Sensitivity of Future Ocean Acidification to Carbon Climate Feedbacks

Abstract. Carbon-climate feedbacks have the potential to significantly impact the future climate by altering atmospheric CO2 concentrations (Zaehle et al., 2010). By modifying the future atmospheric CO2 concentrations, the carbon-climate feedbacks will also influence the future trajectory for ocean acidification. Here, we use the CO2 emissions scenarios from 4 Representative Concentration Pathways (RCPs) with an Earth System Model to project the future trajectories of ocean acidification with the inclusion of carbon-climate feedbacks. We show that simulated carbon-climate feedbacks can significantly impact the onset of under-saturated aragonite conditions in the Southern and Arctic Oceans, the suitable habitat for tropical coral and the deepwater saturation states. Under higher emission scenarios (RCP8.5 and RCP6.0), the carbon-climate feedbacks advance the onset of under-saturation conditions and the reduction in suitable coral reef habitat by a decade or more. The impact of the carbon-climate feedback is most significant for the medium (RCP4.5) and low emission (RCP2.6) scenarios. For RCP4.5 scenario by 2100, the carbon-climate feedbacks nearly double the area of surface water under-saturated respect to aragonite and reduce by 50 % the surface water suitable for coral reefs. For RCP2.6 scenario by 2100, the carbon-climate feedbacks reduce the area suitable for coral reefs by 40 % and increase the area of under-saturated surface water by 20 %. The high sensitivity of the impact of ocean acidification to the carbon-climate feedbacks in the low to medium emissions scenarios is important because our recent commitments to reduce CO2 emissions are trying to move us on to such an emissions scenario. The study highlights the need to better characterise the carbon-climate feedbacks to ensure we do not excessively stress the oceans by under-estimating the future impact of ocean acidification.

Carbon–climate feedbacks accelerate ocean acidification

Biogeosciences ◽

10.5194/bg-15-1721-2018 ◽

2018 ◽

Vol 15 (6) ◽

pp. 1721-1732 ◽

Cited By ~ 4

Author(s):

Richard J. Matear ◽

Andrew Lenton

Keyword(s):

Surface Water ◽

Coral Reefs ◽

Ocean Acidification ◽

Atmospheric Co2 ◽

Suitable Habitat ◽

Climate Feedbacks ◽

Co2 Concentrations ◽

The Future ◽

Emissions Scenarios ◽

Atmospheric Co2 Concentrations

Abstract. Carbon–climate feedbacks have the potential to significantly impact the future climate by altering atmospheric CO2 concentrations (Zaehle et al., 2010). By modifying the future atmospheric CO2 concentrations, the carbon–climate feedbacks will also influence the future ocean acidification trajectory. Here, we use the CO2 emissions scenarios from four representative concentration pathways (RCPs) with an Earth system model to project the future trajectories of ocean acidification with the inclusion of carbon–climate feedbacks. We show that simulated carbon–climate feedbacks can significantly impact the onset of undersaturated aragonite conditions in the Southern and Arctic oceans, the suitable habitat for tropical coral and the deepwater saturation states. Under the high-emissions scenarios (RCP8.5 and RCP6), the carbon–climate feedbacks advance the onset of surface water under saturation and the decline in suitable coral reef habitat by a decade or more. The impacts of the carbon–climate feedbacks are most significant for the medium- (RCP4.5) and low-emissions (RCP2.6) scenarios. For the RCP4.5 scenario, by 2100 the carbon–climate feedbacks nearly double the area of surface water undersaturated with respect to aragonite and reduce by 50 % the surface water suitable for coral reefs. For the RCP2.6 scenario, by 2100 the carbon–climate feedbacks reduce the area suitable for coral reefs by 40 % and increase the area of undersaturated surface water by 20 %. The sensitivity of ocean acidification to the carbon–climate feedbacks in the low to medium emission scenarios is important because recent CO2 emission reduction commitments are trying to transition emissions to such a scenario. Our study highlights the need to better characterise the carbon–climate feedbacks and ensure we do not underestimate the projected ocean acidification.

