scholarly journals Impact of atmospheric and terrestrial CO<sub>2</sub> feedbacks on fertilization-induced marine carbon uptake

2009 ◽  
Vol 6 (8) ◽  
pp. 1603-1613 ◽  
Author(s):  
A. Oschlies
Keyword(s):  
C:N Ratio ◽  
Atmospheric Co2 ◽  
Carbon Uptake ◽  
Co2 Uptake ◽  
Biological Pump ◽  
Terrestrial Carbon ◽  
Terrestrial Biosphere ◽  
Oceanic Carbon ◽  
The Impact ◽  
Atmospheric Pco2

Abstract. The sensitivity of oceanic CO2 uptake to alterations in the marine biological carbon pump, such as brought about by natural or purposeful ocean fertilization, has repeatedly been investigated by studies employing numerical biogeochemical ocean models. It is shown here that the results of such ocean-centered studies are very sensitive to the assumption made about the response of the carbon reservoirs on the atmospheric side of the sea surface. Assumptions made include prescribed atmospheric pCO2, an interactive atmospheric CO2 pool exchanging carbon with the ocean but not with the terrestrial biosphere, and an interactive atmosphere that exchanges carbon with both oceanic and terrestrial carbon pools. The impact of these assumptions on simulated annual to millennial oceanic carbon uptake is investigated for a hypothetical increase in the C:N ratio of the biological pump and for an idealized enhancement of phytoplankton growth. Compared to simulations with interactive atmosphere, using prescribed atmospheric pCO2 overestimates the sensitivity of the oceanic CO2 uptake to changes in the biological pump, by about 2%, 25%, 100%, and >500% on annual, decadal, centennial, and millennial timescales, respectively. The smaller efficiency of the oceanic carbon uptake under an interactive atmosphere is due to the back flux of CO2 that occurs when atmospheric CO2 is reduced. Adding an interactive terrestrial carbon pool to the atmosphere-ocean model system has a small effect on annual timescales, but increases the simulated fertilization-induced oceanic carbon uptake by about 4%, 50%, and 100% on decadal, centennial, and millennial timescales, respectively, for pCO2 sensitivities of the terrestrial carbon storage in the middle range of the C4MIP models (Friedlingstein et al., 2006). For such sensitivities, a substantial fraction of oceanic carbon uptake induced by natural or purposeful ocean fertilization originates, on timescales longer than decades, not from the atmosphere but from the terrestrial biosphere.

scholarly journals Impact of atmospheric and terrestrial CO<sub>2</sub> feedbacks on fertilization-induced marine carbon uptake

2009 ◽  
Vol 6 (2) ◽  
pp. 4493-4525
Author(s):  
A. Oschlies
Keyword(s):  
C:N Ratio ◽  
Ocean Model ◽  
Carbon Uptake ◽  
Co2 Uptake ◽  
Biological Pump ◽  
Terrestrial Carbon ◽  
Terrestrial Biosphere ◽  
Oceanic Carbon ◽  
The Impact ◽  
Atmospheric Pco2

Abstract. The sensitivity of oceanic CO2 uptake to alterations in the marine biological carbon pump, such as brought about by natural or purposeful ocean fertilization, has repeatedly been investigated by studies employing numerical biogeochemical ocean models. It is shown here that the results of such ocean-centered studies are very sensitive to the assumption made about the response of the carbon reservoirs on the atmospheric side of the sea surface. Assumptions made include prescribed atmospheric pCO2, an interactive atmospheric CO2 pool exchanging carbon with the ocean but not with the terrestrial biosphere, and an interactive atmosphere that exchanges carbon with both oceanic and terrestrial carbon pools. The impact of these assumptions on simulated annual to millennial oceanic carbon uptake is investigated for a hypothetical increase in the C:N ratio of the biological pump and for an idealized enhancement of phytoplankton growth. Compared to simulations with interactive atmosphere, using prescribed atmospheric pCO2 overestimates the sensitivity of the oceanic CO2 uptake to changes in the biological pump, by about 2%, 25%, 100%, and >500% on annual, decadal, centennial, and millennial timescales, respectively. Adding an interactive terrestrial carbon pool to the atmosphere-ocean model system has a small effect on annual timescales, but increases the simulated fertilization-induced oceanic carbon uptake by about 4%, 50%, and 100% on decadal, centennial, and millennial timescales, respectively. On longer than decadal timescales, a substantial fraction of oceanic carbon uptake induced by natural or purposeful ocean fertilization may not come from the atmosphere but from the terrestrial biosphere.

