The importance of ocean transport in the fate of anthropogenic CO2 (original) (raw)
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The role of ocean transport in the uptake of anthropogenic CO2
Biogeosciences, 2009
We compare modeled oceanic carbon uptake in response to pulse CO 2 emissions using a suite of global ocean models and Earth system models. In response to a CO 2 pulse emission of 590 Pg C (corresponding to an instantaneous doubling of atmospheric CO 2 from 278 to 556 ppm), the fraction of CO 2 emitted that is absorbed by the ocean is: 37±8%, 56±10%, and 81±4% (model mean ±2σ ) in year 30, 100, and 1000 after the emission pulse, respectively. Modeled oceanic uptake of pulse CO 2 on timescales from decades to about a century is strongly correlated with simulated presentday uptake of chlorofluorocarbons (CFCs) and CO 2 across all models, while the amount of pulse CO 2 absorbed by the ocean from a century to a millennium is strongly correlated with modeled radiocarbon in the deep Southern and Pacific Ocean. However, restricting the analysis to models that are capable of reproducing observations within uncertainty, the correlation is generally much weaker. The rates of surface-Correspondence to: L. Cao (longcao@stanford.edu) to-deep ocean transport are determined for individual models from the instantaneous doubling CO 2 simulations, and they are used to calculate oceanic CO 2 uptake in response to pulse CO 2 emissions of different sizes pulses of 1000 and 5000 Pg C. These results are compared with simulated oceanic uptake of CO 2 by a number of models simulations with the coupling of climate-ocean carbon cycle and without it. This comparison demonstrates that the impact of different ocean transport rates across models on oceanic uptake of anthropogenic CO 2 is of similar magnitude as that of climate-carbon cycle feedbacks in a single model, emphasizing the important role of ocean transport in the uptake of anthropogenic CO 2 .
Physical Science International Journal, 2015
The author has developed one dimensional semi-empirical atmosphere-ocean-biosphere model (1DAOBM) based on the four-box presentation. Firstly, the author has analysed that the model development can be based on the two elements: 1) the four box-model containing two ideal mixing components (the atmosphere and the ocean), one plug flow component with four different residence times (the biosphere), and the outlet (the intermediate & deep ocean), 2) the ocean's capacity to dissolve anthropogenic CO 2 emissions of the present century. The surface ocean part is based on the known dissolution chemical equations. The net flux rate from the surface ocean into the deep ocean is based on the empirical data. The removal of the anthropogenic CO 2 from the atmosphere is based on the huge carbon cycle flux rates of the dissolution pump and the biosphere carbon cycle, which remove yearly about 26% of CO 2 from the atmosphere to other reservoirs and, at the same time, recycle back natural and anthropogenic carbon. The simulations of the atmospheric net CO 2 rate by 1DAOBM from 1960 to 2013 show fairly good similarity to the measured values: r 2 = 0.75 and the standard error of estimate 0.68 GtC/y, which means the standard error of 12% at the present emission rate of about 10 GtC/y. The simulations show that the present anthropogenic CO 2 fraction in the atmosphere is 7.7%, and it explains the observed
Inverse estimates of anthropogenic CO 2 uptake, transport, and storage by the ocean
Global Biogeochemical Cycles, 2006
1] Regional air-sea fluxes of anthropogenic CO2 are estimated using a Green's function inversion method that combines data-based estimates of anthropogenic CO2 in the ocean with information about ocean transport and mixing from a suite of Ocean General Circulation Models (OGCMs). In order to quantify the uncertainty associated with the estimated fluxes owing to modeled transport and errors in the data, we employ 10 OGCMs and three scenarios representing biases in the data-based anthropogenic CO2 estimates. On the basis of the prescribed anthropogenic CO2 storage, we find a global uptake of 2.2 +/-0.25 Pg C yr(-1), scaled to 1995. This error estimate represents the standard deviation of the models weighted by a CFC-based model skill score, which reduces the error range and emphasizes those models that have been shown to reproduce observed tracer concentrations most accurately. The greatest anthropogenic CO2 uptake occurs in the Southern Ocean and in the tropics. The flux estimates imply vigorous northward transport in the Southern Hemisphere, northward cross-equatorial transport, and