Controls of CO<sub>2</sub> sources and sinks in the Earth scale surface ocean: Temperature and nutrients

Volk, Tyler; Liu, Zhongze

doi:10.1029/gb002i002p00073

Cited by 31 publications

(17 citation statements)

References 16 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…This causes the magnitude of the ocean and biospheric-feedback sinks to both increase, as can be seen by comparing Tables I and II. The reason for the increase of the ocean sink is that the atmospheric partial pressure of CO2 continues to increase relative to the deep-ocean partial pressure of CO2; since the ocean sink is limited by mixing between water below and above the thermoctine (for time periods on the order of a century), the magnitude of the ocean sink is related to the difference in partial pressures adjusted for the effects of the biological pumping (which is assumed to be unchanging in time) of carbon by particulate settling (Volk and Liu, 1988) through the thermocline. The reason for the increase in the biospheric feedback sink is the logarithmic dependence of the net primary productivity (NPP) on the partial pressure of CO2 (pCO2):…”

Section: Carbon-cycle Response For Scenarios Of Future Emissionsmentioning

confidence: 99%

Accounting for the missing carbon-sink with the CO2-fertilization effect

Kheshgi

Wuebbles

1996

Climatic Change

View full text Add to dashboard Cite

A terrestrial-biosphere carbon-sink has been included in global carbon-cycle models in order to reproduce past atmospheric CO2, 13C and 14C concentrations. The sink is of large enough magnitude that its effect on projections of future CO2 levels should not be ignored. However, the cause and mechanism of this sink are not well understood, contributing to uncertainty of projections. The estimated magnitude of the biospheric sink is examined with the aid of a global carbon-cycle model. For CO2 emissions scenarios, model estimates are made of the resulting atmospheric CO2 concentration. Next, the response of this model to CO2-emission impulses is broken down to give the fractions of the impulse which reside in the atmosphere, oceans, and terrestrial biosphere -all as a perturbation to background atmospheric CO2 concentration time-profiles that correspond to different emission scenarios. For a biospheric sink driven by the CO2-fertilization effect, we find that the biospheric fraction reaches a maximum of roughly 30% about 50 years after the impulse, which is of the same size as the oceanic fraction at that time. The dependence of these results on emission scenario and the year of the impulse are reported.

show abstract

Section: Carbon-cycle Response For Scenarios Of Future Emissionsmentioning

confidence: 99%

Accounting for the missing carbon-sink with the CO2-fertilization effect

Kheshgi

Wuebbles

1996

Climatic Change

View full text Add to dashboard Cite

show abstract

“…We take the difference between these two models as representing the incremental contribution of the biological pump. The contribution of the solubility and biological pumps to local air-sea fluxes has been explored previously for some regions of the ocean by Volk and Liu [1988] using limited area models. Our study uses a global model thus removing the ambiguities in the Volk and Liu study that arise from not being able to close the carbon budget with a local area model.…”

Section: Introductionmentioning

confidence: 99%

Spatial distribution of air‐sea CO₂ fluxes and the interhemispheric transport of carbon by the oceans

Murnane¹,

Sarmiento²,

Quéré³

1999

Global Biogeochemical Cycles

102

View full text Add to dashboard Cite

Abstract. The dominant processes controlling the magnitude and spatial distribution of the preindustrial air-sea flux of CO2 are atmosphere-ocean heat exchange and the biological pump, coupled with the direct influence of ocean circulation resulting from the slow time-scale of air-sea CO2 gas exchange equilibration. The influence of the biological pump is greatest in surface outcrops of deep water, where the excess deep ocean carbon resulting from net remineralization can escape to the atmosphere. In a steady state other regions compensate for this loss by taking up CO2 to give a global net air-sea CO2 flux of zero. The predominant outcrop region is the Southern Ocean, where the loss to the atmosphere of biological pump CO2 is large enough to cancel the gain of CO 2 due to cooling. The influence of the biological pump on uptake of anthropogenic CO2 is small: a model including biology takes up 4.9% less than a model without it. Our model does not predict the large southward interhemispheric transport of CO2 that has been suggested by atmospheric carbon transport constraints.