scholarly journals Long-term response of oceanic carbon uptake to global warming via physical and biological pumps

2017 ◽  
Author(s):  
Akitomo Yamamoto ◽  
Ayako Abe-Ouchi ◽  
Yasuhiro Yamanaka
Keyword(s):  
Global Warming ◽  
Ocean Circulation ◽  
General Circulation ◽  
Deep Ocean ◽  
Biogeochemical Model ◽  
Carbon Uptake ◽  
Co2 Uptake ◽  
Biological Pump ◽  
Circulation Change ◽  
Oceanic Carbon

Abstract. Global warming is expected to significantly decrease oceanic carbon uptake and therefore accelerate an increase in atmospheric CO2 and global warming. The primary reasons in previous studies for the change in the oceanic carbon uptake are the solubility reduction due to seawater warming and changes in the ocean circulation and biological pump. However, quantifications of the contributions from different processes to the overall reduction in ocean uptake are still unclear. Herein, we investigate multimillennium response of oceanic carbon uptake to global warming and quantify the contributions of the physical and biological pump to the response using an atmosphere–ocean general circulation model and a biogeochemical model. We found that global warming reduced oceanic CO2 uptake by 13 % (30 %) in the first 140 years (at year 2000), which is consistent with previous studies. Sensitivity studies show that changes in the biological pump via ocean circulation change and solubility change due to seawater warming are dominant processes in the uptake reduction. These results are contrary to most previous studies wherein circulation changes and solubility change from seawater warming are the dominant processes. The weakening of biological production and carbon export induced by lower nutrient supply diminishes the vertical gradient of DIC substantially reducing the CO2 uptake. The weaker deep-ocean circulation decreases the downward transport of CO2 from the surface to the deep ocean, leading to a drop in the CO2 uptake in high-latitude regions. Conversely, weaker equatorial upwelling reduces the upward transport of natural CO2 and therefore enhances the CO2 uptake in low-latitude regions. Because these effects cancel each other, the circulation change becomes a second-order process. Our results suggest that the biological pump plays a significant role in the future oceanic carbon uptake through natural carbon cycle.

scholarly journals Long-term response of oceanic carbon uptake to global warming via physical and biological pumps

2018 ◽  
Vol 15 (13) ◽  
pp. 4163-4180 ◽  
Author(s):  
Akitomo Yamamoto ◽  
Ayako Abe-Ouchi ◽  
Yasuhiro Yamanaka
Keyword(s):  
Global Warming ◽  
Ocean Circulation ◽  
General Circulation ◽  
Deep Ocean ◽  
Biogeochemical Model ◽  
Carbon Uptake ◽  
Co2 Uptake ◽  
Biological Pumps ◽  
Circulation Change ◽  
Oceanic Carbon

Abstract. Global warming is expected to significantly decrease oceanic carbon uptake and therefore increase atmospheric CO2 and global warming. The primary reasons given in previous studies for such changes in the oceanic carbon uptake are the solubility reduction due to seawater warming and changes in the ocean circulation and biological pump. However, the quantitative contributions of different processes to the overall reduction in ocean uptake are still unclear. In this study, we investigated multi-millennium responses of oceanic carbon uptake to global warming and quantified the contributions of the physical and biological pumps to these responses using an atmosphere–ocean general circulation model and a biogeochemical model. We found that global warming reduced oceanic CO2 uptake by 13 % (30 %) in the first 140 years (after 2000 model years), consistent with previous studies. Our sensitivity experiments showed that this reduction is primarily driven by changes in the organic matter cycle via ocean circulation change and solubility change due to seawater warming. These results differ from most previous studies, in which circulation changes and solubility change from seawater warming are the dominant processes. The weakening of biological production and carbon export induced by circulation change and lower nutrient supply, diminishes the vertical DIC gradient and substantially reduces the CO2 uptake. The weaker deep-ocean circulation decreases the downward transport of CO2 from the surface to the deep ocean, leading to a drop in CO2 uptake in high-latitude regions. Conversely, weaker equatorial upwelling reduces the upward transport of natural CO2 and therefore enhances the CO2 uptake in low-latitude regions. Because these effects cancel each other out, circulation change plays only a small direct role in the reduction of CO2 uptake due to global warming but a large indirect role through nutrient transport and biological processes.

