scholarly journals Regional Impacts of Climate Change and Atmospheric CO2 on Future Ocean Carbon Uptake: A Multimodel Linear Feedback Analysis

2011 ◽  
Vol 24 (9) ◽  
pp. 2300-2318 ◽  
Author(s):  
Tilla Roy ◽  
Laurent Bopp ◽  
Marion Gehlen ◽  
Birgit Schneider ◽  
Patricia Cadule ◽  
...  
Keyword(s):  
Climate Change ◽  
North Atlantic Ocean ◽  
Climate Change Impacts ◽  
Atmospheric Co2 ◽  
Linear Feedback ◽  
Co2 Uptake ◽  
Co2 Solubility ◽  
Feedback Analysis ◽  
Anthropogenic Co2 ◽  
Atmospheric Co2 Concentrations

Abstract The increase in atmospheric CO2 over this century depends on the evolution of the oceanic air–sea CO2 uptake, which will be driven by the combined response to rising atmospheric CO2 itself and climate change. Here, the future oceanic CO2 uptake is simulated using an ensemble of coupled climate–carbon cycle models. The models are driven by CO2 emissions from historical data and the Special Report on Emissions Scenarios (SRES) A2 high-emission scenario. A linear feedback analysis successfully separates the regional future (2010–2100) oceanic CO2 uptake into a CO2-induced component, due to rising atmospheric CO2 concentrations, and a climate-induced component, due to global warming. The models capture the observation-based magnitude and distribution of anthropogenic CO2 uptake. The distributions of the climate-induced component are broadly consistent between the models, with reduced CO2 uptake in the subpolar Southern Ocean and the equatorial regions, owing to decreased CO2 solubility; and reduced CO2 uptake in the midlatitudes, owing to decreased CO2 solubility and increased vertical stratification. The magnitude of the climate-induced component is sensitive to local warming in the southern extratropics, to large freshwater fluxes in the extratropical North Atlantic Ocean, and to small changes in the CO2 solubility in the equatorial regions. In key anthropogenic CO2 uptake regions, the climate-induced component offsets the CO2-induced component at a constant proportion up until the end of this century. This amounts to approximately 50% in the northern extratropics and 25% in the southern extratropics and equatorial regions. Consequently, the detection of climate change impacts on anthropogenic CO2 uptake may be difficult without monitoring additional tracers, such as oxygen.

Sources and Sinks of Atmospheric CO2

1992 ◽  
Vol 40 (5) ◽  
pp. 407 ◽  
Author(s):  
JA Taylor ◽  
J Lloyd
Keyword(s):  
Climate Change ◽  
Biomass Burning ◽  
Transport Model ◽  
Atmospheric Co2 ◽  
Tropical Rainforests ◽  
Co2 Uptake ◽  
Tracer Transport ◽  
Intergovernmental Panel ◽  
Co2 Concentrations ◽  
Atmospheric Co2 Concentrations

The biosphere plays an important role in determining the sources, sinks, levels and rates of change of atmospheric CO2 concentrations. Significant uncertainties remain in estimates of the fluxes of CO2 from biomass burning and deforestation, and uptake and storage of CO2 by the biosphere arising from increased atmospheric CO2 concentrations. Calculation of probable rates of carbon sequestration for the major ecosystem complexes and global 3-D tracer transport model runs indicate the possibility that a significant net CO2 uptake (> 1 Pg C yr-1), a CO2 'fertilisation effect', may be occurring in tropical rainforests, effectively accounting for much of the 'missing sink'. This sink may currently balance much of the CO2 added to the atmosphere from deforestation and biomass burning. Interestingly, CO2 released from biomass burning may itself be playing an important role in enhanced carbon storage by tropical rainforests. This has important implications for predicting future CO2 concentrations. If tropical rainforest destruction continues then much of the CO2 stored as a result of the CO2 'fertilisation effect' will be rereleased to the atmosphere and much of the 'missing sink' will disappear. These effects have not been considered in the IPCC (Intergovernmental Panel on Climate Change) projections of future atmospheric CO2 concentrations. Predictions which take account of the combined effects of deforestation, the return of carbon previously stored through the CO2 'fertilisation effect' and the loss of a large proportion of the 'missing sink' as a result of deforestation, would result in much higher predicted concentrations and rates of increase of atmospheric CO2 and, as a consequence, accelerated rates of climate change.

