Antarctic coastal waters are home to several established or proposed Marine Protected Areas (MPAs) supporting exceptional biodiversity, which is threatened by anthropogenic climate change. Despite a particular sensitivity to ocean acidification (OA), little is known about the future carbonate chemistry of high-latitude Southern Ocean waters. Here, we use a high resolution ocean–sea ice–biogeochemistry model with realistic ice-shelf geometry to investigate 21st-century OA in Antarctic MPAs under four emission scenarios. By 2100, we project surface pH declines of up to 0.42 (total scale), corresponding to a 161% increase in hydrogen ion concentration relative to the 1990s. End-of-century aragonite undersaturation is ubiquitous across MPAs under the three highest emission scenarios. Vigorous vertical mixing of anthropogenic carbon on the continental shelves produces severe OA within the Weddell Sea, East Antarctic, and Ross Sea MPAs. Our findings call for continuity and expansion of Antarctic MPAs to reduce pressures on ecosystem integrity.
Continue reading ‘Severe 21st-century ocean acidification demands continuance and expansion of Antarctic Marine Protected Areas’Posts Tagged 'mitigation'
Severe 21st-century ocean acidification demands continuance and expansion of Antarctic Marine Protected Areas
Published 14 June 2023 Science ClosedTags: Antarctic, chemistry, mitigation, modeling, regionalmodeling
Demonstration of direct ocean carbon capture using hollow fiber membrane contactors
Published 13 June 2023 Science ClosedTags: chemistry, laboratory, methods, mitigation, modeling
The focus of membrane carbon capture to date has been primarily on point source capture, such as power plants and industrial capture. However, membrane technology can also play a role in negative emissions technology, such as direct air capture and direct ocean capture. Direct ocean capture has a few potential advantages over direct air capture, such as avoiding land use and coupling with offshore wind and offshore storage. The use and feasibility of hollow fiber membrane contactors (HFMCs) for direct ocean carbon capture with benign aqueous basic carbon dioxide solvents is assessed here through a multifaceted approach. A 1D HFMC model incorporates fluid dynamics and the chemical kinetics of both ocean water and aqueous sodium hydroxide solvent in order to simulate CO2 flux behavior in two flow configurations. Lab scale experiments of this system then guide a model refinement and validation process until experimental behaviors are predicted through computation. A preliminary technoeconomic assessment then uses computational and experimental results to estimate the carbon capture cost when the system is scaled to remove 0.98 Mtonnes CO2/year. Computational results suggest that higher seawater flow rates and temperatures relative to the sodium hydroxide solvent improve CO2 flux. The technoeconomic assessment suggests that HFMCs may only be cost-competitive if seawater pH is decreased at the membrane interface, thereby increasing the local concentration of dissolved carbon dioxide. These findings indicate that local pH swing on the seawater side will be necessary to feasibly remove carbon dioxide from seawater using HFMCs.
Continue reading ‘Demonstration of direct ocean carbon capture using hollow fiber membrane contactors’Seawater alkalinity enhancement with magnesium hydroxide and its implication for carbon dioxide removal
Published 13 June 2023 Science ClosedTags: chemistry, laboratory, methods, mitigation
For the first time we used lab and wind-wave tank experiments to prove the concept of using Mg(OH)2 for the ocean alkalinity enhancement and carbon dioxide removal approach (OAE-CDR). Experiment results showed up to 370 μmol kg−1 seawater total alkalinity (TA) increase without precipitation, stable enhanced TA, and OAE-CDR efficiency (ΔDIC/ΔTA) consistent with theoretical calculation. Based on the experimental results, we calculated the global Mg(OH)2 OAE-CDR efficiency and CO2 sink from this approach. The efficiency is in favor of lower initial DIC to TA ratio, lower temperature, and higher atmospheric CO2, and therefore is the lowest at the equator (0.7–0.8) and increases with latitude (1.0–1.2 above 70 N/S). However, factoring in the ocean’s surface area, low latitude regions can absorb more atmospheric CO2. We conservatively estimate that 44. 4 × 109 ton of CO2 (~ 3.3 times of current annual CO2 sink in the ocean) could be removed from the atmosphere with 175 μmol kg−1 Mg(OH)2 (equivalent to 350 μmol kg−1 of TA) added to the top 10 m of the ocean.