The impact of a coccolithophore bloom on oceanic carbon uptake in the northeast Atlantic during summer 1991

1994 ◽  
Vol 41 (2) ◽  
pp. 297-314 ◽  
Author(s):  
J.E. Robertson ◽  
C. Robinson ◽  
D.R. Turner ◽  
P. Holligan ◽  
A.J. Watson ◽  
...  
Keyword(s):  
Carbon Uptake ◽  
Northeast Atlantic ◽  
Oceanic Carbon ◽  
The Impact

scholarly journals The impact of spatiotemporal variability in atmospheric CO<sub>2</sub> concentration on global terrestrial carbon fluxes

2018 ◽  
Author(s):  
Eunjee Lee ◽  
Fan-Wei Zeng ◽  
Randal D. Koster ◽  
Brad Weir ◽  
Lesley E. Ott ◽  
...  
Keyword(s):  
Carbon Cycle ◽  
Temporal Variability ◽  
Gross Primary Production ◽  
Carbon Fluxes ◽  
Atmospheric Co2 ◽  
Spatiotemporal Variability ◽  
Terrestrial Carbon ◽  
Diurnal Variability ◽  
Co2 Concentrations ◽  
The Impact

Abstract. Land carbon fluxes, e.g., gross primary production (GPP) and net biome production (NBP), are controlled in part by the responses of terrestrial ecosystems to atmospheric conditions near the Earth's surface. The Coupled Model Intercomparison Project Phase 6 (CMIP6) has recently proposed increased spatial and temporal resolutions for the surface CO2 concentrations used to calculate GPP, and yet a comprehensive evaluation of the consequences of this increased resolution for carbon cycle dynamics is missing. Here, using global offline simulations with a terrestrial biosphere model, the sensitivity of terrestrial carbon cycle fluxes to multiple facets of the spatiotemporal variability of atmospheric CO2 is quantified. Globally, the spatial variability of CO2 is found to increase the mean global GPP by 0.2 PgC year−1, as more vegetated land areas benefit from higher CO2 concentrations induced by the inter-hemisphere gradient. The temporal variability of CO2, however, compensates for this increase, acting to reduce overall global GPP; in particular, consideration of the diurnal variability of atmospheric CO2 reduces multi-year mean global annual GPP by 0.5 PgC year−1 and net land carbon uptake by 0.1 PgC year−1. The relative contribution of the different facets of CO2 variability to GPP are found to vary regionally and seasonally, with the seasonal variation in atmospheric CO2, for example, having a notable impact on GPP in boreal regions during fall. Overall, in terms of estimating global GPP, the magnitudes of the sensitivities found here are minor, indicating that the common practice of applying spatially-uniform and annually increasing CO2 (without higher frequency temporal variability) in offline studies is a reasonable approach – the small errors induced by ignoring CO2 variability are undoubtedly swamped by other uncertainties in the offline calculations. Still, for certain regional- and seasonal-scale GPP estimations, the proper treatment of spatiotemporal CO2 variability appears important.

scholarly journals The impact of spatiotemporal variability in atmospheric CO<sub>2</sub> concentration on global terrestrial carbon fluxes

2018 ◽  
Vol 15 (18) ◽  
pp. 5635-5652 ◽  
Author(s):  
Eunjee Lee ◽  
Fan-Wei Zeng ◽  
Randal D. Koster ◽  
Brad Weir ◽  
Lesley E. Ott ◽  
...  
Keyword(s):  
Carbon Cycle ◽  
Temporal Variability ◽  
Gross Primary Production ◽  
Carbon Fluxes ◽  
Atmospheric Co2 ◽  
Spatiotemporal Variability ◽  
Terrestrial Carbon ◽  
Diurnal Variability ◽  
Co2 Concentrations ◽  
The Impact