scholarly journals Can seasonal and interannual variation in landscape CO<sub>2</sub> fluxes be detected by atmospheric observations of CO<sub>2</sub> concentrations made at a tall tower?

2014 ◽  
Vol 11 (3) ◽  
pp. 735-747 ◽  
Author(s):  
T. L. Smallman ◽  
M. Williams ◽  
J. B. Moncrieff
Keyword(s):  
Interannual Variation ◽  
Atmospheric Transport ◽  
Co2 Exchange ◽  
Atmospheric Co2 ◽  
Co2 Uptake ◽  
Post Harvest ◽  
Co2 Concentrations ◽  
Prevailing Wind Direction ◽  
Atmospheric Co2 Concentrations ◽  
Tall Tower

Abstract. The coupled numerical weather model WRF-SPA (Weather Research and Forecasting model and Soil-Plant-Atmosphere model) has been used to investigate a 3 yr time series of observed atmospheric CO2 concentrations from a tall tower in Scotland, UK. Ecosystem-specific tracers of net CO2 uptake and net CO2 release were used to investigate the contributions to the tower signal of key land covers within its footprint, and how contributions varied at seasonal and interannual timescales. In addition, WRF-SPA simulated atmospheric CO2 concentrations were compared with two coarse global inversion models, CarbonTrackerEurope and the National Oceanic and Atmospheric Administration's CarbonTracker (CTE-CT). WRF-SPA realistically modelled both seasonal (except post harvest) and daily cycles seen in observed atmospheric CO2 at the tall tower (R2 = 0.67, rmse = 3.5 ppm, bias = 0.58 ppm). Atmospheric CO2 concentrations from the tall tower were well simulated by CTE-CT, but the inverse model showed a poorer representation of diurnal variation and simulated a larger bias from observations (up to 1.9 ppm) at seasonal timescales, compared to the forward modelling of WRF-SPA. However, we have highlighted a consistent post-harvest increase in the seasonal bias between WRF-SPA and observations. Ecosystem-specific tracers of CO2 exchange indicate that the increased bias is potentially due to the representation of agricultural processes within SPA and/or biases in land cover maps. The ecosystem-specific tracers also indicate that the majority of seasonal variation in CO2 uptake for Scotland's dominant ecosystems (forests, cropland and managed grassland) is detectable in observations within the footprint of the tall tower; however, the amount of variation explained varies between years. The between years variation in detectability of Scotland's ecosystems is potentially due to seasonal and interannual variation in the simulated prevailing wind direction. This result highlights the importance of accurately representing atmospheric transport used within atmospheric inversion models used to estimate terrestrial source/sink distribution and magnitude.

scholarly journals The ocean carbon sink – impacts, vulnerabilities, and challenges

2014 ◽  
Vol 5 (2) ◽  
pp. 1607-1672
Author(s):  
C. Heinze ◽  
S. Meyer ◽  
N. Goris ◽  
L. Anderson ◽  
R. Steinfeldt ◽  
...  
Keyword(s):  
Carbon Sink ◽  
Mitigation Strategies ◽  
Atmospheric Co2 ◽  
Co2 Uptake ◽  
Spatial And Temporal Scales ◽  
The Past ◽  
Research Fields ◽  
Co2 Concentrations ◽  
Ocean Carbon ◽  
Atmospheric Co2 Concentrations