equatorward transport at eScholarship provides open access, scholarly publishing services to the University of California and delivers a dynamic research platform to scholars worldwide. high northern latitudes. Compared with forward simulations, we find substantially more uptake in the Southern Ocean, less uptake in the Pacific Ocean, and less global uptake. The large-scale spatial pattern of the estimated flux is generally insensitive to possible biases in the data and the models employed. However, the global uptake scales approximately linearly with changes in the global anthropogenic CO2 inventory. Considerable uncertainties remain in some regions, particularly the Southern Ocean. 2
2019
version 3 (hereafter NESM v3) in simulating the marine biogeochemical cycle and CO2 uptake. Compared with observations, NESM v3 reproduces reasonably well the large-scale patterns of upper ocean biogeochemical fields including nutrients, alkalinity, dissolved inorganic, chlorophyll, and net primary production. The model also reasonably reproduces current-day oceanic CO2 uptake, the total CO2 uptake is 149 PgC from 1850 to 2016. In the 1ptCO2 experiment, the NESM v3 produced carbon-climate (=-7.9 PgC/K) and carbon-concentration sensitivity parameters (= 0.8 PgC/ppm) are comparable with CMIP5 model results. The nonlinearity of carbon uptake in the NESM v3 accounts for 10.3% of the total carbon uptake, which is within the range of CMIP5 model results (3.6%~10.6%). Some regional discrepancies between model simulations and observations are identified and the possible causes are investigated. In the upper ocean, the simulated biases in biogeochemical fields are mainly associated with the shortcoming in simulated ocean circulation. Weak upwelling in the Indian Ocean suppresses the nutrient entrainment to the upper ocean, therefore reducing the biological activities and resulting in underestimation of net primary production and chlorophyll concentration. In the Pacific and the Southern Ocean, high-nutrient and low-chlorophyll result from the strong iron limitation. Alkalinity shows high biases in high-latitude oceans due to the strong convective mixing. The major discrepancy in biogeochemical fields is seen in the deep Northern Pacific. The simulated high concentration of nutrients, alkalinity and dissolved inorganic carbon water is too deep due to the excessive deep ocean remineralization. Despite these model-observation discrepancies, it is
Geoscientific Model Development, 2020
Abstract. In this study, we evaluate the performance of the Nanjing University of Information Science and Technology (NUIST) Earth System Model version 3 (hereafter NESM v3) in simulating the marine biogeochemical cycle and carbon dioxide ( CO2 ) uptake. Compared with observations, the NESM v3 reproduces the large-scale patterns of biogeochemical fields reasonably well in the upper ocean, including nutrients, alkalinity, dissolved inorganic, chlorophyll, and net primary production. Some discrepancies between model simulations and observations are identified and the possible causes are investigated. In the upper ocean, the simulated biases in biogeochemical fields are mainly associated with shortcomings in the simulated ocean circulation. Weak upwelling in the Indian Ocean suppresses the nutrient entrainment to the upper ocean, thus reducing biological activities and resulting in an underestimation of net primary production and the chlorophyll concentration. In the Pacific and the So...
Energy Conversion and Management, 1993
An evaluation of oceanic containment strategies for anthropogenic carbon dioxide is presented. Energy conservation is also addressed through an input hydrocarbon-fuel consumption function. The eft. "veness of these .c~unte .rmeasures is determined from atmospheric C02 concentr~on predictions. A pt~,tous box model wlth a diffusive deep ocean is adapted and applied to the concept of fractional CO2 injection in 500 m deep waters. The contributions of deep seawater renewal and calcium carbonate sediment dissolution are included. Numerical results show that for CO2 direct removal measures to be effective, large fractions of anthropogenic cafl~n dioxide have to be processed. This point favors fuel pre-processing concepts. The global model also indicates that energy conservation, i. e. a liydrocarbonfuel consumption slowdown, remains the most effective way to mitigate the greenhouse effect, because it offers mankind a substantial time delay to implement new energy production alternatives. KEYWORI~ Greenhouse effect; carbon dioxide; ocean disposal; calcium carbonate dissolution.