Continue reading ‘Seawater alkalinity enhancement with magnesium hydroxide and its implication for carbon dioxide removal’Ocean afforestation’s effect on deep-sea biogeochemistry
Published 8 June 2023 Science ClosedTags: biogeochemistry, chemistry, individualmodeling, mitigation, modeling
If climate change is left unchecked it will lead to unprecedented deterioration of human health, economy and ecology. According to the IPCC, in order to avoid severe consequences, global warming will need to be limited to 1.5°C. However, the 1.5°C warming will be exceeded if current trends continue, which is why the need for Carbon Dioxide Removal (CDR) has become increasingly apparent. Ocean afforestation is currently one of the most promising CDR approaches, with the least competition for space, high carbon sequestration potential and high technical feasibility. Ocean afforestation approaches attempt to sequester carbon by sinking seaweed to deep-sea areas. This research looks at the consequences of the seaweed input to deep-seafloor. An early diagenetic model called RADI is used to predict the fate of the carbon and the effect on biogeochemistry. The model was adapted to include new sources of sedimentary organic matter, such as seaweed (Sargassum, Saccharina, Macrocystis) and Sugarcane bagasse, which are currently considered potential candidates for ocean afforestation purposes. Sargassum, an invasive free-floating species, has a large sequestration potential and is readily available. Sinking Sargassum in pulse, large amounts over short times, leads to high carbon retention in the sediment (up to 25% after two years) but leads to hypoxic conditions in the sediment for at least two years after addition. Continuous Sargassum sinking also leads to carbon sequestration but with a much less invasive impact on the seafloor. The carbon from continuous sinking does not remain in the sediment but is remineralized and flows out to the bottom water as inorganic carbon. Saccharina, an edible coastal species, could be used to grow on free floating organic buoy. Having the additional sequestration benefit from the carbon fixed in the organics. Carbon retention is highest for the pulse addition of this seaweed (33% after two years), compared to a continuous approach (30%) in which the seaweed is added over longer timescales in small amounts. Since this pulse input also leads to hypoxic conditions in the sediment, the continuous approach is more favourable for this approach. Macrocystis, the giant kelp known for forming ecosystems, is a fast-growing coastal species. This species requires harvesting and baling for use in carbon sequestration. Carbon retention is much higher for pulse addition (30%). Sugar cane bagasse is an agricultural residue with high carbon content. Sinking this residue to anoxic basins, has been proven to retain more carbon than in oxygenated bottom waters. This can be confirmed with the results which showed a carbon retention of up to 50% after two years. The effect on the benthic biome is also less intense since the low oxygen conditions already necessitate a specialized microbiome. Sugarcane bagasse is furthermore the only addition capable of increasing bottom water pH. Whereas all seaweed approaches had higher dissolved inorganic carbon than alkalinity flow to the bottom water, resulting in net acidification. This research provides a first look into the effects of ocean afforestation on deep sea biogeochemistry, and illustrates the importance of the composition, quantity and input duration of the seaweed used.
Continue reading ‘Ocean afforestation’s effect on deep-sea biogeochemistry’Ocean alkalinity enhancement through restoration of blue carbon ecosystems
Published 1 June 2023 Science ClosedTags: biogeochemistry, chemistry, globalmodeling, mitigation, modeling
Blue carbon ecosystems provide a wide range of ecosystem services, are critical for maintaining marine biodiversity and may potentially serve as sites of economically viable carbon dioxide removal through enhanced organic carbon storage. Here we use biogeochemical simulations to show that restoration of these marine ecosystems can also lead to permanent carbon dioxide removal by driving ocean alkalinity enhancement and atmosphere-to-ocean CO2 fluxes. Most notably, our findings suggest that restoring mangroves, which are common in tropical shallow marine settings, will lead to notable local ocean alkalinity enhancement across a wide range of scenarios. Enhanced alkalinity production is linked to increased rates of anaerobic respiration and to increased dissolution of calcium carbonate within sediments. This work provides further motivation to pursue feasible blue carbon restoration projects and a basis for incorporating inorganic carbon removal in regulatory and economic incentivization of blue carbon ecosystem restoration.