A missing link in the carbon cycle: phytoplankton light absorption

10.5194/esd-2021-91 ◽

2021 ◽

Author(s):

Rémy Asselot ◽

Frank Lunkeit ◽

Philip Holden ◽

Inga Hense

Keyword(s):

Carbon Cycle ◽

Co2 Emissions ◽

Light Absorption ◽

Climate System ◽

Atmospheric Co2 ◽

Co2 Concentrations ◽

Recent Climate ◽

Abstract. Marine biota and biogeophysical mechanisms, such as phytoplankton light absorption, have attracted increasing attention in recent climate studies. Under global warming, the impact of phytoplankton on the climate system is expected to change. Previous studies analyzed the impact of phytoplankton light absorption under prescribed future atmospheric CO2 concentrations. However, the role of this biogeophysical mechanism under freely-evolving atmospheric CO2 concentration and future CO2 emissions remain unknown. To shed light on this research gap, we perform simulations with the EcoGEnIE Earth system model and prescribe CO2 emissions following the four Representative Concentration Pathways (RCP) scenarios. Under all the RCP scenario, our results indicate that phytopankton light absorption increases the surface chlorophyll biomass, the sea surface temperature, the atmospheric CO2 concentrations and the atmospheric temperature. Under the RCP2.6, RCP4.5 and RCP6.0 scenarios, the magnitude of changes due to phytoplankton light absorption are similar. However, under the RCP8.5 scenario, the changes in the climate system are less pronounced due to the temperature limitation of phytoplankton growth, highlighting the reduced effect of phytoplankton light absorption under strong warming. Additionally, this work evidences the major role of phytoplankton light absorption on the climate system, suggesting a highly uncertain feedbacks on the carbon cycle with uncertainties that are in the range of those known from the land biota.

Heterogeneous CO<sub>2</sub> and CH<sub>4</sub> content of glacial meltwater from the Greenland Ice Sheet and implications for subglacial carbon processes

The Cryosphere ◽

10.5194/tc-15-1627-2021 ◽

2021 ◽

Vol 15 (3) ◽

pp. 1627-1644

Author(s):

Andrea J. Pain ◽

Jonathan B. Martin ◽

Ellen E. Martin ◽

Åsa K. Rennermalm ◽

Shaily Rahman

Keyword(s):

Greenhouse Gas ◽

Ice Sheet ◽

Greenland Ice Sheet ◽

Mineral Weathering ◽

Atmospheric Co2 ◽

The Arctic ◽

Co2 Concentrations ◽

Geochemical Models ◽

Abstract. Accelerated melting of the Greenland Ice Sheet has increased freshwater delivery to the Arctic Ocean and amplified the need to understand the impact of Greenland Ice Sheet meltwater on Arctic greenhouse gas budgets. We evaluate subglacial discharge from the Greenland Ice Sheet for carbon dioxide (CO2) and methane (CH4) concentrations and δ13C values and use geochemical models to evaluate subglacial CH4 and CO2 sources and sinks. We compare discharge from southwest (a sub-catchment of the Isunnguata Glacier, sub-Isunnguata, and the Russell Glacier) and southern Greenland (Kiattut Sermiat). Meltwater CH4 concentrations vary by orders of magnitude between sites and are saturated with respect to atmospheric concentrations at Kiattut Sermiat. In contrast, meltwaters from southwest sites are supersaturated, even though oxidation reduces CH4 concentrations by up to 50 % during periods of low discharge. CO2 concentrations range from supersaturated at sub-Isunnguata to undersaturated at Kiattut Sermiat. CO2 is consumed by mineral weathering throughout the melt season at all sites; however, differences in the magnitude of subglacial CO2 sources result in meltwaters that are either sources or sinks of atmospheric CO2. At the sub-Isunnguata site, the predominant source of CO2 is organic matter (OM) remineralization. However, multiple or heterogeneous subglacial CO2 sources maintain atmospheric CO2 concentrations at Russell but not at Kiattut Sermiat, where CO2 is undersaturated. These results highlight a previously unrecognized degree of heterogeneity in greenhouse gas dynamics under the Greenland Ice Sheet. Future work should constrain the extent and controls of heterogeneity to improve our understanding of the impact of Greenland Ice Sheet melt on Arctic greenhouse gas budgets, as well as the role of continental ice sheets in greenhouse gas variations over glacial–interglacial timescales.

