including the increase in atmospheric CO2 plus the sinks of CO2 on land and in the ocean. Flux is in Pg y−1 carbon (left axis) and Pg y−1 CO2 (right axis). Canadell J G et al. PNAS 2007;104:18866-18870 ©2007 by National Academy of Sciences

Fig. 4. Schematic view of the impact of increased winds on the Southern Ocean CO2 sink. Schematic view of the impact of increased winds on the Southern Ocean CO2 sink. The three panels represent conditions in the present ocean (left), under very high atmospheric CO2 (middle), and more than 100 years after the CO2 emissions cease (right). C is the concentration of carbon in the surface and deep oceans in units of μmol kg–1, whereas ΔC′ is the increase in carbon content of the ocean from human CO2 emissions. The observed concentrations are from (15), south of 45°S. C Le Quéré et al. Science 2008;319:570 Published by AAAS