Continue reading ‘Ocean alkalinity enhancement through restoration of blue carbon ecosystems’Carbon dioxide mineralization by electrode separation for quick carbon reduction and sequestration in acidified seawater
Published 22 May 2023 Science ClosedTags: chemistry, laboratory, methods, mitigation, North Pacific
Aiming to sequestrate the excessive carbon dioxide and convert the acidified seawater, an improved method of carbon dioxide mineralization is developed based on electrode separation mechanism and extra oxygen-supplying technique. By electrode separation the neutralizations of the anodic acidity and the cathodic alkalinity, as well as the precipitation and the dissolution of calcium carbonate (CaCO3), are prevented. In addition, the extra-supplied oxygen prevents the evolution of hydrogen, which enhances the electric conductivity of the porous cathode and the deposition of CaCO3. A series of indoor physical experiments were conducted and the results show that the acidified seawater was successfully converted to alkaline in 72h. The speed of carbon mineralizing sequestration is significantly enhanced by supplying extra oxygen. The carbon dioxide mineralization speed increases with the immerse ratio of the aerator due to the more reacted oxygen and the less hydrogen evolution, which gives more porous space in the cathode for more conductive seawater and more deposition of CaCO3. The extra-supplied oxygen increases the CaCO3 -deposition by 100-214% under excessive atmospheric- CO2 conditions and 117-200% under normal atmospheric- CO2 conditions, respectively. This method has an application potential for quick conversion of locally acidified seawater in emergent circumstances.
Continue reading ‘Carbon dioxide mineralization by electrode separation for quick carbon reduction and sequestration in acidified seawater’Potential role of seaweeds in climate change mitigation
Published 11 May 2023 Science ClosedTags: biogeochemistry, mitigation, review
Highlights
- Seaweed carbon accounting is yet to be fully constrained.
- Seaweed products have the potential to lower industrial emissions.
- Seaweed farms sequester carbon at site but at a limited scale to date.
- Quantifying carbon seqestration from wild seaweed restoration remains ellusive.
- Sinking seaweed has scalability but carries many risks and uncertainties.
Abstract
Seaweed (macroalgae) has attracted attention globally given its potential for climate change mitigation. A topical and contentious question is: Can seaweeds’ contribution to climate change mitigation be enhanced at globally meaningful scales? Here, we provide an overview of the pressing research needs surrounding the potential role of seaweed in climate change mitigation and current scientific consensus via eight key research challenges. There are four categories where seaweed has been suggested to be used for climate change mitigation: 1) protecting and restoring wild seaweed forests with potential climate change mitigation co-benefits; 2) expanding sustainable nearshore seaweed aquaculture with potential climate change mitigation co-benefits; 3) offsetting industrial CO2 emissions using seaweed products for emission abatement; and 4) sinking seaweed into the deep sea to sequester CO2. Uncertainties remain about quantification of the net impact of carbon export from seaweed restoration and seaweed farming sites on atmospheric CO2. Evidence suggests that nearshore seaweed farming contributes to carbon storage in sediments below farm sites, but how scalable is this process? Products from seaweed aquaculture, such as the livestock methane-reducing seaweed Asparagopsis or low carbon food resources show promise for climate change mitigation, yet the carbon footprint and emission abatement potential remains unquantified for most seaweed products. Similarly, purposely cultivating then sinking seaweed biomass in the open ocean raises ecological concerns and the climate change mitigation potential of this concept is poorly constrained. Improving the tracing of seaweed carbon export to ocean sinks is a critical step in seaweed carbon accounting. Despite carbon accounting uncertainties, seaweed provides many other ecosystem services that justify conservation and restoration and the uptake of seaweed aquaculture will contribute to the United Nations Sustainable Development Goals. However, we caution that verified seaweed carbon accounting and associated sustainability thresholds are needed before large-scale investment into climate change mitigation from seaweed projects.