The Impact of Energy Production on Atmospheric CO2-Concentrations

Climatic Variations and Variability: Facts and Theories ◽

10.1007/978-94-009-8514-8_36 ◽

1981 ◽

pp. 641-660 ◽

Cited By ~ 2

Author(s):

F. Niehaus

Keyword(s):

Energy Production ◽

Atmospheric Co2 ◽

Co2 Concentrations ◽

ASME 2011 5th International Conference on Energy Sustainability, Parts A, B, and C ◽

Fuel Use and CO2 Emissions Under Uncertainty From Light-Duty Vehicles in the U.S. to 2050

10.1115/es2011-54306 ◽

2011 ◽

Author(s):

Parisa Bastani ◽

John B. Heywood ◽

Chris Hope

Keyword(s):

Co2 Emissions ◽

Alternative Fuels ◽

Fuel Use ◽

Policy Makers ◽

Light Duty ◽

Co2 Equivalent ◽

The Future ◽

Light Duty Vehicles ◽

The Impact ◽

The U.S

On-road transportation contributes 22% of the total CO2 emissions and more than 44% of oil consumption in the U.S. Technological advancements and use of alternative fuels are often suggested as ways to reduce these emissions. However, many parameters and relationships that determine the future characteristics of the light-duty vehicle fleet and how they change over time are inherently uncertain. Policy makers need to make decisions today given these uncertainties, to shape the future of light-duty vehicles. Decision makers thus need to know the impact of uncertainties on the outcome of their decisions and the associated risks. This paper explores a carefully constructed detailed pathway that results in a significant reduction in fuel use and GHG emissions in 2050. Inputs are assigned realistic uncertainty bounds, and the impact of uncertainty on this pathway is analyzed. A novel probabilistic fleet model is used here to quantify the uncertainties within advanced vehicle technology development, and life-cycle emissions of alternative fuels and renewable sources. Based on the results from this study, the expected fuel use is about 500 and 350 billion litres gasoline equivalent, with a standard deviation of about 40 and 80 billion litres in years 2030 and 2050 respectively. The expected CO2 emissions are about 1,360 and 840 Mt CO2 equivalent with a spread of about 130 and 260 Mt CO2 equivalent in 2030 and 2050 respectively. Major contributing factors in determining the future fuel consumption and emissions are also identified and include vehicle scrappage rate, annual growth of vehicle kilometres travelled in the near term, total vehicle sales, fuel consumption of naturally-aspirated engines, and percentage of gasoline displaced by cellulosic ethanol. This type of analysis allows policy makers to better understand the impact of their decisions and proposed policies given the technological and market uncertainties that we face today.

The Scenario Forecasting Analysis of CO2 Emissions of China

Advanced Materials Research ◽

10.4028/www.scientific.net/amr.869-870.836 ◽

2013 ◽

Vol 869-870 ◽

pp. 836-839

Author(s):

Jian Jun Wang ◽

Li Li

Keyword(s):

Economic Development ◽

Energy Consumption ◽

Co2 Emissions ◽

Future Prospect ◽

Ghg Emissions ◽

The Future ◽

Forecasting Analysis ◽

This paper uses STRIPAT models to find the impact of population, economy and technology on CO2 emissions of China. The result shows the impact of population, economy and technology on CO2 emissions are 1.253, 1.076, and 1.077 respectively. According to the future prospect of China, three scenarios of Chinas economic development are given to forecast the CO2 emissions, the forecasting results shows that if Chinas economic, population and energy consumption is increasing 7%, 0.4%, 5% every year, respectively. CO2 emissions will reach 21.05×108t in 2020. The CO2 emissions per unit GDP is decreasing by 45.54% in 2020 compared to 2005, which can fulfill the Chinese governments promise to decrease the GHG emissions per unit GDP by 40-45% in 2020 compared to 2005.

