scholarly journals Historical Increases in Land‐Derived Nutrient Inputs May Alleviate Effects of a Changing Physical Climate on the Oceanic Carbon Cycle

2021 ◽  
Author(s):  
Fabrice Lacroix ◽  
Tatiana Ilyina ◽  
Moritz Mathis ◽  
Goulven G. Laruelle ◽  
Pierre Regnier
Keyword(s):  
Carbon Cycle ◽  
Nutrient Inputs ◽  
Oceanic Carbon

scholarly journals Simulated Variation Characteristics of Oceanic CO2 Uptake, Surface Temperature, and Acidification in Zhejiang Province, China

2021 ◽  
Vol 9 ◽  
Author(s):  
Kuo Wang ◽  
Han Zhang ◽  
Gao-Feng Fan ◽  
Zheng-Quan Li ◽  
Zhen-Yan Yu ◽  
...  
Keyword(s):  
Global Warming ◽  
Carbon Sequestration ◽  
Carbon Cycle ◽  
Surface Temperature ◽  
Ocean Acidification ◽  
Sea Surface ◽  
Co2 Uptake ◽  
Hydrogen Ion Concentration ◽  
Variation Characteristics ◽  
Oceanic Carbon

Since preindustrial times, atmospheric CO2 content increased continuously, leading to global warming through the greenhouse effect. Oceanic carbon sequestration mitigates global warming; on the other hand, oceanic CO2 uptake would reduce seawater pH, which is termed ocean acidification. We perform Earth system model simulations to assess oceanic CO2 uptake, surface temperature, and acidification for Zhejiang offshore, one of the most vulnerable areas to marine disasters. In the last 40 years, atmospheric CO2 concentration increased by 71 ppm, and sea surface temperature (SST) in Zhejiang offshore increased at a rate of 0.16°C/10a. Cumulative oceanic CO2 uptake in Zhejiang offshore is 0.3 Pg C, resulting in an increase of 20% in sea surface hydrogen ion concentration, and the acidification rate becomes faster in the last decade. During 2020–2040, under four RCP scenarios, SST in Zhejiang offshore increases by 0.3–0.5°C, whereas cumulative ocean carbon sequestration is 0.150–0.165 Pg C. Relative to RCP2.6, the decrease of surface pH in Zhejiang offshore is doubled under RCP8.5. Furthermore, simulated results show that the relationship between CO2 scenario and oceanic carbon cycle is nonlinear, which hints that deeper reduction of anthropogenic CO2 emission may be needed if we aim to mitigate ocean acidification in Zhejiang offshore under a higher CO2 concentration scenario. Our study quantifies the variation characteristics of oceanic climate and carbon cycle fields in Zhejiang offshore, and provides new insight into the responses of oceanic carbon cycle and the climate system to oceanic carbon sequestration.

scholarly journals Heterotrophic denitrification vs. autotrophic anammox – quantifying collateral effects on the oceanic carbon cycle

2010 ◽  
Vol 7 (2) ◽  
pp. 1813-1837
Author(s):  
W. Koeve ◽  
P. Kähler
Keyword(s):  
Carbon Cycle ◽  
Open Ocean ◽  
The Black Sea ◽  
Fixed Nitrogen ◽  
Oxygen Minimum Zones ◽  
Collateral Effects ◽  
Nitrogen Conversion ◽  
Diffusive Fluxes ◽  
Oceanic Carbon ◽  
Heterotrophic Denitrification

Abstract. The conversion of fixed nitrogen to N2 in suboxic waters is estimated to contribute roughly a third to total oceanic losses of fixed nitrogen and is hence understood to be of major importance to global oceanic production and, therefore, to the role of the ocean as a sink of atmospheric CO2. At present heterotrophic denitrification and autotrophic anammox are considered the dominant sinks of fixed nitrogen. Recently, it has been suggested that the trophic nature of pelagic N2-production may have additional, "collateral" effects on the carbon cycle, where heterotrophic denitrification provides a shallow source of CO2 and autotrophic anammox a shallow sink. Here, we analyse the stoichiometries of nitrogen and associated carbon conversions in marine oxygen minimum zones (OMZ) focusing on heterotrophic denitrification, autotrophic anammox, and dissimilatory nitrate reduction to nitrite and ammonium in order to test this hypothesis quantitatively. For open ocean OMZs the combined effects of these processes turn out to be clearly heterotrophic, even with high shares of the autotrophic anammox reaction in total N2-production and including various combinations of dissimilatory processes which provide the substrates to anammox. In such systems, the degree of heterotrophy (ΔCO2:ΔN2), varying between 1.7 and 6, is a function of the efficiency of nitrogen conversion. On the contrary, in systems like the Black Sea, where suboxic N-conversions are supported by diffusive fluxes of NH4+ originating from neighbouring waters with sulphate reduction, much lower values of ΔCO2:ΔN2 can be found. However, accounting for concomitant diffusive fluxes of CO2, ratios approach higher values similar to those computed for open ocean OMZs. Based on our analysis, we question the significance of collateral effects concerning the trophic nature of suboxic N-conversions on the marine carbon cycle.