Continue reading ‘Potential role of seaweeds in climate change mitigation’Response of ocean acidification to atmospheric carbon dioxide removal
Published 9 May 2023 Science ClosedTags: chemistry, globalmodeling, mitigation, modeling
Artificial CO2 removal from the atmosphere (also referred to as negative CO2 emissions) has been proposed as a potential means to counteract anthropogenic climate change. Here we use an Earth system model to examine the response of ocean acidification to idealized atmospheric CO2 removal scenarios. In our simulations, atmospheric CO2 is assumed to increase at a rate of 1% per year to four times its pre-industrial value and then decreases to the pre-industrial level at a rate of 0.5%, 1%, 2% per year, respectively. Our results show that the annual mean state of surface ocean carbonate chemistry fields including hydrogen ion concentration ([H+]), pH and aragonite saturation state respond quickly to removal of atmospheric CO2. However, the change of seasonal cycle in carbonate chemistry lags behind the decline in atmospheric CO2. When CO2 returns to the pre-industrial level, over some parts of the ocean, relative to the pre-industrial state, the seasonal amplitude of carbonate chemistry fields is substantially larger. Simulation results also show that changes in deep ocean carbonate chemistry substantially lag behind atmospheric CO2 change. When CO2 returns to its pre-industrial value, the whole-ocean acidity measured by [H+] is 15%-18% larger than the pre-industrial level, depending on the rate of CO2 decrease. Our study demonstrates that even if atmospheric CO2 can be lowered in the future as a result of net negative CO2 emissions, the recovery of some aspects of ocean acidification would take decades to centuries, which would have important implications for the resilience of marine ecosystems.
Continue reading ‘Response of ocean acidification to atmospheric carbon dioxide removal’Ocean acidification and the Anthropocene: an emergency response
Published 5 May 2023 Science ClosedTags: mitigation, policy
This chapter considers the threat of ocean acidification from the perspective of both harm to ocean ecological systems and positive climate feedbacks. A survey of current governance responses demonstrates an alarming failure. No international governance regime currently accounts for ocean acidification by requiring significant and additional reductions in CO2 emissions. In an oceans context, acidification is treated as a gradual background stressor along with a range of climate change impacts. Against this backdrop and employing the Anthropocene concept, together with emerging realization that we face a planetary emergency, this chapter proposes a radical change of approach. It proposes that we begin with emergency closure of a large swath of the ocean – namely areas beyond national jurisdiction. While not an end in itself, emergency closure of the Earth’s largest ecological system is a critical place to begin confronting what the Anthropocene means, the implications for all life, and how humanity must govern itself. Change here may seed a very different understanding of what is required as we confront the reality of an Earth system as a global ecological commons on the verge of abrupt, irreversible, and destructive changes. At the very least, such an emergency response may (not will) slow the rate of accumulating harm while we formulate entirely new human responses fully commensurate with the complex and urgent existential crisis of our making.
Continue reading ‘Ocean acidification and the Anthropocene: an emergency response’Assessing the impacts of simulated ocean alkalinity enhancement on viability and growth of cultures of near-shore species of phytoplankton
Published 27 April 2023 Science ClosedTags: abundance, biological response, BRcommunity, chemistry, community composition, field, growth, laboratory, mitigation, modeling, North Atlantic, otherprocess, photosynthesis, phytoplankton
Over the past 250 years, atmospheric carbon dioxide concentrations have risen steadily from 277 ppm to 405 ppm, leading to the exacerbation of the effects of climate change. As a result, new technologies are being developed to remove carbon from the atmosphere, such as negative emission technologies (NETs). One proposed NET is Ocean Alkalinity Enhancement (OAE), which would mimic the ocean’s natural weathering processes and sequester carbon dioxide from the atmosphere. An analysis of published data investigating the effects of elevated pH on phytoplankton growth rate and experimental assessment of pH dependence of viability and growth rate was used to assess the potential impacts of OAE. Viability was assessed with a modified Serial Dilution Culture – Most Probable Number assay. Chlorophyll a fluorescence was used to test for changes in growth rates and photosynthetic competence. The results from this study suggest that there will be no significant impact on the viability or growth rates of Thalassiosira pseudonana or Pavlova lutheri with short-term (10 minute) exposure to elevated pH. However, when long-term (days) exposure occurs there is a significant decrease in growth rates with elevated pH. Short-term exposure is anticipated to more closely mirror the natural systems in which OAE will be implemented because of system flushing and replenishment of nutrients. These preliminary findings suggest that there will be little to no impact on a variety of taxonomic groups of phytoplankton when OAE occurs in naturally flushed systems.