Abstract. Carbon dioxide (CO2) is, next to water vapour, considered to be the most important natural greenhouse gas on Earth. Rapidly rising atmospheric CO2 concentrations caused by human actions such as fossil-fuel burning, land-use change or cement production over the past 250 years have given cause for concern that changes in Earth's climate system may progress at a much faster pace and larger extent than during the past 20 000 years. Investigating global carbon cycle pathways and finding suitable mitigation strategies has, therefore, become of major concern in many research fields. The oceans have a key role in regulating atmospheric CO2 concentrations and currently take up about 25% of annual anthropogenic carbon emissions to the atmosphere. Questions that yet need to be answered are what the carbon uptake kinetics of the oceans will be in the future and how the increase in oceanic carbon load will affect its ecosystems and their services. This requires comprehensive investigations, including high-quality ocean carbon measurements on different spatial and temporal scales, the management of data in sophisticated data bases, the application of state-of-the-art Earth system models to provide future projections for given emission scenarios as well as a global synthesis and outreach to policy makers. In this paper, the current understanding of the ocean as an important carbon sink is reviewed with respect to these topics. Emphasis is placed on the complex interplay of different physical, chemical, and biological processes that yield both positive and negative air–sea flux values for natural and anthropogenic CO2 as well as on increased CO2 (uptake) as the regulating force of the radiative warming of the atmosphere and the gradual acidification of the oceans. Major future ocean carbon challenges in the fields of ocean observations, modelling, and process research as well as the relevance of other biogeochemical cycles and greenhouse gases are discussed.

scholarly journals Evaluation of atmosphere-biosphere exchange estimations with TCCON measurements

2012 ◽  
Vol 12 (5) ◽  
pp. 12759-12800 ◽  
Author(s):  
J. Messerschmidt ◽  
N. Parazoo ◽  
N. M. Deutscher ◽  
C. Roehl ◽  
T. Warneke ◽  
...  
Keyword(s):  
Boreal Forest ◽  
Large Scale ◽  
Growing Season ◽  
Atmospheric Co2 ◽  
Total Carbon ◽  
Co2 Uptake ◽  
Co2 Concentrations ◽  
Time Period ◽  
Atmospheric Co2 Concentrations ◽  
Biosphere Model

Abstract. Three estimates of the atmosphere-biosphere exchange are evaluated using Total Carbon Column Observing Network (TCCON) measurements. We investigate the Carnegie-Ames-Stanford Approach (CASA), the Simple Biosphere (SiB) and the GBiome-BGC models transported by the GEOS-Chem model to simulate atmospheric CO2 concentrations for the time period between 2006 and 2010. The CO2 simulations are highly dependent on the choice of the atmosphere-biosphere model and large-scale errors in the estimates are identified through a comparison with TCCON data. Enhancing the CO2 uptake in the boreal forest by 40% and shifting the onset of the growing season significantly improve the simulated seasonal CO2 cycle using CASA estimates. The SiB model gives the best estimate for the atmosphere-biosphere exchange in the comparison with TCCON measurements.

scholarly journals A simple model of the anthropogenically forced CO<sub>2</sub> cycle

2015 ◽  
Vol 6 (2) ◽  
pp. 2043-2062
Author(s):  
W. Weber ◽  
H.-J. Lüdecke ◽  
C. O. Weiss
Keyword(s):  
Co2 Emission ◽  
Emission Scenario ◽  
Atmospheric Co2 ◽  
Emission Scenarios ◽  
Information Analysis ◽  
Anthropogenic Co2 ◽  
Long Run ◽  
Analysis Center ◽  
Free Parameters ◽  
Atmospheric Co2 Concentrations