Abstract. Land carbon fluxes, e.g., gross primary production (GPP) and net biome production (NBP), are controlled in part by the responses of terrestrial ecosystems to atmospheric conditions near the Earth's surface. The Coupled Model Intercomparison Project Phase 6 (CMIP6) has recently proposed increased spatial and temporal resolutions for the surface CO2 concentrations used to calculate GPP, and yet a comprehensive evaluation of the consequences of this increased resolution for carbon cycle dynamics is missing. Here, using global offline simulations with a terrestrial biosphere model, the sensitivity of terrestrial carbon cycle fluxes to multiple facets of the spatiotemporal variability in atmospheric CO2 is quantified. Globally, the spatial variability in CO2 is found to increase the mean global GPP by a maximum of 0.05 Pg C year−1, as more vegetated land areas benefit from higher CO2 concentrations induced by the inter-hemispheric gradient. The temporal variability in CO2, however, compensates for this increase, acting to reduce overall global GPP; in particular, consideration of the diurnal variability in atmospheric CO2 reduces multi-year mean global annual GPP by 0.5 Pg C year−1 and net land carbon uptake by 0.1 Pg C year−1. The relative contributions of the different facets of CO2 variability to GPP are found to vary regionally and seasonally, with the seasonal variation in atmospheric CO2, for example, having a notable impact on GPP in boreal regions during fall. Overall, in terms of estimating global GPP, the magnitudes of the sensitivities found here are minor, indicating that the common practice of applying spatially uniform and annually increasing CO2 (without higher-frequency temporal variability) in offline studies is a reasonable approach – the small errors induced by ignoring CO2 variability are undoubtedly swamped by other uncertainties in the offline calculations. Still, for certain regional- and seasonal-scale GPP estimations, the proper treatment of spatiotemporal CO2 variability appears important.

scholarly journals Terrestrial carbon sink observed from space: variation of growth rates and seasonal cycle amplitudes in response to interannual surface temperature variability

2014 ◽  
Vol 14 (1) ◽  
pp. 133-141 ◽  
Author(s):  
O. Schneising ◽  
M. Reuter ◽  
M. Buchwitz ◽  
J. Heymann ◽  
H. Bovensmann ◽  
...  
Keyword(s):  
Surface Temperature ◽  
Growth Rates ◽  
Seasonal Cycle ◽  
Temperature Anomaly ◽  
Carbon Sink ◽  
Atmospheric Co2 ◽  
Climate Feedback ◽  
Terrestrial Carbon ◽  
Terrestrial Carbon Sink ◽  
The Impact

Abstract. The terrestrial biosphere is currently acting as a net carbon sink on the global scale, exhibiting significant interannual variability in strength. To reliably predict the future strength of the land sink and its role in atmospheric CO2 growth, the underlying biogeochemical processes and their response to a changing climate need to be well understood. In particular, better knowledge of the impact of key climate variables such as temperature or precipitation on the biospheric carbon reservoir is essential. It is demonstrated using nearly a decade of SCIAMACHY (SCanning Imaging Absorption spectroMeter for Atmospheric CHartographY) nadir measurements that years with higher temperatures during the growing season can be robustly associated with larger growth rates in atmospheric CO2 and smaller seasonal cycle amplitudes for northern mid-latitudes. We find linear relationships between warming and CO2 growth as well as seasonal cycle amplitude at the 98% significance level. This suggests that the terrestrial carbon sink is less efficient at higher temperatures during the analysed time period. Unless the biosphere has the ability to adapt its carbon storage under warming conditions in the longer term, such a temperature response entails the risk of potential future sink saturation via a positive carbon-climate feedback. Quantitatively, the covariation between the annual CO2 growth rates derived from SCIAMACHY data and warm season surface temperature anomaly amounts to 1.25 ± 0.32 ppm yr−1 K−1 for the Northern Hemisphere, where the bulk of the terrestrial carbon sink is located. In comparison, this relationship is less pronounced in the Southern Hemisphere. The covariation of the seasonal cycle amplitudes retrieved from satellite measurements and temperature anomaly is −1.30 ± 0.31 ppm K−1 for the north temperate zone. These estimates are consistent with those from the CarbonTracker data assimilated CO2 data product, indicating that the temperature dependence of the model surface fluxes is realistic.

scholarly journals Variable C∕P composition of organic production and its effect on ocean carbon storage in glacial-like model simulations

2020 ◽  
Vol 17 (8) ◽  
pp. 2219-2244 ◽  
Author(s):  
Malin Ödalen ◽  
Jonas Nycander ◽  
Andy Ridgwell ◽  
Kevin I. C. Oliver ◽  
Carlye D. Peterson ◽  
...  
Keyword(s):  
Organic Matter ◽  
Carbon Storage ◽  
Co2 Storage ◽  
Organic Production ◽  
Phosphate Concentration ◽  
Atmospheric Co2 ◽  
Carbon Uptake ◽  
Biological Pump ◽  
Redfield Ratio ◽  
Model Simulations