Continue reading ‘Assessing the impacts of simulated ocean alkalinity enhancement on viability and growth of cultures of near-shore species of phytoplankton’Adaptive governance of coral reefs: cases of Florida and the Caribbean
Published 25 April 2023 Science ClosedTags: biological response, BRcommunity, corals, mitigation, policy
Coral reefs are one of the most imperiled yet one of the most valuable ecosystems on the planet, providing food, medicine, and property protection to hundreds of millions of coastal people all over the world. Coral reefs are being lost at an unprecedented rate throughout their range. In the Florida Reef Tract alone, 98% of hard coral has died due to heat waves, disease, and poor water quality, making modern reefs almost unrecognizable. Given the stress that coral reefs are facing due to human and natural causes, there are two key knowledge gaps that are essential to address: the significance of the losses of culturally important benefits that coral reefs provide to people, and the ways that people are adapting to the rapid loss of coral reefs. This dissertation aims to address both gaps.
Continue reading ‘Adaptive governance of coral reefs: cases of Florida and the Caribbean’Ocean acidification as a governance challenge in the Mediterranean Sea: impacts from aquaculture and fisheries
Published 25 April 2023 Science ClosedTags: chemistry, field, fisheries, Mediterranean, mitigation, modeling, policy, regionalmodeling, review
Despite the progress in the international and regional governance efforts at the level of climate change, ocean acidification (OA) remains a global problem with profoundly negative environmental, social, and economical consequences. This requires extensive mitigation and adaptation effective strategies that are hindered by current shortcomings of governance. This multidisciplinary chapter investigates the risks of ocean acidification (OA) for aquaculture and fisheries in the Mediterranean Sea and its sub-basins and the role of regional adaptive governance to tackle the problem. The identified risks are based on the biological sensitivities of the most important aquaculture species and biogenic habitats and their exposure to the current and future predicted (2100) RCP 8.5 conditions. To link OA exposure and biological sensitivity, we produced spatially resolved and depth-related pH and aragonite saturation state exposure maps and overlaid these with the existing aquaculture industry in the coastal waters of the Mediterranean basin to demonstrate potential risk for the aquaculture in the future. We also identified fisheries’ vulnerability through the indirect effects of OA on highly sensitive biogenic habitats that serve as nursery and spawning areas, showing that some of the biogenic habitats are already affected locally under existing OA conditions and will be more severely impacted across the entire Mediterranean basin under 2100 scenarios. This provided a regional vulnerability assessment of OA hotspots, risks and gaps that created the baseline for discussing the importance of adaptive governance and recommendations for future OA mitigation/adaptation strategies. By understanding the risks under future OA scenarios and reinforcing the adaptability of the governance system at the science-policy interface, best informed, “situated” management response capability can be optimised to sustain ecosystem services.
Continue reading ‘Ocean acidification as a governance challenge in the Mediterranean Sea: impacts from aquaculture and fisheries’Aquaculture mapping in the context of climate change
Published 24 April 2023 Science ClosedTags: fisheries, mitigation, North Pacific, policy, socio-economy
The development of aquaculture is facing unprecedented pressures from climate change, resource constraints, environmental pollution, energy consumption, and other factors. For coping with these challenges and for ensuring sustainable development of aquaculture, spatial planning in aquaculture activities become more and more important. An ecosystem-based approach for aquaculture mapping is needed to strategically and comprehensively balance the location, aquaculture type, and stakeholders’ interests. In this chapter, we aim to describe the definition, key steps, and methods of aquaculture zoning, especially in the context of climate change (e.g., global warming, ocean acidification, hypoxia/anoxia, sea level rising, and extreme events). We also provide two case studies of aquaculture mapping in China.
Continue reading ‘Aquaculture mapping in the context of climate change’What conservation strategies support the adaptive capacity of coastal ecosystems in three island states facing a changing climate in Micronesia?