Abstract. From basic physical assumptions we derive a simple linear model of the global CO2 cycle without free parameters. It yields excellent agreement with the observations reported by the carbon dioxide information analysis center (CDIAC) as time series of atmospheric CO2 growth, of sinks in the ocean and of absorption by the biosphere. The agreement extends from the year 1850 until present (2013). Based on anthropogenic CO2 emission scenarios until 2150, future atmospheric CO2 concentrations are calculated. As the model shows, and depending on the emission scenario, the airborne fraction of CO2 begins to decrease in the year ~ 2050 and becomes negative at the latest in ~ 2130. At the same time the concentration of the atmospheric CO2 will reach a maximum between ~ 500 and ~ 900 ppm. As a consequence, increasing anthropogenic CO2 emissions will make the ocean and the biosphere the main reservoirs of anthropogenic CO2 in the long run. Latest in about 150 years, anthropogenic CO2 emission will no longer increase the CO2 content of the atmosphere.

scholarly journals The mechanisms of North Atlantic CO<sub>2</sub> uptake in a large Earth System Model ensemble

2014 ◽  
Vol 11 (10) ◽  
pp. 14551-14585 ◽  
Author(s):  
P. R. Halloran ◽  
B. B. B. Booth ◽  
C. D. Jones ◽  
F. H. Lambert ◽  
D. J. McNeall ◽  
...  
Keyword(s):  
North Atlantic ◽  
Earth System Model ◽  
Atmospheric Co2 ◽  
System Model ◽  
Sink Strength ◽  
Co2 Uptake ◽  
Earth System ◽  
Co2 Sink ◽  
Atmospheric Co2 Concentrations

Abstract. The oceans currently take up around a quarter of the carbon dioxide (CO2) emitted by human activity. While stored in the ocean, this CO2 is not influencing Earth's radiation budget; the ocean CO2 sink therefore plays an important role in mitigating global warming. CO2 uptake by the oceans is heterogeneous, with the subpolar North Atlantic being the strongest CO2 sink region. Observations over the last two decades have indicated that CO2 uptake by the subpolar North Atlantic sink can vary rapidly. Given the importance of this sink and its apparent variability, it is critical that we understand the mechanisms behind its operation. Here we explore subpolar North Atlantic CO2 uptake across a large ensemble of Earth System Model simulations, and find that models show a peak in sink strength around the middle of the century after which CO2 uptake begins to decline. We identify different drivers of change on interannual and multidecadal timescales. Short-term variability appears to be driven by fluctuations in regional seawater temperature and alkalinity, whereas the longer-term evolution throughout the coming century is largely occurring through a counterintuitive response to rising atmospheric CO2 concentrations. At high atmospheric CO2 concentrations the contrasting Ravelle factors between the subtropical and subpolar gyres, combined with the transport of surface waters from the subtropical to subpolar gyre, means that the subpolar CO2 uptake capacity is largely satisfied from its southern boundary rather than through air–sea CO2 flux. Our findings indicate that: (i) we can explain the mechanisms of subpolar North Atlantic CO2 uptake variability across a broad range of Earth System Models, (ii) a focus on understanding the mechanisms behind contemporary variability may not directly tell us about how the sink will change in the future, (iii) to identify long-term change in the North Atlantic CO2 sink we should focus observational resources on monitoring subtropical as well as the subpolar seawater CO2, (iv) recent observations of a weakening subpolar North Atlantic CO2 sink suggests that the sink strength is already in long-term decline.

scholarly journals Climate-change impacts and fisheries management challenges in the North Atlantic Ocean

2020 ◽  
Vol 648 ◽  
pp. 1-17
Author(s):  
A Bryndum-Buchholz ◽  
DG Boyce ◽  
DP Tittensor ◽  
V Christensen ◽  
D Bianchi ◽  
...  
Keyword(s):  
Climate Change ◽  
Fisheries Management ◽  
North Atlantic ◽  
North Atlantic Ocean ◽  
Climate Change Impacts ◽  
Marine Animal ◽  
The North ◽  
The North Atlantic ◽  
Emissions Scenario ◽  
Far Future