Projected impact of deep ocean carbon dioxide discharge on atmospheric CO2 concentrations
Climatic Change, 1994
An evaluation of oceanic containment strategies for anthropogenic carbon dioxide is presented. Energy conservation is also addressed through an input hydrocarbon-fuel consumption function. The effectiveness of the proposed countermeasures is determined from atmospheric CO2 concentration predictions. A previous box model with a diffusive deep ocean is adapted and applied to the concept of fractional CO2 injection in 500 m deep waters. Next, the contributions of oceanic calcium carbonate sediment dissolution, and of deep seawater renewal, are included. Numerical results show that for CO 2 direct removal measures to be effective, large fractions of anthropogenic carbon dioxide have to be processed. This point favors fuel pre-processing concepts. The global model also indicates that energy conservation, i.e. a hydrocarbon-fuel consumption slowdown, remains the most effective way to mitigate the greenhouse effect, because it offers mankind a substantial time delay to implement new energy production alternatives. Nomenclature a: parameter defining the delta family of functions f~ (m) A: ocean surface area (m 2) Alk: seawater alkalinity (millivals/1) Ased: seafloor surface area covered with dissolvable CaCO 3 (m 2) Cd: deep ocean CO2 injection source (kg/m3-yr) D: carbonate diffusion coefficient in sediment (m2/s) f: calcite fraction in seafloor sediments fa: delta family of functions (m-1) F~: CaCO 3 dissolution flux (mole/m2-yr) hm: ocean mixed layer thickness (m) K: deep ocean average vertical eddy diffusivity (m2/s) kam: equilibrium carbon exchange coefficient (atmosphere ~ mixed layer) kma: equilibrium carbon exchange coefficient (mixed layer ~ atmosphere) L: deep ocean thickness (m) M: mixed layer carbon concentration perturbation (kg/m '3) na: atmospheric carbon mass perturbation (kg) nm: mixed layer carbon mass perturbation (kg) N: mixed layer calcium concentration perturbation (kg/m 3) Na: atmospheric carbon source (kg/yr) p: calcite sediment porosity q: two-dimensional deep ocean carbon source (kg/m2-yr) qc~: two-dimensional deep ocean calcium source (kg/m2-yr) qca*: two-dimensional deep ocean recirculation calcium source (kg/m2-yr) Re: fuel-bound carbon reserves (kg) Rca: calcium reserves in dissolvable seafloor sediments (kg) t: time (yr) Tin: mixed layer renewal period (yr) u: deep ocean carbon concentration perturbation (kg/m 3)
Oceanic sources, sinks, and transport of atmospheric CO 2
Global Biogeochemical Cycles, 2009
1] We synthesize estimates of the contemporary net air-sea CO 2 flux on the basis of an inversion of interior ocean carbon observations using a suite of 10 ocean general circulation models and compare them to estimates based on a new climatology of the air-sea difference of the partial pressure of CO 2 (pCO 2 ) . These two independent flux estimates reveal a consistent description of the regional distribution of annual mean sources and sinks of atmospheric CO 2 for the decade of the 1990s and the early 2000s with differences at the regional level of generally less than 0.1 Pg C a À1 . This distribution is characterized by outgassing in the tropics, uptake in midlatitudes, and comparatively small fluxes in the high latitudes. Both estimates point toward a small ($ À0.3 Pg C a À1 ) contemporary CO 2 sink in the Southern Ocean (south of 44°S), a result of the near cancellation between a substantial outgassing of natural CO 2 and a strong uptake of anthropogenic CO 2 . A notable exception in the generally good agreement between the two estimates exists within the Southern Ocean: the ocean inversion suggests a relatively uniform uptake, while the pCO 2 -based estimate suggests strong uptake in the region between 58°S and 44°S, and a source in the region south of 58°S. Globally and for a nominal period between 1995 and 2000, the contemporary net air-sea flux of CO 2 is estimated to be À1.7 ± 0.4 Pg C a À1 (inversion) and À1.4 ± 0.7 Pg C a À1 (pCO 2 -climatology), respectively, consisting of an outgassing flux of river-derived carbon of $+0.5 Pg C a À1 , and an uptake flux of anthropogenic carbon of À2.2 ± 0.3 Pg C a À1 (inversion) and À1.9 ± 0.7 Pg C a À1 (pCO 2 -climatology). The two flux estimates also imply a consistent description of the contemporary meridional transport of carbon with southward ocean transport throughout most of the Atlantic basin, and strong equatorward convergence in the Indo-Pacific basins. Both transport estimates suggest a small hemispheric asymmetry with a southward transport of between À0.2 and À0.3 Pg C a À1 across the equator. While the convergence of these two independent estimates is encouraging and suggests that it is now possible to provide relatively tight constraints for the net air-sea CO 2 fluxes at the regional basis, both studies are limited by their lack of consideration of long-term changes in the ocean carbon cycle, such as the recent possible stalling in the expected growth of the Southern Ocean carbon sink.