Published 20 April 2023 Science ClosedTags: biological response, BRcommunity, corals, mitigation, review, socio-economy, South Pacific
Coastal ecosystems, such as coral reefs, mangroves, and seagrass beds, are highly vulnerable to the impacts of climate change. The degradation and loss of these ecosystems, stemming from the increased impacts of climate change-related drivers, threaten the well-being of island communities in Micronesia, as they are very reliant on and connected with these coastal ecosystems. Supporting the adaptive capacity of ecosystems through climate adaptive conservation, and thus better equipping them to recover from and adapt to the potential impacts, in turn reduces the vulnerability of the social-ecological system. This thesis identified five main climate change-related drivers that impact coastal systems across three selected states in Micronesia. First, based on a conceptual social-ecological systems (SES) framework, a literature review and analysis were conducted to identify and select three ecosystem adaptive capacity (AC) elements: Heterogeneity, connectivity, and ecosystem functioning. Building on that, second, a literature review aided the identification of climate adaptive conservation strategies and related actions that can support the adaptive capacity of ecosystems. Following a qualitative content analysis, eight climate adaptive conservation strategies and 26 activities were selected and categorized. Third, the extent of (1) the strategy effectiveness, (2) their integration in conservation policy and planning documents, and (3) their implementation on a national scale were evaluated through a semi-quantitative expert consultation in each of the selected states, exemplified with coral reefs.
The findings from this research showed that while the climate adaptive strategies and activities were considered effective in supporting the adaptive capacity of coral reefs in Micronesia, the extent of their implementation ranked low. Strategies, such as “Addressing non-climatic drivers” were considered highly effective, however their implementation fell comparably short. Contrary, targeting heterogeneity was considered of least importance. Thus, as their regional implementation ranked low, the ability of the strategies to support coral adaptive capacity was limited for all three countries. Particularly, the upscaling and mainstreaming of these strategies was considered crucial by the experts. Therefore, this research proposed to prioritize addressing non-climatic drivers, supporting coral reef restoration, and recommended to integrate communities in the design of climate adaptive conservation. Further to apply actionable co-produced science to advance the evidence base and applicability of the strategies in supporting ecosystem AC.
Continue reading ‘What conservation strategies support the adaptive capacity of coastal ecosystems in three island states facing a changing climate in Micronesia?’Resilience of a giant clam subsistence fishery in Kiribati to climate change
Published 20 April 2023 Science ClosedTags: fisheries, mitigation, North Pacific, policy, socio-economy
Changes in sea surface temperature have historically impacted the habitat of giant clams in Kiribati. In many islands of Kiribati, the four species of giant clam have largely withstood these environmental changes, through adaptive responses to anthropogenic pressures. The Kiribati giant clam fishery is a data-limited multi-species fishery, so in adopting and applying a comprehensive resilience framework to highlight attributes conferring and limiting resilience across the ecological, governance, and socio-economic aspects of the fishery we used knowledge co-production and the precautionary principle approach to better inform place-based attempts to operationalise resilience measures. We found that the resilience of the fishery to marine heatwaves and ocean acidification, as highlighted by local stakeholders, will depend on the ability of fisheries stakeholders to act collectively, with flexibility, to implement adaptive governance. Climate change, coupled with human impacts, have reduced ecological resilience in the urbanised island of South Tarawa, in contrast to the more remote or sparsely populated islands. In South Tarawa, governance and social processes are less flexible, leading to declines in the local subsistence clam fishery. Conversely, on several remote outer islands, where the social-ecological system has shown promise in combating these anthropogenic influences (e.g., through adaptive community-based fisheries management), the ecological resilience has improved, and the subsistence clam fishery has persisted. Our case study demonstrates the importance of a participatory approach and local knowledge when assessing climate resilience and identifies pathways of resilience in other small-scale fisheries, especially when data are limited.
