The role of CaCO<sub>3</sub> compensation in the glacial to interglacial atmospheric CO<sub>2</sub> change

Broecker, Wallace S.; Peng, Tsung‐Hung

doi:10.1029/gb001i001p00015

Cited by 371 publications

(303 citation statements)

References 14 publications

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“…During the first thousand years after the end of the CO 2 emissions, an oceanic carbon uptake is constrained by CO 2 mixing in the deep ocean and dissolution of carbonate sediments on the ocean floor. On a longer time scale, the oceanic uptake is regulated by an imbalance between terrestrial weathering and carbonate sedimentation (the carbonate compensation mechanism, see Archer et al 1997;Broecker and Peng 1987). In the year 10,000, carbonate compensation results in a small but not negligible carbon uptake (<0.1 GtC/year, Table 1).…”

Section: Resultsmentioning

confidence: 99%

Geoengineering climate by stratospheric sulfur injections: Earth system vulnerability to technological failure

et al. 2008

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We use a coupled climate-carbon cycle model of intermediate complexity to investigate scenarios of stratospheric sulfur injections as a measure to compensate for CO 2 -induced global warming. The baseline scenario includes the burning of 5,000 GtC of fossil fuels. A full compensation of CO 2 -induced warming requires a load of about 13 MtS in the stratosphere at the peak of atmospheric CO 2 concentration. Keeping global warming below 2 • C reduces this load to 9 MtS. Compensation of CO 2 forcing by stratospheric aerosols leads to a global reduction in precipitation, warmer winters in the high northern latitudes and cooler summers over northern hemisphere landmasses. The average surface ocean pH decreases by 0.7, reducing the calcifying ability of marine organisms. Because of the millennial persistence of the fossil fuel CO 2 in the atmosphere, high levels of stratospheric aerosol loading would have to continue for thousands of years until CO 2 was removed from the atmosphere. A termination of stratospheric aerosol loading results in abrupt global warming of up to 5 • C within several decades, a vulnerability of the Earth system to technological failure.V. Brovkin (B) · M. Claussen

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Section: Resultsmentioning

confidence: 99%

Geoengineering climate by stratospheric sulfur injections: Earth system vulnerability to technological failure

et al. 2008

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“…At steady state these two fluxes are equal, and any perturbation of either flux leads to an adjustment in the carbonate ion concentration of seawater and, hence, the fraction of organism-produced CaCO 3 that is preserved and buried, so as to restore the balance [Broecker and Peng, 1987]. This reestablishment of equilibrium occurs on timescales of a few thousand years [Archer et al, 2000].…”

Section: Introductionmentioning

confidence: 99%

Opal burial in the equatorial Atlantic Ocean over the last 30 ka: Implications for glacial‐interglacial changes in the ocean silicon cycle

et al. 2007

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The Silicic Acid Leakage Hypothesis (SALH) suggests that, during glacial periods, excess silicic acid was transported from the Southern Ocean to lower latitudes, which favored diatom production over coccolithophorid production and caused a drawdown of atmospheric CO2. Downcore records of 230Th‐normalized opal fluxes and 231Pa/230Th ratios from seven equatorial Atlantic cores were used to reconstruct diatom productivity over the past 30 ka (where a is years) and to test the SALH. Downcore records of 231Pa/230Th ratios and opal fluxes are highly correlated, suggesting that they constitute a production‐based record of opal flux. Opal flux records support the SALH in that glacial opal burial exceeded Holocene burial by 1.8 Gt opal/ka in the area 0°–40°W and 5°N–5°S. Earlier results from the eastern equatorial Pacific Ocean showed the opposite trend, with greater Holocene than glacial opal burial, but approximately the same magnitude of difference between glacial and interglacial opal burial. We suggest four (nonexclusive) scenarios to explain the data from both basins: (1) Increased upwelling in the equatorial Atlantic and El Niño–like conditions suppressing upwelling in the eastern equatorial Pacific altered the overall nutrient supply to both basins; (2) Si leaked from the Southern Ocean because of Fe fertilization, but was prevented from upwelling in the equatorial Pacific because of El Niño–like conditions during the LGM; (3) Si leaked from the Southern Ocean because diatom productivity was limited by increased sea ice extent and was again prevented from upwelling in the equatorial Pacific; or (4) changes in ocean circulation related to the decreased input of Agulhas water to the glacial South Atlantic provided excess dissolved Si to the equatorial Atlantic Ocean. A deglacial opal pulse is seen in both the Atlantic and Pacific Oceans. All four scenarios and the presence of the common deglacial opal pulse suggest a common driver in the Southern Ocean.