Climate-induced changes in the world’s oceans will have implications for fisheries productivity and management. Using a model ensemble from the Fisheries and Marine Ecosystem Model Intercomparison Project (Fish-MIP), we analyzed future trajectories of climate-change impacts on marine animal biomass and associated environmental drivers across the North Atlantic Ocean and within the Northwest Atlantic Fisheries Organization (NAFO) convention area and evaluated potential consequences for fisheries productivity and management. Our ensemble results showed that the magnitude of projected biomass changes increased over time and from a low (RCP2.6) to high (RCP8.5) emissions scenario. Within individual NAFO divisions, however, projected biomass changes differed in the magnitude and sometimes direction of change between near (the 2030s) and far future (the 2090s) and contrasting emissions scenarios. By the 2090s, most NAFO divisions with historically (1990-1999) high fisheries landings were projected to experience biomass decreases of 5-40%, while Arctic and subarctic divisions with lower historical landings were projected to experience biomass increases between 20 and 70% under RCP8.5. Future trajectories of sea surface temperature and primary production corroborated that the far-future, high-emissions scenario poses the greatest risk to marine ecosystems and the greatest challenges to fisheries management. Our study summarizes future trends of marine animal biomass and underlying uncertainties related to model projections under contrasting climate-change scenarios. Understanding such climate-change impacts on marine ecosystems is imperative for ensuring that marine fisheries remain productive and sustainable in a changing ocean.

scholarly journals El Niño-like climate change in a model with increased atmospheric CO2 concentrations

Nature ◽  
1996 ◽  
Vol 382 (6586) ◽  
pp. 56-60 ◽  
Author(s):  
Gerald A. Meehl ◽  
Warren M. Washington
Keyword(s):  
Climate Change ◽  
El Niño ◽  
El Nino ◽  
Atmospheric Co2 ◽  
Co2 Concentrations ◽  
Atmospheric Co2 Concentrations

scholarly journals Feedbacks in Emission-Driven and Concentration-Driven Global Carbon Budgets

2013 ◽  
Vol 26 (10) ◽  
pp. 3326-3341 ◽  
Author(s):  
G. J. Boer ◽  
V. K. Arora
Keyword(s):  
Co2 Emissions ◽  
Carbon Concentration ◽  
Atmospheric Co2 ◽  
Climate Feedback ◽  
Biogeochemical Processes ◽  
Carbon Budgets ◽  
Feedback Analysis ◽  
Co2 Concentrations ◽  
Atmospheric Co2 Concentrations ◽  
Atmospheric Concentrations

Abstract Emissions of CO2 into the atmosphere affect the carbon budgets of the land and ocean as biogeochemical processes react to increased CO2 concentrations. Biogeochemical processes also react to changes in temperature and other climate parameters. This behavior is characterized in terms of carbon–concentration and carbon–climate feedback parameters. The results of this study include 1) the extension of the direct carbon feedback formalism of Boer and Arora to include results from radiatively coupled simulations, as well as those from the biogeochemically coupled and fully coupled simulations used in earlier analyses; 2) a brief analysis of the relationship between this formalism and the integrated feedback formalism of Friedlingstein et al.; 3) the feedback analysis of simulations based on each of the representative concentration pathways (RCPs) RCP2.6, RCP4.5, and RCP8.5; 4) a comparison of the effects of specifying atmospheric CO2 concentrations or CO2 emissions; and 5) the quantification of the relative importance of the two feedback mechanisms in terms of their cumulative contribution to the change in atmospheric CO2. Feedback results are broadly in agreement with earlier studies in that carbon–concentration feedback is negative for the atmosphere and carbon–climate feedback is positive. However, the magnitude and evolution of feedback behavior depends on the formalism employed, the scenario considered, and the specification of CO2 from emissions or as atmospheric concentrations. Both feedback parameters can differ by factors of two or more, depending on the scenario and on the specification of CO2 emissions or concentrations. While feedback results are qualitatively useful and illustrative of carbon budget behavior, they apply quantitatively to particular scenarios and cases.

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