Continue reading ‘Resilience of a giant clam subsistence fishery in Kiribati to climate change’A biogeochemical model of mineral-based ocean alkalinity enhancement: impacts on the biological pump and ocean carbon uptake
Published 14 April 2023 Science ClosedTags: biogeochemistry, chemistry, globalmodeling, methods, mitigation, modeling
Minimizing anthropogenic climate disruption in the coming century will likely require carbon dioxide removal (CDR) from Earth’s atmosphere in addition to deep and rapid cuts to greenhouse gas emissions. Ocean alkalinity enhancement — the modification of surface ocean chemistry to drive marine uptake of atmospheric CO2 — is seen as a potentially significant component of ocean-based CDR portfolios. However, there has been limited mechanistic exploration of the large-scale CDR potential of mineral-based ocean alkalinity enhancement, potential bottlenecks in alkalinity release, and the biophysical impacts of alkaline mineral feedstocks on marine ecology and the marine biological carbon pump. Here we a series of biogeochemical models to evaluate the gross CDR potential and environmental impacts of ocean alkalinity enhancement using solid mineral feedstocks. We find that natural alkalinity sources — basalt and olivine — lead to very low CDR efficiency while strongly perturbing marine food quality and fecal pellet production by marine zooplankton. Artificial alkalinity sources — the synthetic metal oxides MgO and CaO — are potentially capable of significant CDR with reduced environmental impact, but their deployment at scale faces major challenges associated with substrate limitation and process CO2 emissions during feedstock production. Taken together, our results highlight distinct challenges for ocean alkalinity enhancement as a CDR strategy and indicate that mineral-based ocean alkalinity enhancement should be pursued with caution.
Continue reading ‘A biogeochemical model of mineral-based ocean alkalinity enhancement: impacts on the biological pump and ocean carbon uptake’Simulated carbon cycle and Earth system response to atmospheric CO2 removal
Published 12 April 2023 Science ClosedTags: chemistry, globalmodeling, mitigation, modeling
To project possible future climate change, it is important to understand Earth system response to CO2 removal, a potential key method to limit global warming. Previous studies examined some aspects of Earth system response to different scenarios of CO2 removal, but lacked a systematic analysis of the carbon cycle and climate system response in a consistent modeling framework. We expanded previous studies by using an Earth system model to examine the response of land and ocean carbon cycle, as well as a set of climate variables to idealized scenarios of atmospheric CO2 removal with different removal rates. In the scenarios considered, atmospheric CO2 increases at a rate of 1% per year to four times of its preindustrial level, and then decreases at a rate of 0.5%, 1%, and 2% per year to the preindustrial level. Simulation results show that a reduction of atmospheric CO2 induces CO2 release from both the ocean and terrestrial biosphere, and to keep atmospheric CO2 at a lower level requires the removal of anthropogenic CO2 not only from the atmosphere, but from the ocean and land carbon reservoirs as well. The response of many variables of the Earth system, including temperature, ocean heat content, sea level, deep ocean acidity, and permafrost area and carbon, lags the decrease in atmospheric CO2 ranging from a few years to many centuries. A few centuries after atmospheric CO2 returns to the preindustrial level, sea level is still substantially higher than the preindustrial level, and permafrost continues losing CO2 to the atmosphere. Our study demonstrates that to offset previous positive CO2 emissions by atmospheric CO2 removal does not mean to offset climate consequence of positive CO2 emissions. Rapid and deep reduction in CO2 emissions is key to prevent and limit increasing risks from further warming. Our study provides new insights into the carbon cycle and climate system response to CO2 removal, which would help to assess future climate change and the associated impacts.