show abstract

“…Therefore, the equilibration time of seawater pC02 is roughly 10 times slower than that for 02. This Because of the slow equilibration time for seawater pC02 and the strong temperature effect, the pC02 of warm waters in the surface Ocean tends to be higher than the atmospheric value (supersaturated), while colder waters tend to be undersaturated (see Volk and Liu, 1988 Much of the organic matter produced by photosynthesis is oxidized within the mixed layer; hence nutrients can be recycled several times before they are exported as sinking organic matter. The rate of total ("gross") photosynthesis less phytoplankton respiration is called the "net" production.…”

Section: Gas Equilibrium Chemistrymentioning

confidence: 99%

Modeling pCO{sub 2} in the upper ocean: A review of relevant physical, chemical, and biological processes

1990

View full text Add to dashboard Cite

The pC02 of the surface Ocean is controlled by a combination of physical, chemical, and biological processes. Modeling surface ocean pC02 is analogous to modeling sea surface temperature (SST), in that sea surface pC02 is affected by fluxes across the air-sea interface and by exchange with deeper water. However, pC02 is also affected by chemical and biological processes which have no analog in SST. Seawater pC02 is buffered by pH equilibrium reactions between the species C02, HCO3-, and CO3' . This effect provides an effective reservoir for C02 in seawater that is 10 times larger than it would be for an unbuffered gas. The equilibrium between dissolved and atmospheric C02 is sensitive to temperature, tending to higher pC02 in warmer water.Biological export of carbon as sinking particles maintains a gradient of pC02, with lower values near the surface (this processes is called the "biological pump"). In most of the ocean, biological activity removes all of the available nutrients from the surface water; that is, the rate of carbon export in these locations is limited by the rate of nutrient supply to the euphotic zone. However, in much of the high-latitude oceans, primary production does not deplete the euphotic zone of nutrients, a fact to which the atmospheric pC02 is extraordinarily sensitive.Understanding the limits to phytoplankton growth in the high latitudes, and how these limits might change under different climatic regimes, is essential to prediction of future Ocean uptake of fossil fuel c 0 2 .Because many of the processes controlling sea surface pC02 are driven by mixing in the upper ocean, fluctuations in the depth of the mixed layer are of primary importance to modeling sea surface pC02. The depth of the mixed layer can be predicted using a numerical model of the upper ocean. Fluxes of heat, momentum, and dissolved gases provide the boundary conditions for such a model. A major limitation on the precision of calculated heat fluxes is the effect of clouds on the atmospheric radiative heat fluxes.Three families of mixed layer models have been developed, and although the physical mechanisms by which mixing occurs differ among the model groups, all are successful at predicting the observed Ocean mixed layer depth. The "integrated turbulent kinetic energy" (TKE) models construct a budget for surface Ocean TKE, using the wind stress as source and dissipation as sink for TKE. Eixcess kinetic energy is converted to potential energy by mixing denser water up into the surface mixed layer. The "shear instability" models maintain profiles of current velocity resulting from the wind stress;when the current shear becomes too large relative to density stratification, the model mixes (entrains) deep water into the surface layer. "Turbulence closure" models are the most general and the most complicated of the three: types, and are based on laboratory studies of fluid turbulence. This paper explores behavioral distinctions between the three types of models, and summarizes previously published comparisons of th...

show abstract

Controls of CO₂ sources and sinks in the Earth scale surface ocean: Temperature and nutrients

Cited by 31 publications

References 16 publications

Accounting for the missing carbon-sink with the CO2-fertilization effect

Accounting for the missing carbon-sink with the CO2-fertilization effect

Spatial distribution of air‐sea CO₂ fluxes and the interhemispheric transport of carbon by the oceans

Modeling pCO{sub 2} in the upper ocean: A review of relevant physical, chemical, and biological processes

Contact Info

Product

Resources

About

Controls of CO2 sources and sinks in the Earth scale surface ocean: Temperature and nutrients

Cited by 31 publications

References 16 publications

Accounting for the missing carbon-sink with the CO2-fertilization effect

Accounting for the missing carbon-sink with the CO2-fertilization effect

Spatial distribution of air‐sea CO2 fluxes and the interhemispheric transport of carbon by the oceans

Modeling pCO{sub 2} in the upper ocean: A review of relevant physical, chemical, and biological processes

Contact Info

Product

Resources

About

Controls of CO₂ sources and sinks in the Earth scale surface ocean: Temperature and nutrients

Spatial distribution of air‐sea CO₂ fluxes and the interhemispheric transport of carbon by the oceans