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“…The model was adapted to determine the steady state concentrations of phosphate (PO4), total inorganic carbon (ZCO2), alkalinity (AT), and iron (Fe). Phosphate was used as the controlling macronutrient, as in the work of Broecker and Peng [1987]. For the processes considered here we assumed constant C:N:P Redfield ratios, so nitrate could equally have been used.…”

Section: Description Of the Model We Desired To Model Explicitly The mentioning

confidence: 99%

“…Figure 1 shows the structure of the model with the flow patterns and the particulate fluxes of organic carbon. The magnitude of the water fluxes was chosen to yield the observed •4C distribution in the ocean [Broecker and Peng, 1987]. The model was adapted to determine the steady state concentrations of phosphate (PO4), total inorganic carbon (ZCO2), alkalinity (AT), and iron (Fe).…”

Section: Description Of the Model We Desired To Model Explicitly The mentioning

confidence: 99%

Modeling the geochemical cycle of iron in the oceans and its impact on atmospheric CO₂ concentrations

Lefèvre¹,

Watson²

1999

Global Biogeochemical Cycles

113

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Abstract. Iron occurs at very low concentrations in seawater and seems to be a limiting factor for primary production in the equatorial Pacific and the Southern Ocean. The global distribution of iron is still not well understood because of a lack of data and the complex chemistry of iron. We develop a 1 O-box model to study the oceanic distribution of iron and its effect on atmospheric CO2 concentration. Subject to our assumptions, we find that a lack of interocean fractionation of deep sea iron concentrations, as suggested by Johnson et al.[1997a], is not readily explained by a balance of eolian deposition, scavenging, and regeneration. Incorporation of organic complexation in the model, as suggested by Johnson et al., to reduce the scavenging rate of iron when concentrations fall below some ligandstabilized concentration, is one solution to this difficulty. Alternatively, the deep-sea concentration may be more variable than the current, rather sparse data coverage suggests. In the model, deep-sea iron concentrations are responsive to the atmospheric source, even if we adopt stabilization of concentrations by a ligand as modeled by Johnson et al. [1997a]. In the Southern Ocean, where the model suggests iron supply has an important limiting effect on the biota, more than 99% of the iron supply to the surface in the present day comes from upwelling and not from the local atmospheric flux. In the context of glacial-interglacial changes to atmospheric CO2 the model suggests that increasing atmospheric iron to the entire global ocean by a factor of 2, leads to decreases in atmospheric CO2 of 10-30 ppm, depending on assumptions. However, in our model, CO2 concentrations are almost unaffected by changes in Southern Ocean atmospheric fluxes alone, unless these are unrealistically large (> 100 times present day). The effect on atmospheric carbon dioxide is slightly stronger if accompanied by increased stratification of the Southern Ocean. The model suggests that eolian "iron fertilization" of the ocean could have importantly influenced glacial atmospheric CO2 concentrations but that other processes must also be at work to account for the full magnitude of the glacial-interglacial change.

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The role of CaCO₃ compensation in the glacial to interglacial atmospheric CO₂ change

Cited by 371 publications

References 14 publications

Geoengineering climate by stratospheric sulfur injections: Earth system vulnerability to technological failure

Geoengineering climate by stratospheric sulfur injections: Earth system vulnerability to technological failure

Opal burial in the equatorial Atlantic Ocean over the last 30 ka: Implications for glacial‐interglacial changes in the ocean silicon cycle

Modeling the geochemical cycle of iron in the oceans and its impact on atmospheric CO₂ concentrations

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The role of CaCO3 compensation in the glacial to interglacial atmospheric CO2 change

Cited by 371 publications

References 14 publications

Geoengineering climate by stratospheric sulfur injections: Earth system vulnerability to technological failure

Geoengineering climate by stratospheric sulfur injections: Earth system vulnerability to technological failure

Opal burial in the equatorial Atlantic Ocean over the last 30 ka: Implications for glacial‐interglacial changes in the ocean silicon cycle

Modeling the geochemical cycle of iron in the oceans and its impact on atmospheric CO2 concentrations

Contact Info

Product

Resources

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The role of CaCO₃ compensation in the glacial to interglacial atmospheric CO₂ change

Modeling the geochemical cycle of iron in the oceans and its impact on atmospheric CO₂ concentrations