Continue reading ‘Simulated carbon cycle and Earth system response to atmospheric CO2 removal’Comparison of the carbon cycle and climate response to artificial ocean alkalinization and solar radiation modification
Published 11 April 2023 Science ClosedTags: biogeochemistry, chemistry, globalmodeling, mitigation, modeling
Carbon dioxide removal and solar radiation modification (SRM) are two classes of proposed climate intervention methods. A thorough understanding of climate system response to these methods calls for a good understanding of the carbon cycle response. In this study, we used an Earth system model to examine the response of global climate and carbon cycle to artificial ocean alkalinization (AOA), a method of CO2 removal, and reduction in solar irradiance that represents the overall effect of solar radiation modification. In our simulations, AOA is applied uniformly over the global ice-free ocean under the RCP8.5 scenario to bring down atmospheric CO2 to the level of RCP4.5, and SRM is applied uniformly over the globe under the RCP8.5 scenario to bring down global mean surface temperature to the level of RCP4.5. Our simulations show that with the same goal of temperature stabilization, AOA and SRM cause fundamentally different perturbations of the ocean and land carbon cycle. By the end of the 21st century, relative to the simulation of RCP8.5, AOA-induced changes in ocean carbonate chemistry enhances global oceanic CO2 uptake by 983 PgC and increases global mean surface ocean pH by 0.42. Meanwhile, AOA reduces land CO2 uptake by 79 PgC and reduces atmospheric CO2 concentration by 426 × 10−6. By contrast, relative to the simulation of RCP8.5, SRM has a minor effect on the oceanic CO2 uptake and ocean acidification. SRM-induced cooling enhances land CO2 uptake by 140 PgC and reduces atmospheric CO2 concentration by 63 × 10−6. A sudden termination of SRM causes a rate of temperature change that is much larger than that of RCP8.5. A sudden termination of AOA causes a rate of temperature change that is comparable to that of RCP8.5 and a rate of ocean acidification that is much larger than that of RCP8.5.
Continue reading ‘Comparison of the carbon cycle and climate response to artificial ocean alkalinization and solar radiation modification’Are we ready for ocean acidification? A framework for assessing and advancing policy readiness
Published 29 March 2023 Science ClosedTags: education, mitigation, policy
Effective climate policy that addresses carbon dioxide emissions is essential to minimizing and addressing the impacts of ocean acidification (OA). Here we present a framework to assess the readiness of OA policy, using coral reefs as a focal system. Six dimensions encompass comprehensive preparation by ecosystems and societies for the impacts of OA and other anthropogenic hazards: (1) climate protection measures, (2) OA literacy, (3) area-based management, (4) research and development, (5) adaptive capacity of dependent sectors, and (6) policy coherence. We define standardized indicators, identify leading countries, and evaluate the case study of Australia, the country with the largest coral reef system. The framework provides a rubric for a government unit to self- assess strengths and weaknesses in policy preparedness and to prioritize future endeavors.
Continue reading ‘Are we ready for ocean acidification? A framework for assessing and advancing policy readiness’Assessing synergies and trade-offs of diverging Paris-compliant mitigation strategies with long-term SDG objectives
Published 24 March 2023 Science ClosedTags: mitigation, policy
Highlights
- The Paris Agreement and the Sustainable Development Goals (SDGs) are interlinked.
- Mitigation strategies chosen will affect how SDGs interact.
- Technological and nature-based mitigation pathways increase resource consumption.
- Mitigation strategies relying on behavioural changes limit potential SDG trade-offs.
- Anticipating interdependences supports the design of SDG and Paris-compatible policies.
Abstract
The Sustainable Development Goals (SDGs) and the Paris Agreement are the two transformative agendas, which set the benchmarks for nations to address urgent social, economic and environmental challenges. Aside from setting long-term goals, the pathways followed by nations will involve a series of synergies and trade-offs both between and within these agendas. Since it will not be possible to optimise across the 17 SDGs while simultaneously transitioning to low-carbon societies, it will be necessary to implement policies to address the most critical aspects of the agendas and understand the implications for the other dimensions. Here, we rely on a modelling exercise to analyse the long-term implications of a variety of Paris-compliant mitigation strategies suggested in the recent scientific literature on multiple dimensions of the SDG Agenda. The strategies included rely on technological solutions such as renewable energy deployment or carbon capture and storage, nature-based solutions such as afforestation and behavioural changes in the demand side. Results for a selection of energy-environment SDGs suggest that some mitigation pathways could have negative implications on food and water prices, forest cover and increase pressure on water resources depending on the strategy followed, while renewable energy shares, household energy costs, ambient air pollution and yield impacts could be improved simultaneously while reducing greenhouse gas emissions. Overall, results indicate that promoting changes in the demand side could be beneficial to limit potential trade-offs.
Continue reading ‘Assessing synergies and trade-offs of diverging Paris-compliant mitigation strategies with long-term SDG objectives’