Fuel Use and CO2 Emissions Under Uncertainty From Light-Duty Vehicles in the U.S. to 2050

Journal of Energy Resources Technology ◽

10.1115/1.4007485 ◽

2012 ◽

Vol 134 (4) ◽

Cited By ~ 4

Author(s):

Parisa Bastani ◽

John B. Heywood ◽

Chris Hope

Keyword(s):

Co2 Emissions ◽

Alternative Fuels ◽

Fuel Use ◽

Policy Makers ◽

Light Duty ◽

Co2 Equivalent ◽

The Future ◽

Light Duty Vehicles ◽

The Impact ◽

The U.S

On-road transportation contributes 22% of the total CO2 emissions and more than 44% of oil consumption in the U.S. technological advancements and use of alternative fuels are often suggested as ways to reduce these emissions. However, many parameters and relationships that determine the future characteristics of the light-duty vehicle (LDV) fleet and how they change over time are inherently uncertain. Policy makers need to make decisions today given these uncertainties, to shape the future of light-duty vehicles. Decision makers thus need to know the impact of uncertainties on the outcome of their decisions and the associated risks. This paper explores a carefully constructed detailed pathway that results in a significant reduction in fuel use and greenhouse gases (GHG) emissions in 2050. Inputs are assigned realistic uncertainty bounds, and the impact of uncertainty on this pathway is analyzed. A novel probabilistic fleet model is used here to quantify the uncertainties within advanced vehicle technology development, and life-cycle emissions of alternative fuels and renewable sources. Based on the results from this study, the expected fuel use is about 500 and 350 × 109 l gasoline equivalent, with a standard deviation of about 40 and 80 × 109 l in years 2030 and 2050, respectively. The expected CO2 emissions are about 1360 and 840 Mt CO2 equivalent with a spread of about 130 and 260 Mt CO2 equivalent in 2030 and 2050, respectively. Major contributing factors in determining the future fuel consumption and emissions are also identified and include vehicle scrappage rate, annual growth of vehicle kilometres travelled in the near term, total vehicle sales, fuel consumption of naturally aspirated engines, and percentage of gasoline displaced by cellulosic ethanol. This type of analysis allows policy makers to better understand the impact of their decisions and proposed policies given the technological and market uncertainties that we face today.

Predicting the impact of ocean acidification on coral reefs: evaluating the assumptions involved

ICES Journal of Marine Science ◽

10.1093/icesjms/fsv091 ◽

2015 ◽

Vol 73 (3) ◽

pp. 550-557 ◽

Cited By ~ 15

Author(s):

Paul L. Jokiel

Keyword(s):

Coral Reefs ◽

Ocean Acidification ◽

Bulk Water ◽

Ion Concentration ◽

Calcification Rate ◽

Saturation State ◽

Simplifying Assumptions ◽

Reef Decline ◽

Highly Correlated ◽

Abstract Predictions of future impact of climate change on coral reefs indicate that bleaching mortality due to higher temperature will be the major factor in the decline of coral reefs. Ocean acidification (OA) is increasingly considered to be an important contributing factor, but estimates of its importance vary widely in the literature. Models of future reef decline due to OA generally involve four simplifying assumptions that can lead to contradictions. The assumptions are: (i) Oceanic conditions of Ωarag control or are at least highly correlated with net calcification rate (Gnet) on coral reefs. (ii) Calcification rate is driven by bulk water carbonate ion concentration [CO32−] expressed as Ωarag. (iii) Changes in coral calcification rate can be used to estimate future changes in coral reef calcification rate. (iv) The impact of OA is additive and not synergistic with other environmental factors such as increased temperature. The assumption that aragonite saturation state (Ωarag) of seawater drives calcification is the most widely used and needs to be further evaluated. An alternate hypothesis is that calcification is limited by the ability of the system to rid itself of the protons generated by calcification. Recent studies allow further testing of the assumptions and point the way to resolving shortcomings in our understanding of how OA impacts coral reefs.