Abstract. During the four most recent glacial maxima, atmospheric CO2 has been lowered by about 90–100 ppm with respect to interglacial concentrations. It is likely that most of the atmospheric CO2 deficit was stored in the ocean. Changes in the biological pump, which are related to the efficiency of the biological carbon uptake in the surface ocean and/or of the export of organic carbon to the deep ocean, have been proposed as a key mechanism for the increased glacial oceanic CO2 storage. The biological pump is strongly constrained by the amount of available surface nutrients. In models, it is generally assumed that the ratio between elemental nutrients, such as phosphorus, and carbon (C∕P ratio) in organic material is fixed according to the classical Redfield ratio. The constant Redfield ratio appears to approximately hold when averaged over basin scales, but observations document highly variable C∕P ratios on regional scales and between species. If the C∕P ratio increases when phosphate availability is scarce, as observations suggest, this has the potential to further increase glacial oceanic CO2 storage in response to changes in surface nutrient distributions. In the present study, we perform a sensitivity study to test how a phosphate-concentration-dependent C∕P ratio influences the oceanic CO2 storage in an Earth system model of intermediate complexity (cGENIE). We carry out simulations of glacial-like changes in albedo, radiative forcing, wind-forced circulation, remineralization depth of organic matter, and mineral dust deposition. Specifically, we compare model versions with the classical constant Redfield ratio and an observationally motivated variable C∕P ratio, in which the carbon uptake increases with decreasing phosphate concentration. While a flexible C∕P ratio does not impact the model's ability to simulate benthic δ13C patterns seen in observational data, our results indicate that, in production of organic matter, flexible C∕P can further increase the oceanic storage of CO2 in glacial model simulations. Past and future changes in the C∕P ratio thus have implications for correctly projecting changes in oceanic carbon storage in glacial-to-interglacial transitions as well as in the present context of increasing atmospheric CO2 concentrations.

scholarly journals Terrestrial carbon sink observed from space: variation of growth rates and seasonal cycle amplitudes in response to interannual surface temperature variability

2013 ◽  
Vol 13 (8) ◽  
pp. 22733-22755 ◽  
Author(s):  
O. Schneising ◽  
M. Reuter ◽  
M. Buchwitz ◽  
J. Heymann ◽  
H. Bovensmann ◽  
...  
Keyword(s):  
Surface Temperature ◽  
Growth Rates ◽  
Seasonal Cycle ◽  
Temperature Anomaly ◽  
Carbon Sink ◽  
Atmospheric Co2 ◽  
Climate Feedback ◽  
Terrestrial Carbon ◽  
Terrestrial Carbon Sink ◽  
The Impact

Abstract. The terrestrial biosphere is currently acting as a net carbon sink on the global scale exhibiting significant interannual variability in strength. To reliably predict the future strength of the land sink and its role in atmospheric CO2 growth the underlying processes and their response to a changing climate need to be well understood. In particular, better knowledge of the impact of key climate variables like temperature or precipitation on the biospheric carbon reservoir is essential. It is demonstrated using nearly a decade of SCIAMACHY nadir measurements that years with higher temperatures during the growing season can be robustly associated with larger growth rates in atmospheric CO2 and smaller seasonal cycle amplitudes for northern mid-latitudes. We find linear relationships between warming and CO2 growth as well as seasonal cycle amplitude at the 98% significance level. This suggests that the terrestrial carbon sink is less efficient at higher temperatures, which might lead to future sink saturation via a positive carbon-climate feedback. Quantitatively, the covariation between the annual CO2 growth rates derived from SCIAMACHY data and warm season surface temperature anomaly amounts to 1.25±0.32 ppm yr−1 K−1 for the Northern Hemisphere where the bulk of the terrestrial carbon sink is located. In comparison, the relation is less pronounced in the Southern Hemisphere. The covariation of the seasonal cycle amplitudes derived from satellite and temperature anomaly is −1.30±0.31 ppm K−1 for the north temperate zone. These estimates are consistent with those from the CarbonTracker data assimilated CO2 data product indicating that the temperature dependence of the model surface fluxes is realistic.

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