scholarly journals Heterotrophic denitrification vs. autotrophic anammox – quantifying collateral effects on the oceanic carbon cycle

2010 ◽  
Vol 7 (8) ◽  
pp. 2327-2337 ◽  
Author(s):  
W. Koeve ◽  
P. Kähler
Keyword(s):  
Carbon Cycle ◽  
Open Ocean ◽  
The Black Sea ◽  
Fixed Nitrogen ◽  
Oxygen Minimum Zones ◽  
Collateral Effects ◽  
Nitrogen Conversion ◽  
Diffusive Fluxes ◽  
Oceanic Carbon ◽  
Heterotrophic Denitrification

Abstract. The conversion of fixed nitrogen to N2 in suboxic waters is estimated to contribute roughly a third to total oceanic losses of fixed nitrogen and is hence understood to be of major importance to global oceanic production and, therefore, to the role of the ocean as a sink of atmospheric CO2. At present heterotrophic denitrification and autotrophic anammox are considered the dominant sinks of fixed nitrogen. Recently, it has been suggested that the trophic nature of pelagic N2-production may have additional, "collateral" effects on the carbon cycle, where heterotrophic denitrification provides a shallow source of CO2 and autotrophic anammox a shallow sink. Here, we analyse the stoichiometries of nitrogen and associated carbon conversions in marine oxygen minimum zones (OMZ) focusing on heterotrophic denitrification, autotrophic anammox, and dissimilatory nitrate reduction to nitrite and ammonium in order to test this hypothesis quantitatively. For open ocean OMZs the combined effects of these processes turn out to be clearly heterotrophic, even with high shares of the autotrophic anammox reaction in total N2-production and including various combinations of dissimilatory processes which provide the substrates to anammox. In such systems, the degree of heterotrophy (ΔCO2:ΔN2), varying between 1.7 and 6.5, is a function of the efficiency of nitrogen conversion. On the contrary, in systems like the Black Sea, where suboxic N-conversions are supported by diffusive fluxes of NH4+ originating from neighbouring waters with sulphate reduction, much lower values of ΔCO2:ΔN2 can be found. However, accounting for concomitant diffusive fluxes of CO2, the ratio approaches higher values similar to those computed for open ocean OMZs. Based on this analysis, we question the significance of collateral effects concerning the trophic nature of suboxic N-conversions on the marine carbon cycle.

scholarly journals The influence of dynamic vegetation on the present-day simulation and future projections of the South Asian summer monsoon in the HadGEM2 family

2012 ◽  
Vol 3 (2) ◽  
pp. 245-261 ◽  
Author(s):  
G. M. Martin ◽  
R. C. Levine
Keyword(s):  
Climate Change ◽  
Carbon Cycle ◽  
Summer Monsoon ◽  
Asian Summer Monsoon ◽  
Climate System ◽  
Tropospheric Chemistry ◽  
Earth System ◽  
South Asian Summer Monsoon ◽  
Asian Summer ◽  
Oceanic Carbon

Abstract. Various studies have shown the importance of Earth System feedbacks in the climate system and the necessity of including these in models used for making climate change projections. The HadGEM2 family of Met Office Unified Model configurations combines model components which facilitate the representation of many different processes within the climate system, including atmosphere, ocean and sea ice, and Earth System components including the terrestrial and oceanic carbon cycle and tropospheric chemistry. We examine the climatology of the Asian summer monsoon in present-day simulations and in idealised climate change experiments. Members of the HadGEM2 family are used, with a common physical framework (one of which includes tropospheric chemistry and an interactive terrestrial and oceanic carbon cycle), to investigate whether such components affect the way in which the monsoon changes. We focus particularly on the role of interactive vegetation in the simulations from these model configurations. Using an atmosphere-only HadGEM2 configuration, we investigate how the changes in land cover which result from the interaction between the dynamic vegetation and the model systematic rainfall biases affect the Asian summer monsoon, both in the present-day and in future climate projections. We demonstrate that the response of the dynamic vegetation to biases in regional climate, such as lack of rainfall over tropical dust-producing regions, can affect both the present-day simulation and the response to climate change forcing scenarios.

Biochemical feedbacks in the oceanic carbon cycle

1994 ◽  
Vol 75-76 ◽  
pp. 459-469 ◽  
Author(s):  
O. Klepper ◽  
B.J. de Haan ◽  
H. van Huet
Keyword(s):  
Carbon Cycle ◽  
Oceanic Carbon
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