Modelling coral polyp calcification in relation to ocean acidification

Biogeosciences ◽

10.5194/bg-9-4441-2012 ◽

2012 ◽

Vol 9 (11) ◽

pp. 4441-4454 ◽

Cited By ~ 21

Author(s):

S. Hohn ◽

A. Merico

Keyword(s):

Ocean Acidification ◽

Carbonate System ◽

Co2 Diffusion ◽

Coral Abundance ◽

Coral Polyp ◽

Polyp Tissue ◽

The Impact ◽

Fluid Diffusion ◽

Seawater Pco2

Abstract. Rising atmospheric CO2 concentrations due to anthropogenic emissions induce changes in the carbonate chemistry of the oceans and, ultimately, a drop in ocean pH. This acidification process can harm calcifying organisms like coccolithophores, molluscs, echinoderms, and corals. It is expected that ocean acidification in combination with other anthropogenic stressors will cause a severe decline in coral abundance by the end of this century, with associated disastrous effects on reef ecosystems. Despite the growing importance of the topic, little progress has been made with respect to modelling the impact of acidification on coral calcification. Here we present a model for a coral polyp that simulates the carbonate system in four different compartments: the seawater, the polyp tissue, the coelenteron, and the calcifying fluid. Precipitation of calcium carbonate takes place in the metabolically controlled calcifying fluid beneath the polyp tissue. The model is adjusted to a state of activity as observed by direct microsensor measurements in the calcifying fluid. We find that a transport mechanism for bicarbonate is required to supplement carbon into the calcifying fluid because CO2 diffusion alone is not sufficient to sustain the observed calcification rates. Simulated CO2 perturbation experiments reveal decreasing calcification rates under elevated pCO2 despite the strong metabolic control of the calcifying fluid. Diffusion of CO2 through the tissue into the calcifying fluid increases with increasing seawater pCO2, leading to decreased aragonite saturation in the calcifying fluid. Our modelling study provides important insights into the complexity of the calcification process at the organism level and helps to quantify the effect of ocean acidification on corals.

Quantifying the impact of ocean acidification on our future climate

Biogeosciences ◽

10.5194/bg-11-3965-2014 ◽

2014 ◽

Vol 11 (14) ◽

pp. 3965-3983 ◽

Cited By ~ 15

Author(s):

R. J. Matear ◽

A. Lenton

Keyword(s):

Climate Change ◽

Global Warming ◽

Ocean Acidification ◽

Observational Studies ◽

Emission Scenario ◽

Biogeochemical Cycles ◽

Future Climate ◽

Atmospheric Co2 ◽

First Order ◽

Abstract. Ocean acidification (OA) is the consequence of rising atmospheric CO2 levels, and it is occurring in conjunction with global warming. Observational studies show that OA will impact ocean biogeochemical cycles. Here, we use an Earth system model under the RCP8.5 emission scenario to evaluate and quantify the first-order impacts of OA on marine biogeochemical cycles, and its potential feedback on our future climate. We find that OA impacts have only a small impact on the future atmospheric CO2 (less than 45 ppm) and global warming (less than a 0.25 K) by 2100. While the climate change feedbacks are small, OA impacts may significantly alter the distribution of biological production and remineralisation, which would alter the dissolved oxygen distribution in the ocean interior. Our results demonstrate that the consequences of OA will not be through its impact on climate change, but on how it impacts the flow of energy in marine ecosystems, which may significantly impact their productivity, composition and diversity.